Online Submission
Manuscript Tracking
Peer Review
Editor Work2016 Vol. 24, No. s1
Previous Issue
2016, 24(s1): 1-10.
Abstract
2437KB
Tibet is well known for its high altitude, big elevation, steep terrain and frequent fault activity resulting in many reivers and ecological fragility followed by frequent geological hazards. Adding the widely distributed scenes, it is difficult to build an expressway due to its geological engineering condiditons. So, the design technology for Tibetan expressways should be diffierent from what for the inland expressways. At present, the expressway construction in Tibetan area are basically in the initial stage. How to ensure highway safety, avoid disasters, save economy, protect environment and gain good engineering construction operation is the key problem and the difficulty of Tibetan highway design. In this paper, two typical Tibetan highway are taken as examples to study the main item of expressway subgrade design including general subgrade, high embankment, deep excavation, special Subgrade, earthwork and other contents according to the geological environment in Tibetan area and the humanities. The key issues in design are discussed which should be paid attention to in the design of roadbed. The results may be taken as a good reference and guidance for obtaining high-quality design of the future Tibetan highway.
Tibet is well known for its high altitude, big elevation, steep terrain and frequent fault activity resulting in many reivers and ecological fragility followed by frequent geological hazards. Adding the widely distributed scenes, it is difficult to build an expressway due to its geological engineering condiditons. So, the design technology for Tibetan expressways should be diffierent from what for the inland expressways. At present, the expressway construction in Tibetan area are basically in the initial stage. How to ensure highway safety, avoid disasters, save economy, protect environment and gain good engineering construction operation is the key problem and the difficulty of Tibetan highway design. In this paper, two typical Tibetan highway are taken as examples to study the main item of expressway subgrade design including general subgrade, high embankment, deep excavation, special Subgrade, earthwork and other contents according to the geological environment in Tibetan area and the humanities. The key issues in design are discussed which should be paid attention to in the design of roadbed. The results may be taken as a good reference and guidance for obtaining high-quality design of the future Tibetan highway.
2016, 24(s1): 11-16.
The larger deformation of soft rock tunnel of the Chengdu-Lanzhou railway presented not only the common larger deformation characteristics, such as the lining crack, steel torsion, transect of tunnel reduced in size, and so on; but possessed the regional particularities of the tectonic conditions were intricate and active, for the Chengdu-Lanzhou railway pass through the following three tectonic elements of Longmen Mountain tectonic belt, Songpan-Ganzhi fold tectonic belt and west Qinling Mountains fold structural belt included 10active faults; of the formation lithology condition were extremely weak and cracked, for the 70 percent of rock mass of Chengdu-Lanzhou railway were soft rock of slate, phyllite, schist and carbon slate, suffered seriously by the tectonic and took on the intense crumpled deformation and strong crushing cracked; of the Wenchuan seismic effect were outstanding, for the Chengdu-Lanzhou railway run through the Wenchuan 512 meizoseismal area, the seismic wave damaged to rock mass, which resulted to reduce integrity of rock mass and increase water permeability of rock mass. The crustal stress field of Chengdu-Lanzhou railway were extremely complex, with the tectonic stress field characteristic of obvious high crustal stress. The formation mechanism of larger deformation of the Chengdu-Lanzhou railway were the interaction of the complex tectonic stress, soft and cracked formation lithology, bias of disadvantage discontinuous surface and softening effect of groundwater, summarized the three kinds of the loose large deformation, squeezed large deformation and structural large deformation in high stress field. And the conclusions of this paper is great guiding significance for the building Chengdu-Lanzhou railway and others tunnel construction in similar engineering geological conditions.
The larger deformation of soft rock tunnel of the Chengdu-Lanzhou railway presented not only the common larger deformation characteristics, such as the lining crack, steel torsion, transect of tunnel reduced in size, and so on; but possessed the regional particularities of the tectonic conditions were intricate and active, for the Chengdu-Lanzhou railway pass through the following three tectonic elements of Longmen Mountain tectonic belt, Songpan-Ganzhi fold tectonic belt and west Qinling Mountains fold structural belt included 10active faults; of the formation lithology condition were extremely weak and cracked, for the 70 percent of rock mass of Chengdu-Lanzhou railway were soft rock of slate, phyllite, schist and carbon slate, suffered seriously by the tectonic and took on the intense crumpled deformation and strong crushing cracked; of the Wenchuan seismic effect were outstanding, for the Chengdu-Lanzhou railway run through the Wenchuan 512 meizoseismal area, the seismic wave damaged to rock mass, which resulted to reduce integrity of rock mass and increase water permeability of rock mass. The crustal stress field of Chengdu-Lanzhou railway were extremely complex, with the tectonic stress field characteristic of obvious high crustal stress. The formation mechanism of larger deformation of the Chengdu-Lanzhou railway were the interaction of the complex tectonic stress, soft and cracked formation lithology, bias of disadvantage discontinuous surface and softening effect of groundwater, summarized the three kinds of the loose large deformation, squeezed large deformation and structural large deformation in high stress field. And the conclusions of this paper is great guiding significance for the building Chengdu-Lanzhou railway and others tunnel construction in similar engineering geological conditions.
2016, 24(s1): 17-23.
The project area is a high mountain valley topography that strongly influenced by geological tectonic movements with complex geological conditions。the original design is open-wire, According to the qualitative and quantitative analysis, it doesn't meet safety requirements when the geological conditions changed because of the heavy rain and excavation。in order to avoid its adverse effects, a small angle cross section tunnel structure is used in this project, which divide the large cross section into three segments: Wall area、reducing cross area and enlarging and excavation area, Each area has a special excavation and support design parameters, and this system has been deployed successfully, I hope that this paper will provide some experience and reference significance for similar projects in the future.
The project area is a high mountain valley topography that strongly influenced by geological tectonic movements with complex geological conditions。the original design is open-wire, According to the qualitative and quantitative analysis, it doesn't meet safety requirements when the geological conditions changed because of the heavy rain and excavation。in order to avoid its adverse effects, a small angle cross section tunnel structure is used in this project, which divide the large cross section into three segments: Wall area、reducing cross area and enlarging and excavation area, Each area has a special excavation and support design parameters, and this system has been deployed successfully, I hope that this paper will provide some experience and reference significance for similar projects in the future.
2016, 24(s1): 24-31.
Taking the reinforced embankment of Shifang highway as research object and combing with on-site monitoring data, the deformation and failure characteristics of the reinforced embankment are studied using the elastic-plastic finite element program. On this basis, parametric analysis is carried out on the reinforcement stiffness, reinforcement spacing. The main results show that: ① due to the thick backfill behind the masonry retaining wall, there is an uneven settlement at the bottom of the reinforced embankment, and the reinforcement stiffiness almost has no effect on it, therefore, the compaction degree of the backfill behind the masonry wall should be guaranteed.② maximum strains at all levels of the reinforcement are distributed in the near embankment slope, and the maximum axial force is located in the lower part of the reinforced embankment.③ the failure mode of the reinforced embankment belongs to internal failure, i.e.the reinforcement is pulled off. The failure surface is located near the reinforced embankment slope; the structural strength and stability of masonry retaining wall foundation has an important role on the whole stability of the reinforced embankment.④ with the increasing of the axial stiffness and the decreasing of the reinforcement spacing, the bi-directional displacements are decreased and the safety factor are increased accordingly. However, when the axial stiffness of the reinforced body reaches a certain extent, its influence on the deformation characteristics of the reinforced embankment is greatly weakened. The results have a certain theoretical and reference meaning on the design calculation and construction of the mountaineous reinforced embankment.
Taking the reinforced embankment of Shifang highway as research object and combing with on-site monitoring data, the deformation and failure characteristics of the reinforced embankment are studied using the elastic-plastic finite element program. On this basis, parametric analysis is carried out on the reinforcement stiffness, reinforcement spacing. The main results show that: ① due to the thick backfill behind the masonry retaining wall, there is an uneven settlement at the bottom of the reinforced embankment, and the reinforcement stiffiness almost has no effect on it, therefore, the compaction degree of the backfill behind the masonry wall should be guaranteed.② maximum strains at all levels of the reinforcement are distributed in the near embankment slope, and the maximum axial force is located in the lower part of the reinforced embankment.③ the failure mode of the reinforced embankment belongs to internal failure, i.e.the reinforcement is pulled off. The failure surface is located near the reinforced embankment slope; the structural strength and stability of masonry retaining wall foundation has an important role on the whole stability of the reinforced embankment.④ with the increasing of the axial stiffness and the decreasing of the reinforcement spacing, the bi-directional displacements are decreased and the safety factor are increased accordingly. However, when the axial stiffness of the reinforced body reaches a certain extent, its influence on the deformation characteristics of the reinforced embankment is greatly weakened. The results have a certain theoretical and reference meaning on the design calculation and construction of the mountaineous reinforced embankment.
2016, 24(s1): 32-37.
the essence of the washout mechanism of subgrade for highway along the river, is a process of interaction impact that bedrock scour resistance of soil and subgrade near wall. From the perspective of hydraulic analysis get the flow shear stress is the power source along the river embankment washout, again from the force balance principle, analysis of washout airport on the surface of the soil under the weight of the failure mechanism. According to the practical engineering calculation example to verify this method, the results show that the predicted results compared with the truth. Research on highway roadbed along the river washout prevention and control of waterlogging prediction has positive significance.
the essence of the washout mechanism of subgrade for highway along the river, is a process of interaction impact that bedrock scour resistance of soil and subgrade near wall. From the perspective of hydraulic analysis get the flow shear stress is the power source along the river embankment washout, again from the force balance principle, analysis of washout airport on the surface of the soil under the weight of the failure mechanism. According to the practical engineering calculation example to verify this method, the results show that the predicted results compared with the truth. Research on highway roadbed along the river washout prevention and control of waterlogging prediction has positive significance.
2016, 24(s1): 38-46.
Aiming at the demand of increasing mountain roadway construction, the stress and deformation behavior of reinforced embankment on steep slope with different angles was studied comparatively by finite element method based on the parametric analysis of backslope friction angle, backfill strength and filling height. The results indicate that compared to the conventional embankment constructed on level ground, the decrease of backfill strength and raise of filling height will increase the deformation of reinforced embankment on steep slope more severely, and the reinforced embankment on steep slope may have disadvantages in the control of deformation, base pressure and wall deflection etc.,which is due to the sliding of backfill along the slope. Based on different backslope friction angles, backfill strength and heights, respectively, the deformation of reinforced embankment on 45slope is 6.8%~96.8% and 29.4%~192.3%, 6.8%~33.1% and 29.4%~77.9%, 7.7%~37.9% and 27.2%~91.6% larger than those of the embankment on 63.4(slope ratio=2:1) slope and embankment on 90slope(level ground),respectively. The results can provide guidance for the increasing road construction in mountainous areas.
Aiming at the demand of increasing mountain roadway construction, the stress and deformation behavior of reinforced embankment on steep slope with different angles was studied comparatively by finite element method based on the parametric analysis of backslope friction angle, backfill strength and filling height. The results indicate that compared to the conventional embankment constructed on level ground, the decrease of backfill strength and raise of filling height will increase the deformation of reinforced embankment on steep slope more severely, and the reinforced embankment on steep slope may have disadvantages in the control of deformation, base pressure and wall deflection etc.,which is due to the sliding of backfill along the slope. Based on different backslope friction angles, backfill strength and heights, respectively, the deformation of reinforced embankment on 45slope is 6.8%~96.8% and 29.4%~192.3%, 6.8%~33.1% and 29.4%~77.9%, 7.7%~37.9% and 27.2%~91.6% larger than those of the embankment on 63.4(slope ratio=2:1) slope and embankment on 90slope(level ground),respectively. The results can provide guidance for the increasing road construction in mountainous areas.
2016, 24(s1): 47-53.
in order to study the migration patterns of pollutants in groundwater, this article conduct numerical simulation by taking the chloride in groundwater of a power plant as the predictor. Generalize the aquifer material composition, boundary conditions, initial conditions and source sink term of the study area, establish the hydrogeological model by GMS software, syudy migration patterns of pollutants in groundwater on the simplified hydrogeological model. Research results show that: under the condition that under the condition that contaminant discharge is simplified as a constant point source,(1) Plane migration of pollutant elliptical diffusion with the leak point as center, the long axis of pollution is the direction of groundwater flow.(2) the maximum migration distance and the pollution influence range of the pollutants both increase with time, but the rate of change continues to decrease.(3) Near the location of pollution sources, concentration of pollutants increased with time, but the concentration change rate gradually decreased. Far away from the source of pollution, concentration of pollutants increased with time, the initial concentration change rate increased with time, in the late stage, the concentration change rate decreased gradually with time.
in order to study the migration patterns of pollutants in groundwater, this article conduct numerical simulation by taking the chloride in groundwater of a power plant as the predictor. Generalize the aquifer material composition, boundary conditions, initial conditions and source sink term of the study area, establish the hydrogeological model by GMS software, syudy migration patterns of pollutants in groundwater on the simplified hydrogeological model. Research results show that: under the condition that under the condition that contaminant discharge is simplified as a constant point source,(1) Plane migration of pollutant elliptical diffusion with the leak point as center, the long axis of pollution is the direction of groundwater flow.(2) the maximum migration distance and the pollution influence range of the pollutants both increase with time, but the rate of change continues to decrease.(3) Near the location of pollution sources, concentration of pollutants increased with time, but the concentration change rate gradually decreased. Far away from the source of pollution, concentration of pollutants increased with time, the initial concentration change rate increased with time, in the late stage, the concentration change rate decreased gradually with time.
2016, 24(s1): 54-60.
The tunnel construction project is a important part of a lot of traffic and hydropower construction project. It needs more prospecting and exploration data than other type construction project for information modeling of BIM design and application. However, because of many reasons, it always lacks the local prospecting and exploration data in preliminary design stage of project construction. Because of this, it's difficult to launch the BIM design and application at the beginning. And, that is also not fit of the current usual situation which are short design cycle and the requirement of providing design production in short time.As a new method,the BIM design with little prospecting and exploration could solve the problem that the geological BIM design and application are lack of adequate prospecting and exploration data in preliminary stage. It makes quick providing the trustworthy exploration and design production with little local prospecting and exploration become possible. This paper offered a BIM design of a mountain tunnel project in preliminary stage as an example in order to introduce a information modeling process of the new method which is including some way of getting geological information except local prospecting and exploration. Based on the information model of BIM,the paper provided the BIM applications of a sample tunnel section such as obtaining the rock mass classification and giving some practical geological suggestion by analysis. These presentation provided the reference to promote the further BIM design and application in preliminary stage of project construction for geological engineering. Then, the paper discussed some problem and their solution of this new method. Finally, the paper summarized that the advantages of the method are quick respond and trustworthy production, and,proposed its prospective in the design and the assistance of operating management in preliminary stage of construction project.
The tunnel construction project is a important part of a lot of traffic and hydropower construction project. It needs more prospecting and exploration data than other type construction project for information modeling of BIM design and application. However, because of many reasons, it always lacks the local prospecting and exploration data in preliminary design stage of project construction. Because of this, it's difficult to launch the BIM design and application at the beginning. And, that is also not fit of the current usual situation which are short design cycle and the requirement of providing design production in short time.As a new method,the BIM design with little prospecting and exploration could solve the problem that the geological BIM design and application are lack of adequate prospecting and exploration data in preliminary stage. It makes quick providing the trustworthy exploration and design production with little local prospecting and exploration become possible. This paper offered a BIM design of a mountain tunnel project in preliminary stage as an example in order to introduce a information modeling process of the new method which is including some way of getting geological information except local prospecting and exploration. Based on the information model of BIM,the paper provided the BIM applications of a sample tunnel section such as obtaining the rock mass classification and giving some practical geological suggestion by analysis. These presentation provided the reference to promote the further BIM design and application in preliminary stage of project construction for geological engineering. Then, the paper discussed some problem and their solution of this new method. Finally, the paper summarized that the advantages of the method are quick respond and trustworthy production, and,proposed its prospective in the design and the assistance of operating management in preliminary stage of construction project.
2016, 24(s1): 61-66.
To predicate the steady state of fracture surface of surrounding rock and support system in terms of Bali flat tunnel in the course of excavation and,uncover the mechanism of the tunnel surrounding rock in the aspect of deformation, destruction and stability. Exponential function model is established by the use of the data which is gained on spot in the way of testing the section of surrounding rock ZK77+835according to the horizontal convergence displacement and vault crown settlement displacement. The result, after the regression analysis, precise judgment and monitoring data analysis, Meanwhile conducting BP Neural Network displacement back analysis and numerical simulation, shows that by adopting the exponential function model, it is relatively precise to analysis of regression of the data acquired aiming at surrounding rockZK77+835 displacement; there are three periods of the deformation of surrounding rock, in the light of displacement and the dislocation rate, there will provide a basis for judging the stability of the fracture surface of surrounding rock and can start the secondary lining conduction after monitoring the 15 day; it is accurate to get the parameter of inversion by BP Neural Network displacement back analysis, which is taken to FLAC3D numerical model, there will be no different between the simulation results and the monitoring data in field.
To predicate the steady state of fracture surface of surrounding rock and support system in terms of Bali flat tunnel in the course of excavation and,uncover the mechanism of the tunnel surrounding rock in the aspect of deformation, destruction and stability. Exponential function model is established by the use of the data which is gained on spot in the way of testing the section of surrounding rock ZK77+835according to the horizontal convergence displacement and vault crown settlement displacement. The result, after the regression analysis, precise judgment and monitoring data analysis, Meanwhile conducting BP Neural Network displacement back analysis and numerical simulation, shows that by adopting the exponential function model, it is relatively precise to analysis of regression of the data acquired aiming at surrounding rockZK77+835 displacement; there are three periods of the deformation of surrounding rock, in the light of displacement and the dislocation rate, there will provide a basis for judging the stability of the fracture surface of surrounding rock and can start the secondary lining conduction after monitoring the 15 day; it is accurate to get the parameter of inversion by BP Neural Network displacement back analysis, which is taken to FLAC3D numerical model, there will be no different between the simulation results and the monitoring data in field.
2016, 24(s1): 67-71.
Gongshan-Dongchuanexpressway project is located in the tectogenesis, theformation of debris flow in dongchuan, complicated topographic and geologic conditions. The project survey and design adhere to the sustainable development the layout of thought, with safety as the basis, take the quality as the lifeline, dominated by science and technology, combinedwithcomplex geological conditions in the region, Implementing the standard line selection, security line selection, topography and line selection, the geological line selection, the design principle of ecological environmental protection concept, Scientific reasoning to choose, to ensure the quality of the design. Theories and methods for mountain road line selection should be studied.
Gongshan-Dongchuanexpressway project is located in the tectogenesis, theformation of debris flow in dongchuan, complicated topographic and geologic conditions. The project survey and design adhere to the sustainable development the layout of thought, with safety as the basis, take the quality as the lifeline, dominated by science and technology, combinedwithcomplex geological conditions in the region, Implementing the standard line selection, security line selection, topography and line selection, the geological line selection, the design principle of ecological environmental protection concept, Scientific reasoning to choose, to ensure the quality of the design. Theories and methods for mountain road line selection should be studied.
2016, 24(s1): 72-78.
This paper examines the 147 engineering geological drilling holes through the construction and collection, the Yoco port in the area were divided into 6 engineering layers and 16 sub-layers according to their types of formation, chronology, lithology and mechanics. The authors also made a comprehensive study on the spatial distribution of soil, engineering geology and geotechnical changes of the foundation soil(less than 50 deep),as w ell as the paleo-geog raphy of different areas of engineering geology. The study area was divided into the marine plain of engineering geological zone, delta plain engineering geological zone and beach reclamation engineering geological zones by comprehensive considering geomorphologic unit, genetic types, structural characteristics of soil and the presence of mainly environmental engineering geological problems. On the basis of engineering geological division, the development and utilization of underground space exploitation and utilization of geological conditions are valuated with the main force bearing layer and poor soil mass, which provides basic geological basis for the planning, construction and management of the port area.
This paper examines the 147 engineering geological drilling holes through the construction and collection, the Yoco port in the area were divided into 6 engineering layers and 16 sub-layers according to their types of formation, chronology, lithology and mechanics. The authors also made a comprehensive study on the spatial distribution of soil, engineering geology and geotechnical changes of the foundation soil(less than 50 deep),as w ell as the paleo-geog raphy of different areas of engineering geology. The study area was divided into the marine plain of engineering geological zone, delta plain engineering geological zone and beach reclamation engineering geological zones by comprehensive considering geomorphologic unit, genetic types, structural characteristics of soil and the presence of mainly environmental engineering geological problems. On the basis of engineering geological division, the development and utilization of underground space exploitation and utilization of geological conditions are valuated with the main force bearing layer and poor soil mass, which provides basic geological basis for the planning, construction and management of the port area.
2016, 24(s1): 79-84.
Wave-induced liquefaction of sandy seabed with loose or mediate density, directly affects the safety of marine structures. The liquefaction criterions often used in the literature are mainly based on the conception of effective stress and excess pore pressure. With analysis on physical meaning of 4 liquefaction criterions mainly used in the literature, using the analytical solution of wave-induced seabed stress and pore pressure, the distribution characteristics of transient liquefaction zone by different liquefaction criterion are compared for different computation parameters, and the suitability of the 4 liquefaction criterions is discussed. The mainly conclusions have been drawn as follows. The liquefaction criterion b, which is based on the seabed average effective stress, is not applicable to compute liquefaction of the seabed with saturation no less than 0.99 and seabed thickness no greater than 0.4 times of wave length. The liquefaction criterion d, which is based on the seabed vertical excess pore water pressure and the seabed initial mean effective stress, is not recommended in computation of liquefaction, because the liquefaction depth computed by the criterion d is obviously larger than depth of the plastic zone in most cases and the physical meaning of it is unclear. The liquefaction criterion a, which is based on the seabed vertical effective stress, and the liquefaction criterion c, which is based on the seabed vertical excess pore water pressure and the seabed initial vertical effective stress, are recommended to compute the wave-induced seabed transient liquefaction due to their good suitability.
Wave-induced liquefaction of sandy seabed with loose or mediate density, directly affects the safety of marine structures. The liquefaction criterions often used in the literature are mainly based on the conception of effective stress and excess pore pressure. With analysis on physical meaning of 4 liquefaction criterions mainly used in the literature, using the analytical solution of wave-induced seabed stress and pore pressure, the distribution characteristics of transient liquefaction zone by different liquefaction criterion are compared for different computation parameters, and the suitability of the 4 liquefaction criterions is discussed. The mainly conclusions have been drawn as follows. The liquefaction criterion b, which is based on the seabed average effective stress, is not applicable to compute liquefaction of the seabed with saturation no less than 0.99 and seabed thickness no greater than 0.4 times of wave length. The liquefaction criterion d, which is based on the seabed vertical excess pore water pressure and the seabed initial mean effective stress, is not recommended in computation of liquefaction, because the liquefaction depth computed by the criterion d is obviously larger than depth of the plastic zone in most cases and the physical meaning of it is unclear. The liquefaction criterion a, which is based on the seabed vertical effective stress, and the liquefaction criterion c, which is based on the seabed vertical excess pore water pressure and the seabed initial vertical effective stress, are recommended to compute the wave-induced seabed transient liquefaction due to their good suitability.
2016, 24(s1): 85-92.
Earthquake can trigger post-liquefaction large deformation of saturated sand field, including seismic subsidence which can cause building ground uneven settlement, lateral spreading, resulting in the damage of pile foundations and buried pipelines. With reference to the centrifuge test, this paper is based on the finite element platform of OpenSees, by employing a bounding surface plasticity constitutive suitable for soil liquefaction deformation. The corresponding three-dimensional free field model is simplified into a shear beam. And the influence of different factors on ground lateral deformation is compared and analyzed, including ground inclination, relative density, different seismic wave characteristics and peak acceleration etc. The results show that pulse characteristics of near-fault ground motions cause the time history curves of ground lateral displacement presents certain pulse characteristics, and the effect on the accumulation of pore pressure should not be ignored; the increase of seismic peak acceleration and ground inclination will eventually cause the ground residual displacement value augment; the calcaulation of ground residual displacement is influenced strongly by the realitive density of sand, the more dense sand, smaller the ground lateral displacement is.
Earthquake can trigger post-liquefaction large deformation of saturated sand field, including seismic subsidence which can cause building ground uneven settlement, lateral spreading, resulting in the damage of pile foundations and buried pipelines. With reference to the centrifuge test, this paper is based on the finite element platform of OpenSees, by employing a bounding surface plasticity constitutive suitable for soil liquefaction deformation. The corresponding three-dimensional free field model is simplified into a shear beam. And the influence of different factors on ground lateral deformation is compared and analyzed, including ground inclination, relative density, different seismic wave characteristics and peak acceleration etc. The results show that pulse characteristics of near-fault ground motions cause the time history curves of ground lateral displacement presents certain pulse characteristics, and the effect on the accumulation of pore pressure should not be ignored; the increase of seismic peak acceleration and ground inclination will eventually cause the ground residual displacement value augment; the calcaulation of ground residual displacement is influenced strongly by the realitive density of sand, the more dense sand, smaller the ground lateral displacement is.
2016, 24(s1): 93-99.
Using the elastic-plastic bounding surface model produced by UMAT of Abaqus, the dynamic simple shear test model of a soil element and the three-dimensional analytical model of seismic compression of sand are established. This paper analyze the earthquake subsidence of sand with different relative densities and clay contents under varied seismic waves. The research shows that, the vertical strain of sand decreased with the increasing clay content in sand when the value of clay content is less than 30%; however, when the value of clay content exceed 30%,the vertical strain become increasing. Besides, a large proportion of site settlement is produced when peak acceleration of earthquake occurred; and for a seismic wave that has several peak accelerations, the vertical strain depends on the value of historical maximum peak acceleration.
Using the elastic-plastic bounding surface model produced by UMAT of Abaqus, the dynamic simple shear test model of a soil element and the three-dimensional analytical model of seismic compression of sand are established. This paper analyze the earthquake subsidence of sand with different relative densities and clay contents under varied seismic waves. The research shows that, the vertical strain of sand decreased with the increasing clay content in sand when the value of clay content is less than 30%; however, when the value of clay content exceed 30%,the vertical strain become increasing. Besides, a large proportion of site settlement is produced when peak acceleration of earthquake occurred; and for a seismic wave that has several peak accelerations, the vertical strain depends on the value of historical maximum peak acceleration.
2016, 24(s1): 100-107.
A large number of collapse and landslides triggered by Wenchuan earthquake. Massive loose material is formed.it created the basic conditions for the formation of debris flow. The formation of the dam-breaking debris flows are special.the dam-breaking debris flows has the character of big-scale, sudden outbreak, short duration, strong erosion carrying ability. It often cause serious harm.this paper taken the Qipangou dam-breaking debris flow in Wenchuan area as an example. Basic on the analysis of the debris flow formation conditions and detailed description about the basic characteristics of the collapse, the paper analyzed emphatically the multistage dam-breaking process.it can provide reference for further understanding the formation of dam-breaking debris flows after earthquak, parameter selection and prevention and control measures.
A large number of collapse and landslides triggered by Wenchuan earthquake. Massive loose material is formed.it created the basic conditions for the formation of debris flow. The formation of the dam-breaking debris flows are special.the dam-breaking debris flows has the character of big-scale, sudden outbreak, short duration, strong erosion carrying ability. It often cause serious harm.this paper taken the Qipangou dam-breaking debris flow in Wenchuan area as an example. Basic on the analysis of the debris flow formation conditions and detailed description about the basic characteristics of the collapse, the paper analyzed emphatically the multistage dam-breaking process.it can provide reference for further understanding the formation of dam-breaking debris flows after earthquak, parameter selection and prevention and control measures.
2016, 24(s1): 108-115.
An Mw7.1 earthquake, located in the central Pamir Plateau, struck Tajikistan on December 7, 2015. The location of the earthquake is close to Saraz Lake, formed in February 1911 when a nearby Mw 7.3 earthquake triggered a landslide that dammed the Murghab River. By studying the coseismic deformation of the earthquake, we can reveal the distribution of seismogenic fault and tectonic setting of the area, analyze the development of seismic geological disaster and evaluate the conditions of engineering geology. This paper observed the coseismic deformation by D-InSAR technology, using two periods of images before and after the earthquake from Sentinel-1A,which has advantages in wider range and higher precision. Combined with the geological background of the area and the focal mechanisms parameters from Global CMT and USGS,the following conclusions can be drawn:(1) the seismogenic fault is given priority to NE-SW extend with sinistral slip. It is rare in the central Pamir Syntaxis with priority to the north of arcuate thrust structure.(2) the entire coseismic deformation area is more than 120km in length and 80km in width, as well as the biggest LOS displacement in NW well is-60cm and biggest LOS displacement in SE well is 42cm.(3) the macro-epicenter is located in 30km northeast of Lake Saraz, which indicates this area is most serious damaged by earthquake.(4) the geological and geophysical information obtained from coseismal seismic deformation, observed by InSAR,can lay a foundation of tectonic stable analysis.
An Mw7.1 earthquake, located in the central Pamir Plateau, struck Tajikistan on December 7, 2015. The location of the earthquake is close to Saraz Lake, formed in February 1911 when a nearby Mw 7.3 earthquake triggered a landslide that dammed the Murghab River. By studying the coseismic deformation of the earthquake, we can reveal the distribution of seismogenic fault and tectonic setting of the area, analyze the development of seismic geological disaster and evaluate the conditions of engineering geology. This paper observed the coseismic deformation by D-InSAR technology, using two periods of images before and after the earthquake from Sentinel-1A,which has advantages in wider range and higher precision. Combined with the geological background of the area and the focal mechanisms parameters from Global CMT and USGS,the following conclusions can be drawn:(1) the seismogenic fault is given priority to NE-SW extend with sinistral slip. It is rare in the central Pamir Syntaxis with priority to the north of arcuate thrust structure.(2) the entire coseismic deformation area is more than 120km in length and 80km in width, as well as the biggest LOS displacement in NW well is-60cm and biggest LOS displacement in SE well is 42cm.(3) the macro-epicenter is located in 30km northeast of Lake Saraz, which indicates this area is most serious damaged by earthquake.(4) the geological and geophysical information obtained from coseismal seismic deformation, observed by InSAR,can lay a foundation of tectonic stable analysis.
2016, 24(s1): 116-120.
In the paper, the seismicity and seismotectonic environments of a area is analyzed, which is preselected for low and intermediate-level radioactive waste disposal. The division of potential seismic source zone is revised. Then the different exceedance probability of peak ground acceleration and seismic intensity is calculated by the method of probabilistic seismic hazard analysis, and the spatial distribution characteristics of peak ground acceleration is analyzed. The results show that the peak ground acceleration is closely related with the potential seismic source zone. On this basis suggestions for the site of radioactive waste disposal is gived.
In the paper, the seismicity and seismotectonic environments of a area is analyzed, which is preselected for low and intermediate-level radioactive waste disposal. The division of potential seismic source zone is revised. Then the different exceedance probability of peak ground acceleration and seismic intensity is calculated by the method of probabilistic seismic hazard analysis, and the spatial distribution characteristics of peak ground acceleration is analyzed. The results show that the peak ground acceleration is closely related with the potential seismic source zone. On this basis suggestions for the site of radioactive waste disposal is gived.
2016, 24(s1): 121-127.
After centuries of wind and rain erosion and man-made destruction, most of Ming Great Wall in Qinghai province have been extinct, and only a few exist as earthen sites. Some related studies indicate that earthen sites of Ming Great Wall have developed 6 types of typical deteriorations including scaling off, gullies, sapping, collapses, cracks, holes and biological deteriorations. As a special architectural type of Great Wall, the beacon tower was responsible for transferring information and because of that military mission, most of them are distributed in high elevation areas. This paper selected 17 beacon towers located in Huangzhong county and the authors conducted the investigation of those on site to collect the deteriorations data. Based on such work and collection of their elevations, it did fitting between those deteriorations statistics and elevations, aiming to acquire the effects of elevations on the development of such deteriorations. According to the system analysis of this work, it concluded that the elevations have influence on biological deteriorations, scaling off, holes and sapping, and have pretty obvious correlations with latter three deteriorations. This study could provide a new strategy for the developmental mechanism of deteriorations in earthen sites, and also supply helpful reference to the protection work for Ming Great Wall in future.
After centuries of wind and rain erosion and man-made destruction, most of Ming Great Wall in Qinghai province have been extinct, and only a few exist as earthen sites. Some related studies indicate that earthen sites of Ming Great Wall have developed 6 types of typical deteriorations including scaling off, gullies, sapping, collapses, cracks, holes and biological deteriorations. As a special architectural type of Great Wall, the beacon tower was responsible for transferring information and because of that military mission, most of them are distributed in high elevation areas. This paper selected 17 beacon towers located in Huangzhong county and the authors conducted the investigation of those on site to collect the deteriorations data. Based on such work and collection of their elevations, it did fitting between those deteriorations statistics and elevations, aiming to acquire the effects of elevations on the development of such deteriorations. According to the system analysis of this work, it concluded that the elevations have influence on biological deteriorations, scaling off, holes and sapping, and have pretty obvious correlations with latter three deteriorations. This study could provide a new strategy for the developmental mechanism of deteriorations in earthen sites, and also supply helpful reference to the protection work for Ming Great Wall in future.
2016, 24(s1): 128-136.
Earthen structures, one of the most earliest architectural style, are widely distributed all around the world. There are lots of earthen heritage sites that still remain in northwest of China. The variety of earthen structures ranges from simple forms to vast, and the construction techniques varies from culture to culture and region to region. However, the majority of historic buildings and archaeological sites made of earth exhibit serious conservation problems due to various environmental conditions. Among these styles of deteriorations, fissure is one of the most common and widely developed diseases on earthen sites, which has a great influence on structural stability of sites. According to the in-situ engineering data obtained in recent 5 years, from the ancient rammed-earth ruins in Gansu and Qinghai provinces, which can date back to Ming-Dynasties, this paper analyzes the influence of primary meteorological factors, i.e.rainfall, evaporation, temperature, daily temperature difference and sunshine, on the development of fissures in the rammed-earth sites. The results of this study well reveal the meteorological environment effects on the development of fissures. The analytical data shows that the fissures in the ancient rammed-earth ruins suffer different actions of the meteorological factors in the northwestern of China, such as rainfall, evaporation, temperature and sunshine etc. The main conclusions are as follows:(1) the average fissure length and maximum fissure length tend to increase with the increasing of rainfall, decreasing of evaporation, reducing of temperature and decreasing of sunshine; however, the fissures have a tendency to expand in humidity environment.(2) the average fissure width and maximum fissure width tend to increase with the decreasing of rainfall, increasing of evaporation, increasing of temperature and sunshine; meanwhile, the arid environment can have a positive effect on the development of tiny fissures in the early stage.(3) the impact of the meteorological environment on the sites is a complex process. The factors are various and have a mutual influence which promotes each other. As a result, the impacts of these meteorological factors on earthen sites are similar.
Earthen structures, one of the most earliest architectural style, are widely distributed all around the world. There are lots of earthen heritage sites that still remain in northwest of China. The variety of earthen structures ranges from simple forms to vast, and the construction techniques varies from culture to culture and region to region. However, the majority of historic buildings and archaeological sites made of earth exhibit serious conservation problems due to various environmental conditions. Among these styles of deteriorations, fissure is one of the most common and widely developed diseases on earthen sites, which has a great influence on structural stability of sites. According to the in-situ engineering data obtained in recent 5 years, from the ancient rammed-earth ruins in Gansu and Qinghai provinces, which can date back to Ming-Dynasties, this paper analyzes the influence of primary meteorological factors, i.e.rainfall, evaporation, temperature, daily temperature difference and sunshine, on the development of fissures in the rammed-earth sites. The results of this study well reveal the meteorological environment effects on the development of fissures. The analytical data shows that the fissures in the ancient rammed-earth ruins suffer different actions of the meteorological factors in the northwestern of China, such as rainfall, evaporation, temperature and sunshine etc. The main conclusions are as follows:(1) the average fissure length and maximum fissure length tend to increase with the increasing of rainfall, decreasing of evaporation, reducing of temperature and decreasing of sunshine; however, the fissures have a tendency to expand in humidity environment.(2) the average fissure width and maximum fissure width tend to increase with the decreasing of rainfall, increasing of evaporation, increasing of temperature and sunshine; meanwhile, the arid environment can have a positive effect on the development of tiny fissures in the early stage.(3) the impact of the meteorological environment on the sites is a complex process. The factors are various and have a mutual influence which promotes each other. As a result, the impacts of these meteorological factors on earthen sites are similar.
2016, 24(s1): 137-142.
Based on the detailed geologic survey and drilling data, the basic characteristics of the Dacun landslides are elaborated, including space distribution, material composition, slip band and bed features. The genesis of the Dacun ancient landslide is analyzed and discussed, and then, the internal and external factors affecting the stability of the landslide are combined, and its reviving mechanism is discussed. Finally, we evaluate the stability of the Dacun landslides. The results show that the continuous erosion of the Sanyu river and storm are the direct cause of the ancient landslide and its modern reviving.
Based on the detailed geologic survey and drilling data, the basic characteristics of the Dacun landslides are elaborated, including space distribution, material composition, slip band and bed features. The genesis of the Dacun ancient landslide is analyzed and discussed, and then, the internal and external factors affecting the stability of the landslide are combined, and its reviving mechanism is discussed. Finally, we evaluate the stability of the Dacun landslides. The results show that the continuous erosion of the Sanyu river and storm are the direct cause of the ancient landslide and its modern reviving.
2016, 24(s1): 143-148.
The exploitation of the Lead and Zinc mineral resources in North Guangxi region has different degree of pollution on the red clay. In order to study the effects of lead ions pollution on the mechanical properties of Guilin red clay, the unconsolidated undrained triaxial shear tests were conducted with the different concentration at different action time under various confining pressures. The stress-strain behavior, the elastic modulus and the parameters of shearing strength were measured. The results show that: the mechanical properties of Guilin red clay are affected considerably by the concentration of lead ions, the mechanical properties of soils decreased with increasing of the concentration of lead ions, and it is the worst when the concentration of lead ions reaches the maximum(1.0%) in the test. The stress-strain curves of the red clay which was polluted by the lead ions were presented the hardening type, but its trend was decreased as the increased of the concentration of lead ions and the confining pressures. The elastic modulus, the parameters of shearing strength were decreased considerably as the increased of the concentration of lead ions, but the parameters of shearing strength show less obvious during the change of action time, which means the lead ions can finished the main damage of the structure of the soils.
The exploitation of the Lead and Zinc mineral resources in North Guangxi region has different degree of pollution on the red clay. In order to study the effects of lead ions pollution on the mechanical properties of Guilin red clay, the unconsolidated undrained triaxial shear tests were conducted with the different concentration at different action time under various confining pressures. The stress-strain behavior, the elastic modulus and the parameters of shearing strength were measured. The results show that: the mechanical properties of Guilin red clay are affected considerably by the concentration of lead ions, the mechanical properties of soils decreased with increasing of the concentration of lead ions, and it is the worst when the concentration of lead ions reaches the maximum(1.0%) in the test. The stress-strain curves of the red clay which was polluted by the lead ions were presented the hardening type, but its trend was decreased as the increased of the concentration of lead ions and the confining pressures. The elastic modulus, the parameters of shearing strength were decreased considerably as the increased of the concentration of lead ions, but the parameters of shearing strength show less obvious during the change of action time, which means the lead ions can finished the main damage of the structure of the soils.
2016, 24(s1): 149-155.
In the world at present, while the site protection is a hot issue in the research of the protection of cultural relics, the quantification of earthen site, the correlation between diseases and risk assessment of soil sites are less studied. Based on the field investigation of 17 beacon towers of the Ming Dynasty great wall in Qinghai, the weight and relevance of collapse volume, undercutting volume, gully volume, fracture length, cave volume, surface stripping size, biodeterioration area 7 factors are analysed, and the risk assessment model of these single building is established through the grey correlation theory. On the basis of this model, the risk level of each beacon is finally determined.
In the world at present, while the site protection is a hot issue in the research of the protection of cultural relics, the quantification of earthen site, the correlation between diseases and risk assessment of soil sites are less studied. Based on the field investigation of 17 beacon towers of the Ming Dynasty great wall in Qinghai, the weight and relevance of collapse volume, undercutting volume, gully volume, fracture length, cave volume, surface stripping size, biodeterioration area 7 factors are analysed, and the risk assessment model of these single building is established through the grey correlation theory. On the basis of this model, the risk level of each beacon is finally determined.
2016, 24(s1): 156-159.
Due to the fragile ecological environment and the influence of human engineering activities, the loess slope geological disasters such as landslides have been increasing in Loess Plateau. The loess slope protection by vegetation is the effective means for restoration ecology and geological disaster prevention. in this paper, in order to ascertain the connection between the plant growth characteristics and the slope habitat, the engineering geological characteristic and the vegetation community structure will be studied by field investigation; and then the influence of roots on physical and mechanical parameters of soil will be analyzed by in-situ test, and the slope protection effect of plants will be clarified. On this basis, the theory and techniques of loess slope ecological protection of plants will be established. The research results can promote the engineering application of plants in loess area, and be the guidance of loess slope ecological protection technology in northwest China.
Due to the fragile ecological environment and the influence of human engineering activities, the loess slope geological disasters such as landslides have been increasing in Loess Plateau. The loess slope protection by vegetation is the effective means for restoration ecology and geological disaster prevention. in this paper, in order to ascertain the connection between the plant growth characteristics and the slope habitat, the engineering geological characteristic and the vegetation community structure will be studied by field investigation; and then the influence of roots on physical and mechanical parameters of soil will be analyzed by in-situ test, and the slope protection effect of plants will be clarified. On this basis, the theory and techniques of loess slope ecological protection of plants will be established. The research results can promote the engineering application of plants in loess area, and be the guidance of loess slope ecological protection technology in northwest China.
2016, 24(s1): 160-166.
Research shows that regional stress field affects the distribution of volcanic dikes and craters. Normally, the arrangement of craters parallels to the direction of maximum horizontal principal stress and verticals to the minimum horizontal principal stress. Combining the foreign method of crater survey, this paper studys wudalianchi in heilongjiang province. In the basis of remote sensing images and volcanic data, this paper processes images, analyses volcanic structure diagram and processes linear mode of volcanic craters to inverse wudalianchi regional stress field. Result shows that wudalianchi maximum horizontal principal stress direction is NE.this result coincides with the stress direction information of focal mechanism solution. Abroad has conducted a comprehensive study of the method, however the few domestic research. Inversion result demonstrates that the method is practical, so we can apply this method in the region of the domestic typical volcanoes to compensate regional stress direction information
Research shows that regional stress field affects the distribution of volcanic dikes and craters. Normally, the arrangement of craters parallels to the direction of maximum horizontal principal stress and verticals to the minimum horizontal principal stress. Combining the foreign method of crater survey, this paper studys wudalianchi in heilongjiang province. In the basis of remote sensing images and volcanic data, this paper processes images, analyses volcanic structure diagram and processes linear mode of volcanic craters to inverse wudalianchi regional stress field. Result shows that wudalianchi maximum horizontal principal stress direction is NE.this result coincides with the stress direction information of focal mechanism solution. Abroad has conducted a comprehensive study of the method, however the few domestic research. Inversion result demonstrates that the method is practical, so we can apply this method in the region of the domestic typical volcanoes to compensate regional stress direction information
2016, 24(s1): 167-173.
Tectonic landform is directly formed by earth's crust neotectonic movement with a dynamic and active's topography or terrain. The tectonic geomorphology's evolution which is under fault activity, can be used as an intuitive evidence. This article works through remote sensing interpretation, geological survey and multi-prospecting etc.,studies for tectonic geomorphology's characteristic and quaternary activity at Change-Nan'ao fault zone. The results show: In the north-east and north-west survey area, two of the faults controls geomorphic development in this area, and form a mesh morphological pattern. The fault zone's linear image, has a clear characteristic and zonation. From this point of view, a variety of microtopography development has referential meaning to the fault zone and quaternary activity. It also means a part of fault zone has a certain activity in quaternary era. The activity's direction has two styles, which is perpendicular and horizontal. The fault zone's activity in this area has a certain difference, from northwest to southeast, form inland to coastal, the reactivity is progressively strengthen. The main activities of the fault zone is before in late Pleistocene, but they also have some indications in Holocene at partial section.
Tectonic landform is directly formed by earth's crust neotectonic movement with a dynamic and active's topography or terrain. The tectonic geomorphology's evolution which is under fault activity, can be used as an intuitive evidence. This article works through remote sensing interpretation, geological survey and multi-prospecting etc.,studies for tectonic geomorphology's characteristic and quaternary activity at Change-Nan'ao fault zone. The results show: In the north-east and north-west survey area, two of the faults controls geomorphic development in this area, and form a mesh morphological pattern. The fault zone's linear image, has a clear characteristic and zonation. From this point of view, a variety of microtopography development has referential meaning to the fault zone and quaternary activity. It also means a part of fault zone has a certain activity in quaternary era. The activity's direction has two styles, which is perpendicular and horizontal. The fault zone's activity in this area has a certain difference, from northwest to southeast, form inland to coastal, the reactivity is progressively strengthen. The main activities of the fault zone is before in late Pleistocene, but they also have some indications in Holocene at partial section.
2016, 24(s1): 174-179.
Land subsidence is one of most main geological disasters in the Yangtze river delta economic region. With the ban of Suzhou-Wuxi-Changzhou area groundwater exploitation, the mainly compression deformation of soil is from aquitard at present. This paper took the No.06 drilling from Guangming village, Wuxi city, for an example. The pore size distribution of soil was analyzed based on mercury intrusion porosimetrytest and the relation between the pore of cohesive soil and land subsidence was studied. According to the result of mercury intrusion porosimetry, an evaluation method of aquitard compression potential was proposed using the concept of macro-pore porosity emip. The index emip can evaluate the compression potential of aquitard. The potential of aquitard compression shows a tendency: Ⅰ-1 aquitard Ⅱ aquitard Ⅰ-2 aquitard Ⅰ-3 aquitard. The result is consistent with the compression parameter and the microstructure of soil samples. So it is a effective way to evaluate the compression potential of aquitard stratum.
Land subsidence is one of most main geological disasters in the Yangtze river delta economic region. With the ban of Suzhou-Wuxi-Changzhou area groundwater exploitation, the mainly compression deformation of soil is from aquitard at present. This paper took the No.06 drilling from Guangming village, Wuxi city, for an example. The pore size distribution of soil was analyzed based on mercury intrusion porosimetrytest and the relation between the pore of cohesive soil and land subsidence was studied. According to the result of mercury intrusion porosimetry, an evaluation method of aquitard compression potential was proposed using the concept of macro-pore porosity emip. The index emip can evaluate the compression potential of aquitard. The potential of aquitard compression shows a tendency: Ⅰ-1 aquitard Ⅱ aquitard Ⅰ-2 aquitard Ⅰ-3 aquitard. The result is consistent with the compression parameter and the microstructure of soil samples. So it is a effective way to evaluate the compression potential of aquitard stratum.
2016, 24(s1): 180-185.
Cement, fly ash and mineral powder were used as the main raw materials, according to the mass ratio 16:3:1,foamed concrete with different content of bubbles was prepared under different water-binder ratio(0.43, 0.5, 0.6) respectively. The uniaxial compression tests for samples were conducted and obtained the stress-strain curve, peak stress of foamed concrete. The change rules of foamed concrete stress-strain curve with different water-binder ratio, the influence of water-binder ratio on compressive strength and elasticity modulus were experimentally researched. The experimental results indicate that the change rules of stress-strain curve of foamed concrete with different water-binder ratio are basically coincide and all foamed concrete do experience four stages under uniaxial compression: close-grained, elasticity, yield, destroy. Water-binder ratio has a big influence on the compressive strength and elasticity of foamed concrete with low porosity, while has a small effect on foamed concrete with high porosity. Though with different water-binder ratio, the relationships between compressive strength, elasticity and porosity are exponential with porosity.
Cement, fly ash and mineral powder were used as the main raw materials, according to the mass ratio 16:3:1,foamed concrete with different content of bubbles was prepared under different water-binder ratio(0.43, 0.5, 0.6) respectively. The uniaxial compression tests for samples were conducted and obtained the stress-strain curve, peak stress of foamed concrete. The change rules of foamed concrete stress-strain curve with different water-binder ratio, the influence of water-binder ratio on compressive strength and elasticity modulus were experimentally researched. The experimental results indicate that the change rules of stress-strain curve of foamed concrete with different water-binder ratio are basically coincide and all foamed concrete do experience four stages under uniaxial compression: close-grained, elasticity, yield, destroy. Water-binder ratio has a big influence on the compressive strength and elasticity of foamed concrete with low porosity, while has a small effect on foamed concrete with high porosity. Though with different water-binder ratio, the relationships between compressive strength, elasticity and porosity are exponential with porosity.
2016, 24(s1): 186-191.
The treatment of geological hazards such as landslide has all sorts of difficulties and urgency. There are kinds of deficiencies in the previous treatment methods. The high polymer material, which has been widely used in geotechnical engineering, possesses the merits of high strength, light weight, high expansibility, short setting time, good durability, easy construction and is water-proof and harmless to the existing structures. Through analysis, it is found that the polymer grouting reinforcement technology can handle all kinds of unfavorable conditions in the treatment of landslide well. Therefore, the polymer grouting reinforcement technology for the treatment of landslide is put forward innovatively in this paper. The slope deformation and stability before and after reinforcement with polymer grouting were studied by finite element method. The results indicates that the polymer grouting can deepen the slip circle and increase the sliding path, as a result, it avoids the shallow sliding mode of slope, which leads to the increase of stability and the decrease of slope deformation. After reinforcement, the factor of safety is increased by 38%,the maximum total displacement is reduced by 29% around. Hence, the effectiveness of polymer grouting reinforcement technology is preliminarily verified.
The treatment of geological hazards such as landslide has all sorts of difficulties and urgency. There are kinds of deficiencies in the previous treatment methods. The high polymer material, which has been widely used in geotechnical engineering, possesses the merits of high strength, light weight, high expansibility, short setting time, good durability, easy construction and is water-proof and harmless to the existing structures. Through analysis, it is found that the polymer grouting reinforcement technology can handle all kinds of unfavorable conditions in the treatment of landslide well. Therefore, the polymer grouting reinforcement technology for the treatment of landslide is put forward innovatively in this paper. The slope deformation and stability before and after reinforcement with polymer grouting were studied by finite element method. The results indicates that the polymer grouting can deepen the slip circle and increase the sliding path, as a result, it avoids the shallow sliding mode of slope, which leads to the increase of stability and the decrease of slope deformation. After reinforcement, the factor of safety is increased by 38%,the maximum total displacement is reduced by 29% around. Hence, the effectiveness of polymer grouting reinforcement technology is preliminarily verified.
2016, 24(s1): 192-197.
The seabed covered with deep soft soil and it bearing capacity is very low, the traditional CPTU cannot adapt, so we began study the Full Flow Penetration Probe. Full flow penetration test consider the characteristics of soft soil, changed the shape of the probe, and 10 times bigger projected area can accessing and collecting the basic parameters of the test, for the dividing and calculate the basic physical and mechanical indexes of the soil layer very accurately. It's very useful to the geological engineering. This paper conclude the full flow penetration test types, methods, mechanism of penetration and estimate parameter, analysis the advantages and disadvantages of full flow penetration test and the scope of application, Finally prospects the development direction of future full flow penetration test.
The seabed covered with deep soft soil and it bearing capacity is very low, the traditional CPTU cannot adapt, so we began study the Full Flow Penetration Probe. Full flow penetration test consider the characteristics of soft soil, changed the shape of the probe, and 10 times bigger projected area can accessing and collecting the basic parameters of the test, for the dividing and calculate the basic physical and mechanical indexes of the soil layer very accurately. It's very useful to the geological engineering. This paper conclude the full flow penetration test types, methods, mechanism of penetration and estimate parameter, analysis the advantages and disadvantages of full flow penetration test and the scope of application, Finally prospects the development direction of future full flow penetration test.
2016, 24(s1): 198-202.
3D laser scanning is a new measurement technology which can get real 3D spatial data.It has the characteristics of little restriction, high precision and fast speed which has applied engineering widely. The joints on cliff have a great impact on the formation and development of cultural disease. Joint investigation is important on researching disease causes and conservation recommendations. This paper analyzed disease Causes of stone relics and the role of joint, which also discussed application method of 3D laser scanning in cliff stone protection.
3D laser scanning is a new measurement technology which can get real 3D spatial data.It has the characteristics of little restriction, high precision and fast speed which has applied engineering widely. The joints on cliff have a great impact on the formation and development of cultural disease. Joint investigation is important on researching disease causes and conservation recommendations. This paper analyzed disease Causes of stone relics and the role of joint, which also discussed application method of 3D laser scanning in cliff stone protection.
2016, 24(s1): 203-207.
Accurate assessment of back tension crack depth is very important because it dictates the accuracy in slope stability analysis. In this paper, we reviewed three methods based on the existing literature and provided a brief introduction to the model for derivatives of these formulas. Although three formulas take different forms, they produced the same results. Based on analysis we recommended to use two of them in slope stability analysis. With mathematical analysis of the stripe piece model we determined the minimum extreme height of the strip. The obtained extreme height of the tension crack is equal to those results from three methods. The dip angle of the bottom of the stripe piece is the maximum angle of the sliding surface in the back. From the perspective of mechanical analysis, the slope body behind the stripe with a minimum height can be a stable body that sustains the tension force. The above analysis further our understanding of the condition and mechanism of the tension crack.
Accurate assessment of back tension crack depth is very important because it dictates the accuracy in slope stability analysis. In this paper, we reviewed three methods based on the existing literature and provided a brief introduction to the model for derivatives of these formulas. Although three formulas take different forms, they produced the same results. Based on analysis we recommended to use two of them in slope stability analysis. With mathematical analysis of the stripe piece model we determined the minimum extreme height of the strip. The obtained extreme height of the tension crack is equal to those results from three methods. The dip angle of the bottom of the stripe piece is the maximum angle of the sliding surface in the back. From the perspective of mechanical analysis, the slope body behind the stripe with a minimum height can be a stable body that sustains the tension force. The above analysis further our understanding of the condition and mechanism of the tension crack.
STUDY ON COMPLEX THREE-DIMENSIONAL GEOLOGICAL MODELING OF FLAC3D BASED ON MATLAB AND SURFER PLATFORM
2016, 24(s1): 208-213.
FLAC3D is a widely used software in geological numerical simulation. There are several basic steps to realize the three-dimensional modeling study, establishing the model, defining the constitutive relationship and parameters, setting the initial and boundary conditions, and finally solving the stress field. However, as the complexity of the geological conditions, building up an accurate and complex 3D geological body is always a difficult problem in pre-processing of FLAC3D.Therefore, a new model-building-up method is put forward in this paper, to set up grids with the powerful matrix functions of MATLAB and the powerful interpolation functions of SURFER.The result showed a high matching between the model and the real topography and geological condition. This new method is simple, practical and easy to operate, which makes it a good approach in pre-processing of FLAC3D.
FLAC3D is a widely used software in geological numerical simulation. There are several basic steps to realize the three-dimensional modeling study, establishing the model, defining the constitutive relationship and parameters, setting the initial and boundary conditions, and finally solving the stress field. However, as the complexity of the geological conditions, building up an accurate and complex 3D geological body is always a difficult problem in pre-processing of FLAC3D.Therefore, a new model-building-up method is put forward in this paper, to set up grids with the powerful matrix functions of MATLAB and the powerful interpolation functions of SURFER.The result showed a high matching between the model and the real topography and geological condition. This new method is simple, practical and easy to operate, which makes it a good approach in pre-processing of FLAC3D.
2016, 24(s1): 214-220.
Traditional T-bar sounding probe section is circular, for two extreme probe surface conditions: completely smooth and completely rough, the penetration resistance difference is 26% of the moderate roughness; penetration resistance is strongly influenced by the surface roughness. In order to reduce the influence of the surface roughness on the probe resistance, oval cross section probe is studied. Assume that soft soil strength obey the Tresca strength criterion, using upper and lower limit principle, obtained the analytic solution for the resistance of a infinite long probe with oval cross section in a infinite space of soft clay. Results show that, sounding along the short axis, the influence of surface roughness on the probe resistance reduces with the decreasing of short to long axial ratio. With an axial ratio of 0.3~0.5,the penetration resistance difference is reduced to 9%~14%.
Traditional T-bar sounding probe section is circular, for two extreme probe surface conditions: completely smooth and completely rough, the penetration resistance difference is 26% of the moderate roughness; penetration resistance is strongly influenced by the surface roughness. In order to reduce the influence of the surface roughness on the probe resistance, oval cross section probe is studied. Assume that soft soil strength obey the Tresca strength criterion, using upper and lower limit principle, obtained the analytic solution for the resistance of a infinite long probe with oval cross section in a infinite space of soft clay. Results show that, sounding along the short axis, the influence of surface roughness on the probe resistance reduces with the decreasing of short to long axial ratio. With an axial ratio of 0.3~0.5,the penetration resistance difference is reduced to 9%~14%.
2016, 24(s1): 221-227.
There were bulk accumulation sediments of loose soil and rock in Beichuan area generated by Wenchuan earthquake on May 12, 2008, and continuous rainfall actions resulted in several times of severe landslides and debris flow disasters after a few months to few years of earthquake. Based on field investigation in geology, landform topography and rainfall data, a series of initiation of debris flow model tests under rainfall conditions in laboratory were performed respectively on Beichuan soil and silty fine sand sediments. Moreover, the effects of rainfall duration, rainfall density, slope angle and soil density on the initiation of debris flow were analyzed. Finally, the process and mechanism of debris flow initiation of Beichuan soil and silty fine sand under rainfall conditions were revealed. The results show that:(1) for Beichuan soil sediment, only the full infiltration stage occurs in the process of debris flow initiation and the critical rainfall density is needed much bigger in order to initiate debris flow.(2) for silty fine sand sediment, all the three stages of full infiltration, thin layer and deep surface seepage occur in the process of debris flow initiation, and the rainfall duration is needed much longer when the slope angle is bigger and the rainfall density is beyond a certain value.(3) the initiation of debris flow, whether for Beichuan soil or for silty fine sand, is the result of the combined action of gravity and seepage, but the function of gravity and seepage depends on the grain size distribution of soil. This research provides important reference data for early warning of debris flow disaster under rainfall conditions in Beichuan area.
There were bulk accumulation sediments of loose soil and rock in Beichuan area generated by Wenchuan earthquake on May 12, 2008, and continuous rainfall actions resulted in several times of severe landslides and debris flow disasters after a few months to few years of earthquake. Based on field investigation in geology, landform topography and rainfall data, a series of initiation of debris flow model tests under rainfall conditions in laboratory were performed respectively on Beichuan soil and silty fine sand sediments. Moreover, the effects of rainfall duration, rainfall density, slope angle and soil density on the initiation of debris flow were analyzed. Finally, the process and mechanism of debris flow initiation of Beichuan soil and silty fine sand under rainfall conditions were revealed. The results show that:(1) for Beichuan soil sediment, only the full infiltration stage occurs in the process of debris flow initiation and the critical rainfall density is needed much bigger in order to initiate debris flow.(2) for silty fine sand sediment, all the three stages of full infiltration, thin layer and deep surface seepage occur in the process of debris flow initiation, and the rainfall duration is needed much longer when the slope angle is bigger and the rainfall density is beyond a certain value.(3) the initiation of debris flow, whether for Beichuan soil or for silty fine sand, is the result of the combined action of gravity and seepage, but the function of gravity and seepage depends on the grain size distribution of soil. This research provides important reference data for early warning of debris flow disaster under rainfall conditions in Beichuan area.
2016, 24(s1): 228-232.
Analysis of the performance of CFG pile composite foundation found that a plastic deformation zone surrounding the CFG pile composite foundation with an area of about one time piles distance was formed, and it is the main cause of instability of the whole composite foundation. Comparative analysis of characteristics as stress change, foundation settlement of the composite foundation before and after adding a row of fender piles in the plastic deformation zone, found that foundation performance get obvious change after pile enforcement. In the same conditions, the foundation settlement reduced significantly and the stability improved obviously.
Analysis of the performance of CFG pile composite foundation found that a plastic deformation zone surrounding the CFG pile composite foundation with an area of about one time piles distance was formed, and it is the main cause of instability of the whole composite foundation. Comparative analysis of characteristics as stress change, foundation settlement of the composite foundation before and after adding a row of fender piles in the plastic deformation zone, found that foundation performance get obvious change after pile enforcement. In the same conditions, the foundation settlement reduced significantly and the stability improved obviously.
2016, 24(s1): 233-238.
According to the problem of cracks in the anti-pulling test of filling pile, using the pile test of a new convertor station in Shandong province as an example, the process of cracks, the variation of cracks' width and the distribution of cracks is studied. Based on that, the causes of cracks are presented. Then the corresponding prevention measures are suggested, which can be referred by similar projects.
According to the problem of cracks in the anti-pulling test of filling pile, using the pile test of a new convertor station in Shandong province as an example, the process of cracks, the variation of cracks' width and the distribution of cracks is studied. Based on that, the causes of cracks are presented. Then the corresponding prevention measures are suggested, which can be referred by similar projects.
2016, 24(s1): 239-244.
In order to study the simple and quickevaluation method of volumetric water content in diesel oil-contaminated sands, different proportion of diesel oil and /or water were first artificially added and mixed with initially dry clean sands to prepare organic contaminated soil of different contamination degree. Then Time Domain Reflectometry(TDR)tests were conducted on the sands to study the relationship between the dielectric constantsof the sandsof certain dry density to their water and oil content. Test results indicate that there's siginificant delay in the TDR reflected wave if the sands contain only deionized water or mixture of deionized water and diesel oil, and the calculated dielectric constant increase with the increase of water content. When only diesel oil is contained in the sands, TDR reflected waveform will be slightly delayed with the increase of oil content. Furthermore, the calculated dielectric constant also increases with the increase of oil content. Thus, TDR test can be used for quick detection of the contamination degree of diesel oil contaminated sands.
In order to study the simple and quickevaluation method of volumetric water content in diesel oil-contaminated sands, different proportion of diesel oil and /or water were first artificially added and mixed with initially dry clean sands to prepare organic contaminated soil of different contamination degree. Then Time Domain Reflectometry(TDR)tests were conducted on the sands to study the relationship between the dielectric constantsof the sandsof certain dry density to their water and oil content. Test results indicate that there's siginificant delay in the TDR reflected wave if the sands contain only deionized water or mixture of deionized water and diesel oil, and the calculated dielectric constant increase with the increase of water content. When only diesel oil is contained in the sands, TDR reflected waveform will be slightly delayed with the increase of oil content. Furthermore, the calculated dielectric constant also increases with the increase of oil content. Thus, TDR test can be used for quick detection of the contamination degree of diesel oil contaminated sands.
2016, 24(s1): 245-251.
In recent years, with the development of storage and transportation of hydrocarbon technology. The pipeline has been laid successfully in a variety of complex geomorphology areas and a variety of special geographical environment. But in some special pipe section, such as Collapsible-Loess Area and Mountain-Landslide Area, oil and gas pipeline is restricted by some factors. Even there will be found a variety of problems in the course of laying or operating. In the paper, we will based on mechanical analysis and calculation, and established mechanics model, combined with the similarity simulation experiment, analysis the effect of water flow on oil and gas pipeline where laid at different angles in slope, and referenced the theory and method of pipeline risk-assessment of foreign countries. The risk assessment method of special pipeline section is established in loess area. The result has reference value and guidance significance to the pipeline laying in the loess area.
In recent years, with the development of storage and transportation of hydrocarbon technology. The pipeline has been laid successfully in a variety of complex geomorphology areas and a variety of special geographical environment. But in some special pipe section, such as Collapsible-Loess Area and Mountain-Landslide Area, oil and gas pipeline is restricted by some factors. Even there will be found a variety of problems in the course of laying or operating. In the paper, we will based on mechanical analysis and calculation, and established mechanics model, combined with the similarity simulation experiment, analysis the effect of water flow on oil and gas pipeline where laid at different angles in slope, and referenced the theory and method of pipeline risk-assessment of foreign countries. The risk assessment method of special pipeline section is established in loess area. The result has reference value and guidance significance to the pipeline laying in the loess area.
2016, 24(s1): 252-257.
The stress relaxation test of soil-rock mixtures of 20%, 30% stone-containing under triaxial compression is carried out on the strain triaxial apparatus by step loading method.According to the results, divide the stress relaxation stage of soil-rock mixtures, the stress relaxation characteristics under different stone containing were analyzed and compared. Studies suggest that, with the increase of axial stress, the stress relaxation increases, the stress relaxation ratio decreases. Wiechertmodel can describe stress relaxation characteristics of soil-rock mixtures, theoretical curves fitting with the experimental curve is very good.
The stress relaxation test of soil-rock mixtures of 20%, 30% stone-containing under triaxial compression is carried out on the strain triaxial apparatus by step loading method.According to the results, divide the stress relaxation stage of soil-rock mixtures, the stress relaxation characteristics under different stone containing were analyzed and compared. Studies suggest that, with the increase of axial stress, the stress relaxation increases, the stress relaxation ratio decreases. Wiechertmodel can describe stress relaxation characteristics of soil-rock mixtures, theoretical curves fitting with the experimental curve is very good.
2016, 24(s1): 258-266.
Aiming at the character that the sliding mass acquire a high velocity in the set out-range, it shows that the landslide starting at a high speed is due to the sudden cut of the locking section to produce vibration, so that the sliding body accelerated, under the coupling effect and the force of its own gravity, landslide suddenly set-off. Taking Yunnan touzhai large-scale high-speed landslide as example, according to the field survey results, using fracture mechanics theory to analysis the process of vibration locking section from cut to accelerate. Calculating the strain energy released during the process of shear failure, the magnitude of the earthquake induced by the corresponding magnitude is consistent with the magnitude of the induced earthquake. And it is concluded that the start speed of the landslide is 46.1ms-1.On the basis of this, the PFC2D software is used to simulate the flow of the solid particles. The results show that with the lock solid particle stiffness increases, the particle accumulation of strain energy under the shear stress is larger, which leads to the sliding body to get a larger starting speed.
Aiming at the character that the sliding mass acquire a high velocity in the set out-range, it shows that the landslide starting at a high speed is due to the sudden cut of the locking section to produce vibration, so that the sliding body accelerated, under the coupling effect and the force of its own gravity, landslide suddenly set-off. Taking Yunnan touzhai large-scale high-speed landslide as example, according to the field survey results, using fracture mechanics theory to analysis the process of vibration locking section from cut to accelerate. Calculating the strain energy released during the process of shear failure, the magnitude of the earthquake induced by the corresponding magnitude is consistent with the magnitude of the induced earthquake. And it is concluded that the start speed of the landslide is 46.1ms-1.On the basis of this, the PFC2D software is used to simulate the flow of the solid particles. The results show that with the lock solid particle stiffness increases, the particle accumulation of strain energy under the shear stress is larger, which leads to the sliding body to get a larger starting speed.
2016, 24(s1): 267-274.
With the rapid development of urban construction, precast piles are widely used in engineering because of its good performance. An indoor model experiment and finite element simulation that based on large deformation method were taken to study the change of the stress field andpore pressure in soil around pile. It is found that during the precast pile sinking process, under the same depth, the farther it is from the axial of pile, the smaller excessive pore water pressure of soil around pile, but the faster it dissipates, with the radius of influence of about 10 times pile diameter. There is similar law in depth direction. In pile sinking, radial extrusion remodeling around the pile mainly occurs within 1 time of pile diameter, with the influence range of displacement field at about 5 times pile diameter. During pile sinking, big sideway extrusion stress will be produced, with the influence range of stress field of about 7.5 times pile diameter.
With the rapid development of urban construction, precast piles are widely used in engineering because of its good performance. An indoor model experiment and finite element simulation that based on large deformation method were taken to study the change of the stress field andpore pressure in soil around pile. It is found that during the precast pile sinking process, under the same depth, the farther it is from the axial of pile, the smaller excessive pore water pressure of soil around pile, but the faster it dissipates, with the radius of influence of about 10 times pile diameter. There is similar law in depth direction. In pile sinking, radial extrusion remodeling around the pile mainly occurs within 1 time of pile diameter, with the influence range of displacement field at about 5 times pile diameter. During pile sinking, big sideway extrusion stress will be produced, with the influence range of stress field of about 7.5 times pile diameter.
2016, 24(s1): 275-282.
The most common barrier to the use of cement deep mixing technology is the lack of effective approach to assess the quality of finished piles. Based on previous works and the comparisons between common assessment techniques, SPT with the assistant of visual examination is believed to be able to assess the continuity and strength quality of the whole pile in separate soil layers. The quality assessment system is investigated through a series of SPts on the cement-soil piles from a real project in Shanghai. This research shows that soil properties impact on both SPT blow counts and improvement effect in correspondence with depth and age, and thus should be taken into account in the system. In addition, the maximum probability intervals and the suggested reasonable ranges of pile SPT blow counts are obtained from the statistical analysis in separate soil layers. The suggested reasonable intervals in the third layer is 10-18,while 5-12 in the forth layer and 11-23 in the interlayer. Accordingly, the assessment specifications for cement-soil mixed piles in Shanghai are established so as to provide a reference for future works.
The most common barrier to the use of cement deep mixing technology is the lack of effective approach to assess the quality of finished piles. Based on previous works and the comparisons between common assessment techniques, SPT with the assistant of visual examination is believed to be able to assess the continuity and strength quality of the whole pile in separate soil layers. The quality assessment system is investigated through a series of SPts on the cement-soil piles from a real project in Shanghai. This research shows that soil properties impact on both SPT blow counts and improvement effect in correspondence with depth and age, and thus should be taken into account in the system. In addition, the maximum probability intervals and the suggested reasonable ranges of pile SPT blow counts are obtained from the statistical analysis in separate soil layers. The suggested reasonable intervals in the third layer is 10-18,while 5-12 in the forth layer and 11-23 in the interlayer. Accordingly, the assessment specifications for cement-soil mixed piles in Shanghai are established so as to provide a reference for future works.
2016, 24(s1): 283-289.
The loess landform is one of the important research contents of geomorphology. It has an extensive and important application in the environmental geology, hydrogeology, engineering geology and other subjects. So it has attracted the attention of scholars both at home and abroad for a long time. However, due to the complexity of the distribution, morphology and causes of loess landform, it still does not have an classification system with the peculiarities include systematic, comprehensive and practical. At present many classification and naming of loess landform types are lack of unified definition and specific definition. It caused a lot of confusions and misuses. First, we summarized the research history and causes of loess landform, then summarized the field survey data, at last on the basis of previous work, we try to establish a new set of classification system of loess landform. The principles including combination of causes and forms, systematic, comprehensive, practical and so on was accepted by this classification system. The causes of loess landform include cenozoic tectonic movement(endogenetic agent),geotechnical properties, external agent, the influence of human activity, et al. The old classification system was lack of a lot of types of loess landform. This new classification system adds some types of loess landform to the old system. And the new classification system gives specific connotation to the previous confusing concept of loess landform. At last loess landform is divided into four categories, including Loess erosion-tectonic accumulation landform, Loess modern tectonic(deformation) landform, Loess collapsibility subsidence landform, Loess erosion landform. It has a simple introduction about the four categories in the article. The new classification system not only considers the principles of loess landform classification including comprehensive and systematic, but also takes into account the actual needs of scientific research and production work. So it has more theoretical and practical application value.
The loess landform is one of the important research contents of geomorphology. It has an extensive and important application in the environmental geology, hydrogeology, engineering geology and other subjects. So it has attracted the attention of scholars both at home and abroad for a long time. However, due to the complexity of the distribution, morphology and causes of loess landform, it still does not have an classification system with the peculiarities include systematic, comprehensive and practical. At present many classification and naming of loess landform types are lack of unified definition and specific definition. It caused a lot of confusions and misuses. First, we summarized the research history and causes of loess landform, then summarized the field survey data, at last on the basis of previous work, we try to establish a new set of classification system of loess landform. The principles including combination of causes and forms, systematic, comprehensive, practical and so on was accepted by this classification system. The causes of loess landform include cenozoic tectonic movement(endogenetic agent),geotechnical properties, external agent, the influence of human activity, et al. The old classification system was lack of a lot of types of loess landform. This new classification system adds some types of loess landform to the old system. And the new classification system gives specific connotation to the previous confusing concept of loess landform. At last loess landform is divided into four categories, including Loess erosion-tectonic accumulation landform, Loess modern tectonic(deformation) landform, Loess collapsibility subsidence landform, Loess erosion landform. It has a simple introduction about the four categories in the article. The new classification system not only considers the principles of loess landform classification including comprehensive and systematic, but also takes into account the actual needs of scientific research and production work. So it has more theoretical and practical application value.
2016, 24(s1): 290-298.
Due to the special nature of the occurrence mechanism of shale gas, storage conditions and type of cap affectshale gas reservoir. Dense overburden rock have a great impact on shale gas capping, take a greater role in the decision of reservoir fracturing technology. This article is for theoretical analysis of cap rock fracture mechanism for shale gas reservoir. and establish the numerical simulation model for cap rock. The cap rock fracturing is related to water injection pressure, rock tensile strength and in-situ stress.the fracture mechanism of cap rock includes two stages. The fracturing initial stage, the reservoir deformation, cap rock occurs shear crack, fracturing fluid into cap rock. When water injection pressure is less than the minimum principal stress, shear fracture rock When water injection pressure is the sum of least principal stress and tensile strength of rock, rock occurs tensile failure, the process of fracture involves tensile and shear failure, fracture increase and expand, form a mesh system. Numerical simulation results show that the high pressure water can produce hydraulic destruction in the reservoir area. With water injection pressure rising, hydraulic damage area expanded and occurs superimposition effect, result in the hydraulic failure focus on upper part of the middle water injection. In the whole process of reservoir fracturing, 1 hour later, the cracks of the reservoir develop, the cap rock stability, rock pore water pressure and deformation is small, there are small cracks at the bottom of cap rock. After fracturing 2 hours, cracks at the bottom of cap rock increase, rock pore water pressure rise, and rock occurs deformation, deformation is most obvious in the middle. After fracturing 3 hours, cracks extend from the bottom of the roof to the upper, cracks rock in internal rapidly develop, rock pore water pressure and deformation value increasing. The results of numerical simulation is consistent with the results of mechanism analysis of fracture.
Due to the special nature of the occurrence mechanism of shale gas, storage conditions and type of cap affectshale gas reservoir. Dense overburden rock have a great impact on shale gas capping, take a greater role in the decision of reservoir fracturing technology. This article is for theoretical analysis of cap rock fracture mechanism for shale gas reservoir. and establish the numerical simulation model for cap rock. The cap rock fracturing is related to water injection pressure, rock tensile strength and in-situ stress.the fracture mechanism of cap rock includes two stages. The fracturing initial stage, the reservoir deformation, cap rock occurs shear crack, fracturing fluid into cap rock. When water injection pressure is less than the minimum principal stress, shear fracture rock When water injection pressure is the sum of least principal stress and tensile strength of rock, rock occurs tensile failure, the process of fracture involves tensile and shear failure, fracture increase and expand, form a mesh system. Numerical simulation results show that the high pressure water can produce hydraulic destruction in the reservoir area. With water injection pressure rising, hydraulic damage area expanded and occurs superimposition effect, result in the hydraulic failure focus on upper part of the middle water injection. In the whole process of reservoir fracturing, 1 hour later, the cracks of the reservoir develop, the cap rock stability, rock pore water pressure and deformation is small, there are small cracks at the bottom of cap rock. After fracturing 2 hours, cracks at the bottom of cap rock increase, rock pore water pressure rise, and rock occurs deformation, deformation is most obvious in the middle. After fracturing 3 hours, cracks extend from the bottom of the roof to the upper, cracks rock in internal rapidly develop, rock pore water pressure and deformation value increasing. The results of numerical simulation is consistent with the results of mechanism analysis of fracture.
2016, 24(s1): 299-307.
Three rounds of exploration of marsel in Kazakhstan show that, the area has good petroleum geological conditions, but the exploration degree is low and the resource potential is unclear. The organic carbon content TOC is the standard of effective source rocks and is also the key parameters for the calculation of the amount of resources, however, the previous evaluation of effective source rocks and the calculated amount of resources are based on the residual TOC which gradually decreased with the mass hydrocarbon expulsion, so it will inevitably produce some errors. Therefore, to be more accurate, based on the TOC recovery coefficient formula, we recovered the residual TOC of source rocks, and then revised the criteria of effective source rocks, finally, calculated the resources of Carboniferous and Devonian in marsel. The results are as follows: for source rocks in marsel, the TOC recovery coefficient of carboniferous source rocks is about 1.6,while the Devonian is about 2.0; the revised lower limit of TOC for effective source rocks is 0.3% and 0.25% respectively for Carboniferous and Devonian; after TOC recovery, the total amount of recoverable resources is (2.62~5.10)1012m3 for the main source rocks in marsel. The effective source rocks evaluated based on the recovered TOC and the latter resources can reflect the quanlity of source rocks and the actual resource potential of marsel more accurately. It has a certain significance for the exploration of areas which are with low level of exploration, unclear understanding of resource potential as well as high degree of thermal evolution and low quantity of residual TOC.
Three rounds of exploration of marsel in Kazakhstan show that, the area has good petroleum geological conditions, but the exploration degree is low and the resource potential is unclear. The organic carbon content TOC is the standard of effective source rocks and is also the key parameters for the calculation of the amount of resources, however, the previous evaluation of effective source rocks and the calculated amount of resources are based on the residual TOC which gradually decreased with the mass hydrocarbon expulsion, so it will inevitably produce some errors. Therefore, to be more accurate, based on the TOC recovery coefficient formula, we recovered the residual TOC of source rocks, and then revised the criteria of effective source rocks, finally, calculated the resources of Carboniferous and Devonian in marsel. The results are as follows: for source rocks in marsel, the TOC recovery coefficient of carboniferous source rocks is about 1.6,while the Devonian is about 2.0; the revised lower limit of TOC for effective source rocks is 0.3% and 0.25% respectively for Carboniferous and Devonian; after TOC recovery, the total amount of recoverable resources is (2.62~5.10)1012m3 for the main source rocks in marsel. The effective source rocks evaluated based on the recovered TOC and the latter resources can reflect the quanlity of source rocks and the actual resource potential of marsel more accurately. It has a certain significance for the exploration of areas which are with low level of exploration, unclear understanding of resource potential as well as high degree of thermal evolution and low quantity of residual TOC.
2016, 24(s1): 308-315.
For significantly different of height of fractured water-conducting zone in Yu-shen-fu and the traditional results, Yuyang mine is taked as study area. The height of fractured water-conducting zone was analyzed based on analysis of hydrogeological conditions, situ testing, theoretical analysis and numerical simulation. The results show that the percentage content of sandstone(about 85%) in the overlying strata of the Jurassic coal bed roof than Permo-Carboniferous. The thickness of the overlying strata of the Jurassic coal bed roof is larger and the vertical fracture is not developed. The main reason for the height anomaly of the water flowing fractured zone is that the integrity of the roof covering structure is better. The height of water flowing fractured zone was tested and calculated by using the field measurement and discrete element simulation methods. The results showed that the height of water flowing fractured zone were 60m and 95m for the structural plane development and none development of coal seam overlying strata, respectively, which is proved that the overlying rock structure is the main factor leading to the height of water conducting fractured zone.
For significantly different of height of fractured water-conducting zone in Yu-shen-fu and the traditional results, Yuyang mine is taked as study area. The height of fractured water-conducting zone was analyzed based on analysis of hydrogeological conditions, situ testing, theoretical analysis and numerical simulation. The results show that the percentage content of sandstone(about 85%) in the overlying strata of the Jurassic coal bed roof than Permo-Carboniferous. The thickness of the overlying strata of the Jurassic coal bed roof is larger and the vertical fracture is not developed. The main reason for the height anomaly of the water flowing fractured zone is that the integrity of the roof covering structure is better. The height of water flowing fractured zone was tested and calculated by using the field measurement and discrete element simulation methods. The results showed that the height of water flowing fractured zone were 60m and 95m for the structural plane development and none development of coal seam overlying strata, respectively, which is proved that the overlying rock structure is the main factor leading to the height of water conducting fractured zone.
2016, 24(s1): 316-323.
Xinjiang, Gansu and other areas along the Xinjiang coal gas pipeline distributes a large amount of.Salt heaving and corrosion of salt soil will usually lead to deformation and even leakage of oil and gas pipeline. Therefore, it is a key problem to find out the cause, structure characteristics and corrosion of the saline soil, and then provide effective control measures, which is the vital solution of the current and future development of the pipeline. This paper annlyzes the distribution, origin and microstructure of saline soil on the research route. Based on the experimental study on the corrosion of the gas pipeline in the saline soil, the paper annlyses the corrosion morphology and corrosion rate. The results show that the corrosion of X80 steel in simulated solution of saline soil is serious and accompany the local pitting corrosion. The maximum corrosion rate of the four groups samples produce at the initial stage of corrosion, and the corrosion rate increases with the rise of the temperature. With the time of corrosion prolonging, the corrosion rate of X80 steel in simulate solution will decrease gradually. This paper studys the typical saline soil along Xinjiang coal gas pipeline and analyses the corrosion effect on the pipeline, which provide a practical basis for pipeline construction and operation.
Xinjiang, Gansu and other areas along the Xinjiang coal gas pipeline distributes a large amount of.Salt heaving and corrosion of salt soil will usually lead to deformation and even leakage of oil and gas pipeline. Therefore, it is a key problem to find out the cause, structure characteristics and corrosion of the saline soil, and then provide effective control measures, which is the vital solution of the current and future development of the pipeline. This paper annlyzes the distribution, origin and microstructure of saline soil on the research route. Based on the experimental study on the corrosion of the gas pipeline in the saline soil, the paper annlyses the corrosion morphology and corrosion rate. The results show that the corrosion of X80 steel in simulated solution of saline soil is serious and accompany the local pitting corrosion. The maximum corrosion rate of the four groups samples produce at the initial stage of corrosion, and the corrosion rate increases with the rise of the temperature. With the time of corrosion prolonging, the corrosion rate of X80 steel in simulate solution will decrease gradually. This paper studys the typical saline soil along Xinjiang coal gas pipeline and analyses the corrosion effect on the pipeline, which provide a practical basis for pipeline construction and operation.
2016, 24(s1): 324-330.
The geological exploration work of Xianyou pumped storage power station began in 1993,September and until 2013,December four generating units was put into commercial operation, which took 20 years. With the development of exploration work and condition of engineering construction excavation, engineering geological conditions have gradually become clear. According to revealed engineering geological conditions in the scene, the design of the power station was optimized, which plays an important role in in the works to improve the security, stability or reduce engineering investment. In this paper, aimed at revealed engineering geological condition in the scene conditions, relevant measures in the design are expounded by the comparison in engineering geological conditions of early exploration stage and construction stage and it will be a reference for similar engineering.
The geological exploration work of Xianyou pumped storage power station began in 1993,September and until 2013,December four generating units was put into commercial operation, which took 20 years. With the development of exploration work and condition of engineering construction excavation, engineering geological conditions have gradually become clear. According to revealed engineering geological conditions in the scene, the design of the power station was optimized, which plays an important role in in the works to improve the security, stability or reduce engineering investment. In this paper, aimed at revealed engineering geological condition in the scene conditions, relevant measures in the design are expounded by the comparison in engineering geological conditions of early exploration stage and construction stage and it will be a reference for similar engineering.
2016, 24(s1): 331-334.
Karst problem is one of the complex geological engineering problems in Dayandong HPP.This paper mainly introduces the survey and the evaluation method of the karst problem. The appropriate survey and testing methods have been adopted in preliminary design phase. The main karst development situation have been surveyed and the statistic analysis of main characteristics of karst have been done. Through the summary of the characteristics of karst development, we put forward the division standard of karst development for the project. Combined with the engineering characteristics, the effects of dam foundation seepage is analyzed and evaluated.
Karst problem is one of the complex geological engineering problems in Dayandong HPP.This paper mainly introduces the survey and the evaluation method of the karst problem. The appropriate survey and testing methods have been adopted in preliminary design phase. The main karst development situation have been surveyed and the statistic analysis of main characteristics of karst have been done. Through the summary of the characteristics of karst development, we put forward the division standard of karst development for the project. Combined with the engineering characteristics, the effects of dam foundation seepage is analyzed and evaluated.
2016, 24(s1): 335-340.
There're many geological flaws developed in dam foundation of JinpingⅠHydropower Station, it's necessary to be disposed weak rock zone such as fault, crushed zone and rock vein by cement-chemical composite grouting method. The inspection result after grouting shows that the anti-permeability and deformation capability of the structural plane such as rock massive and rock chips types, rock chips with mud and lamprophyre vein obtained great improvement. The enhance range of the sound wave velocity, deformation modules and all kinds of characteristic index after grouting would be provided reference for the similar projects.
There're many geological flaws developed in dam foundation of JinpingⅠHydropower Station, it's necessary to be disposed weak rock zone such as fault, crushed zone and rock vein by cement-chemical composite grouting method. The inspection result after grouting shows that the anti-permeability and deformation capability of the structural plane such as rock massive and rock chips types, rock chips with mud and lamprophyre vein obtained great improvement. The enhance range of the sound wave velocity, deformation modules and all kinds of characteristic index after grouting would be provided reference for the similar projects.
2016, 24(s1): 341-346.
It has been shown that the genetic mechanism of collapses is one of the key problems for urban-ground-collapse-research. The data has been based on the case of urban-ground-collapse reported in 2014 to 2015. The method of statistical analysis was used to get the characteristics and causes of ground collapse. According to the formation mechanism, the urban ground collapses which weren't caused by grottoes are classified. They are suffusion collapse, scour-burst collapse, vacuum suction type collapse, loose soil creep collapse.
It has been shown that the genetic mechanism of collapses is one of the key problems for urban-ground-collapse-research. The data has been based on the case of urban-ground-collapse reported in 2014 to 2015. The method of statistical analysis was used to get the characteristics and causes of ground collapse. According to the formation mechanism, the urban ground collapses which weren't caused by grottoes are classified. They are suffusion collapse, scour-burst collapse, vacuum suction type collapse, loose soil creep collapse.
2016, 24(s1): 347-353.
The directional drilling crossing technology has been widely used in kinds of pipe laying engineering, but less used in coal conveyed pipeline engineering. The research offeasibility has important engineering significance. In this paper, study basing on the field of Shenmu-Weinan coal conveying pipelines crossing Weihe carried on the analysis through indoor and outdoor test, established the three-dimensional numerical model of curve directional drilling crossing and analyzed the change of the maximum principal stress and maximum shear stress. Simulation results showing, increasingof the maximum principal stress and maximum shear stresswith the increase of depthwhen drilling into and out of the ground tilt section, which exceed a limit balance state of primary stress and shear stress intensity, forminstability segment; Drill to the middle level, the maximum principal stress and maximum shear stress of hole wall basic remains the same, and the ultimate strength in geotechnical engineering are less than segment. The slurry-supported to deal with soil instability period, through the increase of the shear strength of soil around the pipeline, increase the soil strength. After the analysis results show that the slurry supporting the whole soil were in a stable state. This article research results can be used in the design of crossing engineering pipe support, and can provide a reference for later related engineering construction and technical support.
The directional drilling crossing technology has been widely used in kinds of pipe laying engineering, but less used in coal conveyed pipeline engineering. The research offeasibility has important engineering significance. In this paper, study basing on the field of Shenmu-Weinan coal conveying pipelines crossing Weihe carried on the analysis through indoor and outdoor test, established the three-dimensional numerical model of curve directional drilling crossing and analyzed the change of the maximum principal stress and maximum shear stress. Simulation results showing, increasingof the maximum principal stress and maximum shear stresswith the increase of depthwhen drilling into and out of the ground tilt section, which exceed a limit balance state of primary stress and shear stress intensity, forminstability segment; Drill to the middle level, the maximum principal stress and maximum shear stress of hole wall basic remains the same, and the ultimate strength in geotechnical engineering are less than segment. The slurry-supported to deal with soil instability period, through the increase of the shear strength of soil around the pipeline, increase the soil strength. After the analysis results show that the slurry supporting the whole soil were in a stable state. This article research results can be used in the design of crossing engineering pipe support, and can provide a reference for later related engineering construction and technical support.
2016, 24(s1): 354-361.
In this paper, porosity and particle micro and fine structural features of Malan loess in the different regions of the Loess Plateau were analyzed. We selected undisturbed samples from Shaanxi Jingyang, Gansu Zhengning, and Gansu Heifangtai region, which we did particle analysis test. With an optical microscope and image synthesis technology, we accessed to its micro and fine structure of the image. By using the image, the pore area and the equivalent diameter are counted, as well as the quantitative parameters of the pore of the loess are obtained. The results showed that: The average particle diameter of Malan loess showed a decreasing trend from west to east, which in Gansu Heifangtai is largest, in Gansu Zhengning is center, in Jingyang is minimum. The average pore diameter of Gansu loess is rather minimal, and Heifangtai and Jingyang station are similar. The composition and structure of loess are related to the sedimentary environment, as well as, there is a relationship between the pore size distribution and composition.
In this paper, porosity and particle micro and fine structural features of Malan loess in the different regions of the Loess Plateau were analyzed. We selected undisturbed samples from Shaanxi Jingyang, Gansu Zhengning, and Gansu Heifangtai region, which we did particle analysis test. With an optical microscope and image synthesis technology, we accessed to its micro and fine structure of the image. By using the image, the pore area and the equivalent diameter are counted, as well as the quantitative parameters of the pore of the loess are obtained. The results showed that: The average particle diameter of Malan loess showed a decreasing trend from west to east, which in Gansu Heifangtai is largest, in Gansu Zhengning is center, in Jingyang is minimum. The average pore diameter of Gansu loess is rather minimal, and Heifangtai and Jingyang station are similar. The composition and structure of loess are related to the sedimentary environment, as well as, there is a relationship between the pore size distribution and composition.
2016, 24(s1): 362-368.
In order to explore the characteristics of loess microstructure and its relationship with collapsibility,took Q3 loess of Heifangtai at different depth as objects, measured its collapsibility coefficient by using two-test collapsible method, and then used the optical microscope and also utilized image synthesis technology to extract its microstructure image before and after collapse, counted pore area and it's equivalent radius, the composition of the particles and equivalent radius of loess pore were analyzed with their changes by the depth, and also explore the effect the pore distributions have on the collapsibility. With depth increasing, particle size of Heifangtai loess reduced, large pores reduced, small and middle pores increased, the peak pore equivalent radius reduced and the volume of the pore,10m decreases; Soil pore distribution character has a significant impact on its collapsibility, the more large and middle sized pore loess has, the bigger its collapsibility coefficient and the stronger its collapsibility is.
In order to explore the characteristics of loess microstructure and its relationship with collapsibility,took Q3 loess of Heifangtai at different depth as objects, measured its collapsibility coefficient by using two-test collapsible method, and then used the optical microscope and also utilized image synthesis technology to extract its microstructure image before and after collapse, counted pore area and it's equivalent radius, the composition of the particles and equivalent radius of loess pore were analyzed with their changes by the depth, and also explore the effect the pore distributions have on the collapsibility. With depth increasing, particle size of Heifangtai loess reduced, large pores reduced, small and middle pores increased, the peak pore equivalent radius reduced and the volume of the pore,10m decreases; Soil pore distribution character has a significant impact on its collapsibility, the more large and middle sized pore loess has, the bigger its collapsibility coefficient and the stronger its collapsibility is.
2016, 24(s1): 369-374.
The slag used in experimental study got from a city of JiangSu Province municipal solid waste incinerator(MSWI)were sieved through standard analysis sieve to get particles smaller then 2mm in diameter. Some of the particles used in experiment were used before. First different moisture content of reused MSWI were got by mixing the particles of slag with water, then samples with sizes 80mm in height and 39.1mm in diameter of different dry density which were 1.4, 1.5 and 1.6 were made through hierarchical compaction. Unconfined strength test of samples with different dry density and different curing age of 3d, 7d, 14d, 28d, 45d and 60d were studied, and 5 experiments were done to a kind of dry density in a certain curing age in order to reduce the impact of discrete. Through a large number of experimental data, the unconfined compressive strength increases with dry density and moisture content despite of the discreteness but much smaller than the samples made by slag not used before. And the XRD analysis of the slag was done to get the main components of the slag in order to obtain a better understanding of the strength characteristics of the slag sample. The results obtained in this paper provide a reference for the better application of slag to concrete projects.
The slag used in experimental study got from a city of JiangSu Province municipal solid waste incinerator(MSWI)were sieved through standard analysis sieve to get particles smaller then 2mm in diameter. Some of the particles used in experiment were used before. First different moisture content of reused MSWI were got by mixing the particles of slag with water, then samples with sizes 80mm in height and 39.1mm in diameter of different dry density which were 1.4, 1.5 and 1.6 were made through hierarchical compaction. Unconfined strength test of samples with different dry density and different curing age of 3d, 7d, 14d, 28d, 45d and 60d were studied, and 5 experiments were done to a kind of dry density in a certain curing age in order to reduce the impact of discrete. Through a large number of experimental data, the unconfined compressive strength increases with dry density and moisture content despite of the discreteness but much smaller than the samples made by slag not used before. And the XRD analysis of the slag was done to get the main components of the slag in order to obtain a better understanding of the strength characteristics of the slag sample. The results obtained in this paper provide a reference for the better application of slag to concrete projects.
2016, 24(s1): 375-385.
The Sichuan-Tibet Interconnection Project is the first power network engineering entering into Tibet, which stretches more than 3700 kilometers from Xiangcheng County through Batang County to Changdu City. This project, passing through the Jinsha River, Bachu River, Dingqu River and Mekong River, locates in the transition zone between the Qianghai-Tibet Plateau and the Yunnan-Guizhou plateau and the collision zone between the Indian plate and the Euro-Asian plate. There is no doubt that the project with low-lying in West and South and highland in East and North is the highest Interconnection Project in the world for the elevation changing from 2400m to 5000m, the average elevation of 3850m and the highest elevation of 4918m. In addition, the poorest geological condition and the largest number of geological disasters in the world endanger the constructions and operations of the Interconnection Project. According to the geological information, which includes geological disaster investigation and classification information and prospective design information along the power network area, and the remote sensing images, the geological environment information is summed. Apart from the geological environment information, more details about topography, lithology and the distribution of faults and geological disasters are used to divide the project into 5 regions, which are the poorest, poor, little poor, good and best regions, and the engineering geological condition in each region is analyzed in detail to assure the safety in constructionin this paper.
The Sichuan-Tibet Interconnection Project is the first power network engineering entering into Tibet, which stretches more than 3700 kilometers from Xiangcheng County through Batang County to Changdu City. This project, passing through the Jinsha River, Bachu River, Dingqu River and Mekong River, locates in the transition zone between the Qianghai-Tibet Plateau and the Yunnan-Guizhou plateau and the collision zone between the Indian plate and the Euro-Asian plate. There is no doubt that the project with low-lying in West and South and highland in East and North is the highest Interconnection Project in the world for the elevation changing from 2400m to 5000m, the average elevation of 3850m and the highest elevation of 4918m. In addition, the poorest geological condition and the largest number of geological disasters in the world endanger the constructions and operations of the Interconnection Project. According to the geological information, which includes geological disaster investigation and classification information and prospective design information along the power network area, and the remote sensing images, the geological environment information is summed. Apart from the geological environment information, more details about topography, lithology and the distribution of faults and geological disasters are used to divide the project into 5 regions, which are the poorest, poor, little poor, good and best regions, and the engineering geological condition in each region is analyzed in detail to assure the safety in constructionin this paper.
2016, 24(s1): 386-391.
In order to guide and regulate science underground engineering geological environmental technology, improve underground engineering geological environmental protection efficiency, one Underground Engineering Geology Environment Information Systemdatabase platform NET platform based on GIS platform is designed and implemented in Chongqing City. B/S mode and.NET technology is adopted in this system design, with C# as the primary development language SQLserver2012 as the back-end database server andapplication of MapServer and Openlayers technology to realize the map publication and display. The system could realize bothnetworking and visualization of underground engineering geology environment information management, and thus contribute to an intuitive, dynamic information service in research and development of Chongqing city underground engineering, management of ecological environment and geological environment protection.
In order to guide and regulate science underground engineering geological environmental technology, improve underground engineering geological environmental protection efficiency, one Underground Engineering Geology Environment Information Systemdatabase platform NET platform based on GIS platform is designed and implemented in Chongqing City. B/S mode and.NET technology is adopted in this system design, with C# as the primary development language SQLserver2012 as the back-end database server andapplication of MapServer and Openlayers technology to realize the map publication and display. The system could realize bothnetworking and visualization of underground engineering geology environment information management, and thus contribute to an intuitive, dynamic information service in research and development of Chongqing city underground engineering, management of ecological environment and geological environment protection.
2016, 24(s1): 392-399.
Accurate predictionon surface deformation in mining area provides reliable guidance for safe and effective mining. Due to the complexity of geological conditions, in-situ stress and mining methods, surface deformation prediction generally turned out to be difficult. Taking Jingerquan mine in Hami City, Xinjiang Province as an instance, it adopted the shallow-hole shrinkage mining method at the previous stage and severely disturbed the overlying rock mass. Therefore, in the later stage, it employs the filling method instead. Considering the unfavorable geological conditions of the mine, we applied the random medium theory in analyzing the surface deformation. And based on the particular orebody structure, we established a reasonable mathematical model. According to the monitoring results, the surface deformation parameters were determined using back analysis method, and thereby, the surface settlement curve at the final mining stage was obtained. Besides, combining the surface deformation tendency, the mechanism and feature of deformation in different stages were investigated. It is suggested that the research findings in Jingerquan mine could provide some reference for similar metal mines.
Accurate predictionon surface deformation in mining area provides reliable guidance for safe and effective mining. Due to the complexity of geological conditions, in-situ stress and mining methods, surface deformation prediction generally turned out to be difficult. Taking Jingerquan mine in Hami City, Xinjiang Province as an instance, it adopted the shallow-hole shrinkage mining method at the previous stage and severely disturbed the overlying rock mass. Therefore, in the later stage, it employs the filling method instead. Considering the unfavorable geological conditions of the mine, we applied the random medium theory in analyzing the surface deformation. And based on the particular orebody structure, we established a reasonable mathematical model. According to the monitoring results, the surface deformation parameters were determined using back analysis method, and thereby, the surface settlement curve at the final mining stage was obtained. Besides, combining the surface deformation tendency, the mechanism and feature of deformation in different stages were investigated. It is suggested that the research findings in Jingerquan mine could provide some reference for similar metal mines.
2016, 24(s1): 400-407.
The macrovoid structures of loess make it easier to destroy and collapse after immersion, and it will influence the safety of project. This thesis is based on the collapsed loess of Xi'an metro line 5, and investigate the immersion characteristics by site immersion test. The soakaway which diameter are 23.0m is arranged in test site, the time of water injection are 39 days, and there are 19 days observation after stopping injection. The result of tests indicate: ① with the increasing of the immersion time, the indictions of moisture meter both inside and outside change successively, it varies quickly in early days of immersion and varies slowly gradually in later period, and it tends to be reduced after stopping immersion; the osmosis rate of loess in vertical direction is superior obviously to the the horizontal direction.② the shape of soaking influence boundary is like an inverted funnel, it extrudes slightly in buried soil; the influences scope of immersion area and saturated area increase gradually with the increase of depth, on the whole, saturated scope is less than immersion scope.③ Ground settlement develops symmetrically by the centre of Z0 settlement, self-weighe collapse tends to be lower with the increase of distance from the point to the edge of test pits, the settlement profile of combined tests line presents irregular sharp like U; the settlement ratio of shallow punctuation presents the characteristics of smallbigsmallstable.④ the process of collapsibility and the process of moisture diffusion are coincidental, there are four stages of collapse development: collapse delay stage, collapse mutation stage, collapse alleviation stage, collapse stability stage. The research achievements of this thesis can provide the technological supports and reference for engineering constructions from Xi'an metro line 5 and other relevant engineering.
The macrovoid structures of loess make it easier to destroy and collapse after immersion, and it will influence the safety of project. This thesis is based on the collapsed loess of Xi'an metro line 5, and investigate the immersion characteristics by site immersion test. The soakaway which diameter are 23.0m is arranged in test site, the time of water injection are 39 days, and there are 19 days observation after stopping injection. The result of tests indicate: ① with the increasing of the immersion time, the indictions of moisture meter both inside and outside change successively, it varies quickly in early days of immersion and varies slowly gradually in later period, and it tends to be reduced after stopping immersion; the osmosis rate of loess in vertical direction is superior obviously to the the horizontal direction.② the shape of soaking influence boundary is like an inverted funnel, it extrudes slightly in buried soil; the influences scope of immersion area and saturated area increase gradually with the increase of depth, on the whole, saturated scope is less than immersion scope.③ Ground settlement develops symmetrically by the centre of Z0 settlement, self-weighe collapse tends to be lower with the increase of distance from the point to the edge of test pits, the settlement profile of combined tests line presents irregular sharp like U; the settlement ratio of shallow punctuation presents the characteristics of smallbigsmallstable.④ the process of collapsibility and the process of moisture diffusion are coincidental, there are four stages of collapse development: collapse delay stage, collapse mutation stage, collapse alleviation stage, collapse stability stage. The research achievements of this thesis can provide the technological supports and reference for engineering constructions from Xi'an metro line 5 and other relevant engineering.
2016, 24(s1): 408-414.
To study the train induced ground vibrations near Longyang Station of Shanghai Metro line 2,field test was conducted in this area, and the test data was analyzed in detail. The attenuation laws of waves with different frequency bands were evaluated; and the factors which resulted in the distribution fluctuation were determined. In the meantime, three two-dimensional numerical tunnel-soil interaction models were established, based on ANSYS finite element software. The dynamic metro load determined from field test was exerted to the established models to simulate the ground vibrations induced by metro operation. The wave attenuation law was specifically analyzed, and its variation with different tunnel embedded depth was investigated. The research results show that, site topography and soil conditions affected test results significantly. With the distance increasing, the vertical peak displacement decreases continuously, while the horizontal vibration amplitude increases firstly and then decreases. The amplitude attenuation of vertical vibration is relatively slower than that of horizontal vibration. In addition, tunnel embedded depth do have a positive effect on ground vibration mitigation; the ground vibration decreases with deeper embedded depth.
To study the train induced ground vibrations near Longyang Station of Shanghai Metro line 2,field test was conducted in this area, and the test data was analyzed in detail. The attenuation laws of waves with different frequency bands were evaluated; and the factors which resulted in the distribution fluctuation were determined. In the meantime, three two-dimensional numerical tunnel-soil interaction models were established, based on ANSYS finite element software. The dynamic metro load determined from field test was exerted to the established models to simulate the ground vibrations induced by metro operation. The wave attenuation law was specifically analyzed, and its variation with different tunnel embedded depth was investigated. The research results show that, site topography and soil conditions affected test results significantly. With the distance increasing, the vertical peak displacement decreases continuously, while the horizontal vibration amplitude increases firstly and then decreases. The amplitude attenuation of vertical vibration is relatively slower than that of horizontal vibration. In addition, tunnel embedded depth do have a positive effect on ground vibration mitigation; the ground vibration decreases with deeper embedded depth.
2016, 24(s1): 415-421.
Due to the impact of the adjacent construction, the high speed railway is facing the increasingly serious security, environmental and sustainable development issues. The deformation of bridge pile foundations and abutments under without or with isolated piles conditions was studied by using numerical simulation and field monitoring, when a new metro tunnel passing across the existing high-speed railway. Then, the protective effects of the isolated piles was assessed and the suitable depth and length of isolation piles were presented. The results show that isolation piles can effectively control the deformation of bridge piles and abutments. When using isolated piles, vertical and lateral displacement of bridge piles can decrease more than 20%,respectively. The depth of the isolated piles should be taken as 1.2-1.4 times of the length of bridge piles. The longitudinal length of the isolated pile wall should take 2.0 times of the length of bridge abutment.
Due to the impact of the adjacent construction, the high speed railway is facing the increasingly serious security, environmental and sustainable development issues. The deformation of bridge pile foundations and abutments under without or with isolated piles conditions was studied by using numerical simulation and field monitoring, when a new metro tunnel passing across the existing high-speed railway. Then, the protective effects of the isolated piles was assessed and the suitable depth and length of isolation piles were presented. The results show that isolation piles can effectively control the deformation of bridge piles and abutments. When using isolated piles, vertical and lateral displacement of bridge piles can decrease more than 20%,respectively. The depth of the isolated piles should be taken as 1.2-1.4 times of the length of bridge piles. The longitudinal length of the isolated pile wall should take 2.0 times of the length of bridge abutment.
2016, 24(s1): 422-429.
Application of ground penetrating radar on underground pipeline detection has been widely used in municipal engineering, However, the use of ground penetrating radar to detect underground pipeline leak has not yet been widely adopted in China. This Paper investigates the application of GPR in detecting urban water supply pipeline leakage. Firstly the seepage law of pipeline leakage area under different conditions were simulated by Geo-studio seepage Software, the geometric and physical parameters of the leakage area under different line sizes, different leakage sites and different times are analyzed. On this premise, using simulation software GprMax to study the radar geological image simulating of pipeline leakage under different conditions. It provides the basis parametric data and identification information for the actual use of ground penetrating radar in detect water supply pipeline leakage.
Application of ground penetrating radar on underground pipeline detection has been widely used in municipal engineering, However, the use of ground penetrating radar to detect underground pipeline leak has not yet been widely adopted in China. This Paper investigates the application of GPR in detecting urban water supply pipeline leakage. Firstly the seepage law of pipeline leakage area under different conditions were simulated by Geo-studio seepage Software, the geometric and physical parameters of the leakage area under different line sizes, different leakage sites and different times are analyzed. On this premise, using simulation software GprMax to study the radar geological image simulating of pipeline leakage under different conditions. It provides the basis parametric data and identification information for the actual use of ground penetrating radar in detect water supply pipeline leakage.
2016, 24(s1): 430-437.
The metro stop line after the typical station on Xiamen metro line 1 is taken as the engineering background of this paper, based on engineering design drawings, the left tunnel and metro stop line construction by large section mining method(CRD excavation method) and the diameter of tunnel being about 11.53m, the right line tunnel construction by shield tunneling method and the diameter of tunnel being about 6.2m, the clear spacing of double-line tunnels is 3.85m. Through numerical simulation, the construction sequence of different sections, hybrid method, small spacing tunnels were studied, and the influence of tunnel spacing is also analyzed. As shown by calculation, engineers firstly construction the right line tunnel by shield tunneling method, then the large cross-section tunnel construction by mining method can efficiently decrease the surface subsidence, deformation of adjacent buildings and deformation of the tunnel structure. When the spacing between two tunnels greater than 1.5D(D:diameter of the large cross-section tunnel),the after built tunnel has less effect on the former tunnel, the additional deformation of the former tunnel smaller than 3mm. The computed result indicates the surface subsidence and deformation of adjacent buildings appears change suddenly in the stage of center pillar removal, attention should be paid to the rate of change at this time. The research findings would provide some references for the design and construction of similar tunnels.
The metro stop line after the typical station on Xiamen metro line 1 is taken as the engineering background of this paper, based on engineering design drawings, the left tunnel and metro stop line construction by large section mining method(CRD excavation method) and the diameter of tunnel being about 11.53m, the right line tunnel construction by shield tunneling method and the diameter of tunnel being about 6.2m, the clear spacing of double-line tunnels is 3.85m. Through numerical simulation, the construction sequence of different sections, hybrid method, small spacing tunnels were studied, and the influence of tunnel spacing is also analyzed. As shown by calculation, engineers firstly construction the right line tunnel by shield tunneling method, then the large cross-section tunnel construction by mining method can efficiently decrease the surface subsidence, deformation of adjacent buildings and deformation of the tunnel structure. When the spacing between two tunnels greater than 1.5D(D:diameter of the large cross-section tunnel),the after built tunnel has less effect on the former tunnel, the additional deformation of the former tunnel smaller than 3mm. The computed result indicates the surface subsidence and deformation of adjacent buildings appears change suddenly in the stage of center pillar removal, attention should be paid to the rate of change at this time. The research findings would provide some references for the design and construction of similar tunnels.
2016, 24(s1): 438-444.
The object researched here is a high-filled loess slope with the height of 105meters located in Northern Shaanxi. In order to study the engineering properties of the filling material, a great deal of laboratory tests have been done. Based on the geological condition and practical situation of the loess slope, a proper calculation model was established to calculate reliable index and failure probability of the slope at different underground water level under normal weather and heavy rainfall. The results suggest that the high-filled loess slope is in the steady state. Using fuzzy synthesize estimate method in the original design and made by 3 optimize program to choose the best type of optimization model.
The object researched here is a high-filled loess slope with the height of 105meters located in Northern Shaanxi. In order to study the engineering properties of the filling material, a great deal of laboratory tests have been done. Based on the geological condition and practical situation of the loess slope, a proper calculation model was established to calculate reliable index and failure probability of the slope at different underground water level under normal weather and heavy rainfall. The results suggest that the high-filled loess slope is in the steady state. Using fuzzy synthesize estimate method in the original design and made by 3 optimize program to choose the best type of optimization model.
2016, 24(s1): 445-454.
The mining method in mine zone No.2 in Jinchuan nickel mine is continuous under cut- and -fill mining without pillars. The characteristics of mining method and high production caused the issue of filling body general stability of mine zone No.2attracting extensive attention. The article have made numerical simulation analysis of 16-line vertical pillar combined with engineering projects of 1# deposit body exploitation. The results are as follows. As the double-sublevel mining, the degree of stress concentration and the range of stress elevated zone could continue to increase. This increase lead to the vertical pillar more broken, but the vertical pillar could effectively reduce the vertical displacement of residual horizontal ore body and filling body. The mechanics function analysis of 16-line vertical pillar shows vertical pillar could effectively reduce upper body displacement. The support force of pillar is concerned with strength, and the strength is concerned with lateral pressure that pillar suffered. The strength is increased with lateral pressure increased. Therefore, enhanced the rate of roof-contact filling and improved filling body quality during filling process have contributed to the supporting capacity of 16-line vertical pillar.
The mining method in mine zone No.2 in Jinchuan nickel mine is continuous under cut- and -fill mining without pillars. The characteristics of mining method and high production caused the issue of filling body general stability of mine zone No.2attracting extensive attention. The article have made numerical simulation analysis of 16-line vertical pillar combined with engineering projects of 1# deposit body exploitation. The results are as follows. As the double-sublevel mining, the degree of stress concentration and the range of stress elevated zone could continue to increase. This increase lead to the vertical pillar more broken, but the vertical pillar could effectively reduce the vertical displacement of residual horizontal ore body and filling body. The mechanics function analysis of 16-line vertical pillar shows vertical pillar could effectively reduce upper body displacement. The support force of pillar is concerned with strength, and the strength is concerned with lateral pressure that pillar suffered. The strength is increased with lateral pressure increased. Therefore, enhanced the rate of roof-contact filling and improved filling body quality during filling process have contributed to the supporting capacity of 16-line vertical pillar.
2016, 24(s1): 455-462.
On August 24th, 2013, a massive debris flow occurred at about 10:30 pm in Zhonggang gully, Baoxing County, Ya'an City, lasting around 1.5 hours as a heavy rainfall hit the Yongfu town, Baoxing County, Ya'an City around 6 pm and lasted 6 hours. In this paper, the basic characteristics, cause of formation, erosion-deposit properties and damage mode of the debris flow were interpreted in detail in view of the field investigation in Zhonggang gully.
On August 24th, 2013, a massive debris flow occurred at about 10:30 pm in Zhonggang gully, Baoxing County, Ya'an City, lasting around 1.5 hours as a heavy rainfall hit the Yongfu town, Baoxing County, Ya'an City around 6 pm and lasted 6 hours. In this paper, the basic characteristics, cause of formation, erosion-deposit properties and damage mode of the debris flow were interpreted in detail in view of the field investigation in Zhonggang gully.
2016, 24(s1): 463-468.
On July 11, 2015, by the early continuous rainfall and short-term heavy rainfall caused by the Chan Hung Typhoon, a large landslide occurred on the basis of first sliding during the year of 2000 in Shaoxing county, Zhejiang Province. The front of landslide swelled significantly and the landslide boundary expanded rapidly. Life and property safety of about 25 households in front of the landslide were threatened. The crack, surface displacements and deep horizontal displacements monitoring were examined in this paper. Such examinations were combined with site geological investigation, site engineering geological survey, site moisture content test and permeability test. The characteristics of the landslide and the formation and failure mode of the landslide by preliminary understanding were analyzed. The results show that:(1) the plane form of the landslide was shaped like a chair and the main slide direction was about 140nd the plagioclase was about 330meters long and the front and trailing edge were 150~180 meters and 75~105 meters wide, respectively, and the volume was 105104m3 and the landslide was made of eluvial and alluvial silty clay with gravel; (2) heavy rainfall is the major factor in inducing the sliding deformation; (3) the landslide is substantially in state of creep deformation and slides slowly and will remain steady state within the general period, which can be determined for the tractive landslide.
On July 11, 2015, by the early continuous rainfall and short-term heavy rainfall caused by the Chan Hung Typhoon, a large landslide occurred on the basis of first sliding during the year of 2000 in Shaoxing county, Zhejiang Province. The front of landslide swelled significantly and the landslide boundary expanded rapidly. Life and property safety of about 25 households in front of the landslide were threatened. The crack, surface displacements and deep horizontal displacements monitoring were examined in this paper. Such examinations were combined with site geological investigation, site engineering geological survey, site moisture content test and permeability test. The characteristics of the landslide and the formation and failure mode of the landslide by preliminary understanding were analyzed. The results show that:(1) the plane form of the landslide was shaped like a chair and the main slide direction was about 140nd the plagioclase was about 330meters long and the front and trailing edge were 150~180 meters and 75~105 meters wide, respectively, and the volume was 105104m3 and the landslide was made of eluvial and alluvial silty clay with gravel; (2) heavy rainfall is the major factor in inducing the sliding deformation; (3) the landslide is substantially in state of creep deformation and slides slowly and will remain steady state within the general period, which can be determined for the tractive landslide.
2016, 24(s1): 469-477.
Along with the rapidly economic development, the rapid expansion of the city, the construction land demand gradually increase. In hilly and mountainous city, flat land is small, the contradiction between people and land is particularly prominent. In order to scientifically and safely use low-slope hilly region, we must evaluate the engineering construction suitability of low-slope hilly region in hilly town. Taking plannedurban area in Yibin City asthe research area, we firstly establish the engineering construction suitabilityevaluation index system which is composed of 5 first grade evaluation factors and 18 second grade evaluation factors, calculate weight of evaluation factors based on APH.Then we evaluate engineering construction suitability of low-slope hilly region in research area with evaluation model of multi factor weighted index on arcgis 10.0. The results indicate that the low-slope hilly region is very wide in planned urban area in Yibin city, the low-slope hilly region accounts for 68.77% of total area. Suitable area accounts for 18.73% of total low-slope hilly region, relatively suitable area accounts for 42.21%,poorly suitable area accounts for 29.72%, and unsuitable area accounts for 9.34%.The engineering construction suitability of low-slope hilly regionin the research area is well. This paper can provide the scientific basis for use and plan of low-slope hilly region, city plan, optimize layout of land use, and perfect theengineering construction suitability evaluation theory system of low-slope hilly region.
Along with the rapidly economic development, the rapid expansion of the city, the construction land demand gradually increase. In hilly and mountainous city, flat land is small, the contradiction between people and land is particularly prominent. In order to scientifically and safely use low-slope hilly region, we must evaluate the engineering construction suitability of low-slope hilly region in hilly town. Taking plannedurban area in Yibin City asthe research area, we firstly establish the engineering construction suitabilityevaluation index system which is composed of 5 first grade evaluation factors and 18 second grade evaluation factors, calculate weight of evaluation factors based on APH.Then we evaluate engineering construction suitability of low-slope hilly region in research area with evaluation model of multi factor weighted index on arcgis 10.0. The results indicate that the low-slope hilly region is very wide in planned urban area in Yibin city, the low-slope hilly region accounts for 68.77% of total area. Suitable area accounts for 18.73% of total low-slope hilly region, relatively suitable area accounts for 42.21%,poorly suitable area accounts for 29.72%, and unsuitable area accounts for 9.34%.The engineering construction suitability of low-slope hilly regionin the research area is well. This paper can provide the scientific basis for use and plan of low-slope hilly region, city plan, optimize layout of land use, and perfect theengineering construction suitability evaluation theory system of low-slope hilly region.
2016, 24(s1): 478-488.
The main difference between earthquake tremor and microtremor is amplitude, however, both have same election results of frequency for same ground. It means that there is an significant amplication effect for a certain frequency range, soits good for pulsation earthquake and disaster mitigation to understand the characteristics of microtremor. To understand it in loess regions and reveal slope dynamic response characteristics, according to the microtremor observation data of 68measuring points in the west ofloess regions of Tianshui, the predominant period is analyzed using the method of spectral ratio; Based on the geological records of 7 boreholes and shear wave velocity distribution, Accordance with theOne-dimensional dynamic soil response theory tocalculate the soilnatural period, the results are more consistent both methods. In addition, the use of statistical methods to obtain the mathematical relationship between theslopemicrotremor predominant period and slope overburden thickness and height. Provide a reference to analyze the dynamic characteristics of major landslides andnatural slopes in loess regions of Tianshui.
The main difference between earthquake tremor and microtremor is amplitude, however, both have same election results of frequency for same ground. It means that there is an significant amplication effect for a certain frequency range, soits good for pulsation earthquake and disaster mitigation to understand the characteristics of microtremor. To understand it in loess regions and reveal slope dynamic response characteristics, according to the microtremor observation data of 68measuring points in the west ofloess regions of Tianshui, the predominant period is analyzed using the method of spectral ratio; Based on the geological records of 7 boreholes and shear wave velocity distribution, Accordance with theOne-dimensional dynamic soil response theory tocalculate the soilnatural period, the results are more consistent both methods. In addition, the use of statistical methods to obtain the mathematical relationship between theslopemicrotremor predominant period and slope overburden thickness and height. Provide a reference to analyze the dynamic characteristics of major landslides andnatural slopes in loess regions of Tianshui.
2016, 24(s1): 489-494.
Due to larger areas and complex geological conditions in Beijing shallow mountain area, it often encountered uneven foundation problems in project construction. Different from plain buildings foundation, the mountain buildings often involved foundation stability, the requirement for geological investigation and geotechnical design and construction is higher. As a kind of bad phenomenons and problems, if has not Understanding on it, will lead to building deformation and produce instability even destructive. There are more Uneven foundation types in Beijing shallow mountain area, must according to basement stability, bearing capacity and treatment scheme and take appropriate measures combined with the environmental geological conditions in the process of foundation treatment. In order to slow down or avoid the negative impact of the uneven foundation for engineering construction, the paper tries to sum up the types and problems of uneven foundation, from the survey, design, construction and supervision and other aspects, and puts forward the corresponding countermeasures, hoping to provide some references and help for engineering construction safety in Beijing Mountain area and.
Due to larger areas and complex geological conditions in Beijing shallow mountain area, it often encountered uneven foundation problems in project construction. Different from plain buildings foundation, the mountain buildings often involved foundation stability, the requirement for geological investigation and geotechnical design and construction is higher. As a kind of bad phenomenons and problems, if has not Understanding on it, will lead to building deformation and produce instability even destructive. There are more Uneven foundation types in Beijing shallow mountain area, must according to basement stability, bearing capacity and treatment scheme and take appropriate measures combined with the environmental geological conditions in the process of foundation treatment. In order to slow down or avoid the negative impact of the uneven foundation for engineering construction, the paper tries to sum up the types and problems of uneven foundation, from the survey, design, construction and supervision and other aspects, and puts forward the corresponding countermeasures, hoping to provide some references and help for engineering construction safety in Beijing Mountain area and.
2016, 24(s1): 495-501.
The Yuxi-Mohan railway, which was an important part of the mid-channel of Trans-Asian railway in the One Belt, One Road initiative, located in the nearby suture zone between Eurasian plate and Indian plate, and in the Mediterranean-Asia geothermal anomaly zone. The geological condition presented the characteristics of three high four active of the Yuxi-Mohan railway. Based on the formatted and distributed features of areal geological hazards, the comprehensive methods of alignment in this mountain region with strong-high intensively seismic were analyzed, and the technology of geological alignment were researched. The conclusions of this paper can also be widely applied in similar geological condition such as the Sichuan-Tibet railway and the Yunnan-Tibet railway.
The Yuxi-Mohan railway, which was an important part of the mid-channel of Trans-Asian railway in the One Belt, One Road initiative, located in the nearby suture zone between Eurasian plate and Indian plate, and in the Mediterranean-Asia geothermal anomaly zone. The geological condition presented the characteristics of three high four active of the Yuxi-Mohan railway. Based on the formatted and distributed features of areal geological hazards, the comprehensive methods of alignment in this mountain region with strong-high intensively seismic were analyzed, and the technology of geological alignment were researched. The conclusions of this paper can also be widely applied in similar geological condition such as the Sichuan-Tibet railway and the Yunnan-Tibet railway.
2016, 24(s1): 502-508.
With the increasing of domestic demand for subway construction, the subway construction technical requirements are more stringent. This paper aims to solve the technical problem in the upper cross-segment with small angle and clear distance in the subway tunnel. Based on the existing engineering practices of the section of the Qingdao metro, the engineering geologic condition, regional architectural environment and mechanical properties of rock and soil mass are analyzed combining with the related engineering examples. Comprehensive application of the curtain method, advanced small duct, self-advance pipe shed and anchor, grid and other technical means are optimized for the construction scheme. The improved construction scheme utilizes some supporting technology to play an important role in reducing the construction cost and speeding up the construction progress. The research results can provide reference for this kind of projects under similar conditions.
With the increasing of domestic demand for subway construction, the subway construction technical requirements are more stringent. This paper aims to solve the technical problem in the upper cross-segment with small angle and clear distance in the subway tunnel. Based on the existing engineering practices of the section of the Qingdao metro, the engineering geologic condition, regional architectural environment and mechanical properties of rock and soil mass are analyzed combining with the related engineering examples. Comprehensive application of the curtain method, advanced small duct, self-advance pipe shed and anchor, grid and other technical means are optimized for the construction scheme. The improved construction scheme utilizes some supporting technology to play an important role in reducing the construction cost and speeding up the construction progress. The research results can provide reference for this kind of projects under similar conditions.
2016, 24(s1): 509-513.
In hydropower project, the anti-seepage type not only relates to the safety of the project, but also firmly control the engineering investment and schedule. Therefore, choose the right means of anti-seepage type according to the actual conditions is very important. Based on this, the research and design optimization of Yuwa hydropower station's anti-seepage type is proceed on the basis of fully considering the site condition. The main research results are as follows: ①Double loop trial pit water injection method is used to re-check the infiltration parameters of the first layer of cladding, the results show that the permeability coefficient and allow hydraulic gradient value decided based on field pumping and injecting water test are reasonable.②Because of less test data, the allowable hydraulic gradient value decided through the experience of the engineering analogy in early period is conservative, in construction stage, it is changed from 0.07~0.10 to 0.10~0.12 in combination with the results of size distribution testing.③Combined with the adjusted allowable hydraulic gradient value, the anti-seepage type is optimized, the blanket length down to 55m from 80m, which won large economic benefits. The method and thought proposed in this paper can provide certain reference value for similar engineering design.
In hydropower project, the anti-seepage type not only relates to the safety of the project, but also firmly control the engineering investment and schedule. Therefore, choose the right means of anti-seepage type according to the actual conditions is very important. Based on this, the research and design optimization of Yuwa hydropower station's anti-seepage type is proceed on the basis of fully considering the site condition. The main research results are as follows: ①Double loop trial pit water injection method is used to re-check the infiltration parameters of the first layer of cladding, the results show that the permeability coefficient and allow hydraulic gradient value decided based on field pumping and injecting water test are reasonable.②Because of less test data, the allowable hydraulic gradient value decided through the experience of the engineering analogy in early period is conservative, in construction stage, it is changed from 0.07~0.10 to 0.10~0.12 in combination with the results of size distribution testing.③Combined with the adjusted allowable hydraulic gradient value, the anti-seepage type is optimized, the blanket length down to 55m from 80m, which won large economic benefits. The method and thought proposed in this paper can provide certain reference value for similar engineering design.
2016, 24(s1): 514-518.
The firstly planed lines of Kunming metro is an important traffic artery from the south to the north of Kunming city. The interval from the Southern ring road station to the Kunming railway station is designed to construction by the use of shield. The interval has to undercross the Kunming railway which is the most important transportation hub in Yunnan province. The surrounding soil is belong to Dianchi lake sediments, which some shortcoming characteristics such as diversification, hard and soft uneven, diversity of permeability, rich water content with poor regularity. To deal with the big construction risk, the paper has studied the shield parameters according to the requirement of the operation of Kunming railway station and the characteristics of the soil. As the result, the earth pressure, excavated volume, grouting pressure, grouting amount and other parameters have been brought out, which have been actually used and resulted in the safely construction of the interval and the normal operation of Kunming railway station.
The firstly planed lines of Kunming metro is an important traffic artery from the south to the north of Kunming city. The interval from the Southern ring road station to the Kunming railway station is designed to construction by the use of shield. The interval has to undercross the Kunming railway which is the most important transportation hub in Yunnan province. The surrounding soil is belong to Dianchi lake sediments, which some shortcoming characteristics such as diversification, hard and soft uneven, diversity of permeability, rich water content with poor regularity. To deal with the big construction risk, the paper has studied the shield parameters according to the requirement of the operation of Kunming railway station and the characteristics of the soil. As the result, the earth pressure, excavated volume, grouting pressure, grouting amount and other parameters have been brought out, which have been actually used and resulted in the safely construction of the interval and the normal operation of Kunming railway station.
2016, 24(s1): 519-526.
By field test and inner test, the construction technique of CFG pile foundation and control parameters relating to construction are thoroughly studied. CFG pile by long auger is proved to be more appropriate for reinforcing soft foundation of passenger special line of railway than other methods for its good quality and rapidity of pile formation. Low strain reflection method, core drilling method and load test are used not only to analyze the quality of CFG piles but also to evaluate the effects of CFG piles in reinforcing soft ground. The research results show that the way to reinforce the soft foundation of passenger special line of railway can better meet the requirement of bearing capacity and deformation value as well as better control post-construction settlement. All of the results can be used to direct the construction of CFG pie composite foundation of other similar engineering projects.
By field test and inner test, the construction technique of CFG pile foundation and control parameters relating to construction are thoroughly studied. CFG pile by long auger is proved to be more appropriate for reinforcing soft foundation of passenger special line of railway than other methods for its good quality and rapidity of pile formation. Low strain reflection method, core drilling method and load test are used not only to analyze the quality of CFG piles but also to evaluate the effects of CFG piles in reinforcing soft ground. The research results show that the way to reinforce the soft foundation of passenger special line of railway can better meet the requirement of bearing capacity and deformation value as well as better control post-construction settlement. All of the results can be used to direct the construction of CFG pie composite foundation of other similar engineering projects.
2016, 24(s1): 527-532.
With the rapid development of human economic society, metro has been one of the most important facilities in cities. Dealing with complex karst problem during metro construction remains a great challenge, which has resulted in large investment. During the construction of the 6th line of Kunming rail transit project, serious mud loss and collapse of the holes occurred in the punching holes for the No.1 shield well envelop structures. Research on the engineering and hydrological geology is carried out by the use of drilling core experiments, cross hole electromagnetic wave tests, geological and hydrological observations. The research results in that the karsts are very commonly developed in the engineering area, which can be a reference for the karst investigation and for the design and construction of the metro lines in Kunming.
With the rapid development of human economic society, metro has been one of the most important facilities in cities. Dealing with complex karst problem during metro construction remains a great challenge, which has resulted in large investment. During the construction of the 6th line of Kunming rail transit project, serious mud loss and collapse of the holes occurred in the punching holes for the No.1 shield well envelop structures. Research on the engineering and hydrological geology is carried out by the use of drilling core experiments, cross hole electromagnetic wave tests, geological and hydrological observations. The research results in that the karsts are very commonly developed in the engineering area, which can be a reference for the karst investigation and for the design and construction of the metro lines in Kunming.
2016, 24(s1): 533-539.
On March, 2014, Hua-nancun Landslide occurred in Tianshui, Gansu Province, China. It is a loess-mudstone interface landslide which is caused by high pore water pressure of thawing of frozen perched ground water. The area of Hua-nancun landslide is 1.24104m2 and the volume is 1.24105m3. The retaining wall of the 310 national highway in K1428+10~K1428+210 was destroyed by Hua-nancun Landslide, and the road was always in a traffic jam because of 200m road was covered with the amount of accumulation on the 310 national highway since the landslide occurred. We investigated the Hua-nancun landslide in March, 2014; August, 2014; January, 2015, the landslide was in the activity all the time. Also detailed investigation about geological environment and characteristics of Hua-nancun landslide was done in the past time. The conclusion is obtained by studying the geological facters that frozen perched ground water is the main facter of producing Hua-nancun landslide. Continually heavy rain and artificial excavating are the inducing facters of Hua-nancun landslide on the same way.
On March, 2014, Hua-nancun Landslide occurred in Tianshui, Gansu Province, China. It is a loess-mudstone interface landslide which is caused by high pore water pressure of thawing of frozen perched ground water. The area of Hua-nancun landslide is 1.24104m2 and the volume is 1.24105m3. The retaining wall of the 310 national highway in K1428+10~K1428+210 was destroyed by Hua-nancun Landslide, and the road was always in a traffic jam because of 200m road was covered with the amount of accumulation on the 310 national highway since the landslide occurred. We investigated the Hua-nancun landslide in March, 2014; August, 2014; January, 2015, the landslide was in the activity all the time. Also detailed investigation about geological environment and characteristics of Hua-nancun landslide was done in the past time. The conclusion is obtained by studying the geological facters that frozen perched ground water is the main facter of producing Hua-nancun landslide. Continually heavy rain and artificial excavating are the inducing facters of Hua-nancun landslide on the same way.
2016, 24(s1): 540-546.
Hillside Construction will form an artificial filling slope, especially when in the vicinity of the factory and residential areas, calculation and evaluation of its stability is more important. In this paper, artificial fill slope stability analysis and reinforcement design examples presented that using two different analytical methods(limit equilibrium method and strength reduction method) and two large commercial simulation software calculation and comparative analysis before and after evaluation of such Slope respectively, the evaluation findings of its stability, and the slope reinforcement design, located in the top of the hill near the middle point of the monitoring data show that the slope is stable and secure during the rainy season,.In addition, for fill slope toe easily rainfall problems, using a miniature steel pipe pile technology reference for similar projects.
Hillside Construction will form an artificial filling slope, especially when in the vicinity of the factory and residential areas, calculation and evaluation of its stability is more important. In this paper, artificial fill slope stability analysis and reinforcement design examples presented that using two different analytical methods(limit equilibrium method and strength reduction method) and two large commercial simulation software calculation and comparative analysis before and after evaluation of such Slope respectively, the evaluation findings of its stability, and the slope reinforcement design, located in the top of the hill near the middle point of the monitoring data show that the slope is stable and secure during the rainy season,.In addition, for fill slope toe easily rainfall problems, using a miniature steel pipe pile technology reference for similar projects.
2016, 24(s1): 547-551.
Combine with the analysis on collapsibility of loess in different geomorphic unit and the discussion on the current specification we fount out that: Due to the lightening of the diversion pipeline, the value collapse settlement was little than which calculated with the laboratory test data; the incidence of groundwater variation on the collapsibility evaluation of different geomorphic unit was variant; we suggest that the foundation treatment methods of the buried set outdoor pool could be referenced on the buried pipe and box culvert, the difference of the correction factor in different geomorphic unit should be taken into account, and should review the value of the collapsibility in those project which load would be decreases.
Combine with the analysis on collapsibility of loess in different geomorphic unit and the discussion on the current specification we fount out that: Due to the lightening of the diversion pipeline, the value collapse settlement was little than which calculated with the laboratory test data; the incidence of groundwater variation on the collapsibility evaluation of different geomorphic unit was variant; we suggest that the foundation treatment methods of the buried set outdoor pool could be referenced on the buried pipe and box culvert, the difference of the correction factor in different geomorphic unit should be taken into account, and should review the value of the collapsibility in those project which load would be decreases.
2016, 24(s1): 552-558.
In order to reveal the formation law of accumulation layer landslide in the complex mountainous area, we carry out the analysis of influence index of topography and geomorphology factor on landslide development degree by comprehensive influence index analysis based on basic data of accumulation layer landslide at 98 sites of Daguan area, and divide the influence index grade of different factors on landslide development. The influence of different topography and geomorphology conditions on the development and occurrence of accumulation layer landslide is very different. The slow slope(21~35) of medium height(60~90m),North East, West convex type(T) is the most conducive to the development of landslide. Based on the analysis of the results, we establish the initial evaluation criteria of the occurrence level of accumulation layer landslide on the basis of topography and geomorphology factors in the mountain region of the northeast of Yunnan province, thereby provide a rapid identification method of the occurrence level of unstable slope for the geologic disaster investigation.
In order to reveal the formation law of accumulation layer landslide in the complex mountainous area, we carry out the analysis of influence index of topography and geomorphology factor on landslide development degree by comprehensive influence index analysis based on basic data of accumulation layer landslide at 98 sites of Daguan area, and divide the influence index grade of different factors on landslide development. The influence of different topography and geomorphology conditions on the development and occurrence of accumulation layer landslide is very different. The slow slope(21~35) of medium height(60~90m),North East, West convex type(T) is the most conducive to the development of landslide. Based on the analysis of the results, we establish the initial evaluation criteria of the occurrence level of accumulation layer landslide on the basis of topography and geomorphology factors in the mountain region of the northeast of Yunnan province, thereby provide a rapid identification method of the occurrence level of unstable slope for the geologic disaster investigation.
2016, 24(s1): 559-564.
Water inrush and mud burst disasters seriously threatens the safety of tunnel construction. Find out disaster causes, is the foundation of the tunnel construction disasters prevention and control measures of decision. Three causes of water inrush and mud burst disasters were advanced according to the analysis of the lose effectiveness of water-resisting or mud-resisting rock-soil plate, and water inrush and mud burst disaster-causingstructure and its size, based on the description of the definition of water inrush and mud burst, and the comprehensive prevention and control system, includingguaranteeof water-resisting or mud-resisting rock-soil plate thickness, treatment of jointed and cracked water-resisting or mud-resisting rock-soil plate and water inrush disaster-causingstructure, consolidation and supporting of mud burst disaster-causing structure was also advanced in this paper.
Water inrush and mud burst disasters seriously threatens the safety of tunnel construction. Find out disaster causes, is the foundation of the tunnel construction disasters prevention and control measures of decision. Three causes of water inrush and mud burst disasters were advanced according to the analysis of the lose effectiveness of water-resisting or mud-resisting rock-soil plate, and water inrush and mud burst disaster-causingstructure and its size, based on the description of the definition of water inrush and mud burst, and the comprehensive prevention and control system, includingguaranteeof water-resisting or mud-resisting rock-soil plate thickness, treatment of jointed and cracked water-resisting or mud-resisting rock-soil plate and water inrush disaster-causingstructure, consolidation and supporting of mud burst disaster-causing structure was also advanced in this paper.
2016, 24(s1): 565-570.
The settlements in tibet hydropower station has a lot unstable rocks, poor stability~very poor stability, risk of large may collapse, and have a serious threat to people and property in settlements and the highway traffic safety. In this paper, have an evaluation and grading on the risk of unstable rock, by using the Highway Public Corporation Law of Japan and the ROCKFALL software, analysis the falling distance, jumping height, the total kinetic energy, horizontal movement distance of the unstable rock, and obtain the relationship between the movement of unstable rock and the settlements, finally, give a reasonable prevention recommendations and a scientific basis.
The settlements in tibet hydropower station has a lot unstable rocks, poor stability~very poor stability, risk of large may collapse, and have a serious threat to people and property in settlements and the highway traffic safety. In this paper, have an evaluation and grading on the risk of unstable rock, by using the Highway Public Corporation Law of Japan and the ROCKFALL software, analysis the falling distance, jumping height, the total kinetic energy, horizontal movement distance of the unstable rock, and obtain the relationship between the movement of unstable rock and the settlements, finally, give a reasonable prevention recommendations and a scientific basis.
2016, 24(s1): 571-576.
To explore the analysis mothed of natural frequency for the site closing to ground fissure, the recursion formula and implicit analytic solution of single and random multi-layer site were derived based on the traditional shear beam model with the assumption of horizontal displacement continuity. In comparison with the solution of normal site, the fundamental frequency of hanging side site is smaller than normal site's and the heading side site is inverse. Furthermore, the fundamental frequency of hanging and heading side site will close the solution of normal site with the increase of the calculating width. If the order of natural frequency enhance, the solution in this paper will more and more closing the normal site solution. The solution indicate that the implicit analytic solution of closing ground fissure site resented by this paper is reasonable.
To explore the analysis mothed of natural frequency for the site closing to ground fissure, the recursion formula and implicit analytic solution of single and random multi-layer site were derived based on the traditional shear beam model with the assumption of horizontal displacement continuity. In comparison with the solution of normal site, the fundamental frequency of hanging side site is smaller than normal site's and the heading side site is inverse. Furthermore, the fundamental frequency of hanging and heading side site will close the solution of normal site with the increase of the calculating width. If the order of natural frequency enhance, the solution in this paper will more and more closing the normal site solution. The solution indicate that the implicit analytic solution of closing ground fissure site resented by this paper is reasonable.
2016, 24(s1): 577-583.
Mud burst is widely concerned by tunnel engineering due to its universality, burying and severity. Seven mudburst disaster-causingstructures, including water and mud mixed filling karst, clay filled karst communicating with the earth surface, clay filling deep grike and bath, deep clay filled karst, fault mud or fault mylonite in main fault zone, uncemented rich water fault strong compression fracture zone, and clay with crushed rock block filling in bottom of karst, were advancedaccording to the relationship between water inrush and unfavorable geologic bodies. Three principles for classification and four types mud burst disaster-causingstructures(water and mud mixed filling karst, clay filled karst, filling clayand in fracture and gap between broken rock blocks, and fault mud or fault mylonite in main fault zone) also were advanced according to the composition of mudburst disaster-causingstructure, type of mud-resisting rock-soil plate and extensive engineering treatment measures in this paper.
Mud burst is widely concerned by tunnel engineering due to its universality, burying and severity. Seven mudburst disaster-causingstructures, including water and mud mixed filling karst, clay filled karst communicating with the earth surface, clay filling deep grike and bath, deep clay filled karst, fault mud or fault mylonite in main fault zone, uncemented rich water fault strong compression fracture zone, and clay with crushed rock block filling in bottom of karst, were advancedaccording to the relationship between water inrush and unfavorable geologic bodies. Three principles for classification and four types mud burst disaster-causingstructures(water and mud mixed filling karst, clay filled karst, filling clayand in fracture and gap between broken rock blocks, and fault mud or fault mylonite in main fault zone) also were advanced according to the composition of mudburst disaster-causingstructure, type of mud-resisting rock-soil plate and extensive engineering treatment measures in this paper.
2016, 24(s1): 584-591.
The method of reinforcement on MSE wall by micropiles is put forward. The micropiles penetrate the MSE region of highway MSE wall from road surface and are anchored into the foundation, and then road barrier is connected to the micropiles by connecting pieces, which forms the Micropile-MSE Wall that aims to increase the MSE Wall's local stability, global stability and collision resistance of road barrier simultaneously. In order to validate the collision resistance of road barrier of Micropile-MSE Wall preliminarily, by applying collision loading on the barrier, comparative studies were done on the dynamic response of the MSE walls before and after reinforcement with micropiles through numerical method. The results indicate that through the micropiles penetrating the whole MSE wall from top to bottom, the collision-induced deformation can be restrained by the whole retaining structure. Hence, the collision resistance of road barrier is increased significantly, the collision-induced displacement of road barrier can be reduced by 90% around, and the deformation of backfill and geogrid can be reduced obviously as well, which preliminarily validates the reliability of collision resistance of road barrier of Micropile-MSE Wall.
The method of reinforcement on MSE wall by micropiles is put forward. The micropiles penetrate the MSE region of highway MSE wall from road surface and are anchored into the foundation, and then road barrier is connected to the micropiles by connecting pieces, which forms the Micropile-MSE Wall that aims to increase the MSE Wall's local stability, global stability and collision resistance of road barrier simultaneously. In order to validate the collision resistance of road barrier of Micropile-MSE Wall preliminarily, by applying collision loading on the barrier, comparative studies were done on the dynamic response of the MSE walls before and after reinforcement with micropiles through numerical method. The results indicate that through the micropiles penetrating the whole MSE wall from top to bottom, the collision-induced deformation can be restrained by the whole retaining structure. Hence, the collision resistance of road barrier is increased significantly, the collision-induced displacement of road barrier can be reduced by 90% around, and the deformation of backfill and geogrid can be reduced obviously as well, which preliminarily validates the reliability of collision resistance of road barrier of Micropile-MSE Wall.
2016, 24(s1): 592-598.
Affected by Qinghai-Tibet Plateau rapid uplifted and the river fast incised in Western Sichuan plateau since Cenozoic, where develop more and more bank slope and steep cliff that have the characters of high and steep、complex slope type、 and broken rock. Hongjunshan Dangerous-rock Slumping has the characters of large-scale、wide distribution、diversity failure pattern and complex mechanics. On the basis of engineering geological mapping, this paper investigates the distribution of dangerous rock, size, damage characteristics, failure mode, studies for different modes and stability calculates of the dangerous-rocks. Main knowledge:(1) the rock mass structure has obvious regional and zonality.(2) the generation and dangerous rock destruction are mainly block instability, ladder shaped sliding.(3) stability of dangerous-rocks are calculated for considering natural, rainstorm, earthquake conditions according to the characteristics of development、mass deformation and failure mechanics. Biggest dangerous rock mass, the lung deaf dangerous-rock, is stability under natural conditions. But is primary stability to instability under conditions of heavy rains and earthquake. Others are mainly instability under three conditions.(4) We suggest that some prevention measures should be taken, such as remove reinforcement, monitoring and the rainy season cruise screening for dangerous-rocks.
Affected by Qinghai-Tibet Plateau rapid uplifted and the river fast incised in Western Sichuan plateau since Cenozoic, where develop more and more bank slope and steep cliff that have the characters of high and steep、complex slope type、 and broken rock. Hongjunshan Dangerous-rock Slumping has the characters of large-scale、wide distribution、diversity failure pattern and complex mechanics. On the basis of engineering geological mapping, this paper investigates the distribution of dangerous rock, size, damage characteristics, failure mode, studies for different modes and stability calculates of the dangerous-rocks. Main knowledge:(1) the rock mass structure has obvious regional and zonality.(2) the generation and dangerous rock destruction are mainly block instability, ladder shaped sliding.(3) stability of dangerous-rocks are calculated for considering natural, rainstorm, earthquake conditions according to the characteristics of development、mass deformation and failure mechanics. Biggest dangerous rock mass, the lung deaf dangerous-rock, is stability under natural conditions. But is primary stability to instability under conditions of heavy rains and earthquake. Others are mainly instability under three conditions.(4) We suggest that some prevention measures should be taken, such as remove reinforcement, monitoring and the rainy season cruise screening for dangerous-rocks.
2016, 24(s1): 599-607.
After years of investigation and research, hydraulic structures such as sluices and seawall built on silt foundation often produce larger differential settlement between sluice and seawall, which may affect the normal use and even lead to the damage of these structures. Setting the connection section is effective engineering method of controlling differential settlement, but only setting up the connection section always gains limited effect on controlling excessive differential settlement. Based on the finite difference numerical simulation software(FLAC3D),this paper take a seawall in eastern Zhejiang coastal reclamation project as the background and simulate the seawall stacking and the fluid-structure interaction process. Then, by adjusting the connection part of cement mixing pile spacing, the pile length and the pile diameter, we can optimize the foundation treatment measures, and calculate the differential settlement of seawall and water gate under different optimization measure. The analysis results show that with a continuous changing of pile length, adjusting the size of the pile spacing can effectively control the uneven settlement.
After years of investigation and research, hydraulic structures such as sluices and seawall built on silt foundation often produce larger differential settlement between sluice and seawall, which may affect the normal use and even lead to the damage of these structures. Setting the connection section is effective engineering method of controlling differential settlement, but only setting up the connection section always gains limited effect on controlling excessive differential settlement. Based on the finite difference numerical simulation software(FLAC3D),this paper take a seawall in eastern Zhejiang coastal reclamation project as the background and simulate the seawall stacking and the fluid-structure interaction process. Then, by adjusting the connection part of cement mixing pile spacing, the pile length and the pile diameter, we can optimize the foundation treatment measures, and calculate the differential settlement of seawall and water gate under different optimization measure. The analysis results show that with a continuous changing of pile length, adjusting the size of the pile spacing can effectively control the uneven settlement.
2016, 24(s1): 608-613.
The original landform of an engineering plant is mainly low hills, and nearly 20m thick layer of filled soil is formed in the process of construction. The composition of the filled soil is the loess with the mixture of sandstone and mudstone, which size is in variety and its bearing capacity cannot meet the requirements of the main building. The pile foundation is considered for main buildings. Because the filled soil underlying sandstone and shale interbed of bedrock, the percussion boring method is chose to overcome the difficulty of boring in filling and to meet the demand of rock-socketed after considering synthetically with various pore forming process and its adaptability. Therefore, the full scale test and research is conducted by adopting the vertical compressive load experiment, horizontal bearing capacity and pile body stress strain test method, and construction parameter is evaluated and the bearing performance of bored piles is analyzed. A large number of reliable experimental data is obtained, which is valuable for similar projects.
The original landform of an engineering plant is mainly low hills, and nearly 20m thick layer of filled soil is formed in the process of construction. The composition of the filled soil is the loess with the mixture of sandstone and mudstone, which size is in variety and its bearing capacity cannot meet the requirements of the main building. The pile foundation is considered for main buildings. Because the filled soil underlying sandstone and shale interbed of bedrock, the percussion boring method is chose to overcome the difficulty of boring in filling and to meet the demand of rock-socketed after considering synthetically with various pore forming process and its adaptability. Therefore, the full scale test and research is conducted by adopting the vertical compressive load experiment, horizontal bearing capacity and pile body stress strain test method, and construction parameter is evaluated and the bearing performance of bored piles is analyzed. A large number of reliable experimental data is obtained, which is valuable for similar projects.
2016, 24(s1): 614-621.
To select the appropriate type of building foundation and to study the bearing characteristics of pile foundations in deep filling soil, the similarities and differences of the law and distribution of the moment, as well as the axial force and the skin friction along the drilling pile in dig area, dig and fill area and fill area under axial load at different levels are studied by ABAQUS software. In succession to this, the curve of settlement and load in different site of geological conditions was analyzed, Furthermore, the bearing capacity of drilling piles in different sites was predicted. Results shows that the bearing type of the drilling piles behave as end-support friction piles in site of dig and fill area and drilling pile shows larger positive moment and negative friction near the interface of dig and fill area; with the all level to vertical load, the settlement of drilling pile in fill area is greater than the others, the bearing capacity is the weakest, while the settlement of drilling pile in dig area is the minimum, the bearing capacity is the best. The suggestions of bars reinforcement design and construction measures to reduce the negative skin friction and enhance the bearing performance of drilling pile are proposed combined with codes and related literature. The conclusion can provide the reference for design and construction of building pile in this project and projects in other deep filling soil.
To select the appropriate type of building foundation and to study the bearing characteristics of pile foundations in deep filling soil, the similarities and differences of the law and distribution of the moment, as well as the axial force and the skin friction along the drilling pile in dig area, dig and fill area and fill area under axial load at different levels are studied by ABAQUS software. In succession to this, the curve of settlement and load in different site of geological conditions was analyzed, Furthermore, the bearing capacity of drilling piles in different sites was predicted. Results shows that the bearing type of the drilling piles behave as end-support friction piles in site of dig and fill area and drilling pile shows larger positive moment and negative friction near the interface of dig and fill area; with the all level to vertical load, the settlement of drilling pile in fill area is greater than the others, the bearing capacity is the weakest, while the settlement of drilling pile in dig area is the minimum, the bearing capacity is the best. The suggestions of bars reinforcement design and construction measures to reduce the negative skin friction and enhance the bearing performance of drilling pile are proposed combined with codes and related literature. The conclusion can provide the reference for design and construction of building pile in this project and projects in other deep filling soil.
2016, 24(s1): 622-629.
A large number of landslides were produced in the Minjiang River near the epicenter by Wenchuan earthquake. With extreme rainfall weather, debris flows gradually become the main secondary disasters after earthquake. On 3th July 2011,debris flow occurred in Gaojia debris flow under rainstorm condition, destroying woodland, burying old road, almost blocking Minjiang River, and affecting seriously the reconstruction of the tunnel entrance. In order to decrease the losses of blocking river by debris flow in intense seismic area, this article selects Gaojia debris flow in Minjiang river as the research object. Numerical simulation was adopt to simulate Gaojia debris flow movement under different rainfall intensity(5 years, 20 years, 50 years, 100 years), and further analysis the different levels of blocking river pattern. The numerical simulation accuracy can reach 81.4%by field validation. The results show that there are no loose material run out under the condition of 5years rainfall intensity, failed to plugging river in 20 years rainfall intensity, partially blocking river in 20 years rainfall intensity, and completely blocking the river under the condition of 100 years rainfall intensity.
A large number of landslides were produced in the Minjiang River near the epicenter by Wenchuan earthquake. With extreme rainfall weather, debris flows gradually become the main secondary disasters after earthquake. On 3th July 2011,debris flow occurred in Gaojia debris flow under rainstorm condition, destroying woodland, burying old road, almost blocking Minjiang River, and affecting seriously the reconstruction of the tunnel entrance. In order to decrease the losses of blocking river by debris flow in intense seismic area, this article selects Gaojia debris flow in Minjiang river as the research object. Numerical simulation was adopt to simulate Gaojia debris flow movement under different rainfall intensity(5 years, 20 years, 50 years, 100 years), and further analysis the different levels of blocking river pattern. The numerical simulation accuracy can reach 81.4%by field validation. The results show that there are no loose material run out under the condition of 5years rainfall intensity, failed to plugging river in 20 years rainfall intensity, partially blocking river in 20 years rainfall intensity, and completely blocking the river under the condition of 100 years rainfall intensity.
2016, 24(s1): 630-635.
The displacement of the landslide is affected by many nonlinear factors. The prediction of the landslide displacement, which is important for analyzing the development of landslide, is difficult but important. In this paper, wavelet theory and BP neural network were applied to predict the displacement of the landslide. Since the displacement of the landslide comprises accidental factors, such as rainfall and construction vibration, the prediction of the landslide was disturbed. In this paper, the displacement was de-noised by using wavelet theory, and the useful part was extracted. The data was then used to predict by using BP neural network. According to the result, the error between the predicted data and the real data was located in 2%~3%.It is proved that the methods used in this paper can be successfully used in prediction of the landslide displacement.
The displacement of the landslide is affected by many nonlinear factors. The prediction of the landslide displacement, which is important for analyzing the development of landslide, is difficult but important. In this paper, wavelet theory and BP neural network were applied to predict the displacement of the landslide. Since the displacement of the landslide comprises accidental factors, such as rainfall and construction vibration, the prediction of the landslide was disturbed. In this paper, the displacement was de-noised by using wavelet theory, and the useful part was extracted. The data was then used to predict by using BP neural network. According to the result, the error between the predicted data and the real data was located in 2%~3%.It is proved that the methods used in this paper can be successfully used in prediction of the landslide displacement.
STUDY ON REGIONAL RAINFALL-INDUCED-LANDSLIDES PREDICTION BASED ON DAILY AND ANTECEDENT PRECIPITATION
2016, 24(s1): 636-640.
Intraday and cumulative rainfalls were chosen as the meteorological factors of the prediction model through comparing the relationship between the landslides and the precipitation of the early days. The attenuation coefficient of cumulative rainfall was 0.9. The binary logistic regression prediction method is established based on 120 rainfall-induced-landslides data in the Yucheng district, Yaan city in Sichuang province. Analysis is done with the independent variables of the intraday and cumulative rainfall and probability prediction equation is achieved. On this basis, a critical expression of rainfall-induced-landslides is obtained through the scatter plot. The test samples of 5 rainfall-induced-landslides and 5 non-landslides reach up 100 percent accuracy. The predictive values of the ten tests samples are in line with requirements. The prediction of the rainfall-induced-landslides can be provided by forecast equation and critical expression.
Intraday and cumulative rainfalls were chosen as the meteorological factors of the prediction model through comparing the relationship between the landslides and the precipitation of the early days. The attenuation coefficient of cumulative rainfall was 0.9. The binary logistic regression prediction method is established based on 120 rainfall-induced-landslides data in the Yucheng district, Yaan city in Sichuang province. Analysis is done with the independent variables of the intraday and cumulative rainfall and probability prediction equation is achieved. On this basis, a critical expression of rainfall-induced-landslides is obtained through the scatter plot. The test samples of 5 rainfall-induced-landslides and 5 non-landslides reach up 100 percent accuracy. The predictive values of the ten tests samples are in line with requirements. The prediction of the rainfall-induced-landslides can be provided by forecast equation and critical expression.
2016, 24(s1): 641-648.
the research of large-scale landslide risk assessment is a very difficult issue in landslide research in recent years. Luojiagou landslide was taken as an example in order to investigate individual landslide risk. The landslide stability was simulated in different rainfall return period(10, 20, 50 years) to calculate landslide probability. The vulnerability of elements in risk was determined by qualitative method based on detailed field investigation. The total risk of economic risk and personnel risk were analyzed quantitatively under different rainfall conditions, and the annual economic risk and individual risk was calculated quantitatively by exceeding probability method. Based on RS data of the landslide field, the risk change of buildings and personnel was directly shown in the 3D model in ARCGIS platform. The result showed that the value of landslide risk was similar in the conditions of 10-year and 20-year rainfall conditions, while the failure probability of landslide and the value of landslide risk increased in the condition of 50-year rainfall.
the research of large-scale landslide risk assessment is a very difficult issue in landslide research in recent years. Luojiagou landslide was taken as an example in order to investigate individual landslide risk. The landslide stability was simulated in different rainfall return period(10, 20, 50 years) to calculate landslide probability. The vulnerability of elements in risk was determined by qualitative method based on detailed field investigation. The total risk of economic risk and personnel risk were analyzed quantitatively under different rainfall conditions, and the annual economic risk and individual risk was calculated quantitatively by exceeding probability method. Based on RS data of the landslide field, the risk change of buildings and personnel was directly shown in the 3D model in ARCGIS platform. The result showed that the value of landslide risk was similar in the conditions of 10-year and 20-year rainfall conditions, while the failure probability of landslide and the value of landslide risk increased in the condition of 50-year rainfall.
2016, 24(s1): 649-652.
Study of high steep slope stability has always been the focus of research in academia and engineering. The completely~intensely weathered silty mudstone slope of a converter station is high in height and rich in groundwater, and its silty mudstone is vulnerable to weathering. Research was given from the respects of the mechanical parameters, slope shape design, stability calculation, bolt support design, drainage system design and slope greening, which ensured the stability of slope and saved the cost of support. The slope design and supporting scheme are complete, so as to provide reference for similar slope design.
Study of high steep slope stability has always been the focus of research in academia and engineering. The completely~intensely weathered silty mudstone slope of a converter station is high in height and rich in groundwater, and its silty mudstone is vulnerable to weathering. Research was given from the respects of the mechanical parameters, slope shape design, stability calculation, bolt support design, drainage system design and slope greening, which ensured the stability of slope and saved the cost of support. The slope design and supporting scheme are complete, so as to provide reference for similar slope design.
2016, 24(s1): 653-660.
Based on research characteristics of upper reservoir seepage, the paper constructs the engineering geological analysis system of upper reservoir seepage. The application of the system was beneficial to analyze and evaluate issues from upper reservoir seepage of special Pumped Storage Power station. The result shows that seepage lengths in the upper reservoir bank is 90 percent of total length of the ring reservoir, and seepage areas mainly concentrate in the dam area, right bank or tail of reservoir. So the article suggests the upper reservoir bank should adopt seepage control measures for the whole area.
Based on research characteristics of upper reservoir seepage, the paper constructs the engineering geological analysis system of upper reservoir seepage. The application of the system was beneficial to analyze and evaluate issues from upper reservoir seepage of special Pumped Storage Power station. The result shows that seepage lengths in the upper reservoir bank is 90 percent of total length of the ring reservoir, and seepage areas mainly concentrate in the dam area, right bank or tail of reservoir. So the article suggests the upper reservoir bank should adopt seepage control measures for the whole area.
2016, 24(s1): 661-667.
An implicit material point method(MPM) is presented in this paper to simulate long run-out landslide. The generalized interpolation material point method(GIMP) is used to calculate the run-out of landslide with MUSL scheme. The elastoplastic model based on the Drucker-Prager yield criterion is adopted in this paper. Firstly, the effectiveness of the material point method to simulate the large deformation problem is verified by the experiment test. Secondly, the GIMP is used to simulate the failure process of the landslide, and the influence of internal friction angle on the slipping distance of the large deformation landslide is discussed. The results show that the internal friction angle plays a decisive role in the slipping distance of the landslide. The smaller of soil internal friction angle is,the longer of the slipping distance become. For unsaturated soil strength parameters by UU shear test, the internal friction angle is small because of the soil consolidation and drainage is poor. It is important to ensure that the soil is fully consolidated and drained for the landfills, otherwise it is easy to become long run-out landslide.
An implicit material point method(MPM) is presented in this paper to simulate long run-out landslide. The generalized interpolation material point method(GIMP) is used to calculate the run-out of landslide with MUSL scheme. The elastoplastic model based on the Drucker-Prager yield criterion is adopted in this paper. Firstly, the effectiveness of the material point method to simulate the large deformation problem is verified by the experiment test. Secondly, the GIMP is used to simulate the failure process of the landslide, and the influence of internal friction angle on the slipping distance of the large deformation landslide is discussed. The results show that the internal friction angle plays a decisive role in the slipping distance of the landslide. The smaller of soil internal friction angle is,the longer of the slipping distance become. For unsaturated soil strength parameters by UU shear test, the internal friction angle is small because of the soil consolidation and drainage is poor. It is important to ensure that the soil is fully consolidated and drained for the landfills, otherwise it is easy to become long run-out landslide.
2016, 24(s1): 668-672.
Typically, the minimum safety factor is used to evaluate the stability of slopes, which is recommended by many specifications. In fact, the maximum acceleration can also have this capacity and act as an alternative index. The safety factor reflects the reserve in strength of the slope, while the acceleration reflects the reserve in kinematics, i.e., to investigate the current state and sliding state of the slope from the kinematics point of view. In this paper, cohesionless soil slope and cohesive soil slope are analyzed to investigate the main influencing factors of acceleration, and the relationship between the minimum safety factor and the maximum acceleration. Results show that the correlation between the safety factor and the acceleration is more significant when cohesion has smaller weight in shear strength of the soil.
Typically, the minimum safety factor is used to evaluate the stability of slopes, which is recommended by many specifications. In fact, the maximum acceleration can also have this capacity and act as an alternative index. The safety factor reflects the reserve in strength of the slope, while the acceleration reflects the reserve in kinematics, i.e., to investigate the current state and sliding state of the slope from the kinematics point of view. In this paper, cohesionless soil slope and cohesive soil slope are analyzed to investigate the main influencing factors of acceleration, and the relationship between the minimum safety factor and the maximum acceleration. Results show that the correlation between the safety factor and the acceleration is more significant when cohesion has smaller weight in shear strength of the soil.
2016, 24(s1): 673-680.
In this paper, based on taking full account of the landslide site features its own characteristics, then derived prediction formula of landslide movement distance based on kinematics, and collected 44 cases of typical rainfall landslide basic data as sample to carry out nonlinear fitting about this model with two methods of the results and processes. Finally, making use of landslide example to carry out comparative analysis and suitability testing with model. The result shows: The result is well and its correlation coefficients were 0.926 and 0.928 after fitting about the formula result and actual result, the distance of Hongtaoshan landslide is 83.16m using derived theoretical formula, which is smaller than the actual sliding distance that is 89.37m, which the absolute error is 6.21m, the relative error is 6.95%,after result fitting the value of landslide distance is 6.07m smaller than actual and the relative error is 6.80%.therefore after process fitting is 3.52m, the relative error is 3.94%.It showed the formula have a excellent applicability after fitting. The research results provides a new way about distance prediction of landslide movement.
In this paper, based on taking full account of the landslide site features its own characteristics, then derived prediction formula of landslide movement distance based on kinematics, and collected 44 cases of typical rainfall landslide basic data as sample to carry out nonlinear fitting about this model with two methods of the results and processes. Finally, making use of landslide example to carry out comparative analysis and suitability testing with model. The result shows: The result is well and its correlation coefficients were 0.926 and 0.928 after fitting about the formula result and actual result, the distance of Hongtaoshan landslide is 83.16m using derived theoretical formula, which is smaller than the actual sliding distance that is 89.37m, which the absolute error is 6.21m, the relative error is 6.95%,after result fitting the value of landslide distance is 6.07m smaller than actual and the relative error is 6.80%.therefore after process fitting is 3.52m, the relative error is 3.94%.It showed the formula have a excellent applicability after fitting. The research results provides a new way about distance prediction of landslide movement.
2016, 24(s1): 681-686.
Landslides are commonly in loessland which has close relation to loess-bedrock unconformity surface. Furthermore, it is very necessary to conduct prevention and controlling of geological disasters by deeply analyzing the controlling effect of the unconformity surface on loess landslides. Taking Lanzhou area as the research object, this paper discusseed the spatial relationship between density and volume of landslide and the loess-bedrock unconformity surface through the analysis of landslide distribution and general characteristics. The results show that:(1) the length, width, area and volume of landslide present a concentration on certain range along with the increasing of the landslide scale; (2) the correlation between width and volume of the landslide is worse, whereas better correlation presents between length and volume of the landslide, and the fitting relationship between landslide scale indicates that the characteristic of discrete increase with the increasing of landslide scale; (3) landslides are almost symmetrically distributed on the both sides of unconformity surface, moreover a large quantity of loess-bedrock landslides in great size are relatively developed near the unconformity surface; (3) between amount and volume of landslide and the distance of loess-bedrock unconformity surface obeys piecewise power-law distribution.
Landslides are commonly in loessland which has close relation to loess-bedrock unconformity surface. Furthermore, it is very necessary to conduct prevention and controlling of geological disasters by deeply analyzing the controlling effect of the unconformity surface on loess landslides. Taking Lanzhou area as the research object, this paper discusseed the spatial relationship between density and volume of landslide and the loess-bedrock unconformity surface through the analysis of landslide distribution and general characteristics. The results show that:(1) the length, width, area and volume of landslide present a concentration on certain range along with the increasing of the landslide scale; (2) the correlation between width and volume of the landslide is worse, whereas better correlation presents between length and volume of the landslide, and the fitting relationship between landslide scale indicates that the characteristic of discrete increase with the increasing of landslide scale; (3) landslides are almost symmetrically distributed on the both sides of unconformity surface, moreover a large quantity of loess-bedrock landslides in great size are relatively developed near the unconformity surface; (3) between amount and volume of landslide and the distance of loess-bedrock unconformity surface obeys piecewise power-law distribution.
2016, 24(s1): 687-693.
1920 Haiyuan 8.5 Earthquake had induced a large number of Group loess landslides in Xiji county of Ⅸ、Ⅹ Earthquake intensity area, which caused the casualties and serious ecological damage. Based on the field investigation, this paper studies about 314 landslides in research area by using Google Earth image interpretation method. Obtained the space distribution and deformation destruction characteristics of loess earthquake landslide in study area and analyzed the main inherent and external influence factor of landslide formation. According to the research results of this paper, putting forward some suggestions for project location, construction excavation and disaster prevention in the mountain area of Southern Ningxia.
1920 Haiyuan 8.5 Earthquake had induced a large number of Group loess landslides in Xiji county of Ⅸ、Ⅹ Earthquake intensity area, which caused the casualties and serious ecological damage. Based on the field investigation, this paper studies about 314 landslides in research area by using Google Earth image interpretation method. Obtained the space distribution and deformation destruction characteristics of loess earthquake landslide in study area and analyzed the main inherent and external influence factor of landslide formation. According to the research results of this paper, putting forward some suggestions for project location, construction excavation and disaster prevention in the mountain area of Southern Ningxia.
2016, 24(s1): 694-701.
There are a lot of landslide geological disasters in our country, and deformation and failure form of landslide is very complex. In order to explore a more reasonable reinforcement method of landslide, deformation process of three types of landslides is analyzed and deformation failure mode of three types of landslides is put forward. Based on the deformation failure mode and engineering geological characteristics of landslide, and correspondingly retrogressive landslide is divided into traction area(initial slide area) and passive traction area, load-caused landslide is divided into pushed area and loading area, combined landslide is divided into leading edge start area(tractive effect),main slide area and trailing edge start area(loading effect).The deformation sequence and interdependence between different areas during the evolution process of landslide are analyzed, and active deformation area and passive deformation area are defined. In addition, the reinforcement method is put forward for different types of landslides based on the deformation and failure mode of landslide. The main idea of reinforcement method is to control the active deformation area and to ensure the stability of the passive deformation area. That different area uses different safety factor to control. And through the calculation and analysis of three typical examples of landslide, this method which has certain application value in engineering practice is demonstrated.
There are a lot of landslide geological disasters in our country, and deformation and failure form of landslide is very complex. In order to explore a more reasonable reinforcement method of landslide, deformation process of three types of landslides is analyzed and deformation failure mode of three types of landslides is put forward. Based on the deformation failure mode and engineering geological characteristics of landslide, and correspondingly retrogressive landslide is divided into traction area(initial slide area) and passive traction area, load-caused landslide is divided into pushed area and loading area, combined landslide is divided into leading edge start area(tractive effect),main slide area and trailing edge start area(loading effect).The deformation sequence and interdependence between different areas during the evolution process of landslide are analyzed, and active deformation area and passive deformation area are defined. In addition, the reinforcement method is put forward for different types of landslides based on the deformation and failure mode of landslide. The main idea of reinforcement method is to control the active deformation area and to ensure the stability of the passive deformation area. That different area uses different safety factor to control. And through the calculation and analysis of three typical examples of landslide, this method which has certain application value in engineering practice is demonstrated.
2016, 24(s1): 702-709.
A brief review on the development of inclinometer techniques, used in monitoring of landslide deep displacement, was presented, and the principle and current status of inclinometer techniques were analyzed detailedly, which was aimed at summarizing historical experience and provided scientific reference for the future landslide monitoring study. There are two important indicators in monitoring of landslide deep displacement, they are apex angle and azimuth angle represented borehole deformation size and direction respectively. Inclinometers were divided into pendulum and accelerometer inclinometer, which were used for measuring apex angle. Wheel-guide slot, electronic compass, gyroscope and other means were applied to measure azimuth angle. To illustrate all existing kinds of inclinometer techniques clearly, based on the difference between the apex angle and azimuth angle measurement principles, inclinometer techniques were introduced in classification via combining with examples. In addition, upon the literatures and market investigations, the development status of the inclinometers which were widely used at home and abroad in the 1980s and nowadays were contrastive analyzed; and the fact that landslide monitoring with multiparameter became more and more systematic and automatic was point out.
A brief review on the development of inclinometer techniques, used in monitoring of landslide deep displacement, was presented, and the principle and current status of inclinometer techniques were analyzed detailedly, which was aimed at summarizing historical experience and provided scientific reference for the future landslide monitoring study. There are two important indicators in monitoring of landslide deep displacement, they are apex angle and azimuth angle represented borehole deformation size and direction respectively. Inclinometers were divided into pendulum and accelerometer inclinometer, which were used for measuring apex angle. Wheel-guide slot, electronic compass, gyroscope and other means were applied to measure azimuth angle. To illustrate all existing kinds of inclinometer techniques clearly, based on the difference between the apex angle and azimuth angle measurement principles, inclinometer techniques were introduced in classification via combining with examples. In addition, upon the literatures and market investigations, the development status of the inclinometers which were widely used at home and abroad in the 1980s and nowadays were contrastive analyzed; and the fact that landslide monitoring with multiparameter became more and more systematic and automatic was point out.
2016, 24(s1): 710-716.
Perilous rock in limestone area shows quasi-masonry structure characteristics. It appears disintegration failure phenomenon in the process of collapse. For the discussion on the disintegration of quasi-masonry perilous rock, different bonding ways, depth-width ratio and dip angle of perilous rock were chosen to make 81model tests and to get the earliest cracking location feature in the disintegration of perilous rock by different combination. The results showed that, in the model test, the greater depth-width ratio, the cracking location is closer to the lower of perilous rock and the larger dip angle of controlling structure, the initial cracking location is closer to the upper part. In the meantime, it showed that the bonding mode had little influence to the initial cracking location. In the model test, it studied surface cracking features of perilous rock model when the collapse occurred. The research results provide some scientific basis to disintegration mechanism of perilous rock with quasi-masonry structure characteristics in the Three Gorges Reservoir Area.
Perilous rock in limestone area shows quasi-masonry structure characteristics. It appears disintegration failure phenomenon in the process of collapse. For the discussion on the disintegration of quasi-masonry perilous rock, different bonding ways, depth-width ratio and dip angle of perilous rock were chosen to make 81model tests and to get the earliest cracking location feature in the disintegration of perilous rock by different combination. The results showed that, in the model test, the greater depth-width ratio, the cracking location is closer to the lower of perilous rock and the larger dip angle of controlling structure, the initial cracking location is closer to the upper part. In the meantime, it showed that the bonding mode had little influence to the initial cracking location. In the model test, it studied surface cracking features of perilous rock model when the collapse occurred. The research results provide some scientific basis to disintegration mechanism of perilous rock with quasi-masonry structure characteristics in the Three Gorges Reservoir Area.
2016, 24(s1): 717-721.
Granular avalanche happens frequently. The hazard usually causes catastrophic disasters to the manmade system along its passage. In addition, granular avalanche often provides plenty of loose sediment for debris flow, and deposits as loose packing natural dam for avalanche lake formation. A hydrodynamic model is established for granular avalanche, and a high-resolution numerical algorithm is proposed and implemented to simulate its evolution and deposit. Using the numerical model, the classical dam-break problem is at first successfully calculated. Then, the flow and deposit behavior of granular avalanche across a terrain with an obstacle is studied. Based on the results, some preliminary protection schemes for granular avalanche mitigation are discussed.
Granular avalanche happens frequently. The hazard usually causes catastrophic disasters to the manmade system along its passage. In addition, granular avalanche often provides plenty of loose sediment for debris flow, and deposits as loose packing natural dam for avalanche lake formation. A hydrodynamic model is established for granular avalanche, and a high-resolution numerical algorithm is proposed and implemented to simulate its evolution and deposit. Using the numerical model, the classical dam-break problem is at first successfully calculated. Then, the flow and deposit behavior of granular avalanche across a terrain with an obstacle is studied. Based on the results, some preliminary protection schemes for granular avalanche mitigation are discussed.
2016, 24(s1): 722-727.
Based on the Richards's equation which describes the behaviour of capillary conduction of liquids in porous mediums, Iverson derived the equation which expresses the response of the pore-water pressure at any depth in the slope to rainfall infiltration in 2000. The formula which calculates the factor of safety of the shallow landslide trigged by rainfall infiltration was derived on the basis above in this paper. The formula takes account of the variation of the gravity and the degree of saturation in the unsaturated area in the slope under the rainfall infiltration. The results of the case study show that: the factor of safety of the shallow landslide gradually decreases with the rainfall infiltration and reaches the minimum value in a short time after the cease of rainfall infiltration. After that the factor of safety gradually increases with the rate which was lower than the one of decreasing. The variation trends above at the different initial vertical groundwater depths are similar; however, the factor of safety decreases with the increase of initial vertical groundwater depth. The duration of rainfall infiltration and rainfall infiltration rate both have the marked impact on the factor of safety of shallow landslide. The impact show that the larger of the rainfall infiltration rate or longer of the duration of rainfall infiltration, the larger decreasing amount of factor of safety is. However, the impact caused by the rainfall infiltration rate was controlled by the vertical permeability coefficient of the landslide.
Based on the Richards's equation which describes the behaviour of capillary conduction of liquids in porous mediums, Iverson derived the equation which expresses the response of the pore-water pressure at any depth in the slope to rainfall infiltration in 2000. The formula which calculates the factor of safety of the shallow landslide trigged by rainfall infiltration was derived on the basis above in this paper. The formula takes account of the variation of the gravity and the degree of saturation in the unsaturated area in the slope under the rainfall infiltration. The results of the case study show that: the factor of safety of the shallow landslide gradually decreases with the rainfall infiltration and reaches the minimum value in a short time after the cease of rainfall infiltration. After that the factor of safety gradually increases with the rate which was lower than the one of decreasing. The variation trends above at the different initial vertical groundwater depths are similar; however, the factor of safety decreases with the increase of initial vertical groundwater depth. The duration of rainfall infiltration and rainfall infiltration rate both have the marked impact on the factor of safety of shallow landslide. The impact show that the larger of the rainfall infiltration rate or longer of the duration of rainfall infiltration, the larger decreasing amount of factor of safety is. However, the impact caused by the rainfall infiltration rate was controlled by the vertical permeability coefficient of the landslide.
2016, 24(s1): 728-733.
There is high demand for the rock body of riverbed foundation, dam abutments and arch abutment in the process of building arch dam, especiallyWudongdehydropower station is as high as 270m high arch dam, the selection ofriverbed foundation planeis particularly important for the arch dam survey. Based on the conventional survey methods for Wudongdehydropower station, such as small diameter drilling, this paper studiedfoundation plane combined with drilling digital color television, water pressure test, sound wave testing, and so on. Then, the paper put forward the geology suggestions for the selection of riverbed foundation plane through a series of test results, determining the grade Ⅱ1 rock mass as the riverbed foundation, which has intact rock mass and good engineering geological characteristics, the minimum elevationof foundation plane is 718m. The research methods and ideas arereferencedby similar engineering survey.
There is high demand for the rock body of riverbed foundation, dam abutments and arch abutment in the process of building arch dam, especiallyWudongdehydropower station is as high as 270m high arch dam, the selection ofriverbed foundation planeis particularly important for the arch dam survey. Based on the conventional survey methods for Wudongdehydropower station, such as small diameter drilling, this paper studiedfoundation plane combined with drilling digital color television, water pressure test, sound wave testing, and so on. Then, the paper put forward the geology suggestions for the selection of riverbed foundation plane through a series of test results, determining the grade Ⅱ1 rock mass as the riverbed foundation, which has intact rock mass and good engineering geological characteristics, the minimum elevationof foundation plane is 718m. The research methods and ideas arereferencedby similar engineering survey.
2016, 24(s1): 734-741.
Clearing deformation instability mode of dangerous rocks is the premise of prevention and treatment research, but traditional forecasting methods have shortcomings of high-cost and weak practicality, especially under strong earthquake. in this paper, Adopting methods of neural network structure based on Levenberg-Marquardt and three dimensional discrete element numerical simulation, also considering deformation instability mode of dangerous rocks under four main varying conditions, including joint dip angle, length of rock, depth-width ratio and stacking layers of dangerous rocks, and taking deformation instability mode of dangerous rocks for research objects and influencing factors as the breakthrough point, the BP neural network model to predict deformation instability mode of dangerous rocks is established. Then the neural network is trained with samples of deformation instability mode of dangerous rocks calculated by numerical simulation. Finally, the paper analyzes the accuracy of the prediction model. the results show that this model is provided with good learning and generalization ability, and the accuracy of prediction is 86.7%. All these indexes validate that neural network based on Levenberg-Marquardt method to predict deformation instability mode of dangerous rocks is effective and feasible.
Clearing deformation instability mode of dangerous rocks is the premise of prevention and treatment research, but traditional forecasting methods have shortcomings of high-cost and weak practicality, especially under strong earthquake. in this paper, Adopting methods of neural network structure based on Levenberg-Marquardt and three dimensional discrete element numerical simulation, also considering deformation instability mode of dangerous rocks under four main varying conditions, including joint dip angle, length of rock, depth-width ratio and stacking layers of dangerous rocks, and taking deformation instability mode of dangerous rocks for research objects and influencing factors as the breakthrough point, the BP neural network model to predict deformation instability mode of dangerous rocks is established. Then the neural network is trained with samples of deformation instability mode of dangerous rocks calculated by numerical simulation. Finally, the paper analyzes the accuracy of the prediction model. the results show that this model is provided with good learning and generalization ability, and the accuracy of prediction is 86.7%. All these indexes validate that neural network based on Levenberg-Marquardt method to predict deformation instability mode of dangerous rocks is effective and feasible.
2016, 24(s1): 742-747.
Based on the large-scale physical model test, we established a landslide model protected by presressed anchor lattice with the finite difference software Flac3D,simulated the landslide from initial state to limit state and analyzed the mechanics properties during this process. The result indicated that anchor frame technique can restrict the slide of landslide effectively. Under load on the top platform of landslide, the stress of the slide changed, which was stronger at the beam and decreased to the surrounding gradually with the maximum stress at the bottom beam node. The anchor bore uneven axial force. The axial force of the free section was basically equal, while the axial force of anchorage section decreased gradually from the slide surface to the end. On the other hand, the axial force of anchors from top to bottom increases gradually. The intermediate of the beam suffered lateral tension while the node part suffered inner tension and the maximum shear force and bending moment occurred at the node. The forces of horizontal beam get stronger from top to bottom. The force of horizontal and vertical beams is different, so the internal force calculation of lattice beam should be considered respectively.
Based on the large-scale physical model test, we established a landslide model protected by presressed anchor lattice with the finite difference software Flac3D,simulated the landslide from initial state to limit state and analyzed the mechanics properties during this process. The result indicated that anchor frame technique can restrict the slide of landslide effectively. Under load on the top platform of landslide, the stress of the slide changed, which was stronger at the beam and decreased to the surrounding gradually with the maximum stress at the bottom beam node. The anchor bore uneven axial force. The axial force of the free section was basically equal, while the axial force of anchorage section decreased gradually from the slide surface to the end. On the other hand, the axial force of anchors from top to bottom increases gradually. The intermediate of the beam suffered lateral tension while the node part suffered inner tension and the maximum shear force and bending moment occurred at the node. The forces of horizontal beam get stronger from top to bottom. The force of horizontal and vertical beams is different, so the internal force calculation of lattice beam should be considered respectively.
2016, 24(s1): 748-755.
The hydrogeological structure system controls the underground water system. However, the research on the construction of water control is still weak. Fault, fold and other geological structures in the North China type Huainan coalfield are extremely developed. It has guiding role in understanding the characteristics of groundwater enrichment and preventing the coal floor water disaster during mining engineering in the mining area with complex geological structure by studying the control mechanism of these geological structures to the groundwater and summarizing the control law of the formation of the water rich in the geological structure. In this paper, taking the northern part of Huainan coal field as the research object and the geological structure of the study area is complex. The controlling mechanism of typical geological structure to the water-abundance ability of bedrock aquifer has been studied by using the method of analysis of hydrogeological structure system combined with a large number of measured data. It is considered that there are two ways which are direct and indirect approaches to control the water-abundance ability and the action processes of the two approaches are discussed respectively. The theory has important practical significance for the re understanding of mine hydrogeological condition.
The hydrogeological structure system controls the underground water system. However, the research on the construction of water control is still weak. Fault, fold and other geological structures in the North China type Huainan coalfield are extremely developed. It has guiding role in understanding the characteristics of groundwater enrichment and preventing the coal floor water disaster during mining engineering in the mining area with complex geological structure by studying the control mechanism of these geological structures to the groundwater and summarizing the control law of the formation of the water rich in the geological structure. In this paper, taking the northern part of Huainan coal field as the research object and the geological structure of the study area is complex. The controlling mechanism of typical geological structure to the water-abundance ability of bedrock aquifer has been studied by using the method of analysis of hydrogeological structure system combined with a large number of measured data. It is considered that there are two ways which are direct and indirect approaches to control the water-abundance ability and the action processes of the two approaches are discussed respectively. The theory has important practical significance for the re understanding of mine hydrogeological condition.
2016, 24(s1): 756-764.
Several mining areas of YanZhou coalfield now is prepare for mining deep coal seam. For high crustal stress and high water pressure, deep coal seam mining is more difficult than the shallow one. Taking XingLongZhuang coal mine as example, use FLAC3D to simulate the process of coal seam mining repeatedly near the fault under high crustal stress condition. Get the distribution diagram of vertical displacement, vertical stress and plastic zone of surrounding rock. Analysis the difference of the distribution diagram of vertical displacement, vertical stress and plastic zone between the first time mining and the second time. By observe whether plastic zone distribution range had contact with water-bearing fault, the critical distance of water inrush from coal seam floor was got. Compared with the calculation result using the method in national standards, both are basically consistent. This study has important academic and practical significance for the mine water control work and determine the width of the protection coal pillar.
Several mining areas of YanZhou coalfield now is prepare for mining deep coal seam. For high crustal stress and high water pressure, deep coal seam mining is more difficult than the shallow one. Taking XingLongZhuang coal mine as example, use FLAC3D to simulate the process of coal seam mining repeatedly near the fault under high crustal stress condition. Get the distribution diagram of vertical displacement, vertical stress and plastic zone of surrounding rock. Analysis the difference of the distribution diagram of vertical displacement, vertical stress and plastic zone between the first time mining and the second time. By observe whether plastic zone distribution range had contact with water-bearing fault, the critical distance of water inrush from coal seam floor was got. Compared with the calculation result using the method in national standards, both are basically consistent. This study has important academic and practical significance for the mine water control work and determine the width of the protection coal pillar.
2016, 24(s1): 765-772.
This paper based on the landslide deep displacement monitoring data from 3rd High School Landslide in Badong County, analyzing the depth of landslide sliding zone. Making use of the condition of artificial excavation of landslide anti-slide pile, in the process of excavation, comparing the monitoring data with the landslide geological structure and the actual sliding direction and depth of the sliding zone. The results showed that because of the earth's surface influence, the monitoring data have a big accidental error near the earth's surface, while the accuracy is higher for identification of landslide sliding zone in internal landslide. Monitoring the landslide deformation with inclinometer is one of the important means of landslide control design in the future.
This paper based on the landslide deep displacement monitoring data from 3rd High School Landslide in Badong County, analyzing the depth of landslide sliding zone. Making use of the condition of artificial excavation of landslide anti-slide pile, in the process of excavation, comparing the monitoring data with the landslide geological structure and the actual sliding direction and depth of the sliding zone. The results showed that because of the earth's surface influence, the monitoring data have a big accidental error near the earth's surface, while the accuracy is higher for identification of landslide sliding zone in internal landslide. Monitoring the landslide deformation with inclinometer is one of the important means of landslide control design in the future.
2016, 24(s1): 773-782.
Both the corrosive evaluation criteria of water soil and the protective standards for the durability design of concrete structures are independent and interactive. Through 2groundwater samples, this paper has compared the difference of erosive evaluation criteria of water and soil and protective standard for pile foundation and basement slab by different codes. Generally, the more serious the corrosive environment, the greater the difference of durability design of concrete structure. It is necessary to unify the corrosive evaluation criteria of water and soil and the protective standards for the durability design of concrete structures. In view of the large difference in corrosion evaluation of SO42- and CL-,this paper gives a definition of drying-wetting alternating action and drying-wetting alternating strength, and an unified solution of the erosive evaluation index and classification of water and soil is suggested. Drying-wetting alternating action is defined as a phenomenon of alternating conversion or continuous conversion between liquid phase water and gas phase water on the surface of a solid. Drying-wetting alternating strength is defined as the product of relative evaporation rate of liquid water on the surface of a solid and the saturation of a solid cover.
Both the corrosive evaluation criteria of water soil and the protective standards for the durability design of concrete structures are independent and interactive. Through 2groundwater samples, this paper has compared the difference of erosive evaluation criteria of water and soil and protective standard for pile foundation and basement slab by different codes. Generally, the more serious the corrosive environment, the greater the difference of durability design of concrete structure. It is necessary to unify the corrosive evaluation criteria of water and soil and the protective standards for the durability design of concrete structures. In view of the large difference in corrosion evaluation of SO42- and CL-,this paper gives a definition of drying-wetting alternating action and drying-wetting alternating strength, and an unified solution of the erosive evaluation index and classification of water and soil is suggested. Drying-wetting alternating action is defined as a phenomenon of alternating conversion or continuous conversion between liquid phase water and gas phase water on the surface of a solid. Drying-wetting alternating strength is defined as the product of relative evaporation rate of liquid water on the surface of a solid and the saturation of a solid cover.
2016, 24(s1): 783-789.
Two diversion tunnels are arranged on the right bank of Yangfanggou Hydropower Project, it sets a total of thirteen permanent monitoring cross section in construction period, according to the amount of monitoring date and results from the multi-point extensometer, anchor stress and tendon dynameter Installed, it shows that the deformation of diversion tunnels occurs mainly in the left wall, Lower excavation has a big influence to the stability of tunnels, the effect of blasting on the side wall is larger than that on the top arch.the surrounding rock about metamorphic siltstone and the turning segment of both sides walls have the phenomenon of stress adjustment, but the surrounding rock is stable on the whole. Security monitoring better guide the construction management, to escort for the smooth construction project, but also provides valuable experience for similar engineering construction in the future.
Two diversion tunnels are arranged on the right bank of Yangfanggou Hydropower Project, it sets a total of thirteen permanent monitoring cross section in construction period, according to the amount of monitoring date and results from the multi-point extensometer, anchor stress and tendon dynameter Installed, it shows that the deformation of diversion tunnels occurs mainly in the left wall, Lower excavation has a big influence to the stability of tunnels, the effect of blasting on the side wall is larger than that on the top arch.the surrounding rock about metamorphic siltstone and the turning segment of both sides walls have the phenomenon of stress adjustment, but the surrounding rock is stable on the whole. Security monitoring better guide the construction management, to escort for the smooth construction project, but also provides valuable experience for similar engineering construction in the future.
2016, 24(s1): 790-798.
In order to study the force and the deformation behavior of the double-row piles in the deep foundation, Large-scale physical model test was used to simulate deformation of double-row piles in foundation pit excavation based on the principle of the similarity theory in this paper. Choosing the formation in the eastern part of Beijing and discussing the changes of the strain, the displacement and the soil pressure during the deep foundation piles excavation. It is also using the numerical simulation to proof the law and results of the physical model test. That results show that the strain and the displacement of the front row piles is larger than the back row piles. The soil pressure of the front row piles appears to right convex, and there is a change obviously in soil pressure of the soil interface in the back row piles. The results is the same as the numerical simulation and also reliable and reasonable. It can put forward constructive reference for practical engineering.
In order to study the force and the deformation behavior of the double-row piles in the deep foundation, Large-scale physical model test was used to simulate deformation of double-row piles in foundation pit excavation based on the principle of the similarity theory in this paper. Choosing the formation in the eastern part of Beijing and discussing the changes of the strain, the displacement and the soil pressure during the deep foundation piles excavation. It is also using the numerical simulation to proof the law and results of the physical model test. That results show that the strain and the displacement of the front row piles is larger than the back row piles. The soil pressure of the front row piles appears to right convex, and there is a change obviously in soil pressure of the soil interface in the back row piles. The results is the same as the numerical simulation and also reliable and reasonable. It can put forward constructive reference for practical engineering.
2016, 24(s1): 799-805.
Loess was seen as a kind of unique problematic soil around the world. Structural loess always embodies some very high water sensitivities which correlate closely with common engineering problems exiting in loess area. In this paper, a series of direct shear tests were utilized to study the relationships between peak strength, residual strength, ultimate strength, structural strength and water content and normal pressure for undisturbed Q2 loess with different moistures quantitatively. It could be concluded that peak strength of loess has the higher water sensitivity than its' residual and ultimate strength, and exponential function and linear function could be used to depict the relations between peak strength and water content and the relations between residual/ultimate strength and water content, respectively. The relationships between peak strength and water content can be normalized with respect to the maximal peak strength under various normal pressures, and exponential function is suited to describe the normalized relationships. In addition, there is an exponential correlation existing between structural strength and water content. For undisturbed Q2 loess, the shear strains under different normal pressures at failure are in the area of 1%~2% due to its' strong structural strength. Research findings obtained in the paper will be useful in the further comprehension and cognizance on the functioning mechanism and design criteria of shear strength of unsaturated structural loess.
Loess was seen as a kind of unique problematic soil around the world. Structural loess always embodies some very high water sensitivities which correlate closely with common engineering problems exiting in loess area. In this paper, a series of direct shear tests were utilized to study the relationships between peak strength, residual strength, ultimate strength, structural strength and water content and normal pressure for undisturbed Q2 loess with different moistures quantitatively. It could be concluded that peak strength of loess has the higher water sensitivity than its' residual and ultimate strength, and exponential function and linear function could be used to depict the relations between peak strength and water content and the relations between residual/ultimate strength and water content, respectively. The relationships between peak strength and water content can be normalized with respect to the maximal peak strength under various normal pressures, and exponential function is suited to describe the normalized relationships. In addition, there is an exponential correlation existing between structural strength and water content. For undisturbed Q2 loess, the shear strains under different normal pressures at failure are in the area of 1%~2% due to its' strong structural strength. Research findings obtained in the paper will be useful in the further comprehension and cognizance on the functioning mechanism and design criteria of shear strength of unsaturated structural loess.
2016, 24(s1): 806-810.
The settlement difference between widened and spliced bridge-pile and original bridge-pile has a large impact for upper structure, therefore the settlement of new build bridge-pile should be strictly controlled. Post grouting technology could solidify bottom sediment and mud cake around pile, and improve the bearing capacity of pile. However the grouting in mudstone strata has less experience, contrast test was performed in regard to settlement reducing effect between post base-grouting bored pile and non-grouting bored pile socked in mudstone, combined with the expansion project of Changping highway K94+920.9 channel bridge. Then, through analysis of the post grouting load-settlement behavior and skin friction behavior, the results are revealed as follows: Under same level of load, on average, settlement of post grouting pile is 40% smaller than non-grouting one, and settlement reducing effect is obvious; the ultimate skin friction of non-grouting pile socked in completely weathered mudstone is about 120kPa, and the ultimate skin friction of post-grouting pile completely weathered mudstone is about 240kPa, 2 times of non-grouting pile; with water cement ratio of grout of 0.5 and grouting pressure of 2MPa, the maximum grout climbing height up to 4m above pile base. It provides reference for the design of post-grouting bored piles and settlement control at mudstone stratum in this area.
The settlement difference between widened and spliced bridge-pile and original bridge-pile has a large impact for upper structure, therefore the settlement of new build bridge-pile should be strictly controlled. Post grouting technology could solidify bottom sediment and mud cake around pile, and improve the bearing capacity of pile. However the grouting in mudstone strata has less experience, contrast test was performed in regard to settlement reducing effect between post base-grouting bored pile and non-grouting bored pile socked in mudstone, combined with the expansion project of Changping highway K94+920.9 channel bridge. Then, through analysis of the post grouting load-settlement behavior and skin friction behavior, the results are revealed as follows: Under same level of load, on average, settlement of post grouting pile is 40% smaller than non-grouting one, and settlement reducing effect is obvious; the ultimate skin friction of non-grouting pile socked in completely weathered mudstone is about 120kPa, and the ultimate skin friction of post-grouting pile completely weathered mudstone is about 240kPa, 2 times of non-grouting pile; with water cement ratio of grout of 0.5 and grouting pressure of 2MPa, the maximum grout climbing height up to 4m above pile base. It provides reference for the design of post-grouting bored piles and settlement control at mudstone stratum in this area.
2016, 24(s1): 811-816.
Reasearch on the fault zone hydrogeology is a fundamental task for site evaluation of the geological disposal of radioactive waste. Much attention should be paid to study the controlling influence the geological structure on the regional and site groundwater seepage. Based on the extensive domestic and foreign literature, this paper outlined the characteristics, research techniques, study scale of the fault zone permeability structure. And it could be helpful for the hydrogeological evaluation of Radioactive waste disposal site.
Reasearch on the fault zone hydrogeology is a fundamental task for site evaluation of the geological disposal of radioactive waste. Much attention should be paid to study the controlling influence the geological structure on the regional and site groundwater seepage. Based on the extensive domestic and foreign literature, this paper outlined the characteristics, research techniques, study scale of the fault zone permeability structure. And it could be helpful for the hydrogeological evaluation of Radioactive waste disposal site.
2016, 24(s1): 817-822.
Set pair analysis theory(SPA) is a quantitative analysis method for dealing with uncertainty and uncertainty. In the paper, FSPA algorithm is established by using the fuzzy connection degree of the SPA to further explore and analyze the difference coefficient. The aim is to discuss the close degree between the class and the adjacent categories by using the fuzzy relation data mining, and to discuss similarity and difference information. In order to verify the applicability of the model, the risk assessment was carried out by measuring the basic data of six debris flows in Fangshan District and Mentougou area of Beijing, and the evaluation results were compared with the theory of extension theory. the study concluded that Fuzzy set pair analysis theory can depth mining similarities and differences between sample types and adjacent categories inverse relation. By comparing with the field survey data, It was found that FSPA evaluation results of information mining more realistic. The evaluation results of this method are consistent with the results of the extension evaluation. The method has high accuracy and precision.
Set pair analysis theory(SPA) is a quantitative analysis method for dealing with uncertainty and uncertainty. In the paper, FSPA algorithm is established by using the fuzzy connection degree of the SPA to further explore and analyze the difference coefficient. The aim is to discuss the close degree between the class and the adjacent categories by using the fuzzy relation data mining, and to discuss similarity and difference information. In order to verify the applicability of the model, the risk assessment was carried out by measuring the basic data of six debris flows in Fangshan District and Mentougou area of Beijing, and the evaluation results were compared with the theory of extension theory. the study concluded that Fuzzy set pair analysis theory can depth mining similarities and differences between sample types and adjacent categories inverse relation. By comparing with the field survey data, It was found that FSPA evaluation results of information mining more realistic. The evaluation results of this method are consistent with the results of the extension evaluation. The method has high accuracy and precision.
2016, 24(s1): 823-831.
This paper combine Liyao test section of Beijing-Shanghai high-speed rail, compared and analyzed deep and soft soil CFG pile composite foundation various additional stress and settlement calculation methods in reinforcement zone and substratum. The results show:(1) Boussinesq solution can accurately calculate additional stress of reinforcement zone in composite foundation, Mindlin-Geddes solution can accurately calculate additional stress of the substratum in composite foundation.(2) Area weighted method can effectively calculate additional settlement of reinforcement zone in composite foundation.(3) the additional stress of substratum in composite foundation calculated by linear superposition that the method can effectively consider settlement of substratum in composite foundation under pile group.(4) There is very similar for the results between area weighted method and elasticity caculated method, and much larger than the pile-soil modulus ratio method.(5) the settlement underlying layer of composite foundation would increase with the increase of the piles number in the same replacement rate.
This paper combine Liyao test section of Beijing-Shanghai high-speed rail, compared and analyzed deep and soft soil CFG pile composite foundation various additional stress and settlement calculation methods in reinforcement zone and substratum. The results show:(1) Boussinesq solution can accurately calculate additional stress of reinforcement zone in composite foundation, Mindlin-Geddes solution can accurately calculate additional stress of the substratum in composite foundation.(2) Area weighted method can effectively calculate additional settlement of reinforcement zone in composite foundation.(3) the additional stress of substratum in composite foundation calculated by linear superposition that the method can effectively consider settlement of substratum in composite foundation under pile group.(4) There is very similar for the results between area weighted method and elasticity caculated method, and much larger than the pile-soil modulus ratio method.(5) the settlement underlying layer of composite foundation would increase with the increase of the piles number in the same replacement rate.
2016, 24(s1): 832-840.
Construction in expansion soil layer is often adversely affected by swell-shrink, fissure, over-consolidation characteristics of expansion soil, the mechanics and deformation characteristics of expansion soil deep foundation pit during excavation is studied based on coupled thermo numerical simulation. At first, the expansion force of undisturbed expansion soil is measured by laboratory test, and then a ring knife soil sample is simulated using coupled thermo module of FLAC3D,to derive expansion coefficient under target expansion force, finally mechanics and deformation characteristics of deep foundation pit in excavation process under Above-mentioned expansion coefficient is calculated, taking a Yangzhou expansion soil foundation pit as an example, and comparing with the measured data of the foundation pit. The main research conclusions are as follows:(1) Contour line of retaining structure lateral deformation is shaped like a fish belly, the maximum lateral deformation occurs in a certain range above the excavation face, the maximum lateral deformation is approximately(0.15%~0.30%) H; (2) The curve of vertical column displacement is gentle, the value is approximately(-0.04%~0.14%) H; (3) The surface settlement trough behind the retaining wall is type, the influence range is beyond 2.5He,the maximum surface settlement is vm=(0.05%~0.15%) H, the relationship between maximum surface settlement and maximum lateral deformation of retaining structure is approximately vm=(0.33~0.56)hm; (4) The earth pressure values are within the range of the earth pressure envelope by measurement, the value is substantially 1.07He.
Construction in expansion soil layer is often adversely affected by swell-shrink, fissure, over-consolidation characteristics of expansion soil, the mechanics and deformation characteristics of expansion soil deep foundation pit during excavation is studied based on coupled thermo numerical simulation. At first, the expansion force of undisturbed expansion soil is measured by laboratory test, and then a ring knife soil sample is simulated using coupled thermo module of FLAC3D,to derive expansion coefficient under target expansion force, finally mechanics and deformation characteristics of deep foundation pit in excavation process under Above-mentioned expansion coefficient is calculated, taking a Yangzhou expansion soil foundation pit as an example, and comparing with the measured data of the foundation pit. The main research conclusions are as follows:(1) Contour line of retaining structure lateral deformation is shaped like a fish belly, the maximum lateral deformation occurs in a certain range above the excavation face, the maximum lateral deformation is approximately(0.15%~0.30%) H; (2) The curve of vertical column displacement is gentle, the value is approximately(-0.04%~0.14%) H; (3) The surface settlement trough behind the retaining wall is type, the influence range is beyond 2.5He,the maximum surface settlement is vm=(0.05%~0.15%) H, the relationship between maximum surface settlement and maximum lateral deformation of retaining structure is approximately vm=(0.33~0.56)hm; (4) The earth pressure values are within the range of the earth pressure envelope by measurement, the value is substantially 1.07He.
2016, 24(s1): 841-847.
Debris flow is a natural disaster in mountainous areas with great damage, whose hazard assessment has a significant meaning in disaster prevention and reduction. Combining with the applications of support vector machine method in debris flow hazard assessment in the past ten years, this paper focuses on the selection of different evaluation indexes for debris flow, the determination of parameters that influences performance for support vector machine, the influence of unbalanced debris flow data on evaluation results and the generalization of debris flow evaluation model. First of all, introducing the theory of rough set for attribute reduction of debris flow evaluation indexes, then filtering the core indexes which influence the evaluation results of debris flow; secondly, comparing the influences of evaluation results caused by penalty factors and kernel function parameters of support vector machine determined by grid search algorithm, genetic algorithm and particle swarm algorithm respectively; finally, by training and testing the measured data of different evaluation indexes and risk grades for single debris flow ditches, establishing the improved support vector machine model of debris flow hazard assessment, making research on the influence of hazard evaluation results caused by the disequilibrium of debris flow data, and applying the established model in different regions for debris flow hazard assessment to make generalization verification. The results show that the SVM model can be used in the debris flow hazard assessment, but the accuracy of evaluation and the strength of generalization ability are closely related to the selection of evaluation index, the determination of performance parameters for SVM and the equilibrium of debris flow data, only the research of related issues for support vector machine model are strengthened in practical application, can we establish the model of debris flow hazard assessment with better applicability.
Debris flow is a natural disaster in mountainous areas with great damage, whose hazard assessment has a significant meaning in disaster prevention and reduction. Combining with the applications of support vector machine method in debris flow hazard assessment in the past ten years, this paper focuses on the selection of different evaluation indexes for debris flow, the determination of parameters that influences performance for support vector machine, the influence of unbalanced debris flow data on evaluation results and the generalization of debris flow evaluation model. First of all, introducing the theory of rough set for attribute reduction of debris flow evaluation indexes, then filtering the core indexes which influence the evaluation results of debris flow; secondly, comparing the influences of evaluation results caused by penalty factors and kernel function parameters of support vector machine determined by grid search algorithm, genetic algorithm and particle swarm algorithm respectively; finally, by training and testing the measured data of different evaluation indexes and risk grades for single debris flow ditches, establishing the improved support vector machine model of debris flow hazard assessment, making research on the influence of hazard evaluation results caused by the disequilibrium of debris flow data, and applying the established model in different regions for debris flow hazard assessment to make generalization verification. The results show that the SVM model can be used in the debris flow hazard assessment, but the accuracy of evaluation and the strength of generalization ability are closely related to the selection of evaluation index, the determination of performance parameters for SVM and the equilibrium of debris flow data, only the research of related issues for support vector machine model are strengthened in practical application, can we establish the model of debris flow hazard assessment with better applicability.
2016, 24(s1): 848-854.
Water inrush frequently occurs at karst tunnel face because there is no supporting countermeasure over here. In addition, the catastrophe can lead to serious consequences on account of tunnel face which is as the working face of tunnel project. During the process of excavation, safe thickness of surrounding rock mass between tunnel face and front karst structure is very important and determines whether water inrush happens. The affecting factors of safe thickness of surrounding rock mass are analyzed, and quality of rock mass and karst water pressure are regarded as the dominant factors. Three-dimensional finite elements method is utilized to simulate the process of tunnel excavation. As a consequence, the correlations between safe thickness of rock mass and its dominant factors are figured out. Based on non-linear regression method, the forecasting model for safe thickness of rock mass of karst tunnel face is put forward and verified by two typical case studies. A powerful tool is provided for accurately forecasting the safe thickness of rock mass, even preventing the water inrush in karst tunnel.
Water inrush frequently occurs at karst tunnel face because there is no supporting countermeasure over here. In addition, the catastrophe can lead to serious consequences on account of tunnel face which is as the working face of tunnel project. During the process of excavation, safe thickness of surrounding rock mass between tunnel face and front karst structure is very important and determines whether water inrush happens. The affecting factors of safe thickness of surrounding rock mass are analyzed, and quality of rock mass and karst water pressure are regarded as the dominant factors. Three-dimensional finite elements method is utilized to simulate the process of tunnel excavation. As a consequence, the correlations between safe thickness of rock mass and its dominant factors are figured out. Based on non-linear regression method, the forecasting model for safe thickness of rock mass of karst tunnel face is put forward and verified by two typical case studies. A powerful tool is provided for accurately forecasting the safe thickness of rock mass, even preventing the water inrush in karst tunnel.
2016, 24(s1): 855-860.
Study the disintegration characteristics of the soil to guide the project construction. According to the geotechnical engineering specification for soil classification standards, select different graded distribution of soil, sandy silt、clay silt and silty clay, each has two samples to do the disintegration characteristic researchs, Conelusions can be drawn as follows:(1) at the start of the disintegration process, the disintegration speed was fast, small dispersed particles at the surface of the samples fell into the water, this phenomenon of sand powder was obvious. A large amount of soils fell off, the disintegrating speed was very fast. Degree of sand particle size was larger, the porosity and permeability of soil were larger, so the disintegrating speed was faster, the two specimens nearly completely collapsed in 1 h. Clay silt has sandy silt and silty clay, the disintegrating speed is between sandy silt and silty clay. The disintegration time of silty clay samples was longer, disintegrating process was relatively slow, even its couldn't collapse a few days later; (2) the disintegration process was not a regular process, physical properties were related, and in the process of disintegration, samples collapsed in different ways. Mainly started with small powder and fragmental, Started to crack after immersing for a long time, with the increasing of fracture with powder during caving, soils cracked in blocks, bubbles escaped, water was dturbidity.
Study the disintegration characteristics of the soil to guide the project construction. According to the geotechnical engineering specification for soil classification standards, select different graded distribution of soil, sandy silt、clay silt and silty clay, each has two samples to do the disintegration characteristic researchs, Conelusions can be drawn as follows:(1) at the start of the disintegration process, the disintegration speed was fast, small dispersed particles at the surface of the samples fell into the water, this phenomenon of sand powder was obvious. A large amount of soils fell off, the disintegrating speed was very fast. Degree of sand particle size was larger, the porosity and permeability of soil were larger, so the disintegrating speed was faster, the two specimens nearly completely collapsed in 1 h. Clay silt has sandy silt and silty clay, the disintegrating speed is between sandy silt and silty clay. The disintegration time of silty clay samples was longer, disintegrating process was relatively slow, even its couldn't collapse a few days later; (2) the disintegration process was not a regular process, physical properties were related, and in the process of disintegration, samples collapsed in different ways. Mainly started with small powder and fragmental, Started to crack after immersing for a long time, with the increasing of fracture with powder during caving, soils cracked in blocks, bubbles escaped, water was dturbidity.
2016, 24(s1): 861-867.
How to choose a reasonable bridge pile in slope Valley, has important significance for saving the construction cost. In this paper combined with a large highway bridge pile position selection problem, under full analysis of the engineering geological conditions of the bridge site and take the limit equilibrium method, finite element method slope stability analysis method, according to the three conditions, the stability of different design schemes of bridge pile slope are calculated and analyzed. According to the slope stability of different bridge pile analysis results, determine the optimal design of the bridge pile.
How to choose a reasonable bridge pile in slope Valley, has important significance for saving the construction cost. In this paper combined with a large highway bridge pile position selection problem, under full analysis of the engineering geological conditions of the bridge site and take the limit equilibrium method, finite element method slope stability analysis method, according to the three conditions, the stability of different design schemes of bridge pile slope are calculated and analyzed. According to the slope stability of different bridge pile analysis results, determine the optimal design of the bridge pile.
2016, 24(s1): 868-873.
The rock strength involves the interaction and inter-coupling of many influencing factors. The conventional methodis unable to evaluate the interaction relationship among the influencing factorsaccurately. Therefore according to previous scholars' achievements and practical experience, the essay introducesthe interactive matrix of Rock Engineering System(RES) theory, and applies the increscent coefficient ofhyperbolic tangent function asthe BP network coding way of activation function. The thesis also presents the predicted model ofinteractive matrix of BP network of rock strength based on RES and involves network training. The final result shows that applying theanalytical thought of REstheoretical system on the basis of the construction of interactive matrix and with the improved BP networknot only predict the rock strengthquickly, but also improve the prediction accuracy. This research not only provides a new idea for rock strength prediction, but also provides a new way forrock mass engineering evaluation.
The rock strength involves the interaction and inter-coupling of many influencing factors. The conventional methodis unable to evaluate the interaction relationship among the influencing factorsaccurately. Therefore according to previous scholars' achievements and practical experience, the essay introducesthe interactive matrix of Rock Engineering System(RES) theory, and applies the increscent coefficient ofhyperbolic tangent function asthe BP network coding way of activation function. The thesis also presents the predicted model ofinteractive matrix of BP network of rock strength based on RES and involves network training. The final result shows that applying theanalytical thought of REstheoretical system on the basis of the construction of interactive matrix and with the improved BP networknot only predict the rock strengthquickly, but also improve the prediction accuracy. This research not only provides a new idea for rock strength prediction, but also provides a new way forrock mass engineering evaluation.
2016, 24(s1): 874-880.
QinLing tunnel of the water diversion project from Han river to Wei river is a key water diversion project in Shaanxi province. Passing through the Qinling Mountain, complex geological structures, deeply buried, large in situ stress, and variable geological conditions are encountered. Geological information, design data, lab testing data and related literature are reviewed in this paper. Data on occurrence of rock burst in Qinling tunnel are recorded systematically; the characteristics of rock burst in the area are analyzed carefully. Engineering analogy method, theoretical analysis and FLAC3D numerical simulation method were applied in section K20+500 and K27+740 with depth 1170m and 750m respectively, the corresponding rock type is quartz schist and granite, drill and blasting method and TBM construction methods. Two section forms, horseshoe section and circular section were analyzed. With the increase of buried depth, the probability of rockburst increased, as well as the magnitude of rockburst. Stress concentration area mainly occurs in tunnel vault and bottom of arch. Secondary micro cracks in rock mass are roughly generated along tunnel tangential direction, when tangential stress exceeds dilation threshold stress. Prevention measures of rockburst and parameter selection for drilling and blasting method and TBM are proposed in the paper.
QinLing tunnel of the water diversion project from Han river to Wei river is a key water diversion project in Shaanxi province. Passing through the Qinling Mountain, complex geological structures, deeply buried, large in situ stress, and variable geological conditions are encountered. Geological information, design data, lab testing data and related literature are reviewed in this paper. Data on occurrence of rock burst in Qinling tunnel are recorded systematically; the characteristics of rock burst in the area are analyzed carefully. Engineering analogy method, theoretical analysis and FLAC3D numerical simulation method were applied in section K20+500 and K27+740 with depth 1170m and 750m respectively, the corresponding rock type is quartz schist and granite, drill and blasting method and TBM construction methods. Two section forms, horseshoe section and circular section were analyzed. With the increase of buried depth, the probability of rockburst increased, as well as the magnitude of rockburst. Stress concentration area mainly occurs in tunnel vault and bottom of arch. Secondary micro cracks in rock mass are roughly generated along tunnel tangential direction, when tangential stress exceeds dilation threshold stress. Prevention measures of rockburst and parameter selection for drilling and blasting method and TBM are proposed in the paper.
2016, 24(s1): 881-888.
In order to research the conditions of full section excavation incomplicatedgeological conditions, choose the Ping-an tunnel of Chengdu-Lanzhou Railway as case study, based on the construction site investigation, establishment the fast evaluation system of rock physics mechanics parameters. Combine with the shear strength reduction and fast lagrangian methods, make a final judgement on suitability of full section excavation and prove the result. Theresearchshows: based on rockstrength parameter fast test, structure surface strength parameter fast test, structure surface rest angle test and GSI rock mass strength parameter test, the test results with the characteristics of fast, accurate and reliable; Under the premise of use the full section excavation, the safety coefficient is greater than the reference safety coefficient of surrounding rock in the case of grade IV rock, it indicates that the surrounding rock can undertake the stability requirements in full section excavation, the result of numerical analysis and field monitoring have strong consistency; Through the tunnel single cycle progress excavation optimization calculation, Ping-an tunnel single cycle excavate progress should be controlled in the range of 2.5m; Similar to the four typical tunnel surface rock mechanical parameters in that Ping-an tunnel of full face excavation is completely feasible.
In order to research the conditions of full section excavation incomplicatedgeological conditions, choose the Ping-an tunnel of Chengdu-Lanzhou Railway as case study, based on the construction site investigation, establishment the fast evaluation system of rock physics mechanics parameters. Combine with the shear strength reduction and fast lagrangian methods, make a final judgement on suitability of full section excavation and prove the result. Theresearchshows: based on rockstrength parameter fast test, structure surface strength parameter fast test, structure surface rest angle test and GSI rock mass strength parameter test, the test results with the characteristics of fast, accurate and reliable; Under the premise of use the full section excavation, the safety coefficient is greater than the reference safety coefficient of surrounding rock in the case of grade IV rock, it indicates that the surrounding rock can undertake the stability requirements in full section excavation, the result of numerical analysis and field monitoring have strong consistency; Through the tunnel single cycle progress excavation optimization calculation, Ping-an tunnel single cycle excavate progress should be controlled in the range of 2.5m; Similar to the four typical tunnel surface rock mechanical parameters in that Ping-an tunnel of full face excavation is completely feasible.
2016, 24(s1): 889-895.
To investigate the subway induced long-term settlement of soft soils in Shanghai, a bounding surface constitutive model combined with the theory of elastoplastic dynamic consolidation is employed in this finite element analysis using ABAQUS software. A three dimensional track-tunnel-soil interaction model is established; and two kinds of tunnel layout are covered, that is single tunnel and double-tube parallel tunnel, respectively. The settlement regulations of subway tunnel under single and multiple train loads are studied. On this basis, three empirical calculation methods are applied to estimate the long-term settlement of the subgrade, the amplitude of dynamic stress and settlement caused by moving trainload under three different loading conditions are obtained as well. In addition, the settlement characteristics of single and double tube tunnels are compared, and the numerical solution is also compared with the measured values. The analysis shows that, the calculated result is consistent with the field test result. The subgrade settlement of the double tube tunnel is not merely a linear superstition of two single tube tunnel, amplification existed.
To investigate the subway induced long-term settlement of soft soils in Shanghai, a bounding surface constitutive model combined with the theory of elastoplastic dynamic consolidation is employed in this finite element analysis using ABAQUS software. A three dimensional track-tunnel-soil interaction model is established; and two kinds of tunnel layout are covered, that is single tunnel and double-tube parallel tunnel, respectively. The settlement regulations of subway tunnel under single and multiple train loads are studied. On this basis, three empirical calculation methods are applied to estimate the long-term settlement of the subgrade, the amplitude of dynamic stress and settlement caused by moving trainload under three different loading conditions are obtained as well. In addition, the settlement characteristics of single and double tube tunnels are compared, and the numerical solution is also compared with the measured values. The analysis shows that, the calculated result is consistent with the field test result. The subgrade settlement of the double tube tunnel is not merely a linear superstition of two single tube tunnel, amplification existed.
2016, 24(s1): 896-901.
The assessment of permeability stability is made based on the permeability deformation type of soil. At present, the views are same on the permeability deformation types of crushed gravel and cohesive soil, but different on the permeability deformation type of sandy soil, furthermore, the specific study is insufficient. In order to further study on the sandy soil permeability deformation type, statistical analysis is made on the permeability deformation base on 131 samples of different type sandy soil taken from 12 projects. The results indicate that the permeability deformation types for each sandy soil are both soil flow. And further theoretical analysis also shows the same conclusion.
The assessment of permeability stability is made based on the permeability deformation type of soil. At present, the views are same on the permeability deformation types of crushed gravel and cohesive soil, but different on the permeability deformation type of sandy soil, furthermore, the specific study is insufficient. In order to further study on the sandy soil permeability deformation type, statistical analysis is made on the permeability deformation base on 131 samples of different type sandy soil taken from 12 projects. The results indicate that the permeability deformation types for each sandy soil are both soil flow. And further theoretical analysis also shows the same conclusion.
2016, 24(s1): 902-908.
The structure of a new type of reinforced retaining wall is studied here. It contains the prefabricated panel, the high strength cell and the soil reinforcement. It has the following features: convenient transportation, convenient construction, resistant to sunlight or rain, and long-term chemical stability. It can overcome the uneven settlement of the soil. And it provides enough anti slide forces. So it can be used for rapid disposal of landslide disaster. The structure, the material selection, the structure design and the production technology are introduced in details in this paper. Large scale physical simulation experiments were carried out. Tests show that the new structure greatly improves the bearing capacity of the retaining wall, which is about 45%higher than that without the reinforced material and 25% higher than that of the traditional reinforcement method. The field carrying capacity test was carried out. The soil reinforcing agent is added in two of the tests. The soil reinforcing agent is composed of cement, calcium chloride, sodium silicate mixture by certain proportion. Field tests show that, compared with the traditional retaining wall bearing capacity improved 63.4%.It has a short construction period, and its environmental protection performance is good. It has the anti-sliding ability of slurry retaining wall of the build by laying bricks or stones, less than the concrete retaining wall by about 30%.Its cost is lower than the concrete retaining wall slightly, far higher than that of slurry retaining wall of build by stones of construction cost. The new technology has great application prospects in the emergency disposal of landslide.
The structure of a new type of reinforced retaining wall is studied here. It contains the prefabricated panel, the high strength cell and the soil reinforcement. It has the following features: convenient transportation, convenient construction, resistant to sunlight or rain, and long-term chemical stability. It can overcome the uneven settlement of the soil. And it provides enough anti slide forces. So it can be used for rapid disposal of landslide disaster. The structure, the material selection, the structure design and the production technology are introduced in details in this paper. Large scale physical simulation experiments were carried out. Tests show that the new structure greatly improves the bearing capacity of the retaining wall, which is about 45%higher than that without the reinforced material and 25% higher than that of the traditional reinforcement method. The field carrying capacity test was carried out. The soil reinforcing agent is added in two of the tests. The soil reinforcing agent is composed of cement, calcium chloride, sodium silicate mixture by certain proportion. Field tests show that, compared with the traditional retaining wall bearing capacity improved 63.4%.It has a short construction period, and its environmental protection performance is good. It has the anti-sliding ability of slurry retaining wall of the build by laying bricks or stones, less than the concrete retaining wall by about 30%.Its cost is lower than the concrete retaining wall slightly, far higher than that of slurry retaining wall of build by stones of construction cost. The new technology has great application prospects in the emergency disposal of landslide.
2016, 24(s1): 909-912.
This paper briefly presents the background of West Syntaxis Section of China-Pakistan Economic Corridor, and concluded 4 categories and 17 classes engineering problems, then spatial zoning the 8 divisions with different problems and safety levels.
This paper briefly presents the background of West Syntaxis Section of China-Pakistan Economic Corridor, and concluded 4 categories and 17 classes engineering problems, then spatial zoning the 8 divisions with different problems and safety levels.
2016, 24(s1): 913-917.
Duncan-Chang nonlinear model has been widely used in numerical analysis of stress-strain in engineering. Duncan-Chang model has K、n、Rf、c、 and other material parameters. These parameters of Duncan-Chang model are confirmed through analysis of triaxial test data in the Hangzhou Bay area. In the calculation process, it is found that the discreteness of some parameters is too large, so that the selection of parametersis more difficult, and the application of the model in engineering is also affected, the main reason is that the change of the value of Rf. We put forward a method, it is assumed that the value of Rf is a certain value, and then to obtain other parameters. This data processing method can not only simplify the model calculation, but also can improve the efficiency and accuracy of the model calculation.
Duncan-Chang nonlinear model has been widely used in numerical analysis of stress-strain in engineering. Duncan-Chang model has K、n、Rf、c、 and other material parameters. These parameters of Duncan-Chang model are confirmed through analysis of triaxial test data in the Hangzhou Bay area. In the calculation process, it is found that the discreteness of some parameters is too large, so that the selection of parametersis more difficult, and the application of the model in engineering is also affected, the main reason is that the change of the value of Rf. We put forward a method, it is assumed that the value of Rf is a certain value, and then to obtain other parameters. This data processing method can not only simplify the model calculation, but also can improve the efficiency and accuracy of the model calculation.
2016, 24(s1): 918-926.
A existing building is located on the slope crest. To increase the usable floor areas, the top edge of the slope needed to move outside for 10meters. The refore a retaining wall was demanded to reinforce the slope. According to the project's topographical, geological and surrounding environment conditions, variable cross-section pile-plank Retaining Wall was adopted. To control the displacement of the pile-top, cemented soil was used as backfill soil. The monitor results show that the deformation of the piles and the existing building on slope crest is quite small. The above monitor results prove that the supporting system is safe and reliable.
A existing building is located on the slope crest. To increase the usable floor areas, the top edge of the slope needed to move outside for 10meters. The refore a retaining wall was demanded to reinforce the slope. According to the project's topographical, geological and surrounding environment conditions, variable cross-section pile-plank Retaining Wall was adopted. To control the displacement of the pile-top, cemented soil was used as backfill soil. The monitor results show that the deformation of the piles and the existing building on slope crest is quite small. The above monitor results prove that the supporting system is safe and reliable.
2016, 24(s1): 927-932.
The Guiyang-Kunming, Xiangfan-Chongqing Yichang-Wanzhou and Chengdu-Kunming railway lines in China have suffered a lot of karst geological disaster. Combined with these obout existing engineering, the harm of karst on tunnel engineering is reflected not only in construction, in the post-operation process will also pose a threat. During the construction of tunnel engineering that karst have appeared, landslides is very vulnerable to happen, go with water gushing, burst mud and other phenomena, even collapse will appear, which cause downtime of tunnel construction and casualties and property losses. During post-operation process, the covered karst with a strong concealment and will pose a threat to traffic safety. In a word, the tunnel karst is one of the geological disasters can not be ignored. In the vast section of Guizhou area, which the high-speed railway of Shanghai-Kunming line cross, the karst developed widely. The hidden karst under the tunnels has a strong concealment and will be a threat to the safety of the train. Therefore, it is essential and important to find out the distribution of the hidden karst. This paper mainly talk about the basic principles and how it works about the seismic imaging method, combined with on tunnel, we found many karst cavities and fractured zones, and proved this method is effective and efficient in the complicated geologic condition.
The Guiyang-Kunming, Xiangfan-Chongqing Yichang-Wanzhou and Chengdu-Kunming railway lines in China have suffered a lot of karst geological disaster. Combined with these obout existing engineering, the harm of karst on tunnel engineering is reflected not only in construction, in the post-operation process will also pose a threat. During the construction of tunnel engineering that karst have appeared, landslides is very vulnerable to happen, go with water gushing, burst mud and other phenomena, even collapse will appear, which cause downtime of tunnel construction and casualties and property losses. During post-operation process, the covered karst with a strong concealment and will pose a threat to traffic safety. In a word, the tunnel karst is one of the geological disasters can not be ignored. In the vast section of Guizhou area, which the high-speed railway of Shanghai-Kunming line cross, the karst developed widely. The hidden karst under the tunnels has a strong concealment and will be a threat to the safety of the train. Therefore, it is essential and important to find out the distribution of the hidden karst. This paper mainly talk about the basic principles and how it works about the seismic imaging method, combined with on tunnel, we found many karst cavities and fractured zones, and proved this method is effective and efficient in the complicated geologic condition.
2016, 24(s1): 933-939.
The Hangzhou Bay is located in the north plain area of Zhejiang Province, also the deep-incised valley of Qian Tang river located, and it can be know that the depth and thickness of Holocene Sediments are of special nature.The shallow silty clay in this area is divided into the Holocene transgression in the ③2 layer of Fuyang transgression and the deep silty clay is divided into the Late Pleistocene in the ④2 layer of Hangzhou transgression in the engineering field. Through comparative study, the stratification method does not match the research results of the sedimentary and sedimentary sequences of soft soil in the area. With determination of the stratigraphic deposition time by determining the formation of 14C, and the sedimentary sequence of the of the deep-incised valley of Qian Tang River by some geological scholars, thenit can be concluded that the deep silt clay layer was formed about ten thousand years ago which we called the Fuyang transgression period, and it should belong to the ③2 layer of the Holocene. The particularity of this area should be considered in the specification, the two soft soil layers in Holocene are divided into ③2 layer and ③3 layer.
The Hangzhou Bay is located in the north plain area of Zhejiang Province, also the deep-incised valley of Qian Tang river located, and it can be know that the depth and thickness of Holocene Sediments are of special nature.The shallow silty clay in this area is divided into the Holocene transgression in the ③2 layer of Fuyang transgression and the deep silty clay is divided into the Late Pleistocene in the ④2 layer of Hangzhou transgression in the engineering field. Through comparative study, the stratification method does not match the research results of the sedimentary and sedimentary sequences of soft soil in the area. With determination of the stratigraphic deposition time by determining the formation of 14C, and the sedimentary sequence of the of the deep-incised valley of Qian Tang River by some geological scholars, thenit can be concluded that the deep silt clay layer was formed about ten thousand years ago which we called the Fuyang transgression period, and it should belong to the ③2 layer of the Holocene. The particularity of this area should be considered in the specification, the two soft soil layers in Holocene are divided into ③2 layer and ③3 layer.
2016, 24(s1): 940-946.
The phenomenon of the sliding face cross over the anti-siding pile has often occurred in the actual engineering, but at present its calculation theory is not mature at all, and many problems in the calculation process are dependent on artificial hypothesis. The Chenglongyihao landslide of Sichuan As an example, the author using FLAC3D to simulate the variation of the stress field, displacement, shear strain increment and distribution characteristics of the plastic zone of the landslide in the dynamic deformation, and calculate the stability by using strength reduction method. Besides, the author has also studied the mechanism of the Sliding Face Cross over the Anti-side pile of high slope under rainfall condition, and tried to solve the reasonable position of anti-sliding pile. The results show that:(1) There is a potential slip surface in Chenglong landslide before setting anti-sliding pile. After setting pile, the landeslide generate new shear surface on the top of piles and will cross over the anti-slide pile; (2) the failure of the sliding face cross over the anti-slide pile of high slope was controlled by the position of anti-sliding pile. The increasement of anti-sliding piles height and when the piles were arranged on the position of the shear outlet of the sliding surface, the ability of anti-sliding can be full used, in addition, which can prevent occurrence of the phenomenon of the sliding face cross over the anti-siding pile effectively. The reliability of FLAC3D numerical simulation results is verified by the field monitoring data, which indicates that the method is suitable for the analysis of overtopping, and can be popularized in the field of rock and soil research.
The phenomenon of the sliding face cross over the anti-siding pile has often occurred in the actual engineering, but at present its calculation theory is not mature at all, and many problems in the calculation process are dependent on artificial hypothesis. The Chenglongyihao landslide of Sichuan As an example, the author using FLAC3D to simulate the variation of the stress field, displacement, shear strain increment and distribution characteristics of the plastic zone of the landslide in the dynamic deformation, and calculate the stability by using strength reduction method. Besides, the author has also studied the mechanism of the Sliding Face Cross over the Anti-side pile of high slope under rainfall condition, and tried to solve the reasonable position of anti-sliding pile. The results show that:(1) There is a potential slip surface in Chenglong landslide before setting anti-sliding pile. After setting pile, the landeslide generate new shear surface on the top of piles and will cross over the anti-slide pile; (2) the failure of the sliding face cross over the anti-slide pile of high slope was controlled by the position of anti-sliding pile. The increasement of anti-sliding piles height and when the piles were arranged on the position of the shear outlet of the sliding surface, the ability of anti-sliding can be full used, in addition, which can prevent occurrence of the phenomenon of the sliding face cross over the anti-siding pile effectively. The reliability of FLAC3D numerical simulation results is verified by the field monitoring data, which indicates that the method is suitable for the analysis of overtopping, and can be popularized in the field of rock and soil research.
2016, 24(s1): 947-951.
in recent years, with the rapid development of the national economy, people are more dependent on oil. The buildings of oil and gas pipeline are increasing year by year, huge pipeline engineering across themountain torrent areasinevitably, the bank slop landslide on both sides cause hazard to the shallow buried laying pipelineeasily. This paper takes a pipeline crossing bank slop as example in eastern Sichuan, analysis thehazard of bankslop landslide to the crossing oil pipeline, and put forwardprevention and control measures for such bank slop landslide hazard.
in recent years, with the rapid development of the national economy, people are more dependent on oil. The buildings of oil and gas pipeline are increasing year by year, huge pipeline engineering across themountain torrent areasinevitably, the bank slop landslide on both sides cause hazard to the shallow buried laying pipelineeasily. This paper takes a pipeline crossing bank slop as example in eastern Sichuan, analysis thehazard of bankslop landslide to the crossing oil pipeline, and put forwardprevention and control measures for such bank slop landslide hazard.
2016, 24(s1): 952-957.
The three-dimensional numerical simulation combined with strength reduction was used to study the face stability of shield tunnel under seepage condition. According to the non-convergence condition in numerical simulation, the safety factors in active and passive deformation modes were obtained. The relationship between the safety factor and the support pressure ratio were obtained by summarizing the numerical results. Safety factor shows a maximum value, which correspond s the optimal support pressure. The optimal support pressure without seepage equals to the lateral earth pressure at rest, and the optimal support pressure under seepage condition is higher than the lateral earth pressure at rest. The limit support pressures of tunnel face under active and passive failure condition with seepage are higher than those without seepage.
The three-dimensional numerical simulation combined with strength reduction was used to study the face stability of shield tunnel under seepage condition. According to the non-convergence condition in numerical simulation, the safety factors in active and passive deformation modes were obtained. The relationship between the safety factor and the support pressure ratio were obtained by summarizing the numerical results. Safety factor shows a maximum value, which correspond s the optimal support pressure. The optimal support pressure without seepage equals to the lateral earth pressure at rest, and the optimal support pressure under seepage condition is higher than the lateral earth pressure at rest. The limit support pressures of tunnel face under active and passive failure condition with seepage are higher than those without seepage.
2016, 24(s1): 958-969.
Rapid long run-out landslide is a sort of geo-hazard with catastrophic property, and the formational mechanism and the motive process of which are rather complex. Therefore, it has always been a sticky task in the field of landslid eresearching. In this regard, this paper takes an overall review on the achievements obtained in the last few decades upon the study of rapid long run-out landslide, including the mechanisms of it, the relative tests methods, and the numerical methods applying in simulation, respectively. The numerical simulation methods for rapid long run-out landslide totally fall into three categories based on landslide character and medium, including Discrete Medium Models, Continuum Medium Models, and Coupled Models, respectively. Among these models, typical Discrete Medium Models are based on Discrete Element Method(DEM),Discontinuous Deformation Analysis(DDA), and Numerical Manifold Method(NMM); while frequently used Continuum Medium Models are based on methods developed form the Hydrodynamics, such as Finite Difference Method(FDM),Finite Volume Method(FVM),Smoothed Particle Hydrodynamics(SPH),Arbitrary Lagrangian-Eulerian Method(ALEM),Cellular Automaton(CA),Lattice Boltzmann Method(LBM), and so on. In spite of the genres of numerical methods is various, each model has their own characteristics and applications. Generally speaking, Discrete Medium Models is suitable for the simulation of rockslides or rock avalanches, and Continuum Medium Models is suitable for the simulation of flow-like landslides. However, as rapid long run-out landslide is a phenomenon encompassing many complex motive characters, which cannot be reflected by simple block medium or fluid medium, therefore both Continuum Medium Models and Discrete Medium Models has their own limits in delineating the motive process of rapid long run-out landslide. To get rid of this dilemma, many scholars have developed variousCoupled Models with amore widely scope of application, which are combined by Continuum Medium Models and Discrete Medium Models, and it turn out to be aneffective approach and thus has gradually become a developmental tendency. In addition, the fact is widely acknowledged that the calculated quantity for rapid long run-out landslide in numerical simulation is astronomical, and it usually turns out to be time-consuming and difficult. It suggests that to develop and employ computing technology like GPU(Graphics Processing Unit) or other kind of parallel computation methods seems to be a good optionforthe solution of this problem. Presently, numerical methods like NNM,ALEM,CA, and FVM are still in the primary stage of their application in the simulation of rapid long run-out landslide, but these methods are very valuable in both theoretical and practical point of view. Therefore, this paper points out that duly effort should be distributed to the development and application of these methods. Still, many challenges remain unsolved in this field, like dynamic entrainment problems(the phenomenon that material on the path of moving takes away by the landslide) and air-blast caused by this kind of landslides, and the interaction between the sliding mass and the infrastructures. These aspects are still the weaknesses in the research of rapid long run-out landslide, and the tests and the numerical simulation methods in these aspects are still undeveloped, which need to be emphasized in the future.
Rapid long run-out landslide is a sort of geo-hazard with catastrophic property, and the formational mechanism and the motive process of which are rather complex. Therefore, it has always been a sticky task in the field of landslid eresearching. In this regard, this paper takes an overall review on the achievements obtained in the last few decades upon the study of rapid long run-out landslide, including the mechanisms of it, the relative tests methods, and the numerical methods applying in simulation, respectively. The numerical simulation methods for rapid long run-out landslide totally fall into three categories based on landslide character and medium, including Discrete Medium Models, Continuum Medium Models, and Coupled Models, respectively. Among these models, typical Discrete Medium Models are based on Discrete Element Method(DEM),Discontinuous Deformation Analysis(DDA), and Numerical Manifold Method(NMM); while frequently used Continuum Medium Models are based on methods developed form the Hydrodynamics, such as Finite Difference Method(FDM),Finite Volume Method(FVM),Smoothed Particle Hydrodynamics(SPH),Arbitrary Lagrangian-Eulerian Method(ALEM),Cellular Automaton(CA),Lattice Boltzmann Method(LBM), and so on. In spite of the genres of numerical methods is various, each model has their own characteristics and applications. Generally speaking, Discrete Medium Models is suitable for the simulation of rockslides or rock avalanches, and Continuum Medium Models is suitable for the simulation of flow-like landslides. However, as rapid long run-out landslide is a phenomenon encompassing many complex motive characters, which cannot be reflected by simple block medium or fluid medium, therefore both Continuum Medium Models and Discrete Medium Models has their own limits in delineating the motive process of rapid long run-out landslide. To get rid of this dilemma, many scholars have developed variousCoupled Models with amore widely scope of application, which are combined by Continuum Medium Models and Discrete Medium Models, and it turn out to be aneffective approach and thus has gradually become a developmental tendency. In addition, the fact is widely acknowledged that the calculated quantity for rapid long run-out landslide in numerical simulation is astronomical, and it usually turns out to be time-consuming and difficult. It suggests that to develop and employ computing technology like GPU(Graphics Processing Unit) or other kind of parallel computation methods seems to be a good optionforthe solution of this problem. Presently, numerical methods like NNM,ALEM,CA, and FVM are still in the primary stage of their application in the simulation of rapid long run-out landslide, but these methods are very valuable in both theoretical and practical point of view. Therefore, this paper points out that duly effort should be distributed to the development and application of these methods. Still, many challenges remain unsolved in this field, like dynamic entrainment problems(the phenomenon that material on the path of moving takes away by the landslide) and air-blast caused by this kind of landslides, and the interaction between the sliding mass and the infrastructures. These aspects are still the weaknesses in the research of rapid long run-out landslide, and the tests and the numerical simulation methods in these aspects are still undeveloped, which need to be emphasized in the future.
2016, 24(s1): 970-976.
Based on the vertical slice method, the debris flow is divided into different parts along the sliding direction. And combined with imbalanced thrust force method, the force between the initial article, initial acceleration and the initial velocity of debris flow is calculated. In the process of movement, the depth of entrainment scraping of debris flowis calculated using Voellmy model and Mohr coulomb criterion. And when the spring-block model is applied, the velocity of each sliding block is obtained at different time. Through constant iterative method, the debris flow breaks down when the velocity of each sliding block reach to zero. Therefore, the distance and depth of entrainment are calculated. In order to verify the correctness and practicability of the model, the comparison between calculation result of this article and experiment result of physical modeling test for entrainment effect of debris flow is conducted.
Based on the vertical slice method, the debris flow is divided into different parts along the sliding direction. And combined with imbalanced thrust force method, the force between the initial article, initial acceleration and the initial velocity of debris flow is calculated. In the process of movement, the depth of entrainment scraping of debris flowis calculated using Voellmy model and Mohr coulomb criterion. And when the spring-block model is applied, the velocity of each sliding block is obtained at different time. Through constant iterative method, the debris flow breaks down when the velocity of each sliding block reach to zero. Therefore, the distance and depth of entrainment are calculated. In order to verify the correctness and practicability of the model, the comparison between calculation result of this article and experiment result of physical modeling test for entrainment effect of debris flow is conducted.
2016, 24(s1): 977-982.
Longchang-Huangtong railway from Xuyong to Bijie is located in the transition zone between the sichuan basin and the yunnan-guizhou plateau, and is located in the slope area of the yunnan-guizhou plateau. Based on the detailed investigation of geological disasters along the railway, this paper summarizes the types of geological disasters along the railway. There are four major disasters: collapse, landslides, debris flow and potential unstable slopes, the disasters are mainly small scale. On this basis, the developing characters of disasters and distributing rules are studied. The results show that the geological disasters along the railway have significant spatiality and timeliness. The disasters are mainly occur in June to August and controlled by vegetation obviously. The disasters mostly located along the valley and in the area where human activities are frequent. The study is of great significance to the prevention and control of geological disasters along the railway.
Longchang-Huangtong railway from Xuyong to Bijie is located in the transition zone between the sichuan basin and the yunnan-guizhou plateau, and is located in the slope area of the yunnan-guizhou plateau. Based on the detailed investigation of geological disasters along the railway, this paper summarizes the types of geological disasters along the railway. There are four major disasters: collapse, landslides, debris flow and potential unstable slopes, the disasters are mainly small scale. On this basis, the developing characters of disasters and distributing rules are studied. The results show that the geological disasters along the railway have significant spatiality and timeliness. The disasters are mainly occur in June to August and controlled by vegetation obviously. The disasters mostly located along the valley and in the area where human activities are frequent. The study is of great significance to the prevention and control of geological disasters along the railway.
2016, 24(s1): 983-989.
Taking the round tunnel and square tunnel as an example, the stress and deformation of the surrounding rock in deep-buried tunnel at different lateral pressure coefficient are simulated by FLAC3D.The research showed that the stress and deformation are relationship with the side pressure coefficient. When 1,the maximum of major principal stress and shear strain increment of the surrounding rock are located in the left and right sides of the tunnel, the maximum of displacements are located in the top of the tunnel, meanwhile, the distribution of the shear strain increment is approximately like an oval with it's longer axis are parallel to the Z-axis; When 1,the maximum of major principal stress and shear strain increment of the surrounding rock are located in the top and bottom of the tunnel, the maximum of displacements are located in the left and right sides of the tunnel, the distribution of the shear strain increment is approximately like an oval with it's longer axis are parallel to the X-axis. Furthermore, the variation law of major principal stress, shear stress, displacements and shear strain increment of the surrounding rock at different lateral pressure coefficient were analyzes and obtained. The research results can be helpful to the study on the relationship between horizontal stress and cavern excavation; also, it can be useful on the selection of cross sectional shape of tunnel.
Taking the round tunnel and square tunnel as an example, the stress and deformation of the surrounding rock in deep-buried tunnel at different lateral pressure coefficient are simulated by FLAC3D.The research showed that the stress and deformation are relationship with the side pressure coefficient. When 1,the maximum of major principal stress and shear strain increment of the surrounding rock are located in the left and right sides of the tunnel, the maximum of displacements are located in the top of the tunnel, meanwhile, the distribution of the shear strain increment is approximately like an oval with it's longer axis are parallel to the Z-axis; When 1,the maximum of major principal stress and shear strain increment of the surrounding rock are located in the top and bottom of the tunnel, the maximum of displacements are located in the left and right sides of the tunnel, the distribution of the shear strain increment is approximately like an oval with it's longer axis are parallel to the X-axis. Furthermore, the variation law of major principal stress, shear stress, displacements and shear strain increment of the surrounding rock at different lateral pressure coefficient were analyzes and obtained. The research results can be helpful to the study on the relationship between horizontal stress and cavern excavation; also, it can be useful on the selection of cross sectional shape of tunnel.
2016, 24(s1): 990-995.
Ecologically fragile area of northern Shaanxi has coal resources with large mining thicknesses and shallow burial depths, so surface ecological environment is more sensitive and dramatic impact caused by underground mining, and it can easily lead to serious environmental engineering geological problems. Hongliulin was taken as a case study, and considered the main conditioning factors impacts on water resourcesand their quantitative indicators caused by coal mining, environmental engineering geological pattern of water contain with coal mining was mapped for the study area. Based on characteristic analysis of environmental engineering geology pattern types, we discussed the impact factors of environmental engineering geological pattern, and selected the thickness of seam, the thickness of laterite, the thickness of loess, the thickness of cover rock, and the spacing between seam and phreatic water, as the key impact factors of environmental engineering geological model. Using artificial neural network, evaluation model of environmental engineering geological patternin Hongliulin mine filed in GIS platform was built. And the environmental engineering geological pattern in the study area was zoned. The results show that the study area has four kinds of environmental engineering geological patternnamely, the environment-friendly, environment gradual recovery, environment gradual deterioration, and the environmental hazardpatterntype.
Ecologically fragile area of northern Shaanxi has coal resources with large mining thicknesses and shallow burial depths, so surface ecological environment is more sensitive and dramatic impact caused by underground mining, and it can easily lead to serious environmental engineering geological problems. Hongliulin was taken as a case study, and considered the main conditioning factors impacts on water resourcesand their quantitative indicators caused by coal mining, environmental engineering geological pattern of water contain with coal mining was mapped for the study area. Based on characteristic analysis of environmental engineering geology pattern types, we discussed the impact factors of environmental engineering geological pattern, and selected the thickness of seam, the thickness of laterite, the thickness of loess, the thickness of cover rock, and the spacing between seam and phreatic water, as the key impact factors of environmental engineering geological model. Using artificial neural network, evaluation model of environmental engineering geological patternin Hongliulin mine filed in GIS platform was built. And the environmental engineering geological pattern in the study area was zoned. The results show that the study area has four kinds of environmental engineering geological patternnamely, the environment-friendly, environment gradual recovery, environment gradual deterioration, and the environmental hazardpatterntype.
2016, 24(s1): 996-1002.
Ganhaizi landslide is a large-scale landslide nearest to Xiluodu dam site in Reservoir zone. And with the water level fluctuation a certain deformation and partial collapse occurred in this landslide body. Because of its big volume and the distance to dam site less than 14km, disastrous consequences will be result in the event of large-scale instability. In this paper based on the systematic analyses about the macro deformation signs and the deformation monitoring data during the operation period, the dynamic response rules of Ganhaizi to reservoir water level fluctuation were studied in detail, including the slope deformation trend, failure mode, potential failure range and influence degree. Some technical supports for project operation management, disaster prevention and mitigation were provided.
Ganhaizi landslide is a large-scale landslide nearest to Xiluodu dam site in Reservoir zone. And with the water level fluctuation a certain deformation and partial collapse occurred in this landslide body. Because of its big volume and the distance to dam site less than 14km, disastrous consequences will be result in the event of large-scale instability. In this paper based on the systematic analyses about the macro deformation signs and the deformation monitoring data during the operation period, the dynamic response rules of Ganhaizi to reservoir water level fluctuation were studied in detail, including the slope deformation trend, failure mode, potential failure range and influence degree. Some technical supports for project operation management, disaster prevention and mitigation were provided.
2016, 24(s1): 1003-1009.
The Haihe River using Qionghai Lake as the coresurrounds beautiful Xichang City. Due to the limit of the geological environment conditions, there are many geological disastersin the basin. On the basic of high precision geological disastersinvestigationin mapsheet, we found that there are many large-medium landslides which volume is more than 105m3 and often resulted in serious disasters. Basing on case, the paperanalyzesdeveloping characteristics of,summarizes the main form and disaster laws of large-medium landslide in Haihe River Basin. The results show that:(1) Large-medium landslides inHaihe River Basindistributed mainly in Panxi red bed region. The petrographic characters influence failure mode of large-medium landslides inHaihe River Basin.(2) Thefault plane and fault-induced cleavage planes lay a foundation for landslide.it controls slippage of large-medium landslides inHaihe River Basin.(3) Large-medium landslides inHaihe River Basin induced by multiple-factor coupling such as rainfall, flood, earthquake.(4) Affected by human engineering activity, the disaster laws of large-medium landslide in Haihe River Basinis that direct damage is little and indirect effect is great, chain effect is marked.
The Haihe River using Qionghai Lake as the coresurrounds beautiful Xichang City. Due to the limit of the geological environment conditions, there are many geological disastersin the basin. On the basic of high precision geological disastersinvestigationin mapsheet, we found that there are many large-medium landslides which volume is more than 105m3 and often resulted in serious disasters. Basing on case, the paperanalyzesdeveloping characteristics of,summarizes the main form and disaster laws of large-medium landslide in Haihe River Basin. The results show that:(1) Large-medium landslides inHaihe River Basindistributed mainly in Panxi red bed region. The petrographic characters influence failure mode of large-medium landslides inHaihe River Basin.(2) Thefault plane and fault-induced cleavage planes lay a foundation for landslide.it controls slippage of large-medium landslides inHaihe River Basin.(3) Large-medium landslides inHaihe River Basin induced by multiple-factor coupling such as rainfall, flood, earthquake.(4) Affected by human engineering activity, the disaster laws of large-medium landslide in Haihe River Basinis that direct damage is little and indirect effect is great, chain effect is marked.
2016, 24(s1): 1010-1018.
With the rapid infrastructure development in China, there are more and more high and steep man-made slopes, so we have higher requirements to develop for accurate and real-time slope stability analysis methods. In recent years, slope stability analysis method based on reliability theory has been greatly developed. This paper briefly reviews the development of slope reliability analysis theory, and summarizes the important research advances and latest achievements in this aspect. The features of several commonly used methods are described and compared in detail. On this basis, some comments and suggestions are given to the research weakness and future development trends in slope reliability analysis theory.
With the rapid infrastructure development in China, there are more and more high and steep man-made slopes, so we have higher requirements to develop for accurate and real-time slope stability analysis methods. In recent years, slope stability analysis method based on reliability theory has been greatly developed. This paper briefly reviews the development of slope reliability analysis theory, and summarizes the important research advances and latest achievements in this aspect. The features of several commonly used methods are described and compared in detail. On this basis, some comments and suggestions are given to the research weakness and future development trends in slope reliability analysis theory.
2016, 24(s1): 1019-1026.
Casing failure is a common geological disaster in the process of oil and gas exploration. Most previous studies in this field mainly focused on vertical casing damage of conventional oil and gas. However, because of the angle's difference between two casings and steep fault and the creep strength's distinction between two reservoir media, the horizontal casing failures in shale gas have different mechanism from the vertical in conventional oil and gas. For this reason, this paper studied the damage of horizontal casing which through fault in shale gas. Through mechanical analysis and numerical simulation of casing deformation, it was found that creep force of the surrounding rocks could cause necking before fault slip. And it performed differential deformation near the fault because of the lithological difference between hanging wall and footwall. With the activation of fault caused by hydrofracking and reservoir exploitation, the shear force from fault deformation played a major role in casing bending or dislocation problems. The result of numerical simulation is consistent well with the mechanical analysis which indicates that horizontal casing failure is the combined action of compressional force from rock creep and shear force from fault slip.
Casing failure is a common geological disaster in the process of oil and gas exploration. Most previous studies in this field mainly focused on vertical casing damage of conventional oil and gas. However, because of the angle's difference between two casings and steep fault and the creep strength's distinction between two reservoir media, the horizontal casing failures in shale gas have different mechanism from the vertical in conventional oil and gas. For this reason, this paper studied the damage of horizontal casing which through fault in shale gas. Through mechanical analysis and numerical simulation of casing deformation, it was found that creep force of the surrounding rocks could cause necking before fault slip. And it performed differential deformation near the fault because of the lithological difference between hanging wall and footwall. With the activation of fault caused by hydrofracking and reservoir exploitation, the shear force from fault deformation played a major role in casing bending or dislocation problems. The result of numerical simulation is consistent well with the mechanical analysis which indicates that horizontal casing failure is the combined action of compressional force from rock creep and shear force from fault slip.
2016, 24(s1): 1027-1033.
The dynamic triaxial test is carried out on the saturated intact loess sample with dynamic triaxial apparatus on the drainage condition. And analyze the characteristics of the deformation, pore pressure, hysteresis loop and microstructure of the sample. The analysis results shows: the deformation stages on the drainage condition is obviously different from the three stages on undrainage condition, the pore pressure is on a stable level during the experiment, the hysteresis loops are similar in the vibration times of N=1,N=50 and N=100,but the similarity is a bit low compared with the traditional oval-shaped hysteresis loops. The microstructure analysis tests were obtained with SEM and Mercury porosimetry analyzer. The analysis result shows that the micro-structure of the soil samples, the contact between the particles and the size of the pores all change significantly. The changes of soil particles before and after the dynamic triaxial test are obtained by analyzing the results of microstructure tests. The main conclusions about the microstructure are as followings: the relative statuses between the soil particles change from a relatively loose state into a relatively dense state, the contact relationship from scaffold contact become to mosaic contact and the contact area increase after the test, the percentage of various pore diameter change greatly and the most obvious changes are the big pore diameter. The number of large pores obviously decreases and small and micro pores increases in the number.
The dynamic triaxial test is carried out on the saturated intact loess sample with dynamic triaxial apparatus on the drainage condition. And analyze the characteristics of the deformation, pore pressure, hysteresis loop and microstructure of the sample. The analysis results shows: the deformation stages on the drainage condition is obviously different from the three stages on undrainage condition, the pore pressure is on a stable level during the experiment, the hysteresis loops are similar in the vibration times of N=1,N=50 and N=100,but the similarity is a bit low compared with the traditional oval-shaped hysteresis loops. The microstructure analysis tests were obtained with SEM and Mercury porosimetry analyzer. The analysis result shows that the micro-structure of the soil samples, the contact between the particles and the size of the pores all change significantly. The changes of soil particles before and after the dynamic triaxial test are obtained by analyzing the results of microstructure tests. The main conclusions about the microstructure are as followings: the relative statuses between the soil particles change from a relatively loose state into a relatively dense state, the contact relationship from scaffold contact become to mosaic contact and the contact area increase after the test, the percentage of various pore diameter change greatly and the most obvious changes are the big pore diameter. The number of large pores obviously decreases and small and micro pores increases in the number.
2016, 24(s1): 1034-1039.
In the engineering, the existence of the weak interlayer has an important influence on the slope stability. Weak interlayer is a vital reason of instability and failure of slope. Since the orthogonal design method has great advantages in the sensitivity analysis of slope stability, the method is applied to the analysis of slope stability with weak interlayer. The cohesion, internal friction angle and unit weight of quartz sand gravel rock, the cohesion, internal friction angle and unit weight of the weak interlayer(Mica-quartzose schist) as well as earthquake acceleration were selected to carry out the stability analysis of the slope with weak interlayer based on the orthogonal design method. The influence of each parameter on the slope stability coefficient was analyzed by range method and variance method, and the results of the two calculation methods and the advantages and disadvantages of the two methods were compared and analyzed. It is found that, combined with the actual situation as well as the results of these two calculation methods, the influence of parameters on the stability of the hydropower station slope with weak interlayer is as follows: earthquake acceleration internal friction angle of the weak interlayer cohesion of the weak interlayer cohesion of quartz sand gravel rock. Three other parameters had litter effect on the stability of the slope, it is unnecessary to rank these three parameters. Compared with the variance method, although the range method is more simple and rapid, the calculation results are too coarse. Therefore, it is recommended to use the variance method to analyze the results of the orthogonal test.
In the engineering, the existence of the weak interlayer has an important influence on the slope stability. Weak interlayer is a vital reason of instability and failure of slope. Since the orthogonal design method has great advantages in the sensitivity analysis of slope stability, the method is applied to the analysis of slope stability with weak interlayer. The cohesion, internal friction angle and unit weight of quartz sand gravel rock, the cohesion, internal friction angle and unit weight of the weak interlayer(Mica-quartzose schist) as well as earthquake acceleration were selected to carry out the stability analysis of the slope with weak interlayer based on the orthogonal design method. The influence of each parameter on the slope stability coefficient was analyzed by range method and variance method, and the results of the two calculation methods and the advantages and disadvantages of the two methods were compared and analyzed. It is found that, combined with the actual situation as well as the results of these two calculation methods, the influence of parameters on the stability of the hydropower station slope with weak interlayer is as follows: earthquake acceleration internal friction angle of the weak interlayer cohesion of the weak interlayer cohesion of quartz sand gravel rock. Three other parameters had litter effect on the stability of the slope, it is unnecessary to rank these three parameters. Compared with the variance method, although the range method is more simple and rapid, the calculation results are too coarse. Therefore, it is recommended to use the variance method to analyze the results of the orthogonal test.
2016, 24(s1): 1040-1046.
In order to analyze the deformation and internal force conditions of circular section stabilizing piles under different distribution patterns of landslide thrusts, the CPSP program developed by Lei Guoping based on pile-soil separation model was used to calculate the circular section stabilizing piles embedded in rock, it is easy to obtained the deflection and internal force of piles under different conditions, comparing the analytic results calculated by CPSP program with numerical simulation results calculated by ABAQUS software, it can be validated that the CPSP program is applicable for circular cross section stabilizing piles based on pile-rock separation model. By inputting different parameters through CPSP program, the deformation and internal force distribution results of circular cross section stabilizing piles in different conditions can be obtained, and some relationships about the maximum displacements, the maximum bending moment and the maximum shear force have been also summed up. In addition, based on the calculation result of CPSP and taking the continuous condition of stabilizing pile in the slip surface into consideration, the deflection curve of loading section of stabilizing pile is obtained, and deflection and internal fore results of stabilizing piles under different distribution patterns of landslides thrust is calculated and comparisons is made between these result, and influences of distribution patterns of landslides thrust on the deflection and inner force of piles are analyzed.
In order to analyze the deformation and internal force conditions of circular section stabilizing piles under different distribution patterns of landslide thrusts, the CPSP program developed by Lei Guoping based on pile-soil separation model was used to calculate the circular section stabilizing piles embedded in rock, it is easy to obtained the deflection and internal force of piles under different conditions, comparing the analytic results calculated by CPSP program with numerical simulation results calculated by ABAQUS software, it can be validated that the CPSP program is applicable for circular cross section stabilizing piles based on pile-rock separation model. By inputting different parameters through CPSP program, the deformation and internal force distribution results of circular cross section stabilizing piles in different conditions can be obtained, and some relationships about the maximum displacements, the maximum bending moment and the maximum shear force have been also summed up. In addition, based on the calculation result of CPSP and taking the continuous condition of stabilizing pile in the slip surface into consideration, the deflection curve of loading section of stabilizing pile is obtained, and deflection and internal fore results of stabilizing piles under different distribution patterns of landslides thrust is calculated and comparisons is made between these result, and influences of distribution patterns of landslides thrust on the deflection and inner force of piles are analyzed.
2016, 24(s1): 1047-1053.
Rock falls are a common geologic hazard of rock slopes in mountainous regions. It normally causes significant hazards to human lives and lifeline facilities. Rock fragmentation is frequently observed in rock fall events. However, rock fragmentation upon impact is usually not accounted for in the design of defense structure. The trajectories of rock fragments are much different from that of intact block(used to design barrier) and are more difficult to predict with an increase in the risk of causing damage to properties and lives. Therefore, the mechanism of rock fall impact breakage plays an important role in the prevention of rock fall hazards. In particular, predicting the size, shape and number of fragments generated under impact is fundamental to design more efficient protection systems. In this paper, the Discrete Element Method(DEM) has been used to simulate the impact process of rock fall, such as the potential rock mass fragmentations induced by the dynamic impact. In these simulations, the spherical rock sample is regarded as an assembly of particles in which the adjacent particles are connected by a breakable bond, and the ground is represented by a rigid plate with a layer of particles fixed on the surface for the purpose of simulating the elastic deformation and friction of the ground. Employing the open source DEM code EsyS-Particle, the general features of rock fall are illustrated in details, regarding the rock block damage patterns(rebound, fragmentation and crush).Meanwhile, this study reveals how the evolutions of the number of broken bonds and the kinetic energy of the model are influenced by the micro-parameters, such as the bond Young's modulus, inter-particle cohesion and friction angle. Based on the numerical results, for sufficiently low ratios of the Young's modulus to cohesion, the rock block does not fracture but rebound. For using medium ratios, the rock block can break into many fragments. For sufficiently high ratios, the rock block can be crushed into very small dispersed grains. Our results indicate that the potential for impact fragmentation tends to reduce with the decreasing ratio of the Young's modulus to cohesion, while the friction angle has a little influence on the impact process.
Rock falls are a common geologic hazard of rock slopes in mountainous regions. It normally causes significant hazards to human lives and lifeline facilities. Rock fragmentation is frequently observed in rock fall events. However, rock fragmentation upon impact is usually not accounted for in the design of defense structure. The trajectories of rock fragments are much different from that of intact block(used to design barrier) and are more difficult to predict with an increase in the risk of causing damage to properties and lives. Therefore, the mechanism of rock fall impact breakage plays an important role in the prevention of rock fall hazards. In particular, predicting the size, shape and number of fragments generated under impact is fundamental to design more efficient protection systems. In this paper, the Discrete Element Method(DEM) has been used to simulate the impact process of rock fall, such as the potential rock mass fragmentations induced by the dynamic impact. In these simulations, the spherical rock sample is regarded as an assembly of particles in which the adjacent particles are connected by a breakable bond, and the ground is represented by a rigid plate with a layer of particles fixed on the surface for the purpose of simulating the elastic deformation and friction of the ground. Employing the open source DEM code EsyS-Particle, the general features of rock fall are illustrated in details, regarding the rock block damage patterns(rebound, fragmentation and crush).Meanwhile, this study reveals how the evolutions of the number of broken bonds and the kinetic energy of the model are influenced by the micro-parameters, such as the bond Young's modulus, inter-particle cohesion and friction angle. Based on the numerical results, for sufficiently low ratios of the Young's modulus to cohesion, the rock block does not fracture but rebound. For using medium ratios, the rock block can break into many fragments. For sufficiently high ratios, the rock block can be crushed into very small dispersed grains. Our results indicate that the potential for impact fragmentation tends to reduce with the decreasing ratio of the Young's modulus to cohesion, while the friction angle has a little influence on the impact process.
2016, 24(s1): 1054-1059.
In order to further study the occurrence conditions and mechanism of the Covered Karst Ground Collapse(CKGC),on the basis of Luo Xiaojie's theory about CKGC,the geological phenomena, geological model, physical model and mathematical expression of the mud-flow type ground collapse are studied. According to the characteristics of the kinematic response of soft soil and the deformation of surrounding soil during collapse, the geological model of mud-flow type karst collapse is established. The soft soil is regarded as high viscosity fluid based on its characteristics of higher water content and liquid limit, lower shear strength, flowablity, and it flows in laminar state in the course of collapse. A generalized physical model of the Mud-flow type ground collapse is proposed, the corresponding mathematical expressions are given according to the law of Newton inner friction and Limit Equilibrium Theory, the basic characteristics of Mud-flow type ground collapse is discussed.it is that Mud-flow type ground collapse will occur at a fixed rate, and the collapse speed is proportional to the square of the diameter of the karst channel, the density and natural moisture content of the soft soil, and is inversely proportional to the viscosity coefficient. the duration of the collapse is proportional to the coefficient of viscosity and thickness of the soft soil, is inversely proportional to the density of soft soil and the square of the diameter of the karst channel.
In order to further study the occurrence conditions and mechanism of the Covered Karst Ground Collapse(CKGC),on the basis of Luo Xiaojie's theory about CKGC,the geological phenomena, geological model, physical model and mathematical expression of the mud-flow type ground collapse are studied. According to the characteristics of the kinematic response of soft soil and the deformation of surrounding soil during collapse, the geological model of mud-flow type karst collapse is established. The soft soil is regarded as high viscosity fluid based on its characteristics of higher water content and liquid limit, lower shear strength, flowablity, and it flows in laminar state in the course of collapse. A generalized physical model of the Mud-flow type ground collapse is proposed, the corresponding mathematical expressions are given according to the law of Newton inner friction and Limit Equilibrium Theory, the basic characteristics of Mud-flow type ground collapse is discussed.it is that Mud-flow type ground collapse will occur at a fixed rate, and the collapse speed is proportional to the square of the diameter of the karst channel, the density and natural moisture content of the soft soil, and is inversely proportional to the viscosity coefficient. the duration of the collapse is proportional to the coefficient of viscosity and thickness of the soft soil, is inversely proportional to the density of soft soil and the square of the diameter of the karst channel.
2016, 24(s1): 1060-1066.
Since 2000,the infrastructure such as traffic, water conservancy and hydropower construction has obtained the accomplishments that have astonished the world in the western region. Based on a large-scale infrastructure construction projects, by about ten years hard work, the author and his colleagues have been systematically studied disasters of large and complex landslide, High slope, and also they have researched the permafrost engineering, the loess and geological problems of tunnel. This paper introduce the main achievements and the new development which were achieved by us, and it is hoped that used for reference for A similar problem.
Since 2000,the infrastructure such as traffic, water conservancy and hydropower construction has obtained the accomplishments that have astonished the world in the western region. Based on a large-scale infrastructure construction projects, by about ten years hard work, the author and his colleagues have been systematically studied disasters of large and complex landslide, High slope, and also they have researched the permafrost engineering, the loess and geological problems of tunnel. This paper introduce the main achievements and the new development which were achieved by us, and it is hoped that used for reference for A similar problem.
2016, 24(s1): 1067-1073.
Research purposes: Debris-flow is generally existed in the world of natural disasters, especially in central and Western China terrain complex area, debris flow every year caused great loss of life and property. Common gravity arresting dam control measures has the characteristics of big construction difficulty, high cost, large-scale governance project is difficult to spread, therefore, easy construction, low cost of new structure need to develop, in recent years, new flexible arresting net structure is considered to be gravity arresting structure effective alternative structures. Based on the model test of debris flow, set the two flexible arresting net and a gravity dam, by arresting structure at the rear part of the impact force and analysis is arresting provenance analysis, draws the following conclusions:(1) the flexible structure of arresting the arresting effects obvious, can effectively the solid substance intercept.(2) the porosity of arresting structure intercepted source particle size sorting, but porosity less than 0.8 of a median particle diameter has little effect, is greater than 0.8,the impact of increased dramatically.(3) flexible arresting structure can effectively relieve Mizoguchi position of impact pressure, the most upstream blocking structures subjected to impact is greater than downstream arresting structure.
Research purposes: Debris-flow is generally existed in the world of natural disasters, especially in central and Western China terrain complex area, debris flow every year caused great loss of life and property. Common gravity arresting dam control measures has the characteristics of big construction difficulty, high cost, large-scale governance project is difficult to spread, therefore, easy construction, low cost of new structure need to develop, in recent years, new flexible arresting net structure is considered to be gravity arresting structure effective alternative structures. Based on the model test of debris flow, set the two flexible arresting net and a gravity dam, by arresting structure at the rear part of the impact force and analysis is arresting provenance analysis, draws the following conclusions:(1) the flexible structure of arresting the arresting effects obvious, can effectively the solid substance intercept.(2) the porosity of arresting structure intercepted source particle size sorting, but porosity less than 0.8 of a median particle diameter has little effect, is greater than 0.8,the impact of increased dramatically.(3) flexible arresting structure can effectively relieve Mizoguchi position of impact pressure, the most upstream blocking structures subjected to impact is greater than downstream arresting structure.
2016, 24(s1): 1074-1081.
Anti-sliding pile is a common engineering method in treatment of geological hazards, which is widely used in rail, road, and water conservancy engineering. And engineer pay more and more attention to the seismic problem of this anti-slide structure, it has already been an important research direction to study how to improve the seismic performance of retaining structures. Currently, it has caught the engineers' attention and achieved good results to improve the seismic performance by adding EPS flexible materials to engineering. Based on this, in order to improve and meet seismic performance request of anti-sliding pile in engineering, EPS material is applied to anti-sliding and a new anti-sliding is designed called EPS pile. By shaking table test, the dynamic response and seismic performance of EPS pile and ordinary pile indoor are researched and compared. Conclusions could be drawn from trail that:(1) the acceleration magnified effect is different with different seismic waves; with more lager EL seismic peak acceleration, the more obvious of acceleration magnified effect; (2) the acceleration magnified effect of ordinary pile is more obvious than of EPS pile under the same peak acceleration of seismic wave.(3) Pile head angle and acceleration magnified effect show that: EPS anti-sliding has better seismic performance; EPS material can clearly improve the passive earth pressure of anti-sliding pile under pole shaking condition and Bi-directional vibration.(4) Besides, it can be found in this experimental that sliding surface cracks to the deep extension and may induce deep sliding with the increase of seismic wave speed.
Anti-sliding pile is a common engineering method in treatment of geological hazards, which is widely used in rail, road, and water conservancy engineering. And engineer pay more and more attention to the seismic problem of this anti-slide structure, it has already been an important research direction to study how to improve the seismic performance of retaining structures. Currently, it has caught the engineers' attention and achieved good results to improve the seismic performance by adding EPS flexible materials to engineering. Based on this, in order to improve and meet seismic performance request of anti-sliding pile in engineering, EPS material is applied to anti-sliding and a new anti-sliding is designed called EPS pile. By shaking table test, the dynamic response and seismic performance of EPS pile and ordinary pile indoor are researched and compared. Conclusions could be drawn from trail that:(1) the acceleration magnified effect is different with different seismic waves; with more lager EL seismic peak acceleration, the more obvious of acceleration magnified effect; (2) the acceleration magnified effect of ordinary pile is more obvious than of EPS pile under the same peak acceleration of seismic wave.(3) Pile head angle and acceleration magnified effect show that: EPS anti-sliding has better seismic performance; EPS material can clearly improve the passive earth pressure of anti-sliding pile under pole shaking condition and Bi-directional vibration.(4) Besides, it can be found in this experimental that sliding surface cracks to the deep extension and may induce deep sliding with the increase of seismic wave speed.
2016, 24(s1): 1082-1092.
The influence factors analysis of the slope stability is the important basis for understanding the deformation failure mechanism, evaluating stability and forecasting deformation trend of the slope. For secondary layered structure slope in the slope engineering, first of all, the main cause mechanism of the secondary layered structure rock mass was briefly analyzed; then the important factors that affect this kind of slope stability were selected according to the characteristics of secondary layered structure slope and the engineering experience, and the quantitative results of influence degree of these factors on theslope deformation and destruction were obtained through the orthogonal test of parameter selection and the numerical simulation software UDEC.The results show that: this type of layered structure is a kind secondary structure within the rock mass near the surface, because of the stress releasefrom three aspects including stress differentiation, unloading rebound with the differencesand dynamic load; all of the primary and secondary ordersof the factors effect on the stability of consequent secondary layered structure slope.were not identical; When the single factor change, the slope stability coefficient, maximum open degree of secondary layer and slope top displacement also showed different characteristics. The study results have important theoretical and practical significance for the excavation design and supporting measures of secondary layered structure slope.
The influence factors analysis of the slope stability is the important basis for understanding the deformation failure mechanism, evaluating stability and forecasting deformation trend of the slope. For secondary layered structure slope in the slope engineering, first of all, the main cause mechanism of the secondary layered structure rock mass was briefly analyzed; then the important factors that affect this kind of slope stability were selected according to the characteristics of secondary layered structure slope and the engineering experience, and the quantitative results of influence degree of these factors on theslope deformation and destruction were obtained through the orthogonal test of parameter selection and the numerical simulation software UDEC.The results show that: this type of layered structure is a kind secondary structure within the rock mass near the surface, because of the stress releasefrom three aspects including stress differentiation, unloading rebound with the differencesand dynamic load; all of the primary and secondary ordersof the factors effect on the stability of consequent secondary layered structure slope.were not identical; When the single factor change, the slope stability coefficient, maximum open degree of secondary layer and slope top displacement also showed different characteristics. The study results have important theoretical and practical significance for the excavation design and supporting measures of secondary layered structure slope.
2016, 24(s1): 1093-1099.
Esheng open-pit mine of limestone in Sichuan province is taken as the study object, on the basis of the mine on engineering geological zoning, stereographic projection is used to analysis the failure modes of working bench slopes, ending stairs slopes, then numerical simulation method is used to analysis the failure modes of ending large slopes, finally the stability of the slopes of each area is evaluated based on the FLAC3D strength reduction method. The results show that: ① Under the control of discontinuities, there are 3 failure modes of working bench slopes and ending stairs slopes: wedge failure, collapse and bedding sliding.② Under the control of stratum, there are 4 failure modes of ending large slopes: bedding sliding, sliding-ripping, creeping-pressure induced ripping and flowing-ripping.③ in this study, for the dip slope, the stability coefficient of the two-dimensional model is larger than that of the three-dimensional model. As for the skew slopes, the result is just the opposite, and the average value of stability coefficient ratio of two dimensional and three dimensional model is 0.83.
Esheng open-pit mine of limestone in Sichuan province is taken as the study object, on the basis of the mine on engineering geological zoning, stereographic projection is used to analysis the failure modes of working bench slopes, ending stairs slopes, then numerical simulation method is used to analysis the failure modes of ending large slopes, finally the stability of the slopes of each area is evaluated based on the FLAC3D strength reduction method. The results show that: ① Under the control of discontinuities, there are 3 failure modes of working bench slopes and ending stairs slopes: wedge failure, collapse and bedding sliding.② Under the control of stratum, there are 4 failure modes of ending large slopes: bedding sliding, sliding-ripping, creeping-pressure induced ripping and flowing-ripping.③ in this study, for the dip slope, the stability coefficient of the two-dimensional model is larger than that of the three-dimensional model. As for the skew slopes, the result is just the opposite, and the average value of stability coefficient ratio of two dimensional and three dimensional model is 0.83.
2016, 24(s1): 1100-1107.
The stability of soil-similar slope is controlled by the strength of soil mass and geological structural planes simultaneously, and its mechanism of landslide and distribution of slide zone are quite different from those of rock slope and homogeneous soil slope. In this study, a numerical analysis method, which is mainly based on the deviatoric stress, was proposed to predict the loosened zone distribution of the soil-similar slope. This method was performed by the FLAC3D software, and the post-processing program for deviatoric stress was written by the FISH language. A cutting slope was chosen for the case verification, and its stability state in both excavation and rainfall condition was calculated. It is shown that the new and original deviatoric stress contours will be characterized by the phenomena of cross, separation, coincidence or gradient mutation, which are especially remarkable near the structural planes. So the potential failure mode and range of loosened zone can be found out according to change of deviatoric stress contours, on the combination with plastic zone, displacement field and construction record. For the slope case in excavation condition, the deviatoric stress decreased at the early elastically unloading state driven by crustal stress; then increased because of the transformation of gravitational potential energy; and decreased again when getting into nonlinear unloading stage of plastic damage. After large deformation and landslide took place, obvious partition between increase and decrease of deviatoric stress would come into being. Correspondingly, the slope in excavation condition was characterized by the unloading rebound, crack propagation and shallow slide in sequential order fundamentally. The completely weathered stratum slid along the interface with the intensely weathered stratum in rainfall condition, and deep landslide with circular slip-surface occurred further in overall saturated state.
The stability of soil-similar slope is controlled by the strength of soil mass and geological structural planes simultaneously, and its mechanism of landslide and distribution of slide zone are quite different from those of rock slope and homogeneous soil slope. In this study, a numerical analysis method, which is mainly based on the deviatoric stress, was proposed to predict the loosened zone distribution of the soil-similar slope. This method was performed by the FLAC3D software, and the post-processing program for deviatoric stress was written by the FISH language. A cutting slope was chosen for the case verification, and its stability state in both excavation and rainfall condition was calculated. It is shown that the new and original deviatoric stress contours will be characterized by the phenomena of cross, separation, coincidence or gradient mutation, which are especially remarkable near the structural planes. So the potential failure mode and range of loosened zone can be found out according to change of deviatoric stress contours, on the combination with plastic zone, displacement field and construction record. For the slope case in excavation condition, the deviatoric stress decreased at the early elastically unloading state driven by crustal stress; then increased because of the transformation of gravitational potential energy; and decreased again when getting into nonlinear unloading stage of plastic damage. After large deformation and landslide took place, obvious partition between increase and decrease of deviatoric stress would come into being. Correspondingly, the slope in excavation condition was characterized by the unloading rebound, crack propagation and shallow slide in sequential order fundamentally. The completely weathered stratum slid along the interface with the intensely weathered stratum in rainfall condition, and deep landslide with circular slip-surface occurred further in overall saturated state.
2016, 24(s1): 1108-1111.
Under complex terrain and formation condition, the use of single foundation treatment measures is often difficult to meet the requirements of building foundation bearing capacity and deformation coordination at the same time. This paper, taking a foundation treatment project of Beijing Changping district as an example, analyzes the selection methods and thoughts of foundation treatment under complicated conditions, introduces the processing method using two or more foundation treatment technology, discusses the advantages, disadvantages and its application in the engineering characteristics of the foundation treatment measures such as CFG pile, ground replacement and foundation weakening. Based on the summary of the engineering monitoring data analysis, this paper draw a conclusion that comprehensive foundation treatment technology in selection of reasonable conditions could give full play to all kinds of treatment measures, it could also effective coordinating and controlling building deformation and saving the project cost.
Under complex terrain and formation condition, the use of single foundation treatment measures is often difficult to meet the requirements of building foundation bearing capacity and deformation coordination at the same time. This paper, taking a foundation treatment project of Beijing Changping district as an example, analyzes the selection methods and thoughts of foundation treatment under complicated conditions, introduces the processing method using two or more foundation treatment technology, discusses the advantages, disadvantages and its application in the engineering characteristics of the foundation treatment measures such as CFG pile, ground replacement and foundation weakening. Based on the summary of the engineering monitoring data analysis, this paper draw a conclusion that comprehensive foundation treatment technology in selection of reasonable conditions could give full play to all kinds of treatment measures, it could also effective coordinating and controlling building deformation and saving the project cost.
2016, 24(s1): 1112-1117.
Frozen rock-soil mixture is a special geotechnical material. Its mechanical behavior varies with temperature and ice content is still poorly understood. Direct shear tests were conducted to investigate the influence of temperature, ice content and normal stress on shear strength of rock-soil mixture. Results indicate that temperature, ice content and normal stress all have significant influence on shear strength of rock-soil mixture. For constant ice content and normal stress, shear strength of rock-soil mixture rises rapidly with temperature when the temperature is higher than-5℃.When temperature drops below -5℃,most free water is frozen and only small amount bond water is left,shear strength only has a slight increase with temperature. The shear strength of rock-soil mixture increases sharply when ice content is low. The shear strength reaches a peak value when the ice content is about 11% by weight. After that point, the shear strength has a slight decrease. Detailed research reveals that the cohesion of rock-soil material increases with ice content until the ice content reaches 11%, and then it tends to level off. But the internal friction angle decreases monotonously with ice content.The shear strength of frozen rock-soil mixture increases with the normal stress increasing. The plasticity of frozen rock-soil mixture increases under high normal stress.
Frozen rock-soil mixture is a special geotechnical material. Its mechanical behavior varies with temperature and ice content is still poorly understood. Direct shear tests were conducted to investigate the influence of temperature, ice content and normal stress on shear strength of rock-soil mixture. Results indicate that temperature, ice content and normal stress all have significant influence on shear strength of rock-soil mixture. For constant ice content and normal stress, shear strength of rock-soil mixture rises rapidly with temperature when the temperature is higher than-5℃.When temperature drops below -5℃,most free water is frozen and only small amount bond water is left,shear strength only has a slight increase with temperature. The shear strength of rock-soil mixture increases sharply when ice content is low. The shear strength reaches a peak value when the ice content is about 11% by weight. After that point, the shear strength has a slight decrease. Detailed research reveals that the cohesion of rock-soil material increases with ice content until the ice content reaches 11%, and then it tends to level off. But the internal friction angle decreases monotonously with ice content.The shear strength of frozen rock-soil mixture increases with the normal stress increasing. The plasticity of frozen rock-soil mixture increases under high normal stress.
2016, 24(s1): 1118-1126.
Bailongjiang Valley is one of the four major geological disaster prone areas.1030 landslides are found by the combination of remote sensing technology and on-the-spot investigation in the research areas. Based on the GIS space analysis method, two statistical indicators, namely landslide number and density, were used to count 8 parameters of formation lithology, slope height, slope direction, slope angle, the fault buffer, the river buffer, the road buffer and the land types. The statistical results of 1030 landslides distributed in 6 counties suggest that, landslide distribution of Bailongjiang valley in Gansu province mainly showed the following characteristics:(1) the landslides mainly distribute in the S and SE slope, the range of 0~20 degree, and mainly distribute in the phyllite, slate, thin limestone rock group and the thick layer of limestone, slate rock group district; (2) the height of 1300~2000m occupies in the largest number of landslide, while landslide density maximum in 600~1300m height; (3) the number and density of the landslide decreases with the increase of fracture, river and road distance; (4) the landslide mainly concentrated in the farming area, followed by the grass area.
Bailongjiang Valley is one of the four major geological disaster prone areas.1030 landslides are found by the combination of remote sensing technology and on-the-spot investigation in the research areas. Based on the GIS space analysis method, two statistical indicators, namely landslide number and density, were used to count 8 parameters of formation lithology, slope height, slope direction, slope angle, the fault buffer, the river buffer, the road buffer and the land types. The statistical results of 1030 landslides distributed in 6 counties suggest that, landslide distribution of Bailongjiang valley in Gansu province mainly showed the following characteristics:(1) the landslides mainly distribute in the S and SE slope, the range of 0~20 degree, and mainly distribute in the phyllite, slate, thin limestone rock group and the thick layer of limestone, slate rock group district; (2) the height of 1300~2000m occupies in the largest number of landslide, while landslide density maximum in 600~1300m height; (3) the number and density of the landslide decreases with the increase of fracture, river and road distance; (4) the landslide mainly concentrated in the farming area, followed by the grass area.
2016, 24(s1): 1127-1132.
Zhongdu landslide was the largest, strongest harm, and most difficulty management in Erlang town. Although after many governance, the landslide was still in the creep deformation. Through the field survey, they were analyzed firstly that the geological structure, landform, stratum lithology, and human activities in the landslide area. And then combined with regional geological structure, cause of the mechanism of the landslide are analyzed in detail. Zhongdu landslide was the ancient landslide collapse and local resurrection. In the ancient, there was a massive landslide in Erlang town caused by the Xiangjiachang fracture and the Chishui river erosion on the front of the slope. And the river was blocked by the landslide deposit. After, the landslide dam was failure, the front edge of the slope was long-term erosion by the river, and lead to the resistance sliding section of the slope reduced. In addition, Shajing fracture was hydraulic conductivity, and the tendency to the deposit landslide, dip Angle of 75.And the human activities on the slope were frequent. These were the main factors which caused the landslide sliding.
Zhongdu landslide was the largest, strongest harm, and most difficulty management in Erlang town. Although after many governance, the landslide was still in the creep deformation. Through the field survey, they were analyzed firstly that the geological structure, landform, stratum lithology, and human activities in the landslide area. And then combined with regional geological structure, cause of the mechanism of the landslide are analyzed in detail. Zhongdu landslide was the ancient landslide collapse and local resurrection. In the ancient, there was a massive landslide in Erlang town caused by the Xiangjiachang fracture and the Chishui river erosion on the front of the slope. And the river was blocked by the landslide deposit. After, the landslide dam was failure, the front edge of the slope was long-term erosion by the river, and lead to the resistance sliding section of the slope reduced. In addition, Shajing fracture was hydraulic conductivity, and the tendency to the deposit landslide, dip Angle of 75.And the human activities on the slope were frequent. These were the main factors which caused the landslide sliding.
2016, 24(s1): 1133-1139.
Shield tunnel is more and more widely used in underground traffic engineering and underground pipeline structures. Shield tunnel structure health monitoring is an important project to ensure the long-term health of the tunnel and the safety of the tunnel. BOFDA is a new technology of distributed optical fiber sensing developed in recent years and has begun to apply to monitoring the interior deformation of rock mass and soil mass. In this paper, according to the Suzhou metro shield tunnel structural health monitoring project, the distributed optical fiber sensing technology based on BOFDA is applied to the construction and operation of the shield tunnel structure's safety and health monitoring. The writer formulates detailed and feasible monitoring scheme, designs the reasonable optical fiber sensor and the supporting fixture to monitor the tunnel's circumferential convergence, longitudinal settlement and expansion joints and analyzes the tunnel's health status using the data reflecting the shield tunnel structure's safety and health condition got from the monitor. The monitoring results have shown that BOFDA can position and monitor the places of abnormal deformation, common tunnel leakage and segment dislocation precisely and effectively. Also, BOFDA has the technical advantages of distributed, long distance, corrosion resistance and high survival rate and it's a new and effective method to monitor the shield tunnel structure's safety and health status during the construction and operation period.
Shield tunnel is more and more widely used in underground traffic engineering and underground pipeline structures. Shield tunnel structure health monitoring is an important project to ensure the long-term health of the tunnel and the safety of the tunnel. BOFDA is a new technology of distributed optical fiber sensing developed in recent years and has begun to apply to monitoring the interior deformation of rock mass and soil mass. In this paper, according to the Suzhou metro shield tunnel structural health monitoring project, the distributed optical fiber sensing technology based on BOFDA is applied to the construction and operation of the shield tunnel structure's safety and health monitoring. The writer formulates detailed and feasible monitoring scheme, designs the reasonable optical fiber sensor and the supporting fixture to monitor the tunnel's circumferential convergence, longitudinal settlement and expansion joints and analyzes the tunnel's health status using the data reflecting the shield tunnel structure's safety and health condition got from the monitor. The monitoring results have shown that BOFDA can position and monitor the places of abnormal deformation, common tunnel leakage and segment dislocation precisely and effectively. Also, BOFDA has the technical advantages of distributed, long distance, corrosion resistance and high survival rate and it's a new and effective method to monitor the shield tunnel structure's safety and health status during the construction and operation period.
2016, 24(s1): 1140-1145.
In order to study the seismic response characteristics of high fill foundation after cutting hills to backfill ditchs in northern Shaanxi.we did a seismic simulation about the filling test area with true 3D model by using FLAC3D numerical analysis tool. Analyzed the stress and the plastic zone distribution characteristics of high fill foundation under the action of gravity stress and earthquake dynamics, and carried on the deep discussion about the dynamic deformation and dynamic response characteristic under the action of the earthquake. The study shows that in the area with large slope, the stress is relatively concentrated, and shear failure occurred more often. The earthquake action will aggravate the settlement of the filling area, and the existence of the combined surface is unfavorable to the earthquake resistance. Suggested that in this kind of high fill foundation engineering, It is better to dig up the steps to reduce the slope and enhance the integrity of the fill soil and the original formation to improve the seismic performance of high fill foundation.
In order to study the seismic response characteristics of high fill foundation after cutting hills to backfill ditchs in northern Shaanxi.we did a seismic simulation about the filling test area with true 3D model by using FLAC3D numerical analysis tool. Analyzed the stress and the plastic zone distribution characteristics of high fill foundation under the action of gravity stress and earthquake dynamics, and carried on the deep discussion about the dynamic deformation and dynamic response characteristic under the action of the earthquake. The study shows that in the area with large slope, the stress is relatively concentrated, and shear failure occurred more often. The earthquake action will aggravate the settlement of the filling area, and the existence of the combined surface is unfavorable to the earthquake resistance. Suggested that in this kind of high fill foundation engineering, It is better to dig up the steps to reduce the slope and enhance the integrity of the fill soil and the original formation to improve the seismic performance of high fill foundation.
2016, 24(s1): 1146-1151.
In order to understand the influence of different excavation sequence for tunnel surrounding rock in soft soil, taking the excavation of double-layer tunnel in Chaoyang District as background, the construction is simulated by 3D numerical simulation method. Results are as follows: the better solution is found by considering the change of the surface subsidence, horizontal convergence of the side wall, stress field and plasticized zone distribution; in both two solutions, removal of temporary invert is the most vulnerable step in construction. The result can provide reference and guidance for the follow-up program.
In order to understand the influence of different excavation sequence for tunnel surrounding rock in soft soil, taking the excavation of double-layer tunnel in Chaoyang District as background, the construction is simulated by 3D numerical simulation method. Results are as follows: the better solution is found by considering the change of the surface subsidence, horizontal convergence of the side wall, stress field and plasticized zone distribution; in both two solutions, removal of temporary invert is the most vulnerable step in construction. The result can provide reference and guidance for the follow-up program.
2016, 24(s1): 1152-1155.
This paper investigatesandproposes the breaking of cavity layered overlying strata effecting caving zone height, and provides the determination method and criterion of caving zone height of salt single well solution cavity by the key stratum theory. This paper establishes the determination model of key stratum of salt single well solution cavity layered overlying strata by the elastic thin circular plate theory, provides the determination method of key stratum of salt single well solution cavity layered overlying strata, establishes that the hanging dew diameter of ke y stratum of salt single well solution cavity layered overlying strata less than the 2a1 is the criterion of key stratum breaking, and provides the criterion for judging the key stratum producing hinge and does not collapse, or direct collapse when breaking, according to the mechanical relationship between the formation of key stratum fractured rocks.
This paper investigatesandproposes the breaking of cavity layered overlying strata effecting caving zone height, and provides the determination method and criterion of caving zone height of salt single well solution cavity by the key stratum theory. This paper establishes the determination model of key stratum of salt single well solution cavity layered overlying strata by the elastic thin circular plate theory, provides the determination method of key stratum of salt single well solution cavity layered overlying strata, establishes that the hanging dew diameter of ke y stratum of salt single well solution cavity layered overlying strata less than the 2a1 is the criterion of key stratum breaking, and provides the criterion for judging the key stratum producing hinge and does not collapse, or direct collapse when breaking, according to the mechanical relationship between the formation of key stratum fractured rocks.
2016, 24(s1): 1156-1160.
Fine grain content criterion is a main discriminant method for the seepage deformation type of cohesionless coarse grained soil. However the seepage deformation type(piping) of crushed gravel(Pc35%) does not conform to the fine grain content criterion. According to the statistical analysis on seepage deformation testing results with 310 specimens from 46 projects(in which, the number of samples(Pc35%) is 35),the grain grading curves have such an unique characteristic that the slope of both ends of the gradation curve is steeper, and the slope of the middle segment is slow, so up to 87.5% of sampling particles are poorly-graded. Further analysis shows that the ratios of D15/d8 are more than 5,which means that the test results of seepage deformation are consistent with the filter criteria. Therefore the filter criteria are taken as a discriminant method for this kind of soil, and as a beneficial supplement for the fine grain content discrimination method as well.
Fine grain content criterion is a main discriminant method for the seepage deformation type of cohesionless coarse grained soil. However the seepage deformation type(piping) of crushed gravel(Pc35%) does not conform to the fine grain content criterion. According to the statistical analysis on seepage deformation testing results with 310 specimens from 46 projects(in which, the number of samples(Pc35%) is 35),the grain grading curves have such an unique characteristic that the slope of both ends of the gradation curve is steeper, and the slope of the middle segment is slow, so up to 87.5% of sampling particles are poorly-graded. Further analysis shows that the ratios of D15/d8 are more than 5,which means that the test results of seepage deformation are consistent with the filter criteria. Therefore the filter criteria are taken as a discriminant method for this kind of soil, and as a beneficial supplement for the fine grain content discrimination method as well.
2016, 24(s1): 1161-1167.
The excessive pumping of groundwater is the main cause of land subsidence, and artificial recharge can delay the land subsidence rate and can make the ground rebound to a certain extent. To study the law of soil deformation in precipitation and recharge process, this paper designs the indoor model test of sandy soil-clay-sandy soil sand interbed model tests. The model test selected specific fiber, studied the technology of embedded optical fiber, using distributed optical fiber sensing technology to capture the strain data in each layer of soil during the water level change process; using the results of traditional settlement pole and measuring tube of water level monitoring the change of settlement deformation and free water surface. The experiment analyses the accuracy and reliability of soil deformation monitoring by using distributed sensing fiber through comparing with the monitoring results and studying the response law of soil deformation under the effect of the changing water levels. The research results provide the experimental basis for the rational analysis of the long term observation data of groundwater level and soil deformation, and is helpful to promote the application of distributed optical fiber sensing technology in the field monitoring of land subsidence.
The excessive pumping of groundwater is the main cause of land subsidence, and artificial recharge can delay the land subsidence rate and can make the ground rebound to a certain extent. To study the law of soil deformation in precipitation and recharge process, this paper designs the indoor model test of sandy soil-clay-sandy soil sand interbed model tests. The model test selected specific fiber, studied the technology of embedded optical fiber, using distributed optical fiber sensing technology to capture the strain data in each layer of soil during the water level change process; using the results of traditional settlement pole and measuring tube of water level monitoring the change of settlement deformation and free water surface. The experiment analyses the accuracy and reliability of soil deformation monitoring by using distributed sensing fiber through comparing with the monitoring results and studying the response law of soil deformation under the effect of the changing water levels. The research results provide the experimental basis for the rational analysis of the long term observation data of groundwater level and soil deformation, and is helpful to promote the application of distributed optical fiber sensing technology in the field monitoring of land subsidence.
2016, 24(s1): 1168-1172.
Collectingeightstatistical relationships of Cc~n that proposed by domestic researchers in different southest coastal regions of China(Shanghai, Lianyungang, Guangzhou, Shenzhen, coastal areas of Zhejiang province and Bohai bay), and 276 published datasof Cc and n in these regions and other coastal areas(Tianjin, Hangzhou, Wenzhou, et al.),it is founded that there is a good linear relationship between Cc and n of soft soil in Chinese southest coastal areas, which cann't be expressed by a unique statistical formulation. The Cc~n relationship can be divided into two categories, which are steepincreasing type and slow increasing type, and slow changing type is close to the foreign statistical results. In addititon, by comparing the test results of two kinds of soil samples, the influence of the soil disturbance on the statistical relationship of Cc~n is discussed.
Collectingeightstatistical relationships of Cc~n that proposed by domestic researchers in different southest coastal regions of China(Shanghai, Lianyungang, Guangzhou, Shenzhen, coastal areas of Zhejiang province and Bohai bay), and 276 published datasof Cc and n in these regions and other coastal areas(Tianjin, Hangzhou, Wenzhou, et al.),it is founded that there is a good linear relationship between Cc and n of soft soil in Chinese southest coastal areas, which cann't be expressed by a unique statistical formulation. The Cc~n relationship can be divided into two categories, which are steepincreasing type and slow increasing type, and slow changing type is close to the foreign statistical results. In addititon, by comparing the test results of two kinds of soil samples, the influence of the soil disturbance on the statistical relationship of Cc~n is discussed.
2016, 24(s1): 1173-1178.
Geothermal exploration involves a high degree of uncertainty and financial risk. Establishing spatial relation between the known hot springs and evidence factor maps based on GIS technology. Then the assessment of geothermal resources in the study area was made. Earthquake epicenter, faults, Bouger gravity anomaly, magnetic anomaly, intrusive rock and heat flux datasets are selected as evidence factors. The fuzzy logic model was built and illustrated in western Anatolia, Turkey. Fuzzy logic model was applied to the evaluation of geothermal potential in Fujian Province. The geothermal potential of Fujian Province was divided into four levels; extremely high, high, medium and low potential area. The area with extremely high and high potential accounts for about 28.24% of the study area, including 59.11% of the total known hot springs. The research results have theoretical and practical significance for the development of concealed geothermal.
Geothermal exploration involves a high degree of uncertainty and financial risk. Establishing spatial relation between the known hot springs and evidence factor maps based on GIS technology. Then the assessment of geothermal resources in the study area was made. Earthquake epicenter, faults, Bouger gravity anomaly, magnetic anomaly, intrusive rock and heat flux datasets are selected as evidence factors. The fuzzy logic model was built and illustrated in western Anatolia, Turkey. Fuzzy logic model was applied to the evaluation of geothermal potential in Fujian Province. The geothermal potential of Fujian Province was divided into four levels; extremely high, high, medium and low potential area. The area with extremely high and high potential accounts for about 28.24% of the study area, including 59.11% of the total known hot springs. The research results have theoretical and practical significance for the development of concealed geothermal.
2016, 24(s1): 1179-1183.
Monitoring results showed that the current land subsidence in wuxi area mainly comes from the aquitard, evaluating the compressibility of aquitard is very important, it make us know the development trend of land subsidence. This paper, which taked Quaternary soil layer in a drilling in wuxi Guangming village as the research object, used scanning electron microscope(SEM) to study the pore distribution characteristics of silty clay in different aquitard from micro-scale, and compared the result with the consolidation test data. The study found that the SEM image quantitative analysis result is correct and it can quantitatively indicate the amount of compressible pores and the complexity of the pores,; Porosity and the probability distribution index can reflect the pore density in soil and compressibility of soil. Research results can provided evidence for Suxichang regional land subsidence prediction from the microscopic.
Monitoring results showed that the current land subsidence in wuxi area mainly comes from the aquitard, evaluating the compressibility of aquitard is very important, it make us know the development trend of land subsidence. This paper, which taked Quaternary soil layer in a drilling in wuxi Guangming village as the research object, used scanning electron microscope(SEM) to study the pore distribution characteristics of silty clay in different aquitard from micro-scale, and compared the result with the consolidation test data. The study found that the SEM image quantitative analysis result is correct and it can quantitatively indicate the amount of compressible pores and the complexity of the pores,; Porosity and the probability distribution index can reflect the pore density in soil and compressibility of soil. Research results can provided evidence for Suxichang regional land subsidence prediction from the microscopic.
2016, 24(s1): 1184-1188.
Having investigated Pliocene epoch lateritein Yushe, Shilou, Jiexiu and Xiangyuan in the middle and southern Shanxi Province and having observed the laterite distribution, Physical parameters of Pliocene undisturbed laterite samples and overlying the quaternary loess samples were tested. According to similar sedimentary characteristics and similar particle composition distribution characteristics of the Pliocenelaterite and Quaternary loess, the wind power genesis type of the laterite was deduced. According to the measured laterite physical parameter values, Pliocene laterite in the middle and southern Shanxi Province was recognized as clay or silty clay. Water limit has a linear relation to clay content of the laterite in the study areas, plasticity index has an exponent relation to clay content of the laterite in the study areas. The research resultsare the reliable basic data for the engineering characteristics study in the middle and southern Shanxi Province in the future.
Having investigated Pliocene epoch lateritein Yushe, Shilou, Jiexiu and Xiangyuan in the middle and southern Shanxi Province and having observed the laterite distribution, Physical parameters of Pliocene undisturbed laterite samples and overlying the quaternary loess samples were tested. According to similar sedimentary characteristics and similar particle composition distribution characteristics of the Pliocenelaterite and Quaternary loess, the wind power genesis type of the laterite was deduced. According to the measured laterite physical parameter values, Pliocene laterite in the middle and southern Shanxi Province was recognized as clay or silty clay. Water limit has a linear relation to clay content of the laterite in the study areas, plasticity index has an exponent relation to clay content of the laterite in the study areas. The research resultsare the reliable basic data for the engineering characteristics study in the middle and southern Shanxi Province in the future.
2016, 24(s1): 1189-1195.
Through Brazilian experiment which we used tight sandstone rock samples from tight oil and gas reservoirs in Ordos Basin, the rock failure process of time-load curve, as well as the cumulative number of AE and AE energy rate curve over time was obtained. The relations between Acoustic Emission characteristics and load value was analyzedby observing the entire process of rock failure. The difference of rock Acoustic Emission between two different drilling state was compared. The results show that using AE characteristic parameter can represent the whole process of rock failure very well. The void space of AE event is closely related with rock formation.whenthe position of macro rupture is relatively complete, it is generally able to monitor the AE void space,when position of macro rupture is incomplete, the AE void space may not happen. According to the above features, we can judge the integrity of the crack at the position of macro crack coalescence. As can be seen from the spectrum of AE events, there are two main different types of AE in rock failure process, namely the original initial crack defect closure AE and rock fracture generated AE,the difference between the two is obvious.
Through Brazilian experiment which we used tight sandstone rock samples from tight oil and gas reservoirs in Ordos Basin, the rock failure process of time-load curve, as well as the cumulative number of AE and AE energy rate curve over time was obtained. The relations between Acoustic Emission characteristics and load value was analyzedby observing the entire process of rock failure. The difference of rock Acoustic Emission between two different drilling state was compared. The results show that using AE characteristic parameter can represent the whole process of rock failure very well. The void space of AE event is closely related with rock formation.whenthe position of macro rupture is relatively complete, it is generally able to monitor the AE void space,when position of macro rupture is incomplete, the AE void space may not happen. According to the above features, we can judge the integrity of the crack at the position of macro crack coalescence. As can be seen from the spectrum of AE events, there are two main different types of AE in rock failure process, namely the original initial crack defect closure AE and rock fracture generated AE,the difference between the two is obvious.
2016, 24(s1): 1196-1202.
Aiming at the research of the water and salt transport problem of saline soil in Zhenlai County, Jilin Province, large amount of fractures were found in the soil, which was called cracked soil.In order to study the water-salt transport problem in saline soil effectively, this paper mainly discussed the pore characteristics of the fractured soils with different depth in the vertical direction. Mercury intrusion porosimetry test(MIP test) was done to obtain the micro pore distribution of undisturbed soil samples after field investigation and in-situ sampling. The quantitative analysis result shows that the micro pore distribution of the cracked soil has obvious bimodal distribution characteristics. The two peaks located between small pore and large pore range respectively. And the pore fractal dimension of soil sample is larger the volume content of fractures in the soil is much larger, and the maximum of fracture rate is 34.9% in the soil with 0.2m depth, in addition the fracture rate decreases with the increase of depth.
Aiming at the research of the water and salt transport problem of saline soil in Zhenlai County, Jilin Province, large amount of fractures were found in the soil, which was called cracked soil.In order to study the water-salt transport problem in saline soil effectively, this paper mainly discussed the pore characteristics of the fractured soils with different depth in the vertical direction. Mercury intrusion porosimetry test(MIP test) was done to obtain the micro pore distribution of undisturbed soil samples after field investigation and in-situ sampling. The quantitative analysis result shows that the micro pore distribution of the cracked soil has obvious bimodal distribution characteristics. The two peaks located between small pore and large pore range respectively. And the pore fractal dimension of soil sample is larger the volume content of fractures in the soil is much larger, and the maximum of fracture rate is 34.9% in the soil with 0.2m depth, in addition the fracture rate decreases with the increase of depth.
2016, 24(s1): 1203-1210.
Soil-rock mixture is a kind of special geological material and has a wide spread in nature. It is comprised of rock blocks, fine soil particleand pore which is filled in. With the increase and development of all kinds of large scale engineering construction, geological disasters related to soil-rock mixture has seriously affected and restricted the engineering construction and human safety. Thus, it is important to study the soil-rock mixture. In this paper, the contact characteristic of rock and soil in soil-rock mixture has been focused on from the perspective of meso-structure. In order to simulate the gravel-soil interface in soil-rock mixture, the interface element in FLAC3D was used and then a three-dimensional numerical model of soil-rock mixture containing interface element was built. The reasonable variation range of interface parameters was selected. By analyzing the numerical simulation results, the sensitivity of parameters was investigated. It was found that stiffness, especially the normal stiffness has the significant effect on stress-strain curve of the soil-rock mixture as well as the relative movement between gravel and soil. Cohesion follows and the influence of friction angle is minimal. By comparing with the model without interface element, the feasibility and rationality of three-dimensional model of soil-rock mixture containing interface element are verified. The application of interface element makes it possible to accurately describe the macroscopic deformation characteristics of soil-rock mixture and the interaction mechanism between the gravel and soil.
Soil-rock mixture is a kind of special geological material and has a wide spread in nature. It is comprised of rock blocks, fine soil particleand pore which is filled in. With the increase and development of all kinds of large scale engineering construction, geological disasters related to soil-rock mixture has seriously affected and restricted the engineering construction and human safety. Thus, it is important to study the soil-rock mixture. In this paper, the contact characteristic of rock and soil in soil-rock mixture has been focused on from the perspective of meso-structure. In order to simulate the gravel-soil interface in soil-rock mixture, the interface element in FLAC3D was used and then a three-dimensional numerical model of soil-rock mixture containing interface element was built. The reasonable variation range of interface parameters was selected. By analyzing the numerical simulation results, the sensitivity of parameters was investigated. It was found that stiffness, especially the normal stiffness has the significant effect on stress-strain curve of the soil-rock mixture as well as the relative movement between gravel and soil. Cohesion follows and the influence of friction angle is minimal. By comparing with the model without interface element, the feasibility and rationality of three-dimensional model of soil-rock mixture containing interface element are verified. The application of interface element makes it possible to accurately describe the macroscopic deformation characteristics of soil-rock mixture and the interaction mechanism between the gravel and soil.
2016, 24(s1): 1211-1218.
Taking the remolded sample of soil rock mixtures as research objective, Consolidated undrained(CU)triaxial shear tests were performed to study the effect of volumetric block proportions(VBP) and confining pressures on mechanical behaviors of soil rock mixtures by using large-scale triaxial shear apparatus, the trends of the initial shear stiffness and shear strength of soil rock mixtures under different volumetric block proportions(VBP) and different confining pressure conditions are analyzed. The results show that: the degeneration failure mode of soil rock mixtures is different from conventional rock and soil mass, stress jump exists in the curve of stress-strain relationship, and the degeneration failure mode of soil rock mixtures is different between each other under different volumetric block proportions(VBP) and different confining pressure conditions. The Shear strength of soil rock mixtures increases with the increase of confining pressure, however, it increases initially then decrease with the the increase of the volumetric block proportions(VBP),when the confining pressure doubled, the trends of shear strength of soil rock mixtures is different at different levels of confining pressure; the initial shear stiffness of soil rock mixtures increases with the increase of confining pressure, and it increases initially then decrease with the the increase of the volumetric block proportions(VBP),when the confining pressure doubled, the trends of initial shear stiffness in accordance with the trends of shear strength.
Taking the remolded sample of soil rock mixtures as research objective, Consolidated undrained(CU)triaxial shear tests were performed to study the effect of volumetric block proportions(VBP) and confining pressures on mechanical behaviors of soil rock mixtures by using large-scale triaxial shear apparatus, the trends of the initial shear stiffness and shear strength of soil rock mixtures under different volumetric block proportions(VBP) and different confining pressure conditions are analyzed. The results show that: the degeneration failure mode of soil rock mixtures is different from conventional rock and soil mass, stress jump exists in the curve of stress-strain relationship, and the degeneration failure mode of soil rock mixtures is different between each other under different volumetric block proportions(VBP) and different confining pressure conditions. The Shear strength of soil rock mixtures increases with the increase of confining pressure, however, it increases initially then decrease with the the increase of the volumetric block proportions(VBP),when the confining pressure doubled, the trends of shear strength of soil rock mixtures is different at different levels of confining pressure; the initial shear stiffness of soil rock mixtures increases with the increase of confining pressure, and it increases initially then decrease with the the increase of the volumetric block proportions(VBP),when the confining pressure doubled, the trends of initial shear stiffness in accordance with the trends of shear strength.
2016, 24(s1): 1219-1223.
The Ganges delta region is located in the Bangladesh area of South Asia, including Bangladesh and Bengal of western India, rivers pouring into the Bay of Bengal. This is one of the biggest delta in the world, and also one of the most fertile areas in the world. The region has a wide distribution in soft soil, which is loose and has a large thickness. The soft soil foundation usually lead to larger or uneven settlement, and affect the safety of engineering structures. This article mainly study and summarize the Ganges delta soft soil engineering properties according to Dasherkandi sewage treatment plant project combined with several nearby projects of Bangladesh.
The Ganges delta region is located in the Bangladesh area of South Asia, including Bangladesh and Bengal of western India, rivers pouring into the Bay of Bengal. This is one of the biggest delta in the world, and also one of the most fertile areas in the world. The region has a wide distribution in soft soil, which is loose and has a large thickness. The soft soil foundation usually lead to larger or uneven settlement, and affect the safety of engineering structures. This article mainly study and summarize the Ganges delta soft soil engineering properties according to Dasherkandi sewage treatment plant project combined with several nearby projects of Bangladesh.
2016, 24(s1): 1224-1228.
According to many projects of Sichuan, Tibet, and so on, there are engineering geological problems of deep overburden with depth of dozens meters even hundred meters in most southwest valley. During construction, the study of compression feature which is limited of depth of overburden is often based on borehole samples in earlier stage, mainly including testing in borehole and laboratory test of borehole sample. Because of disturbance and stress change of borehole sample, there is influence to testing result. In this article, the main composition of riverbed substance is generally classified firstly, then the typical projects is chosen, and the sample of foundation pit is reviewed during excavation, the difference between borehole sample and the sample of foundation pit is compared, and the reasons of generation difference of partial parameters are analyzed.
According to many projects of Sichuan, Tibet, and so on, there are engineering geological problems of deep overburden with depth of dozens meters even hundred meters in most southwest valley. During construction, the study of compression feature which is limited of depth of overburden is often based on borehole samples in earlier stage, mainly including testing in borehole and laboratory test of borehole sample. Because of disturbance and stress change of borehole sample, there is influence to testing result. In this article, the main composition of riverbed substance is generally classified firstly, then the typical projects is chosen, and the sample of foundation pit is reviewed during excavation, the difference between borehole sample and the sample of foundation pit is compared, and the reasons of generation difference of partial parameters are analyzed.
2016, 24(s1): 1229-1237.
ABSTRACT in order to further study the occurrence conditions and mechanism of the Covered Karst Ground Collapse(CKGC),on the basis of Luo Xiaojie's theory about CKGC,the geological phenomena, geological model, physical model and mathematical expression of the soil-cave type ground collapse are studied. The formation and development of soil-cave and ground collapse are two different phases of soil-cave type karst ground collapse. According to the macroscopic geological phenomena in the process of collapse, combined with the kinematic response characteristics of soil body and deformation of surrounding soil in process of deformation, the geological model of soil-cave type karst ground collapse is established. On the basis of this, the physical model of soil-cave collapse is further simplified. Combined with other major collapse mechanisms in the literature, the stress analysis on the roof of the soil-cave is carried out. Based on the limit equilibrium theory, a universal mathematical expression is proposed. After discussing the influencing factors of the critical thickness of soil-cave roof, it is pointed out that the critical thickness is positively correlated with the cave diameter, the load increment, and higher shear strength of the roof, negatively with lower shear strength.
ABSTRACT in order to further study the occurrence conditions and mechanism of the Covered Karst Ground Collapse(CKGC),on the basis of Luo Xiaojie's theory about CKGC,the geological phenomena, geological model, physical model and mathematical expression of the soil-cave type ground collapse are studied. The formation and development of soil-cave and ground collapse are two different phases of soil-cave type karst ground collapse. According to the macroscopic geological phenomena in the process of collapse, combined with the kinematic response characteristics of soil body and deformation of surrounding soil in process of deformation, the geological model of soil-cave type karst ground collapse is established. On the basis of this, the physical model of soil-cave collapse is further simplified. Combined with other major collapse mechanisms in the literature, the stress analysis on the roof of the soil-cave is carried out. Based on the limit equilibrium theory, a universal mathematical expression is proposed. After discussing the influencing factors of the critical thickness of soil-cave roof, it is pointed out that the critical thickness is positively correlated with the cave diameter, the load increment, and higher shear strength of the roof, negatively with lower shear strength.
2016, 24(s1): 1238-1242.
In order to investigate the effect of grain size composition and structure on the matric suction of unsaturated loess, the washing method is used to measure the SWCC and the particle density distribution curves with the preparation of the original state, remodeling, separation of fine and coarse particle size of a total of four L5 loess samples at Jingyang country. The experimental results show that the structure of the samples of undisturbed loess increases the maximum pore radius, increases the uniformity of the pore distribution of the loess, and leads to the decrease of the Air entry value of SWCC, and the slope inthe rapid descending segment of the water content becomes gradual. The dominant peak value of the density distribution of the soil particle size distribution of the structure has a significant effect on the Air entry value of SWCC.
In order to investigate the effect of grain size composition and structure on the matric suction of unsaturated loess, the washing method is used to measure the SWCC and the particle density distribution curves with the preparation of the original state, remodeling, separation of fine and coarse particle size of a total of four L5 loess samples at Jingyang country. The experimental results show that the structure of the samples of undisturbed loess increases the maximum pore radius, increases the uniformity of the pore distribution of the loess, and leads to the decrease of the Air entry value of SWCC, and the slope inthe rapid descending segment of the water content becomes gradual. The dominant peak value of the density distribution of the soil particle size distribution of the structure has a significant effect on the Air entry value of SWCC.
2016, 24(s1): 1243-1249.
In this paper, in-situ tests and laboratory tests through soil excavation of the deep overburden dam foundation demonstrated that with the cover layer deposition time older, the greater depth and under covering overburden, deep overburden's anti permeability performance and machnical property is improved obviously. In order to make full use of the covering layer under the dam foundation, save construction period and reduce the manufacture cost, we have summarized domestic and international experiences about the overburden utilization. The principle of overburden utilization is put forward.At the same time, This study can promote the technical development of dam in deep overburden layer, can provide reference for water conservancy and hydropower engineering technical personnel
In this paper, in-situ tests and laboratory tests through soil excavation of the deep overburden dam foundation demonstrated that with the cover layer deposition time older, the greater depth and under covering overburden, deep overburden's anti permeability performance and machnical property is improved obviously. In order to make full use of the covering layer under the dam foundation, save construction period and reduce the manufacture cost, we have summarized domestic and international experiences about the overburden utilization. The principle of overburden utilization is put forward.At the same time, This study can promote the technical development of dam in deep overburden layer, can provide reference for water conservancy and hydropower engineering technical personnel
2016, 24(s1): 1250-1254.
Nawenmuren community is located in the downstream of auxiliary dam of Ni'erji Reservoir, belonging to the second terrace of right bank of Nenjiang River. The reservoir start impounding in 2005,in recent years the flooding phenomenon, including ground moisture, building cracking, and vegetable cellar ponding had appeared in some part of the fields, making some influence on the inhabitants' living. It has a special groundwater motion law as a result of the existence of a thicker clay formation under the ground. In recent years there is a certain research on this aspect; however the relative information is far beyond enough. It has been found that some flooding has presented in the downstream of the right auxiliary dam, however it is still not clear that whether or not the reservoir caused the flooding. The discussion of this project can offer some reference functions to the similar engineering.
Nawenmuren community is located in the downstream of auxiliary dam of Ni'erji Reservoir, belonging to the second terrace of right bank of Nenjiang River. The reservoir start impounding in 2005,in recent years the flooding phenomenon, including ground moisture, building cracking, and vegetable cellar ponding had appeared in some part of the fields, making some influence on the inhabitants' living. It has a special groundwater motion law as a result of the existence of a thicker clay formation under the ground. In recent years there is a certain research on this aspect; however the relative information is far beyond enough. It has been found that some flooding has presented in the downstream of the right auxiliary dam, however it is still not clear that whether or not the reservoir caused the flooding. The discussion of this project can offer some reference functions to the similar engineering.
2016, 24(s1): 1255-1262.
TIMAH TASOH Lake Tunnel Project was located at the Perlis province, most northern of the west coast of Malaysia Peninsular. The study area was known for karst topography, ground limestone tower hills very common. Combined with field geological survey and preliminary information, it was mainly introduced of the tunnel project area with lithology, geological structure, meteorology and hydrology. On this basis, starting from the basic necessary conditions analysis of karst, combined with regional macro micro karst law analysis, the evaluation of karst development degree and karst tunnel surrounding rock classification were carried out by the application of fractal theory.karst geology engineering problems probably faced when tunnel constructing were elaborate detailly, and the corresponding countermeasures of design and construction were proposed. Well verified by the tunnel construction practice with the karst geological conditions analysis results, it was worthy of the reference for the same tunnel project construction and design.
TIMAH TASOH Lake Tunnel Project was located at the Perlis province, most northern of the west coast of Malaysia Peninsular. The study area was known for karst topography, ground limestone tower hills very common. Combined with field geological survey and preliminary information, it was mainly introduced of the tunnel project area with lithology, geological structure, meteorology and hydrology. On this basis, starting from the basic necessary conditions analysis of karst, combined with regional macro micro karst law analysis, the evaluation of karst development degree and karst tunnel surrounding rock classification were carried out by the application of fractal theory.karst geology engineering problems probably faced when tunnel constructing were elaborate detailly, and the corresponding countermeasures of design and construction were proposed. Well verified by the tunnel construction practice with the karst geological conditions analysis results, it was worthy of the reference for the same tunnel project construction and design.
2016, 24(s1): 1263-1269.
The study area is located in North-East Sudan near the Red Sea, belongs to the southern margin of the Sahara desert, where the desert-hilly topography, with hot and dry climate, very unequal rainfall and strong evaporation, so it was relative seriously scarce of surface water and groundwater resources. On the one hand, the mining area development requires plenty of water as a capacity safeguard; on the other hand, the imbalance of groundwater and the mineral waste water emissions will seriously affect the already extremely fragile ecological environment. In this paper, according to the mining engineering geology, hydrogeology and environmental geology survey, combined with related data, regional hydrogeological conditions research are analyzed, then suggestions of the mine hydrogeology work and the environment work are put forward, which is hoped to be worthy of the following work.
The study area is located in North-East Sudan near the Red Sea, belongs to the southern margin of the Sahara desert, where the desert-hilly topography, with hot and dry climate, very unequal rainfall and strong evaporation, so it was relative seriously scarce of surface water and groundwater resources. On the one hand, the mining area development requires plenty of water as a capacity safeguard; on the other hand, the imbalance of groundwater and the mineral waste water emissions will seriously affect the already extremely fragile ecological environment. In this paper, according to the mining engineering geology, hydrogeology and environmental geology survey, combined with related data, regional hydrogeological conditions research are analyzed, then suggestions of the mine hydrogeology work and the environment work are put forward, which is hoped to be worthy of the following work.
2016, 24(s1): 1270-1275.
Pile static load test is a common method to determine ultimate bearing capacity of single pile, the research about domestic project is abundant at present, however the cases from overseas projects are scanty, and most of the studies did not reach limit stat of pile foundation, test data were incomplete, so it is necessary to carry out destructive tests of pile foundation. Therefore, the study, combining with a project of Southeast Asia, finished destructive test of single pile ultimate bearing capacity of vertical compressive by static load test to 6 test piles of subsidiary factory in this project, analyzed the process of the vertical ultimate bearing capacity of single pile test by Q~t curve and S~t curve, determined single pile vertical ultimate bearing capacity according to the specifications, accumulated experiences for similar project in the region, contributed the precious experiment data for further research.
Pile static load test is a common method to determine ultimate bearing capacity of single pile, the research about domestic project is abundant at present, however the cases from overseas projects are scanty, and most of the studies did not reach limit stat of pile foundation, test data were incomplete, so it is necessary to carry out destructive tests of pile foundation. Therefore, the study, combining with a project of Southeast Asia, finished destructive test of single pile ultimate bearing capacity of vertical compressive by static load test to 6 test piles of subsidiary factory in this project, analyzed the process of the vertical ultimate bearing capacity of single pile test by Q~t curve and S~t curve, determined single pile vertical ultimate bearing capacity according to the specifications, accumulated experiences for similar project in the region, contributed the precious experiment data for further research.
2016, 24(s1): 1276-1282.
Saline soil foundation is a common engineering geological problem in engineering construction, domestic scholars had carried out some studies on micro-mechanism, engineering properties, treatment technology of saline soil, but research of saline soil is still in the relatively backward state. So, it is important to research prospecting and evaluating, micro-mechanism, engineering properties of saline soil foundation and discuss treatment measures of projects. The research analyses the constituent, type, distribution of saline soil and evaluate saline soil foundation in the project of Oil/Gas power station in Irap base on the record of engineering investigation, propose some principles and measures of saline soil for the projects, put forward foundation scheme and some problems needing attention in construction of geotechnical engineering according to the features of sites, which can provide certain references for similar geotechnical investigation.
Saline soil foundation is a common engineering geological problem in engineering construction, domestic scholars had carried out some studies on micro-mechanism, engineering properties, treatment technology of saline soil, but research of saline soil is still in the relatively backward state. So, it is important to research prospecting and evaluating, micro-mechanism, engineering properties of saline soil foundation and discuss treatment measures of projects. The research analyses the constituent, type, distribution of saline soil and evaluate saline soil foundation in the project of Oil/Gas power station in Irap base on the record of engineering investigation, propose some principles and measures of saline soil for the projects, put forward foundation scheme and some problems needing attention in construction of geotechnical engineering according to the features of sites, which can provide certain references for similar geotechnical investigation.
2016, 24(s1): 1283-1289.
There are lots of slow-moving landslides in Hongza valley of Karakoram Mountain along China-Pakistan Economic Corridor, under the geological setting of active tectonic movement, steep terrain, vertical climate, abundant snow, glacier erosion, et al. This study employs the InSAR technology with characteristics of high accuracy, larger region coverage, and untouch, to observe ground surface deformation. Assisting the optical remote sensing interpretation and field validation, we recognize the slow-moving landslides, and further analyze their deformation feature and distribution, draw the following conclusions.(1) Combination of PS-InSAR and D-InSAR can achieved the velocity scale from mm/yr to dm/yr, which not only overcome the lose coherence of SAR date, but also gain the bigger velocity deformation, demonstrating the InSAR technique with PALSAR data is possible and accurate for the slow-moving landslide observationin this area; (2) Slow-moving landslide trailing edge rupture is clear commonly, the deformation between the end of 2008 and the earlier of 2009 is larger than that of other periods, which may be affected by storm rainfall in the second half year of 2008; (3) the velocities of slow-moving landslides ranger from 10 to 30mmyr-1,while the failed Attabad landslide blocked the Karakoram road in 2010 has the abnormal velocity of 27.8~83.8cmyr-1,which provides evidence for the further study for monitoring and early warming.
There are lots of slow-moving landslides in Hongza valley of Karakoram Mountain along China-Pakistan Economic Corridor, under the geological setting of active tectonic movement, steep terrain, vertical climate, abundant snow, glacier erosion, et al. This study employs the InSAR technology with characteristics of high accuracy, larger region coverage, and untouch, to observe ground surface deformation. Assisting the optical remote sensing interpretation and field validation, we recognize the slow-moving landslides, and further analyze their deformation feature and distribution, draw the following conclusions.(1) Combination of PS-InSAR and D-InSAR can achieved the velocity scale from mm/yr to dm/yr, which not only overcome the lose coherence of SAR date, but also gain the bigger velocity deformation, demonstrating the InSAR technique with PALSAR data is possible and accurate for the slow-moving landslide observationin this area; (2) Slow-moving landslide trailing edge rupture is clear commonly, the deformation between the end of 2008 and the earlier of 2009 is larger than that of other periods, which may be affected by storm rainfall in the second half year of 2008; (3) the velocities of slow-moving landslides ranger from 10 to 30mmyr-1,while the failed Attabad landslide blocked the Karakoram road in 2010 has the abnormal velocity of 27.8~83.8cmyr-1,which provides evidence for the further study for monitoring and early warming.
2016, 24(s1): 1290-1294.
With BCIM Economic Corridor and maritime silk road speed up, a large number of Chinese enterprises are investing in infrastructure in Bangladesh. The European and American standards is used in Bangladesh, there is a considerable difference with Chinese standards, it brings great difficulties for Chinese enterprises to go out. The exploration and test results of Dasherkandi sewage treatment plant are analyzed in detail. The bearing capacity for Shallow foundation, ultimate compression capacity and Ultimate tension capacity of a single pile were calculated with Bangladesh code, European and US standards. And Compared calculation results with Chinese code, it has certain guiding significance for foreign similar projects.
With BCIM Economic Corridor and maritime silk road speed up, a large number of Chinese enterprises are investing in infrastructure in Bangladesh. The European and American standards is used in Bangladesh, there is a considerable difference with Chinese standards, it brings great difficulties for Chinese enterprises to go out. The exploration and test results of Dasherkandi sewage treatment plant are analyzed in detail. The bearing capacity for Shallow foundation, ultimate compression capacity and Ultimate tension capacity of a single pile were calculated with Bangladesh code, European and US standards. And Compared calculation results with Chinese code, it has certain guiding significance for foreign similar projects.
2016, 24(s1): 1295-1298.
Littoral Facies Foundation Soil widely distributs in Mozambique and has engineering characteristics, such as high natural moisture content, big void ratio, high compressibility, low soil shear strength. Taking Ma Duola 210 Hectares Land in Maputo City for Example and combining with domestic research related to littoral facies foundation soil, the paper presents engineering properties of Mozambique littoral facies foundation soil, main engineering geological problems and relevant dealing with method. Therefore, this paper has an important and positive significance for the development of Mozambique international project.
Littoral Facies Foundation Soil widely distributs in Mozambique and has engineering characteristics, such as high natural moisture content, big void ratio, high compressibility, low soil shear strength. Taking Ma Duola 210 Hectares Land in Maputo City for Example and combining with domestic research related to littoral facies foundation soil, the paper presents engineering properties of Mozambique littoral facies foundation soil, main engineering geological problems and relevant dealing with method. Therefore, this paper has an important and positive significance for the development of Mozambique international project.
2016, 24(s1): 1299-1302.
In early stage of design work of PosoI HPP in Indonesia, the data provided by owner was less. It's hard to analyze the physical and mechanical properties of overburden and the engineering geological conditions. In order to solve the engineering problem, the field geological survey and borehole core appraisal have been carried out. According to field geological survey and analysis of borehole test data provided by the Owner as well as actual experience in China's projects, we have used engineering analogy method to propose recommended values of physical and mechanical parameters for overburden in the project area. The solution of engineering problem is worthy of reference for the similar project abroad.
In early stage of design work of PosoI HPP in Indonesia, the data provided by owner was less. It's hard to analyze the physical and mechanical properties of overburden and the engineering geological conditions. In order to solve the engineering problem, the field geological survey and borehole core appraisal have been carried out. According to field geological survey and analysis of borehole test data provided by the Owner as well as actual experience in China's projects, we have used engineering analogy method to propose recommended values of physical and mechanical parameters for overburden in the project area. The solution of engineering problem is worthy of reference for the similar project abroad.
2016, 24(s1): 1303-1306.
Through the uniaxial tensile test of loess samples,the tensile fracture characteristics of undisturbed loess in the south bank of Jinghe river. The study shows that the moisture content is the important factor for the tensile strength of loess, and they have decreasing power function relationship with the tensile strength of loess. Under uniaxial tensile test of the loess, the ultimate tensile strain of loess is several over ten thousand, and the tensile strength is several or tens of KPa. Under the condition of rain and irrigation, the tensile strength of loess future decreases and the fissure of the rear edge of the loess slope further development, it is the one of factors that results in the loess landslide.
Through the uniaxial tensile test of loess samples,the tensile fracture characteristics of undisturbed loess in the south bank of Jinghe river. The study shows that the moisture content is the important factor for the tensile strength of loess, and they have decreasing power function relationship with the tensile strength of loess. Under uniaxial tensile test of the loess, the ultimate tensile strain of loess is several over ten thousand, and the tensile strength is several or tens of KPa. Under the condition of rain and irrigation, the tensile strength of loess future decreases and the fissure of the rear edge of the loess slope further development, it is the one of factors that results in the loess landslide.
2016, 24(s1): 1307-1312.
Water quality is an important focus of water resources development and utilization, and zaodu river water resources development plan, Chongqing City, a comprehensive monitoring of the River, from upstream to downstream, the principal mining sites, important tributaries converge, town reach specific locations has laid the monitoring section of, and in accordance with the environmental quality standards for surface water(GB3838-2004) monitoring, water quality monitoring results show that part of the monitoring section there are different degrees of iron and manganese concentrations exceeded, and concentrated in 4~8months(flood) each year, through the analysis of inter-water quality monitoring in iron and manganese exceedances and with various other chemical components correlation, along During the year the monthly research process and changes in concentration trends, the basin geological environment, obtain(1) between the iron and manganese with good correlation between the two companions; (2) ferromanganese mainly from the Permian strata in particular two Permian statistically Coal Seam mine drainage and other major conclusions, and proposed a reasonable set of water intake and mine drainage treatment measures suggested terms of reference for the relevant.
Water quality is an important focus of water resources development and utilization, and zaodu river water resources development plan, Chongqing City, a comprehensive monitoring of the River, from upstream to downstream, the principal mining sites, important tributaries converge, town reach specific locations has laid the monitoring section of, and in accordance with the environmental quality standards for surface water(GB3838-2004) monitoring, water quality monitoring results show that part of the monitoring section there are different degrees of iron and manganese concentrations exceeded, and concentrated in 4~8months(flood) each year, through the analysis of inter-water quality monitoring in iron and manganese exceedances and with various other chemical components correlation, along During the year the monthly research process and changes in concentration trends, the basin geological environment, obtain(1) between the iron and manganese with good correlation between the two companions; (2) ferromanganese mainly from the Permian strata in particular two Permian statistically Coal Seam mine drainage and other major conclusions, and proposed a reasonable set of water intake and mine drainage treatment measures suggested terms of reference for the relevant.
2016, 24(s1): 1313-1319.
High-density electrical resistivity survey has been generally used in engineering geology and environmental geology. However, electrical resistivity is not enough to find water and mineral, and polarizability has better effect in these region. But, there has the problem of polarization of current electrode. We used a new software and hardware to compensate self-potential. Meanwhile, filtering technique associated software and hardware is use to restrain disturbance from natural electric field. It increases the accuracy and anti-jamming capability of the instrument. General steel metal electrodes can perform polarization measurement. This affords change to find water and mineral using high-density electrical resistivity method. A large number of practical application has shown that the combination of high-density electrical resistivity and high density polarization have obtained good effects in engineering geology and environmental geology, as well as mineral geology and hydrological geology exploration.
High-density electrical resistivity survey has been generally used in engineering geology and environmental geology. However, electrical resistivity is not enough to find water and mineral, and polarizability has better effect in these region. But, there has the problem of polarization of current electrode. We used a new software and hardware to compensate self-potential. Meanwhile, filtering technique associated software and hardware is use to restrain disturbance from natural electric field. It increases the accuracy and anti-jamming capability of the instrument. General steel metal electrodes can perform polarization measurement. This affords change to find water and mineral using high-density electrical resistivity method. A large number of practical application has shown that the combination of high-density electrical resistivity and high density polarization have obtained good effects in engineering geology and environmental geology, as well as mineral geology and hydrological geology exploration.
2016, 24(s1): 1320-1325.
Failure modes of rock mass isdetermined by the rock mass structureswhich influence the characteristics of the rock mass. Based on the observations for rock burst in Qirehataerdivisiontunnel, this paper proposes a concept of rock-burst burst-body which is used to describe thecritical state of failure for textured rock mass. Rock-burst burst-body isinitiated, evolved and controlled by the micro structuresof rock mass, the geostress features and the engineering layout, et al.Moreover, the forming process, failure modes and the mechanisms of rock-burst burst-body are exploredby studying the features of rock burst in different place of Qirehataer diversion tunnel. The concept and study of rock-burst burst-bodypresented in this paper will be helpful to further study of rock burst.
Failure modes of rock mass isdetermined by the rock mass structureswhich influence the characteristics of the rock mass. Based on the observations for rock burst in Qirehataerdivisiontunnel, this paper proposes a concept of rock-burst burst-body which is used to describe thecritical state of failure for textured rock mass. Rock-burst burst-body isinitiated, evolved and controlled by the micro structuresof rock mass, the geostress features and the engineering layout, et al.Moreover, the forming process, failure modes and the mechanisms of rock-burst burst-body are exploredby studying the features of rock burst in different place of Qirehataer diversion tunnel. The concept and study of rock-burst burst-bodypresented in this paper will be helpful to further study of rock burst.
2016, 24(s1): 1326-1335.
In order to study the relationships between goaf collapse caused by underground coal-mining and the safety of buildingsandsurface deformation, we analyzed the deformation of pylon foundation affecting by different mine goaf due to different mining methods, as well as the stability of adjacentslope in an area. This area is located in the district of Z149#~Z154# transmission line, which is based on the 750kV power transmission project. A MIDAS numerical simulation software is used to establish a three-dimensional analysis model and two working conditions are simulated in this paper, some conclusions are obtained as follows:(1) under the existing working conditions, the goaf mainly affected the tower of 149# and the tower of 150#, and the simulation results show thatbetween the tower of 149# and the tower of 150#,vertical displacement have its peakat 0.7259m, which is in consonance with the actual observation of the maximum surface settlement of 0.65m, showing that the simulation results can approximately reflect the actual deformation results; exploitation can cause 149#, 150# and 151# tower' foundation uneven settlement, the maximum difference in settlement between towel foots reachto 0.0091m, which is in accordance with the measured value of 150# tower with its maximum difference in settlement is 0.0085m, and likewise, the simulation results suit actual results well; and the least favorable profiles only appear in slopes in the vicinity between the 149# tower and 150# tower, but no continuous slip surface is formed, and no slope instability would be formed.(2) Under the final working condition, all the already formedgoaf in this field have impacts on pylon foundations, and compared with the existing working conditions, the vertical displacementsof each towel display an increasing trend; the mining-caused maximum settlement in tower foots could reach as high as 0.0120m, and tower of 150#, 151# and 152# produced an oversized subsidence difference, so strengthened monitoring should be warranted; although slopes near the tower are all influencedby mining activities, there are not continuous slip surface formed, as a result, no slope instability would occur. This paper can provide technical support and reference for the safe operation and control of the transmission line and other related structures which are located in the goaf areas.
In order to study the relationships between goaf collapse caused by underground coal-mining and the safety of buildingsandsurface deformation, we analyzed the deformation of pylon foundation affecting by different mine goaf due to different mining methods, as well as the stability of adjacentslope in an area. This area is located in the district of Z149#~Z154# transmission line, which is based on the 750kV power transmission project. A MIDAS numerical simulation software is used to establish a three-dimensional analysis model and two working conditions are simulated in this paper, some conclusions are obtained as follows:(1) under the existing working conditions, the goaf mainly affected the tower of 149# and the tower of 150#, and the simulation results show thatbetween the tower of 149# and the tower of 150#,vertical displacement have its peakat 0.7259m, which is in consonance with the actual observation of the maximum surface settlement of 0.65m, showing that the simulation results can approximately reflect the actual deformation results; exploitation can cause 149#, 150# and 151# tower' foundation uneven settlement, the maximum difference in settlement between towel foots reachto 0.0091m, which is in accordance with the measured value of 150# tower with its maximum difference in settlement is 0.0085m, and likewise, the simulation results suit actual results well; and the least favorable profiles only appear in slopes in the vicinity between the 149# tower and 150# tower, but no continuous slip surface is formed, and no slope instability would be formed.(2) Under the final working condition, all the already formedgoaf in this field have impacts on pylon foundations, and compared with the existing working conditions, the vertical displacementsof each towel display an increasing trend; the mining-caused maximum settlement in tower foots could reach as high as 0.0120m, and tower of 150#, 151# and 152# produced an oversized subsidence difference, so strengthened monitoring should be warranted; although slopes near the tower are all influencedby mining activities, there are not continuous slip surface formed, as a result, no slope instability would occur. This paper can provide technical support and reference for the safe operation and control of the transmission line and other related structures which are located in the goaf areas.
2016, 24(s1): 1336-1341.
Through the study of chloride ion in cracked concrete, a coupling model is established, which considers diffusion, binding and electric potential and the crack influence. Predicting the concrete service life. The model was verified by experimental data. In Nantong saline soil, the chloride ion migration in different width and depth crack and the variation law of concrete service life was analyzed by Comol Multiphysics. The research shows that the chloride ion concentration decreases with the increase of intrusion depth, and increases over time. When moving into concrete, the chloride concentration dropping suddenly. The concrete service life increases with the increase of the protective cover thickness, and decreases with the increase of the crack depth, and the exponential function relation with the increase of the crack width.
Through the study of chloride ion in cracked concrete, a coupling model is established, which considers diffusion, binding and electric potential and the crack influence. Predicting the concrete service life. The model was verified by experimental data. In Nantong saline soil, the chloride ion migration in different width and depth crack and the variation law of concrete service life was analyzed by Comol Multiphysics. The research shows that the chloride ion concentration decreases with the increase of intrusion depth, and increases over time. When moving into concrete, the chloride concentration dropping suddenly. The concrete service life increases with the increase of the protective cover thickness, and decreases with the increase of the crack depth, and the exponential function relation with the increase of the crack width.
2016, 24(s1): 1342-1346.
Based on the study that has been done, the slaking mechanism of red beds interaction with temperature, water and stress, was studied. Some results were obtained as following: (1) the engines of mudstone slaking are the difference value of stress, concentration, temperature, water pressure, atmospheric pressure, which were evoked by the change of the situation of red beds depositing; (2) the irreversible breaking of red beds' structures were induced by some physical chemistry processes related to water, temperature and stress, such as stress redistribution, solution, swelling, evaporation, capillary, seepage, erosion, et al.; (3) the structure breaking of mudstone was accumulated though the cycling between water and temperature and the seasonal cycling, until the structure destroy happened; (4) It is the difference value of factors that evoke various physical chemistry processes; then some stresses above and beyond the strength of mudstone were set up; the structure breaking are produced, until the rock fragment break away the rock mass though the cycling between water and temperature and the seasonal cycling.
Based on the study that has been done, the slaking mechanism of red beds interaction with temperature, water and stress, was studied. Some results were obtained as following: (1) the engines of mudstone slaking are the difference value of stress, concentration, temperature, water pressure, atmospheric pressure, which were evoked by the change of the situation of red beds depositing; (2) the irreversible breaking of red beds' structures were induced by some physical chemistry processes related to water, temperature and stress, such as stress redistribution, solution, swelling, evaporation, capillary, seepage, erosion, et al.; (3) the structure breaking of mudstone was accumulated though the cycling between water and temperature and the seasonal cycling, until the structure destroy happened; (4) It is the difference value of factors that evoke various physical chemistry processes; then some stresses above and beyond the strength of mudstone were set up; the structure breaking are produced, until the rock fragment break away the rock mass though the cycling between water and temperature and the seasonal cycling.
2016, 24(s1): 1347-1354.
The determination of characteristic parameters of hydraulic fracturing in-situ stress measurement is very important to improve the accuracy of measurement results. In order to avoid personnel errors and repeating operations due to manual processing of recording data, one software was developed to define the stress measurement parameters of hydraulic fracturing recording curve automatically by computers. This interactive software includes three modules: data acquisition, data processing and database management. The core is the data processing module, which include all the methods for the determination of stress measurement parameters, Pr and Ps. This software was realized using VB development platform, with friendly interfaces and reliable functions. The application in the stress measurement campaigns in a borehole in Honghe town, Weifang City, Shandong Province proves the reliability and convenience of the software.
The determination of characteristic parameters of hydraulic fracturing in-situ stress measurement is very important to improve the accuracy of measurement results. In order to avoid personnel errors and repeating operations due to manual processing of recording data, one software was developed to define the stress measurement parameters of hydraulic fracturing recording curve automatically by computers. This interactive software includes three modules: data acquisition, data processing and database management. The core is the data processing module, which include all the methods for the determination of stress measurement parameters, Pr and Ps. This software was realized using VB development platform, with friendly interfaces and reliable functions. The application in the stress measurement campaigns in a borehole in Honghe town, Weifang City, Shandong Province proves the reliability and convenience of the software.
2016, 24(s1): 1355-1361.
the determination of residual strength of sliding belt is a very important for analysis of reactivated landslides. The silty sand(SM) is the erratic soil which behaves complex shear behavior. This study investigated the influence of over-consolidation ratio(OCR)on the shear strength of SM type landslide soil using the multistage ring shear test under different pre-consolidation pressure. A series of ring shear tests were conducted to measure the drained residual strength under OCrs of 1~12 at shear rates of 0.06mmmin-1.The test results showed that peak strength of SM type landslide soil increased linearly with increasing OCrs under the same normal stress during shearing, but residual strength of SM type landslide soil was not affected significantly by the over-consolidation process.
the determination of residual strength of sliding belt is a very important for analysis of reactivated landslides. The silty sand(SM) is the erratic soil which behaves complex shear behavior. This study investigated the influence of over-consolidation ratio(OCR)on the shear strength of SM type landslide soil using the multistage ring shear test under different pre-consolidation pressure. A series of ring shear tests were conducted to measure the drained residual strength under OCrs of 1~12 at shear rates of 0.06mmmin-1.The test results showed that peak strength of SM type landslide soil increased linearly with increasing OCrs under the same normal stress during shearing, but residual strength of SM type landslide soil was not affected significantly by the over-consolidation process.
2016, 24(s1): 1362-1369.
The microtremor characteristics of the construction site can reflect the geological information of the formation structure to a certain extent. In recent years, it has been applied in the engineering geological investigation, but the mechanism of the generation of microtremor and the relationship with the formation structure have yet to be further studied. This paper chooses the areas with the same strata structure which has large undulating in the layer's level, and then half-year microtremor tests had been done based on the study of the method of H/V spectral ratios. Then the researches on the change of cover thickness of the large undulating formation which had an effect on dynamic characteristics and time characteristics of the microtremor is done by H/V spectral ratio method to process and interpreter data. These results show that the H/V spectrum transformed from a single peak to two, and finally to the platform with the cover thickness decrease. The range and frequency of the peak is gradually increased, while the spectral ratio is decreased. The morphology of H/V spectrum appears a peak platform with high frequency values and large range, which is extremely unfavorable to the seismic resistance of low rise buildings with relatively high natural frequency, and it should be given enough attention in the study of seismic hazard assessment.
The microtremor characteristics of the construction site can reflect the geological information of the formation structure to a certain extent. In recent years, it has been applied in the engineering geological investigation, but the mechanism of the generation of microtremor and the relationship with the formation structure have yet to be further studied. This paper chooses the areas with the same strata structure which has large undulating in the layer's level, and then half-year microtremor tests had been done based on the study of the method of H/V spectral ratios. Then the researches on the change of cover thickness of the large undulating formation which had an effect on dynamic characteristics and time characteristics of the microtremor is done by H/V spectral ratio method to process and interpreter data. These results show that the H/V spectrum transformed from a single peak to two, and finally to the platform with the cover thickness decrease. The range and frequency of the peak is gradually increased, while the spectral ratio is decreased. The morphology of H/V spectrum appears a peak platform with high frequency values and large range, which is extremely unfavorable to the seismic resistance of low rise buildings with relatively high natural frequency, and it should be given enough attention in the study of seismic hazard assessment.
2016, 24(s1): 1370-1377.
The construction of the western region in China is accelerating gradually with the development of national economy. Exploring the characteristics of regional in-situ stress field can provide references to scientific research, mitigation of earthquake disasters and engineering construction. The article resumes four measurement methods widely used in Tianshan region which include hydraulic fracturing, overcoring method, earthquake focal mechanisms and fault slip data. Based on fundamental data base of crustal stress environment in continental China, this paper disposed the locations, depths, values, orientations and dips for in-situ stress measurement in recent years by means of literature search. The disposed data shows that the locations of in-situ stress measuring were widely distributed in Tianshan area. And the orientation of the maximum principal stress is N-S; the intermediate principal stress is W-E; the minimum principal stress is WWN-EES.The relationship of principal stresses is H h v.The state of in-situ stress in Hutubi area can be got by fault slip data. The orientation of 1 in Hutubi is N19W; and 3 is N71E which closes to horizontal. The dip of 2 is 78which closes to vertical. The orientations of principal stresses in Hutubi area which correspond Tianshan area, however, the relationship of principal stresses is H v h.The relationship of in-situ stress between Hutubi area and Tianshan area can be discovered by disposal of the in-situ stress measuring data in Tianshan area. It can provide reference to engineering construction in Hutubi area.
The construction of the western region in China is accelerating gradually with the development of national economy. Exploring the characteristics of regional in-situ stress field can provide references to scientific research, mitigation of earthquake disasters and engineering construction. The article resumes four measurement methods widely used in Tianshan region which include hydraulic fracturing, overcoring method, earthquake focal mechanisms and fault slip data. Based on fundamental data base of crustal stress environment in continental China, this paper disposed the locations, depths, values, orientations and dips for in-situ stress measurement in recent years by means of literature search. The disposed data shows that the locations of in-situ stress measuring were widely distributed in Tianshan area. And the orientation of the maximum principal stress is N-S; the intermediate principal stress is W-E; the minimum principal stress is WWN-EES.The relationship of principal stresses is H h v.The state of in-situ stress in Hutubi area can be got by fault slip data. The orientation of 1 in Hutubi is N19W; and 3 is N71E which closes to horizontal. The dip of 2 is 78which closes to vertical. The orientations of principal stresses in Hutubi area which correspond Tianshan area, however, the relationship of principal stresses is H v h.The relationship of in-situ stress between Hutubi area and Tianshan area can be discovered by disposal of the in-situ stress measuring data in Tianshan area. It can provide reference to engineering construction in Hutubi area.
2016, 24(s1): 1378-1383.
The corresponding relationship between the macroscopic and microscopic mechanical parameters is investigated through numerical simulation method. Based on the results of large number of three-dimensional particle flow code numerical tests, a quick calibration method for calibrating the microscopic mechanical parameters of Rock-like material in PFC3D is proposed, and the reference value of microscopic mechanical parameters are determined by the fitting relationship between the macroscopic and microscopic mechanical parameters. A cylinder numerical model for rock-like material is established according to the proposed micro-parameters. The common triaxial tests for the cylinder model are simulated. The simulated results have a good consistency with the laboratory model triaxial tests, and reliability of the proposed method for microscopic mechanical parameters is validated.
The corresponding relationship between the macroscopic and microscopic mechanical parameters is investigated through numerical simulation method. Based on the results of large number of three-dimensional particle flow code numerical tests, a quick calibration method for calibrating the microscopic mechanical parameters of Rock-like material in PFC3D is proposed, and the reference value of microscopic mechanical parameters are determined by the fitting relationship between the macroscopic and microscopic mechanical parameters. A cylinder numerical model for rock-like material is established according to the proposed micro-parameters. The common triaxial tests for the cylinder model are simulated. The simulated results have a good consistency with the laboratory model triaxial tests, and reliability of the proposed method for microscopic mechanical parameters is validated.
2016, 24(s1): 1384-1389.
The climate of the north area of downstream of Kongque river in Xinjiang belongs to the typical north temperate continental arid climate, drought and rainless, but evaporation is large, therefore the groundwater resource of this area is lacking and the water quality is worst, and then restricts the development and utilization of mineral resources of this area. In this paper, the groundwater distribution and hydrochemical characteristics in the north area of downstream of KongQue river are studied, and the causes are analyzed. The results show that the distribution of groundwater in the study area is uneven, in the northwestern mountainous area rainfall is rich, and the supply condition is good, and then the water is rich and the quality is better in the intermountain depression, fracture and the fault position, the TDS 0.8~2.0gL-1,hydrochemical type is SO4-Cl-Na-Ca, SO4-Cl-Na, SO4-Na; in the southeast rainless area, groundwater resource is lacking. If have a certain condition, there also form a water-rich area in some resistance water fault, but the TDS is larger than 10gL-1, and hydrochemical type is Cl-Na.
The climate of the north area of downstream of Kongque river in Xinjiang belongs to the typical north temperate continental arid climate, drought and rainless, but evaporation is large, therefore the groundwater resource of this area is lacking and the water quality is worst, and then restricts the development and utilization of mineral resources of this area. In this paper, the groundwater distribution and hydrochemical characteristics in the north area of downstream of KongQue river are studied, and the causes are analyzed. The results show that the distribution of groundwater in the study area is uneven, in the northwestern mountainous area rainfall is rich, and the supply condition is good, and then the water is rich and the quality is better in the intermountain depression, fracture and the fault position, the TDS 0.8~2.0gL-1,hydrochemical type is SO4-Cl-Na-Ca, SO4-Cl-Na, SO4-Na; in the southeast rainless area, groundwater resource is lacking. If have a certain condition, there also form a water-rich area in some resistance water fault, but the TDS is larger than 10gL-1, and hydrochemical type is Cl-Na.
2016, 24(s1): 1390-1394.