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Editor Work2013 Vol. 21, No. 3
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2013, 21(3): 337-344.
Abstract
1758KB
To describe well the stress-stain behaviour of sands, generally, a state parameter is used. It is based on the critical state void to established the elastoplastic constitutive relations. However, it is difficult to obtain the critical state parameter in triaxial drained tests for dense sands. The phase transformation state is a characteristic state. Its related parameters are easy to measure. So this paper defines the state parameter that is based on the phase transformation state void. It introduces the stress ration expressions for dilatancy and boundary, and establishes the elastoplastic constitutive model for sands. Finally, based on the provided model parameters, the simulated results fit well with the test results and realistically reflect the strain hardening and softening characteristics for dense sands.
To describe well the stress-stain behaviour of sands, generally, a state parameter is used. It is based on the critical state void to established the elastoplastic constitutive relations. However, it is difficult to obtain the critical state parameter in triaxial drained tests for dense sands. The phase transformation state is a characteristic state. Its related parameters are easy to measure. So this paper defines the state parameter that is based on the phase transformation state void. It introduces the stress ration expressions for dilatancy and boundary, and establishes the elastoplastic constitutive model for sands. Finally, based on the provided model parameters, the simulated results fit well with the test results and realistically reflect the strain hardening and softening characteristics for dense sands.
2013, 21(3): 345-350.
Capillary suction is one of the vital physical parameters to porous media and has been widely concerned in engineering practice. This paper combines the Gardner soil-water characteristic curve model and the structure parameters obtained by Micro-CT tomography at first. The unsaturated capillary rise model and a specific quantification for capillary rise in the porous media are then developed using the fitting relationship between suction and saturation and the finite difference method. Furthermore, laboratory experiments are carried out to confirm the availability of the model, where the narrow sub-washed sand is chosen as object. Parameters of the capillary rise process and the stable distribution of moisture are measured actually. Results indicate that a good agreement is presented between test and theoretical values. The proposed theory is feasible to predict the capillary rise and the moisture distribution of sand.
Capillary suction is one of the vital physical parameters to porous media and has been widely concerned in engineering practice. This paper combines the Gardner soil-water characteristic curve model and the structure parameters obtained by Micro-CT tomography at first. The unsaturated capillary rise model and a specific quantification for capillary rise in the porous media are then developed using the fitting relationship between suction and saturation and the finite difference method. Furthermore, laboratory experiments are carried out to confirm the availability of the model, where the narrow sub-washed sand is chosen as object. Parameters of the capillary rise process and the stable distribution of moisture are measured actually. Results indicate that a good agreement is presented between test and theoretical values. The proposed theory is feasible to predict the capillary rise and the moisture distribution of sand.
2013, 21(3): 351-356.
Reclamation through technology of dredger fill can relieve the problem of short earth resources effectively. So it is urgent to improve this technology. Dredger fill has a high content of clay, organic and moisture, high compressibility and low strength, which cause the characteristic of low consolidation efficiency and slow settling velocity for the reclaimed land. For most of the projects, long-term settlement observation has been omitted due to the big requirement of resources. It usually takes 2-3 years to form the hard mantle layer on the surface of dredger fill. Such duration is too long. The effect is not ideal. Furthermore, there is a big difference between the actual settlement after construction and the expected one. In order to satisfy the deformation requirements, the problems of the prediction of long-term settlement based on the observation data of short-term settlement have to be addressed. In addition, the method that can be taken based on the long-term settlement prediction needs to be solved. The time series-dynamic neural network is established through self programming in this article. This method is applied in the prediction of long-term settlement and the analysis of results in Dredger Fill. The results show that the method of dynamic neural network can be reasonably applied to the prediction of soft soil consolidation settlement with minor error and better feasibility. The prediction has high precision and stability.
Reclamation through technology of dredger fill can relieve the problem of short earth resources effectively. So it is urgent to improve this technology. Dredger fill has a high content of clay, organic and moisture, high compressibility and low strength, which cause the characteristic of low consolidation efficiency and slow settling velocity for the reclaimed land. For most of the projects, long-term settlement observation has been omitted due to the big requirement of resources. It usually takes 2-3 years to form the hard mantle layer on the surface of dredger fill. Such duration is too long. The effect is not ideal. Furthermore, there is a big difference between the actual settlement after construction and the expected one. In order to satisfy the deformation requirements, the problems of the prediction of long-term settlement based on the observation data of short-term settlement have to be addressed. In addition, the method that can be taken based on the long-term settlement prediction needs to be solved. The time series-dynamic neural network is established through self programming in this article. This method is applied in the prediction of long-term settlement and the analysis of results in Dredger Fill. The results show that the method of dynamic neural network can be reasonably applied to the prediction of soft soil consolidation settlement with minor error and better feasibility. The prediction has high precision and stability.
2013, 21(3): 357-362.
To apply the random field theory to the properties of a soil needs the spatial distribution of the soil properties to meet the stationarity and ergodicity. Most domestic researchers applied the vanmarcke model under the assumption that it meets the conditions of stationary random field theory. The investigations on loess also did not examine its stationarity and ergodicity. Based on the 29 drilling CPT data from a project in Xi'an Qujiang, this paper discusses the homogeneous processing of the raw data firstly(elimination of the trend component).And then it tests the stationarity and ergodicity of the loess soil properties.
To apply the random field theory to the properties of a soil needs the spatial distribution of the soil properties to meet the stationarity and ergodicity. Most domestic researchers applied the vanmarcke model under the assumption that it meets the conditions of stationary random field theory. The investigations on loess also did not examine its stationarity and ergodicity. Based on the 29 drilling CPT data from a project in Xi'an Qujiang, this paper discusses the homogeneous processing of the raw data firstly(elimination of the trend component).And then it tests the stationarity and ergodicity of the loess soil properties.
2013, 21(3): 363-369.
The Niuganchong avalanche is at Shangyangshui river mining area in Jinzhong, Kaiyang, Guizhou. The mining area is affected by Yangshui anticline and NNE trending fracture. Cliffs in the mining area are of zonal distribution. Combining with the intensive mining activities, the roof dolomite cliff covering the lower phosphate rock layer is liable to develop unstable rock zone. Thus there have been many avalanches in the last 20 years. The Niuganchong avalanche studied in this paper occurred in 2005.Its colluvial deposits are accumulated in the form of belts in the valley and formed three significant regions. Their movements and accumulation characteristics are obviously different. Field investigation and analysis are carried out on the accumulations characteristics. Rock movement path is also simulated. Then, this paper propose that the colluvial deposits are usually rolling to the valley and forming rubbles. But a few chunks of falling rocks are influenced by micro-relief and begin with rolling and end with leaping along a small gully nearby the right side of the rubbles. Each drop point is easy to find out. Finally complex movement characteristics and numerical simulation of the avalanche are studied to forecast the damaging range of dangerous rocks in future.
The Niuganchong avalanche is at Shangyangshui river mining area in Jinzhong, Kaiyang, Guizhou. The mining area is affected by Yangshui anticline and NNE trending fracture. Cliffs in the mining area are of zonal distribution. Combining with the intensive mining activities, the roof dolomite cliff covering the lower phosphate rock layer is liable to develop unstable rock zone. Thus there have been many avalanches in the last 20 years. The Niuganchong avalanche studied in this paper occurred in 2005.Its colluvial deposits are accumulated in the form of belts in the valley and formed three significant regions. Their movements and accumulation characteristics are obviously different. Field investigation and analysis are carried out on the accumulations characteristics. Rock movement path is also simulated. Then, this paper propose that the colluvial deposits are usually rolling to the valley and forming rubbles. But a few chunks of falling rocks are influenced by micro-relief and begin with rolling and end with leaping along a small gully nearby the right side of the rubbles. Each drop point is easy to find out. Finally complex movement characteristics and numerical simulation of the avalanche are studied to forecast the damaging range of dangerous rocks in future.
2013, 21(3): 370-376.
As its occurrence conditions changes, the quality of rock mass has corresponding dynamic change. So the dynamic evaluation of rock mass quality for dam foundation is of great significance for the safety of dam operation. This paper is based on a large number of tests and monitoring data of the foundation rock mass at Xiaowan Dam. It summarizes the dynamic characteristics of the quality of rock mass and then puts forward the evaluation index of rock mass qualitys degradation and recovery. It also uses the BQ system and RMR system to evaluate dynamically the characteristics of the change of the rock mass quality in the four-dimensional space. Furthermore the relationship between Vp and E0(Vp-E0) is established and the Hoek-Brown strength criterion is adopted to determine the strength index of the feature points of the rock mass. At the same time, the relaxation degree coefficient of rock mass is used as indicators to examine a kind of simple and easy forecasting method of rock mass quality.
As its occurrence conditions changes, the quality of rock mass has corresponding dynamic change. So the dynamic evaluation of rock mass quality for dam foundation is of great significance for the safety of dam operation. This paper is based on a large number of tests and monitoring data of the foundation rock mass at Xiaowan Dam. It summarizes the dynamic characteristics of the quality of rock mass and then puts forward the evaluation index of rock mass qualitys degradation and recovery. It also uses the BQ system and RMR system to evaluate dynamically the characteristics of the change of the rock mass quality in the four-dimensional space. Furthermore the relationship between Vp and E0(Vp-E0) is established and the Hoek-Brown strength criterion is adopted to determine the strength index of the feature points of the rock mass. At the same time, the relaxation degree coefficient of rock mass is used as indicators to examine a kind of simple and easy forecasting method of rock mass quality.
2013, 21(3): 377-384.
The paper solves rock mass classification problem for design and construction of a railroad tunnel through the brittle ductile shear zone(faults) and its secondary ductile shear belt in mountainous area. It discusses the characteristics of ductile shear zones including the aspects of geometry, structure, movement track, tectonic, deformation and metamorphic mylonite, and mechanical action. It summarizes the construction surrounding rock classification from the aspects of macroscopical, microcosmic, field research and testing, analog, and compares engineering properties of rock mass and engineering design of the classification of surrounding rock between ductile shear zone(brittle ductile and brittle) and joint concentrated zone. Based on these results, the paper concludes that the mountain tunnel by ductile shear zone should be studied separately, especially on rock mass classification indexes and surrounding rock classification principle. Special attention should be paid on its design and construction.
The paper solves rock mass classification problem for design and construction of a railroad tunnel through the brittle ductile shear zone(faults) and its secondary ductile shear belt in mountainous area. It discusses the characteristics of ductile shear zones including the aspects of geometry, structure, movement track, tectonic, deformation and metamorphic mylonite, and mechanical action. It summarizes the construction surrounding rock classification from the aspects of macroscopical, microcosmic, field research and testing, analog, and compares engineering properties of rock mass and engineering design of the classification of surrounding rock between ductile shear zone(brittle ductile and brittle) and joint concentrated zone. Based on these results, the paper concludes that the mountain tunnel by ductile shear zone should be studied separately, especially on rock mass classification indexes and surrounding rock classification principle. Special attention should be paid on its design and construction.
2013, 21(3): 385-390.
Pure bentonite mixes with quartz sand can effectively improve the thermo conductivity, mechanical strength and long-term stability of the mixture. It also can reduce the construction cost of the engineering barrier system. Meanwhile, it may make changes of the water retention property of the mixture. This paper uses osmotic technique and vapor equilibrium technique and tests water retention characteristics of highly compacted GMZ01 bentonite-quartz sand mixtures at different temperatures(20℃, 40℃ and 60℃)under confined conditions. Results show that, for given suction and constant volume, water content of GMZ01 bentonite-sand mixtures decreases as temperature increases. But the changing rate depends on suction level. For low suctions, degree of saturation is higher than 1,which may result from the higher density of the absorbed water. Water retention characteristics of GMZ01 bentonite-sand mixtures fitted by the revised Wan Min model are consistent with the measured ones.
Pure bentonite mixes with quartz sand can effectively improve the thermo conductivity, mechanical strength and long-term stability of the mixture. It also can reduce the construction cost of the engineering barrier system. Meanwhile, it may make changes of the water retention property of the mixture. This paper uses osmotic technique and vapor equilibrium technique and tests water retention characteristics of highly compacted GMZ01 bentonite-quartz sand mixtures at different temperatures(20℃, 40℃ and 60℃)under confined conditions. Results show that, for given suction and constant volume, water content of GMZ01 bentonite-sand mixtures decreases as temperature increases. But the changing rate depends on suction level. For low suctions, degree of saturation is higher than 1,which may result from the higher density of the absorbed water. Water retention characteristics of GMZ01 bentonite-sand mixtures fitted by the revised Wan Min model are consistent with the measured ones.
2013, 21(3): 391-399.
The BJ-1 tunnel is a municipal Engineering. It has shallow, bias condition, seriously weathered clay and shale, rock crushing, karst and groundwater development, underground pipelines and surface buildings intensive. So, the tunnel construction safety contained great risky. To ensure the safety of the tunnel construction, to protect surface buildings and the safety of the residents, it was very important to carry out the tunnel construction geological prediction and monitoring measurement. On the basis of analysis of the main engineering geological problems that may exist in the tunnel, the important and difficult geological prediction contents were determined. The comprehensive advanced geological forecast technology were put out. The geological methods were the basic methods. The ground penetrating radar and acoustic wave reflection method were the main geophysical means. According to the construction safety control needs, the implementation outline of the BJ-1 tunnel monitoring was formulated for construction safety control, focused on level convergence, vault sink, surface subsidence and blasting vibration monitoring. The monitoring and early warning system was established for the tunnel. By comprehensive analysis of advanced geological forecast and tunnel monitoring results, a reliable basis was given for the tunnel safety construction decisions. Dangerous incidents were avoided in the tunnel construction process. The research methods had important reference value for construction and design of similar city tunnel projects.
The BJ-1 tunnel is a municipal Engineering. It has shallow, bias condition, seriously weathered clay and shale, rock crushing, karst and groundwater development, underground pipelines and surface buildings intensive. So, the tunnel construction safety contained great risky. To ensure the safety of the tunnel construction, to protect surface buildings and the safety of the residents, it was very important to carry out the tunnel construction geological prediction and monitoring measurement. On the basis of analysis of the main engineering geological problems that may exist in the tunnel, the important and difficult geological prediction contents were determined. The comprehensive advanced geological forecast technology were put out. The geological methods were the basic methods. The ground penetrating radar and acoustic wave reflection method were the main geophysical means. According to the construction safety control needs, the implementation outline of the BJ-1 tunnel monitoring was formulated for construction safety control, focused on level convergence, vault sink, surface subsidence and blasting vibration monitoring. The monitoring and early warning system was established for the tunnel. By comprehensive analysis of advanced geological forecast and tunnel monitoring results, a reliable basis was given for the tunnel safety construction decisions. Dangerous incidents were avoided in the tunnel construction process. The research methods had important reference value for construction and design of similar city tunnel projects.
2013, 21(3): 400-407.
With the development of urban construction, underground structures including subways, underground parks and underground markets have become more and more widespread. Their development trends are diversified, complicated and deep-going. It can be known that anti-floating stability of underground structures become an outstanding problem. So, one of main project measures is to set up uplift piles. This paper mainly analyzes the ground failure mode of uplift pile and pile group, and reveals the work mechanism of uplift pile. The mode of uplift pile and pile group is numerically simulated using ABAQUS finite element software. The influence factors of uplift capacity and pile group effect are investigated in different aspects such as pile stress, soil around pile and pile side resistance. It further studies the effect of the distance-diameter ratio of uplift pile group on uplift capacity and foundation deformation combined with practical works. The analyzing results show that, under the action of uplift force, pile stress mainly acts in axis, which decreases with increasing radius and depth. The pile side friction force decreases gradually from upper depth to lower depth. It increases with increasing upward displacement. When the distance-diameter ratio() of foundation pile decreases, the capacity reduction factor() increases, the pile group effect is more significant, and there is an uplift trend in piles and soil between piles that go against the anti-floating stability of construction.=3 and =6 can be used as the limit ti determine the degree of pile group.
With the development of urban construction, underground structures including subways, underground parks and underground markets have become more and more widespread. Their development trends are diversified, complicated and deep-going. It can be known that anti-floating stability of underground structures become an outstanding problem. So, one of main project measures is to set up uplift piles. This paper mainly analyzes the ground failure mode of uplift pile and pile group, and reveals the work mechanism of uplift pile. The mode of uplift pile and pile group is numerically simulated using ABAQUS finite element software. The influence factors of uplift capacity and pile group effect are investigated in different aspects such as pile stress, soil around pile and pile side resistance. It further studies the effect of the distance-diameter ratio of uplift pile group on uplift capacity and foundation deformation combined with practical works. The analyzing results show that, under the action of uplift force, pile stress mainly acts in axis, which decreases with increasing radius and depth. The pile side friction force decreases gradually from upper depth to lower depth. It increases with increasing upward displacement. When the distance-diameter ratio() of foundation pile decreases, the capacity reduction factor() increases, the pile group effect is more significant, and there is an uplift trend in piles and soil between piles that go against the anti-floating stability of construction.=3 and =6 can be used as the limit ti determine the degree of pile group.
2013, 21(3): 408-415.
Long urban metro tunnel will make some effects on groundwater environment during their operation. This paper analyses it with Beijing Metro 8(Northern Part of Period 2) as an example. A system of evaluation method is set up in this paper. The damming effect on groundwater environment is quantified based on some calculations. Some environmental and engineering problems are evaluated. The conclusions can give the scientific base for protecting groundwater environment and economizing the construction of this urban metro. In addition, this paper can be a good reference for other metro constructions and evaluation.
Long urban metro tunnel will make some effects on groundwater environment during their operation. This paper analyses it with Beijing Metro 8(Northern Part of Period 2) as an example. A system of evaluation method is set up in this paper. The damming effect on groundwater environment is quantified based on some calculations. Some environmental and engineering problems are evaluated. The conclusions can give the scientific base for protecting groundwater environment and economizing the construction of this urban metro. In addition, this paper can be a good reference for other metro constructions and evaluation.
2013, 21(3): 416-421.
To describe the stability and operation safety of buildings on soft soil area, this article carries out a series of shear creep tests of soft soil in Tianjin littoral area. Different vertical loads and load ratios are adopted in the shear creep instrument. It obtains the relationship of stain and stress and time in different conditions. It analyzes the structural effect and influence factors of the shear creep properties. It then establishes the corresponding constitutive model. The test results show that the shear creep properties of Tianjin littoral soft soil are obviously restricted by stress. The soil turns up attenuation creep and steady creep in low stress and destructive creep in high stress. The stress-strain presents a linear characteristics in lower stress and shows the nonlinear creep characteristics in higher stress. The smaller load ratio can not only reduce the final creep, but also improve the soft soil capacity. The nonlinear creep constitutive equation of Tianjin littoral soft soil is established with the theory of half experience and half theoretical method. The equation has the character of simple to understand, less parameters and strong practical. The model can well fit the Tianjin littoral soft soil creep characteristics through the compared analysis of experimental results and the creep model.
To describe the stability and operation safety of buildings on soft soil area, this article carries out a series of shear creep tests of soft soil in Tianjin littoral area. Different vertical loads and load ratios are adopted in the shear creep instrument. It obtains the relationship of stain and stress and time in different conditions. It analyzes the structural effect and influence factors of the shear creep properties. It then establishes the corresponding constitutive model. The test results show that the shear creep properties of Tianjin littoral soft soil are obviously restricted by stress. The soil turns up attenuation creep and steady creep in low stress and destructive creep in high stress. The stress-strain presents a linear characteristics in lower stress and shows the nonlinear creep characteristics in higher stress. The smaller load ratio can not only reduce the final creep, but also improve the soft soil capacity. The nonlinear creep constitutive equation of Tianjin littoral soft soil is established with the theory of half experience and half theoretical method. The equation has the character of simple to understand, less parameters and strong practical. The model can well fit the Tianjin littoral soft soil creep characteristics through the compared analysis of experimental results and the creep model.
2013, 21(3): 422-432.
In busy city the geophysical exploration methods are interfered with the noise from vibration of heavy traffic and strong electromagnetic field and stray electricity. An conquering of the interference of rugged landform in mountain land also are the problem of all the geophysical method. Surveying of single karst cave with small or middle sizes is difficult. They are more required to put energy into the new development of technology and new method. Landsonar and its instrument can avoid the interference of noise from vibration of cars and pedestrains with frequency generally less than 300 Hz in city by exciting and receiving elastic waves of 10～4000 Hz. The instrument C-1 can avoid the interference of strong electromagnetic field and stray electricity with supplying narrow frequency alternating current of 11～19 Hz. Because of the zero offset and high and wide frequency band, Landsonar can avoid the interference of landform and have high resolution on single karst cave with small to middle sizes. Because of the especial electrode arrangement, Differential Electric Sounding(DES)method can survey karst cave of 1m high within 100m deep. KS marine acoustics prospecting instrument have better transverse and longitudinal resolution, can distinguish the silt layer, sand layer, cobble layer and riprap layer with thickness more than 1m and geologic structure under sub-bottom, and can work with broken survey line and curve survey line.
In busy city the geophysical exploration methods are interfered with the noise from vibration of heavy traffic and strong electromagnetic field and stray electricity. An conquering of the interference of rugged landform in mountain land also are the problem of all the geophysical method. Surveying of single karst cave with small or middle sizes is difficult. They are more required to put energy into the new development of technology and new method. Landsonar and its instrument can avoid the interference of noise from vibration of cars and pedestrains with frequency generally less than 300 Hz in city by exciting and receiving elastic waves of 10～4000 Hz. The instrument C-1 can avoid the interference of strong electromagnetic field and stray electricity with supplying narrow frequency alternating current of 11～19 Hz. Because of the zero offset and high and wide frequency band, Landsonar can avoid the interference of landform and have high resolution on single karst cave with small to middle sizes. Because of the especial electrode arrangement, Differential Electric Sounding(DES)method can survey karst cave of 1m high within 100m deep. KS marine acoustics prospecting instrument have better transverse and longitudinal resolution, can distinguish the silt layer, sand layer, cobble layer and riprap layer with thickness more than 1m and geologic structure under sub-bottom, and can work with broken survey line and curve survey line.
2013, 21(3): 433-437.
Estuaries are the primary gates for pollutants entering into sea. It is important to analyze the distribution and assess the pollution of sediments, because pollutants can settle into the sediments and repeat release after flowing into sea. This paper aids to provide a scientific basis for ocean remediation and marine environmental protecting project by the way of finding out the pollution characters and assessing the polluted degree. The results show the following. Condemnation content has a trend of higher from top to bottom in space, while sulfide and total nitrogen are main pollutants. Sediments in estuaries are at a level of clean-cleaner based on synthetic index(p),while they are at the level of cleaner to light-polluted in profiles. At the same time, sediments in estuaries are at a level of low to lower-moderate based on potential ecological risk index(ir),while they are at a level of low to moderate in profiles.
Estuaries are the primary gates for pollutants entering into sea. It is important to analyze the distribution and assess the pollution of sediments, because pollutants can settle into the sediments and repeat release after flowing into sea. This paper aids to provide a scientific basis for ocean remediation and marine environmental protecting project by the way of finding out the pollution characters and assessing the polluted degree. The results show the following. Condemnation content has a trend of higher from top to bottom in space, while sulfide and total nitrogen are main pollutants. Sediments in estuaries are at a level of clean-cleaner based on synthetic index(p),while they are at the level of cleaner to light-polluted in profiles. At the same time, sediments in estuaries are at a level of low to lower-moderate based on potential ecological risk index(ir),while they are at a level of low to moderate in profiles.
2013, 21(3): 438-442.
The excavation engineering is very special in round gravel area. The experience of option assessment for supporting and retaining structures needs to be summarized. On the other hand, many parameters such as the strength index of soil are uncertain. The partial coefficients of excavation stability cant be solved well using the reliability theory. This paper investigates many successful excavation engineering examples located in round gravel area. It arranges those relative parameters of retaining structures form selection. It calculates the several main stability partial coefficients of these excavation examples respectively. It establishes a data base finally. After having analyzed this data base statistically, this paper discovers the law of excavation retaining structures form selection. It obtains the several main stability partial coefficients by the lower limit method. The result shows that the overall stability partial coefficient is 1.3.The resist-overturn partial coefficient is 1.2.And the resist-seepage partial coefficient is 1.5.
The excavation engineering is very special in round gravel area. The experience of option assessment for supporting and retaining structures needs to be summarized. On the other hand, many parameters such as the strength index of soil are uncertain. The partial coefficients of excavation stability cant be solved well using the reliability theory. This paper investigates many successful excavation engineering examples located in round gravel area. It arranges those relative parameters of retaining structures form selection. It calculates the several main stability partial coefficients of these excavation examples respectively. It establishes a data base finally. After having analyzed this data base statistically, this paper discovers the law of excavation retaining structures form selection. It obtains the several main stability partial coefficients by the lower limit method. The result shows that the overall stability partial coefficient is 1.3.The resist-overturn partial coefficient is 1.2.And the resist-seepage partial coefficient is 1.5.
2013, 21(3): 443-449.
It is very important to investigate geological relics landscapes for urban geological work. The Cuihua rock avalanche is a marvellous spectacle of seismic avalanches in China. Based on dynamic discrete element method, the dynamic response and failure process are simulated under a typical natural earthquake loading. The failure process of Cuihua rock avalanche is reproduced with the numerical simulation. The following results are obtained. Firstly, the amplification effect of velocity and acceleration is the reason of earthquake inertia force. The maximum magnification factor reaches 2.0 on the top of slope. Secondly, high speed and long run out are the characteristic of the rock avalanche. The results shown the maximum horizontal velocity reaches up to 44ms-1 and the horizontal movement distance for some rocks reaches 460m at the front of the rock avalanche. Thirdly, the whole failure process include four stages: starting up stage, accelerating stage, decelerating stage and accumulation stage.
It is very important to investigate geological relics landscapes for urban geological work. The Cuihua rock avalanche is a marvellous spectacle of seismic avalanches in China. Based on dynamic discrete element method, the dynamic response and failure process are simulated under a typical natural earthquake loading. The failure process of Cuihua rock avalanche is reproduced with the numerical simulation. The following results are obtained. Firstly, the amplification effect of velocity and acceleration is the reason of earthquake inertia force. The maximum magnification factor reaches 2.0 on the top of slope. Secondly, high speed and long run out are the characteristic of the rock avalanche. The results shown the maximum horizontal velocity reaches up to 44ms-1 and the horizontal movement distance for some rocks reaches 460m at the front of the rock avalanche. Thirdly, the whole failure process include four stages: starting up stage, accelerating stage, decelerating stage and accumulation stage.
2013, 21(3): 450-458.
There are many geological disasters and potential geohazards in Laoshan Mountain region, Qingdao City. Human engineering geological activities have increased under the background of rapid developments of tourism in the mountains. These activities have not only increased the numbers of geological disasters and potential geohazards(e.g.landslide, rock fall, debris flow),but also improved dangerous levels. In recent years the geological disaster and potential geohazards are threatening human life and property safety. Some have caused losses. It is necessary to carry out the study of the geological disasters, and reduce the losses. The paper carries out research on geohazards in Laoshan Mountain region of Qingdao. The dangerous regions were established with disaster monitoring system. The main aim of this paper is to analyze the variation of monitoring data and find rules. Through the analyzing the variation of monitoring data and climate data, the result shows difference that climate data affects monitoring data changes. The development of tourism has increased much human engineering activities that have obviously affected the geological disasters and potential geohazards. The purpose of this paper is to provides reference of geological disasters on disaster monitoring and early warning. It broadens the new ideas for the tourist area of geological hazards analysis under the influence of human activities.
There are many geological disasters and potential geohazards in Laoshan Mountain region, Qingdao City. Human engineering geological activities have increased under the background of rapid developments of tourism in the mountains. These activities have not only increased the numbers of geological disasters and potential geohazards(e.g.landslide, rock fall, debris flow),but also improved dangerous levels. In recent years the geological disaster and potential geohazards are threatening human life and property safety. Some have caused losses. It is necessary to carry out the study of the geological disasters, and reduce the losses. The paper carries out research on geohazards in Laoshan Mountain region of Qingdao. The dangerous regions were established with disaster monitoring system. The main aim of this paper is to analyze the variation of monitoring data and find rules. Through the analyzing the variation of monitoring data and climate data, the result shows difference that climate data affects monitoring data changes. The development of tourism has increased much human engineering activities that have obviously affected the geological disasters and potential geohazards. The purpose of this paper is to provides reference of geological disasters on disaster monitoring and early warning. It broadens the new ideas for the tourist area of geological hazards analysis under the influence of human activities.
2013, 21(3): 459-463.
The background of this paper is the excavation at Guangxi University Station for Nanning Orbit Transit Line 1.It analyzes the dynamic monitoring data during construction. It summarizes the deformation behavior of diaphragm wall and surrounding surface subsidence. The data shows that the subsidence due to excavation is relatively small and its main influence range is 0 to 2H(H is the excavation depth).The position of the maximum settlement value is at 0.5H to 0.7H away from the diaphragm wall. The influence range of subsidence deformation is extended to 4H away from the edge of excavation. According to the deformation behavior, the subsidence estimation curve and environment protection degree division to excavations in gravel area are obtained.
The background of this paper is the excavation at Guangxi University Station for Nanning Orbit Transit Line 1.It analyzes the dynamic monitoring data during construction. It summarizes the deformation behavior of diaphragm wall and surrounding surface subsidence. The data shows that the subsidence due to excavation is relatively small and its main influence range is 0 to 2H(H is the excavation depth).The position of the maximum settlement value is at 0.5H to 0.7H away from the diaphragm wall. The influence range of subsidence deformation is extended to 4H away from the edge of excavation. According to the deformation behavior, the subsidence estimation curve and environment protection degree division to excavations in gravel area are obtained.
2013, 21(3): 464-469.
Compression modulus is an important index in the evaluation and calculation of coastal soil foundation compressibility, especially in projects with strict requirements on deformation. So it is of great significance to study its determination methods. The deformation characteristics of soft soil distributed in land reclamation site in north China were studied through in-situ and laboratory method. Pressuremeter test and cone penetrometer test were conducted on the basis of field fixed platform to obtain compression modulus of each soil stratum. The deformation parameters of soil were also determined through indoor test. The relationship between parameters achieved through in-situ and laboratory tests are compared and examined. The results show a better coincidence degree of compression modulus obtained by these three methods. The results provide a helpful reference for the reasonable selection of deformation calculation parameter of soft soil.
Compression modulus is an important index in the evaluation and calculation of coastal soil foundation compressibility, especially in projects with strict requirements on deformation. So it is of great significance to study its determination methods. The deformation characteristics of soft soil distributed in land reclamation site in north China were studied through in-situ and laboratory method. Pressuremeter test and cone penetrometer test were conducted on the basis of field fixed platform to obtain compression modulus of each soil stratum. The deformation parameters of soil were also determined through indoor test. The relationship between parameters achieved through in-situ and laboratory tests are compared and examined. The results show a better coincidence degree of compression modulus obtained by these three methods. The results provide a helpful reference for the reasonable selection of deformation calculation parameter of soft soil.
2013, 21(3): 470-475.
With the rapid increase of energy consumption in China, the construction of the crude oil reserves is urgent. At present, ground storage tank is commonly used to store crude oil at home and aboard. There have been many ground storage tanks over the word. The technology is mature and the construction period is short. The other method is the underground storage of crude oil. In China it has been a rising technology in recent years. Currently granite rock mass is generally selected as building mass in China. Underground construction of underground structure has a strict requirement on the rock conditions. Several underground storages under construction are distributed in the eastern coastal granite areas. This paper mainly studies the feasibility of using waste storage crude gypsum mine. Some engineering geological characteristics and hydrogeological characteristics of gypsum mines in China are studied. The stability analysis of surrounding rocks, oil immersion test, and comprehensive analysis of crude oil reserves have been carried out. Preliminary findings indicate that the plaster has good geological conditions of mining area. Intensity of regional stability is examined with no fault. Gypsum ore body on average is 458.42meters thick. The average saturated uniaxial compressive strength of gypsum mine sample is 55.45MPa. Gypsum ore body has the grade Ⅱ on rock mass quality. The studies cover the room and all kinds of roadway surrounding rock stability. Gypsum mine bibulous rate ranges in 0.014% ～0.036%.The oil absorption rate range is 0.060% ～0.060%.Meanwhile gypsum mine reserves of crude oil has the advantages of low land saving, investment province, operating capacity, high safety, less environmental pollution, long service life. Through the above studies, this paper has concluded that the gypsum mining area are the basic conditions of construction of underground crude oil reserves.
With the rapid increase of energy consumption in China, the construction of the crude oil reserves is urgent. At present, ground storage tank is commonly used to store crude oil at home and aboard. There have been many ground storage tanks over the word. The technology is mature and the construction period is short. The other method is the underground storage of crude oil. In China it has been a rising technology in recent years. Currently granite rock mass is generally selected as building mass in China. Underground construction of underground structure has a strict requirement on the rock conditions. Several underground storages under construction are distributed in the eastern coastal granite areas. This paper mainly studies the feasibility of using waste storage crude gypsum mine. Some engineering geological characteristics and hydrogeological characteristics of gypsum mines in China are studied. The stability analysis of surrounding rocks, oil immersion test, and comprehensive analysis of crude oil reserves have been carried out. Preliminary findings indicate that the plaster has good geological conditions of mining area. Intensity of regional stability is examined with no fault. Gypsum ore body on average is 458.42meters thick. The average saturated uniaxial compressive strength of gypsum mine sample is 55.45MPa. Gypsum ore body has the grade Ⅱ on rock mass quality. The studies cover the room and all kinds of roadway surrounding rock stability. Gypsum mine bibulous rate ranges in 0.014% ～0.036%.The oil absorption rate range is 0.060% ～0.060%.Meanwhile gypsum mine reserves of crude oil has the advantages of low land saving, investment province, operating capacity, high safety, less environmental pollution, long service life. Through the above studies, this paper has concluded that the gypsum mining area are the basic conditions of construction of underground crude oil reserves.
2013, 21(3): 476-480.
At beginning, dredger fill in reclaimed area has a slurry state and has a high water content and big initial void ratio. A laboratory test is carried out for the consolidation behavior. The relationship between void ratio and consolidation stress is obtained from the indoor test. The relationship of permeability coefficient and void ratio is proposed. At last, the permeability coefficient and consolidation stress relationship is put forward. The Barrons consolidation theory is improved by considering the permeability coefficient variable with time. A calculation is conducted to a vacuum preloading model test. The result is in accord with the test data. It shows that the improved consolidation theory is suitable to the vacuum preloading of dredgerfill.
At beginning, dredger fill in reclaimed area has a slurry state and has a high water content and big initial void ratio. A laboratory test is carried out for the consolidation behavior. The relationship between void ratio and consolidation stress is obtained from the indoor test. The relationship of permeability coefficient and void ratio is proposed. At last, the permeability coefficient and consolidation stress relationship is put forward. The Barrons consolidation theory is improved by considering the permeability coefficient variable with time. A calculation is conducted to a vacuum preloading model test. The result is in accord with the test data. It shows that the improved consolidation theory is suitable to the vacuum preloading of dredgerfill.
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