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Editor Work2018 Vol. 26, No. s1
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2018, 26(s1): 1-5.
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In order to study characteristics of saline soil in high speed test ring road of Xinjiang test track, 399 experiments were carried out to reveal the plane and vertical distribution laws of saline soil, double-line method and collapsibility test were carried out to study the melt sinking characteristic, salt-heaving tests were carried out to get the salt-heaving laws of soil samples which have different salt content. The results show that the saline soil has variety, high salinity and even surface assembled, grade of foundation dissolution within 2m below the natural terrain is judged as the first level of weak collapsibility, and the salt-heaving can be restricted by increase of load and decrease of sulphate content.
In order to study characteristics of saline soil in high speed test ring road of Xinjiang test track, 399 experiments were carried out to reveal the plane and vertical distribution laws of saline soil, double-line method and collapsibility test were carried out to study the melt sinking characteristic, salt-heaving tests were carried out to get the salt-heaving laws of soil samples which have different salt content. The results show that the saline soil has variety, high salinity and even surface assembled, grade of foundation dissolution within 2m below the natural terrain is judged as the first level of weak collapsibility, and the salt-heaving can be restricted by increase of load and decrease of sulphate content.
2018, 26(s1): 6-13.
Hengduan Mountains area has various types of landforms, fragile and complex geological environment, changeable climate and frequent seismic activities, which makes this one of the regions with the largest number and the most serious harm of mountain hazards such as collapse, landslides, debris flow, and so on. In this paper, collapse, landslides, debris flow hazards in Hengduan Mountains area are taken as research objects, based on the environmental background, field investigation and data collection in the study area, using GIS spatial analysis and mathematical statistical analysis, the correlation between mountain hazards and environmental background conditions is analyzed, and the regional distribution characteristics and dynamic evolution of mountain hazards in Hengduan Mountains area are discussed.
Hengduan Mountains area has various types of landforms, fragile and complex geological environment, changeable climate and frequent seismic activities, which makes this one of the regions with the largest number and the most serious harm of mountain hazards such as collapse, landslides, debris flow, and so on. In this paper, collapse, landslides, debris flow hazards in Hengduan Mountains area are taken as research objects, based on the environmental background, field investigation and data collection in the study area, using GIS spatial analysis and mathematical statistical analysis, the correlation between mountain hazards and environmental background conditions is analyzed, and the regional distribution characteristics and dynamic evolution of mountain hazards in Hengduan Mountains area are discussed.
2018, 26(s1): 14-21.
With the development of InSAR technology and the richness of SAR data sources, experts and scholars from various countries have solved the problems of SAR data coherence, registration, orbit error and terrain error correction. It is very effective for observing small-scale deformations such as landslides(relative to tectonic movement and land subsidence).Nowadays, atmospheric phase error is still an important factor affecting InSAR applications. The use of spatial correlation to remove regional low-frequency atmospheric phase delay is a simple and efficient method, and we do not need any external weather data. However, in the existing commercial software for processing InSAR,such as GAMMA,the atmospheric model uses a linear curve model of elevation and phase, which cannot adapt to the complex atmospheric phase wet delay in the southwestern mountainous region of China, and often introduces additional errors. In this paper, I studied the distribution characteristics and optimal fitting function of atmospheric phase with elevation, and implements it on Matlab software platform. In this way, I can remove the simulated atmospheric phase from the unwrapped phase, and make the deformation information of the landslide clearer. We used the bank slope of the Qiaojia section of the Jinsha River Valley as the study area, and performed the identification verification of the creep deformation slope. Result shows that the use of elevation phase fitting polynomial is easier to identify the landslide range than a single linear fit, and reduce the omission of geological disasters. That is of great significance for the observation of landslide deformation on the D-InSAR reservoir bank in southwestern China.
With the development of InSAR technology and the richness of SAR data sources, experts and scholars from various countries have solved the problems of SAR data coherence, registration, orbit error and terrain error correction. It is very effective for observing small-scale deformations such as landslides(relative to tectonic movement and land subsidence).Nowadays, atmospheric phase error is still an important factor affecting InSAR applications. The use of spatial correlation to remove regional low-frequency atmospheric phase delay is a simple and efficient method, and we do not need any external weather data. However, in the existing commercial software for processing InSAR,such as GAMMA,the atmospheric model uses a linear curve model of elevation and phase, which cannot adapt to the complex atmospheric phase wet delay in the southwestern mountainous region of China, and often introduces additional errors. In this paper, I studied the distribution characteristics and optimal fitting function of atmospheric phase with elevation, and implements it on Matlab software platform. In this way, I can remove the simulated atmospheric phase from the unwrapped phase, and make the deformation information of the landslide clearer. We used the bank slope of the Qiaojia section of the Jinsha River Valley as the study area, and performed the identification verification of the creep deformation slope. Result shows that the use of elevation phase fitting polynomial is easier to identify the landslide range than a single linear fit, and reduce the omission of geological disasters. That is of great significance for the observation of landslide deformation on the D-InSAR reservoir bank in southwestern China.
2018, 26(s1): 22-29.
In order to reveal the mechanism of loess landslide disaster in Binchang area, based on the analyzing the characteristics of landslides and distribution, typical loess landslide cases were studied using field investigation and theoretical analysis method. Analysis were made for the activation mechanism of the excavation loess landslide, the mining type loess landslide and the active loess landslide in goaf. The results show that:in the unloading process, the stress at the toe of the slope appears concentrated, and the pulling tension cracks appear on the top of the slope, while the pressure on the toe of the slope is strengthened. The fracture and compressive stress increase alternately, causing mutual cause and effect until they develop into an upward and downward crack zone, and the entire slope is unstable. In the mining disturbance, the overlying rock instability caused by the uneven settlement of the surface layer of loess, the displacement vector of slope direction on both sides of the valley in the goaf center and the inclination along the slope of the displacement vector dynamic superposition under the action of failure, after the arrival of the side slope mining often early in the first to one side slope landslide. Gob activation of loess landslide occurs mainly in the upper goaf of the Loess Plateau, the relative stability of the goaf, the infiltration of surface water and underground water level. Under the conditions of surface water infiltration and groundwater level uplift in relatively stable goaf, the coal pillar is unstable and collapses under the action of hydrodynamic erosion, and the stress of the rock mass is redistributed, which causes the two times of the surface loess layer to be unstable and eventually triggers the landslide.
In order to reveal the mechanism of loess landslide disaster in Binchang area, based on the analyzing the characteristics of landslides and distribution, typical loess landslide cases were studied using field investigation and theoretical analysis method. Analysis were made for the activation mechanism of the excavation loess landslide, the mining type loess landslide and the active loess landslide in goaf. The results show that:in the unloading process, the stress at the toe of the slope appears concentrated, and the pulling tension cracks appear on the top of the slope, while the pressure on the toe of the slope is strengthened. The fracture and compressive stress increase alternately, causing mutual cause and effect until they develop into an upward and downward crack zone, and the entire slope is unstable. In the mining disturbance, the overlying rock instability caused by the uneven settlement of the surface layer of loess, the displacement vector of slope direction on both sides of the valley in the goaf center and the inclination along the slope of the displacement vector dynamic superposition under the action of failure, after the arrival of the side slope mining often early in the first to one side slope landslide. Gob activation of loess landslide occurs mainly in the upper goaf of the Loess Plateau, the relative stability of the goaf, the infiltration of surface water and underground water level. Under the conditions of surface water infiltration and groundwater level uplift in relatively stable goaf, the coal pillar is unstable and collapses under the action of hydrodynamic erosion, and the stress of the rock mass is redistributed, which causes the two times of the surface loess layer to be unstable and eventually triggers the landslide.
2018, 26(s1): 30-36.
As a frequent geological hazard in the construction of mountainous area, slope rockfall is a serious threat to the construction and operation safety of railway and other transportation projects. Under the influence of various factors, the trajectory of rockfall has the characteristics of random probability distribution, and its energy state and impact size are closely related to the movement state of rockfall. The realistic description of the trajectory of the rockfall, thus solving its energy state and impact force is the premise and main reference basis for the subsequent targeted development of protective measures. This article summarizes the software that already exists at home and abroad, on the basis of introducing the probability calculation method based on normal distribution, improving the practical model of rockfall trajectory calculation, and compiling a set of rockfall analysis calculation software, on the basis of probability calculation, putting forward the two worst rockfall movement trajectory, using a variety of methods to calculate the most unfavorable rockfall impact. The software has been successfully applied to the rockfall site of Hewu bridge in Gui-Guang Railway, which has achieved good results, and can be applied in the follow-up work points.
As a frequent geological hazard in the construction of mountainous area, slope rockfall is a serious threat to the construction and operation safety of railway and other transportation projects. Under the influence of various factors, the trajectory of rockfall has the characteristics of random probability distribution, and its energy state and impact size are closely related to the movement state of rockfall. The realistic description of the trajectory of the rockfall, thus solving its energy state and impact force is the premise and main reference basis for the subsequent targeted development of protective measures. This article summarizes the software that already exists at home and abroad, on the basis of introducing the probability calculation method based on normal distribution, improving the practical model of rockfall trajectory calculation, and compiling a set of rockfall analysis calculation software, on the basis of probability calculation, putting forward the two worst rockfall movement trajectory, using a variety of methods to calculate the most unfavorable rockfall impact. The software has been successfully applied to the rockfall site of Hewu bridge in Gui-Guang Railway, which has achieved good results, and can be applied in the follow-up work points.
2018, 26(s1): 37-42.
A railway deep cutting with the maximum excavation height of 120m gives great challenges to design and construction because of dualistic layer structure and multi-stage blasting excavation. In this paper, considering the characteristics of the dualistic layer of the slope and the structural plane of rock mass, the static and dynamic simulation of the five-stage excavation and support is carried out with both the finite element limit equilibrium method and the dynamic finite element method, thus the failure mode and factor of safety is obtained. The simulation results show that:(1)The stability of the deep cutting is gradually controlled by the fully weathered sandstone, the dualistic layer interface and the most unfavorable structural plane of the limestone along with top-down multi-stage excavation. And as the excavation increases, the ground stress is gradually released, the shear stress field is deflected, and the plastic zone becomes smaller. (2)The displacement field caused by blasting decays approximately spherically with the distance from the blast source and is amplified at the interface of the dualistic layer. The research results have important implications for the design and construction of the railway deep cutting.
A railway deep cutting with the maximum excavation height of 120m gives great challenges to design and construction because of dualistic layer structure and multi-stage blasting excavation. In this paper, considering the characteristics of the dualistic layer of the slope and the structural plane of rock mass, the static and dynamic simulation of the five-stage excavation and support is carried out with both the finite element limit equilibrium method and the dynamic finite element method, thus the failure mode and factor of safety is obtained. The simulation results show that:(1)The stability of the deep cutting is gradually controlled by the fully weathered sandstone, the dualistic layer interface and the most unfavorable structural plane of the limestone along with top-down multi-stage excavation. And as the excavation increases, the ground stress is gradually released, the shear stress field is deflected, and the plastic zone becomes smaller. (2)The displacement field caused by blasting decays approximately spherically with the distance from the blast source and is amplified at the interface of the dualistic layer. The research results have important implications for the design and construction of the railway deep cutting.
2018, 26(s1): 43-52.
Currently the research on general layered rock slope have been quite thoroughly, but for thin-layer rock slope, due to its special form of rock mass structure, the drill core is always broken. It is difficult to collect rock samples which are comply with the laboratory test requirements thus we cannot acquire the physical and mechanical properties by conventional means, which directly affects the analysis of slope failure mechanism and stability. So it's necessary to take further study on this type of slope. This paper is based on a thin-layer phyllite slope in south Shaanxi, the natural and saturated gravity of strongly weathered and moderately weathered rock masses are respectively acquired by site gravity test and equivalent volume method. The natural and saturated uniaxial compressive strength of rock masses are determined by point loading test. For strongly weathered rock masses which are cut broken by structural planes, the strength is controlled by structural planes, and the shear strength is acquired by JRC-JCS method which is proposed by Barton. For moderately weathered rock masses, Hoek-Brown criterion which bases on RMR classification system is employed to weaken rock strength. The shear strength is estimated by weakening strength and the strength of structural planes. Meanwhile, based on the topographic and hydro-geological features of this slope, establish a two-dimensional model via M-C criterion to analysis the stress-strain characteristics and steady state under natural and heavy rain conditions, so as to reveal the failure mechanism and stability of thin-layer rock slope and provide a reference for analysis and prevention of slope of the same type.
Currently the research on general layered rock slope have been quite thoroughly, but for thin-layer rock slope, due to its special form of rock mass structure, the drill core is always broken. It is difficult to collect rock samples which are comply with the laboratory test requirements thus we cannot acquire the physical and mechanical properties by conventional means, which directly affects the analysis of slope failure mechanism and stability. So it's necessary to take further study on this type of slope. This paper is based on a thin-layer phyllite slope in south Shaanxi, the natural and saturated gravity of strongly weathered and moderately weathered rock masses are respectively acquired by site gravity test and equivalent volume method. The natural and saturated uniaxial compressive strength of rock masses are determined by point loading test. For strongly weathered rock masses which are cut broken by structural planes, the strength is controlled by structural planes, and the shear strength is acquired by JRC-JCS method which is proposed by Barton. For moderately weathered rock masses, Hoek-Brown criterion which bases on RMR classification system is employed to weaken rock strength. The shear strength is estimated by weakening strength and the strength of structural planes. Meanwhile, based on the topographic and hydro-geological features of this slope, establish a two-dimensional model via M-C criterion to analysis the stress-strain characteristics and steady state under natural and heavy rain conditions, so as to reveal the failure mechanism and stability of thin-layer rock slope and provide a reference for analysis and prevention of slope of the same type.
2018, 26(s1): 53-61.
In this paper, we mainly describe the research results of the engineering characteristics of expansive soil, and the deformation and failure mechanism of the expansive soil slope. Relying on the survey and research of the middle route of the South to North Water Transfer Project for more than half a century, with the projects of the National Science and Technology Support Program, we studied through field investigation and laboratory experiment, developed a lot of tests include slope monitoring, field anatomy and numerical value simulation in the large prototype channel, and researched the engineering characteristics of expansive soil structure and slope failure characteristics. The results show that the expansive soil has obvious vertical zoning characteristics in the macro structure. The failure of the shallow layer is mainly on the slope erosion and shallow surface creep. The deep sliding failure is affected by the internal structure surface of the expansive soil, and the strength of the soil slope depends on the strength of the weak structure surface. Based on the experimental research results, we proposes a new failure mechanism of shallow creep and deep broken line sliding failure of expansive soil.
In this paper, we mainly describe the research results of the engineering characteristics of expansive soil, and the deformation and failure mechanism of the expansive soil slope. Relying on the survey and research of the middle route of the South to North Water Transfer Project for more than half a century, with the projects of the National Science and Technology Support Program, we studied through field investigation and laboratory experiment, developed a lot of tests include slope monitoring, field anatomy and numerical value simulation in the large prototype channel, and researched the engineering characteristics of expansive soil structure and slope failure characteristics. The results show that the expansive soil has obvious vertical zoning characteristics in the macro structure. The failure of the shallow layer is mainly on the slope erosion and shallow surface creep. The deep sliding failure is affected by the internal structure surface of the expansive soil, and the strength of the soil slope depends on the strength of the weak structure surface. Based on the experimental research results, we proposes a new failure mechanism of shallow creep and deep broken line sliding failure of expansive soil.
2018, 26(s1): 62-68.
Shangjiang Hydropower Station has not only complex regional tectonic background, but also high frequency of seismic activity, and the site seismic risk assessment is the key technical problem to be solved in this project. The study of regional geology, seismic structure and seismic risk shows that the frequency of regional destructive earthquakes and the level of seismic activity are very high, and 2 earthquakes of MS 7 occur in the region. The earthquake with magnitude 7 or so may still occur in the prediction area, 5destructive earthquakes with magnitude MS 4 ¾ occurring in the near field, the maximum magnitude being 6 ¼, and the earthquake with magnitude 6 or so likely to occur in the near field area. Because the dam site and its adjacent area are confined by active faults on the outer margin, and the site of the dam site is relatively stable for dam construction. Finally, according to the method of determining the relation of potential source area, seismic activity parameter and ground motion attenuation, the results of seismic hazard analysis and ground motion parameters of five kinds of probability beyond the probability level of dam site are calculated, which can provide engineering seismic basis for project design and construction.
Shangjiang Hydropower Station has not only complex regional tectonic background, but also high frequency of seismic activity, and the site seismic risk assessment is the key technical problem to be solved in this project. The study of regional geology, seismic structure and seismic risk shows that the frequency of regional destructive earthquakes and the level of seismic activity are very high, and 2 earthquakes of MS 7 occur in the region. The earthquake with magnitude 7 or so may still occur in the prediction area, 5destructive earthquakes with magnitude MS 4 ¾ occurring in the near field, the maximum magnitude being 6 ¼, and the earthquake with magnitude 6 or so likely to occur in the near field area. Because the dam site and its adjacent area are confined by active faults on the outer margin, and the site of the dam site is relatively stable for dam construction. Finally, according to the method of determining the relation of potential source area, seismic activity parameter and ground motion attenuation, the results of seismic hazard analysis and ground motion parameters of five kinds of probability beyond the probability level of dam site are calculated, which can provide engineering seismic basis for project design and construction.
2018, 26(s1): 69-75.
Check dam is an important project commonly used in the prevention and control of landslide disasters. It has the functions of raising the base of erosion, retaining silt, and stabilizing the channel. In the current research on debris flow control, simple geometry is often used to replace the actual shape of a check dam and gullies, and there is a lack of detailed research on the flow field around a reality check dam. To optimize the check dam design, improve the erosion resistance of debris flow, and extend the service life of check, this paper explores a three-dimensional multi-physics coupling model for RANS k- turbulence of a dilute debris flow under continuous-phase Euler coordinates to investigate the flow field distribution, turbulent kinetic energy, and impact load change of dilute debris flow around check dam in the event of a three-year rainfall event. The results show that:the downstream surface of check dam can effectively reduce the turbulent flow before the dam. Check dam has different types of backflow vortex at the crest and back surface. There are high-energy side cut and undercut turbulence at the back surface of check dam, in the back of check dam. Protective measures should be taken on both sides of the abutment and the bottom of the check dam. The research results can provide a reference for the design of check dam and prevention of debris flow.
Check dam is an important project commonly used in the prevention and control of landslide disasters. It has the functions of raising the base of erosion, retaining silt, and stabilizing the channel. In the current research on debris flow control, simple geometry is often used to replace the actual shape of a check dam and gullies, and there is a lack of detailed research on the flow field around a reality check dam. To optimize the check dam design, improve the erosion resistance of debris flow, and extend the service life of check, this paper explores a three-dimensional multi-physics coupling model for RANS k- turbulence of a dilute debris flow under continuous-phase Euler coordinates to investigate the flow field distribution, turbulent kinetic energy, and impact load change of dilute debris flow around check dam in the event of a three-year rainfall event. The results show that:the downstream surface of check dam can effectively reduce the turbulent flow before the dam. Check dam has different types of backflow vortex at the crest and back surface. There are high-energy side cut and undercut turbulence at the back surface of check dam, in the back of check dam. Protective measures should be taken on both sides of the abutment and the bottom of the check dam. The research results can provide a reference for the design of check dam and prevention of debris flow.
2018, 26(s1): 76-84.
Deformation and failure of the interbeded slope of sand and mud stones is a serious geological problem during the engineering construction. In this paper, taking the Three Gorges Reservoir Area(Changshou-Fengdu section) as an example, the slope structure, evolution process and failure characteristics are studied based on field investigation. And then the failure coefficients of the 38slopes were calculated based on the factor of topographic concave-convex degree and the SOM model. The results show that 70% of the slopes along the Three Gorges Reservoir Area(Changshou-Fengdu section) are consisted of mudstone interbeded with sandstone. There is a certain difference in the failure mechanism between the slope which consisted of mudstone interbedded with sandstone and the slope consisted of sandstone interbeded with mudstone. According to the failure mechanism and stability assessment, the failure coefficients of the 7slopes in Three Gorges Reservoir area(Changshou-Fengdu section) are bigger than 0.4,indicating comprehensive prevention methods should be adopted, especially for the slopes consisted of sandstone above and mudstone below.
Deformation and failure of the interbeded slope of sand and mud stones is a serious geological problem during the engineering construction. In this paper, taking the Three Gorges Reservoir Area(Changshou-Fengdu section) as an example, the slope structure, evolution process and failure characteristics are studied based on field investigation. And then the failure coefficients of the 38slopes were calculated based on the factor of topographic concave-convex degree and the SOM model. The results show that 70% of the slopes along the Three Gorges Reservoir Area(Changshou-Fengdu section) are consisted of mudstone interbeded with sandstone. There is a certain difference in the failure mechanism between the slope which consisted of mudstone interbedded with sandstone and the slope consisted of sandstone interbeded with mudstone. According to the failure mechanism and stability assessment, the failure coefficients of the 7slopes in Three Gorges Reservoir area(Changshou-Fengdu section) are bigger than 0.4,indicating comprehensive prevention methods should be adopted, especially for the slopes consisted of sandstone above and mudstone below.
2018, 26(s1): 85-91.
Rockfall disaster is an important geological environment issue for the Tibet border port traffic line. With the Yadong Port in Shigatse, Tibet as the research area, this paper carries out quantitative assessment of the hazards along major highways and the surrounding communities. Through remote sensing interpretation and field survey methods, information on historical rockfall disasters, the spatial distribution of dangerous rock masses along the route, topography, geology and stability status are obtained. Considering the controlled lithologyand terrain conditions formed by the rockfall, the identification of the source area of rockfall is realized based on GIS. Based on Holmgre's correction algorithm, inertial algorithm and friction loss function, Flow-R software was used to simulate the range of the rockfall movement and the threatened traffic zone at Yadong Port was determined. The results show that the coincidence of the scope of GIS identification in the source area of rockfall and the actual field survey is 76.9%, and the fitting precision of the range of the motion simulation and the actual rockfall rolling range is 60.3%. The simulated high-risk impact area accounts for 12.5% of the total study area. The traffic sections affected by the simulation are mainly distributed on the high slope slope body in the southwest direction of the Yadong Port, affecting the length of the road section more than 7000m. The number of grids with a falling rock reaching probability exceeding 0.7 is 2647,which accounts for 1.5% of the total number of grids in the rockfall simulation range, and is concentrated at the place where the curvature value at the bottom of the gulch is large. The research results of this paper have certain reference significance for the evaluation and prevention and control of the impact range of the rockfall of important traffic routes in Tibet port.
Rockfall disaster is an important geological environment issue for the Tibet border port traffic line. With the Yadong Port in Shigatse, Tibet as the research area, this paper carries out quantitative assessment of the hazards along major highways and the surrounding communities. Through remote sensing interpretation and field survey methods, information on historical rockfall disasters, the spatial distribution of dangerous rock masses along the route, topography, geology and stability status are obtained. Considering the controlled lithologyand terrain conditions formed by the rockfall, the identification of the source area of rockfall is realized based on GIS. Based on Holmgre's correction algorithm, inertial algorithm and friction loss function, Flow-R software was used to simulate the range of the rockfall movement and the threatened traffic zone at Yadong Port was determined. The results show that the coincidence of the scope of GIS identification in the source area of rockfall and the actual field survey is 76.9%, and the fitting precision of the range of the motion simulation and the actual rockfall rolling range is 60.3%. The simulated high-risk impact area accounts for 12.5% of the total study area. The traffic sections affected by the simulation are mainly distributed on the high slope slope body in the southwest direction of the Yadong Port, affecting the length of the road section more than 7000m. The number of grids with a falling rock reaching probability exceeding 0.7 is 2647,which accounts for 1.5% of the total number of grids in the rockfall simulation range, and is concentrated at the place where the curvature value at the bottom of the gulch is large. The research results of this paper have certain reference significance for the evaluation and prevention and control of the impact range of the rockfall of important traffic routes in Tibet port.
2018, 26(s1): 92-98.
Luojin ditch, located in the outer edge of Detuo Township in Luding County, Sichuan Province, is connected with the bank of Dagangshan Hydropower Station. The existence of debris flow in Luojin gully threatens the safety of people's life and property and the operation of Dagangshan Hydropower Station. In this paper, using Luojin ditch debris flow as an example, I try Gray relational method to evaluate the danger of debris flow. The size, frequency, main groove length, watershed area, watershed cutting density, relative height difference, and unstable trench bed ratio was selected as evaluation factors. Concluded as follow:(1)Luojin ditch debris flow is rich in resources, the total amount of about 21.95104m3. The debris flow velocity is estimated at 5.33ms-1 and the debris flow peak flow is 487.3m3s-1. (2)The fall of the Luojin ditch debris flow is mainly controlled by the torrential rain. Its bulk density is estimated as 1.8tm-3. (3)According to the risk calculation, the calculated risk is equal to 0.45, and it is concluded that Luojin ditch belongs to moderate dangerous debris flow.
Luojin ditch, located in the outer edge of Detuo Township in Luding County, Sichuan Province, is connected with the bank of Dagangshan Hydropower Station. The existence of debris flow in Luojin gully threatens the safety of people's life and property and the operation of Dagangshan Hydropower Station. In this paper, using Luojin ditch debris flow as an example, I try Gray relational method to evaluate the danger of debris flow. The size, frequency, main groove length, watershed area, watershed cutting density, relative height difference, and unstable trench bed ratio was selected as evaluation factors. Concluded as follow:(1)Luojin ditch debris flow is rich in resources, the total amount of about 21.95104m3. The debris flow velocity is estimated at 5.33ms-1 and the debris flow peak flow is 487.3m3s-1. (2)The fall of the Luojin ditch debris flow is mainly controlled by the torrential rain. Its bulk density is estimated as 1.8tm-3. (3)According to the risk calculation, the calculated risk is equal to 0.45, and it is concluded that Luojin ditch belongs to moderate dangerous debris flow.
2018, 26(s1): 99-106.
At present, the traditional strength reduction method is still widely used in the stability analysis of large multi-slip slope. The traditional strength reduction method, known as synchronous reduction method, is to synchronously reduce the values of c and Pauline of the whole slope rock and soil mass, without considering the difference in anti-shear effect of c and Pauline values in the process of slope instability. In this paper, the numerical simulation software FLAC3D is used to simulate the slope instability. And then the SSR is programmed to calculate the reduction coefficient of c and ,selecting the same set of safety coefficients and the lower limit value, and making a separate reduction. The reduction coefficient of c and is different, which proves that the attenuation of c and is different in the process of slope failure. Based on this, a new double-fold subtraction method is proposed, which is called the synchrotron and post-asynchronous subtraction. The method is used to analyze multi-sliding surfaces slopes and the simultaneous reduction method is used as the reference for calculating method. The comparisons show that the result of synchronization reduction is larger, and more conservative than synchronous and asynchronous reduction. Numerical simulation results of synchronous and asynchronous reduction are in good agreement with the actual monitoring data.
At present, the traditional strength reduction method is still widely used in the stability analysis of large multi-slip slope. The traditional strength reduction method, known as synchronous reduction method, is to synchronously reduce the values of c and Pauline of the whole slope rock and soil mass, without considering the difference in anti-shear effect of c and Pauline values in the process of slope instability. In this paper, the numerical simulation software FLAC3D is used to simulate the slope instability. And then the SSR is programmed to calculate the reduction coefficient of c and ,selecting the same set of safety coefficients and the lower limit value, and making a separate reduction. The reduction coefficient of c and is different, which proves that the attenuation of c and is different in the process of slope failure. Based on this, a new double-fold subtraction method is proposed, which is called the synchrotron and post-asynchronous subtraction. The method is used to analyze multi-sliding surfaces slopes and the simultaneous reduction method is used as the reference for calculating method. The comparisons show that the result of synchronization reduction is larger, and more conservative than synchronous and asynchronous reduction. Numerical simulation results of synchronous and asynchronous reduction are in good agreement with the actual monitoring data.
2018, 26(s1): 107-113.
Based on the latest research results on geological structure, earthquake and investigation in Lanzhou New Area, combined of the environmental geological problems that collapses, landslides, debris flow, instability slope and salinization have been developing in Lanzhou new areas during the process of urbanization and other serious threats to the city, by means of the existed classifications of topography and divisions of rocks and soils type, and according to the rules of similarity and differences for classifying the engineering geological conditions, the urban engineering geological conditions in Lanzhou new area were studied by dividing the whole new area into 2 kinds of zones-soil body stability and by further dividing them into three sub zones, with the conclusion that new area could be divided into accumulation basin district area of engineering geology and engineering geology area at the two districts. Among them, the hills of engineering geology is divided into stable, relatively stable, poor stability three sub zones. Engineering geology accumulation basin area and the stability of engineering geology area at the rock(soil) mass good stability and good engineering geological conditions. Relatively stability of the engineering geology area at the rock(soil) mass stability is better. The engineering geological condition is good, and can be used as the focused development and construction areas in Lanzhou new area in the future.
Based on the latest research results on geological structure, earthquake and investigation in Lanzhou New Area, combined of the environmental geological problems that collapses, landslides, debris flow, instability slope and salinization have been developing in Lanzhou new areas during the process of urbanization and other serious threats to the city, by means of the existed classifications of topography and divisions of rocks and soils type, and according to the rules of similarity and differences for classifying the engineering geological conditions, the urban engineering geological conditions in Lanzhou new area were studied by dividing the whole new area into 2 kinds of zones-soil body stability and by further dividing them into three sub zones, with the conclusion that new area could be divided into accumulation basin district area of engineering geology and engineering geology area at the two districts. Among them, the hills of engineering geology is divided into stable, relatively stable, poor stability three sub zones. Engineering geology accumulation basin area and the stability of engineering geology area at the rock(soil) mass good stability and good engineering geological conditions. Relatively stability of the engineering geology area at the rock(soil) mass stability is better. The engineering geological condition is good, and can be used as the focused development and construction areas in Lanzhou new area in the future.
2018, 26(s1): 114-119.
In this paper, the material point software(Anura 3D) is used to set up the contact algorithm and fluid-solid coupling. Based on the M-C strength criterion, the whole process of the true submarine landslide in the South Mediterranean is simulated and back-analyzed. The coefficient of friction is 0.052. The landslide starts at the foot of the slope and gradually develops to the interior to form a whole landslide body. The whole body of the landslide accelerates and slides along the slope. At the 15th second, the maximum speed is 14.52ms-1,after which the friction is due to friction. ResistanceSlide force, the landslide body begins to decelerate. At the 21st second, the landslide body slides into a gentle section(slope is 1.1),the sliding force is close to 0, and the speeds of different particles are different, so the diffusion occurs in the horizontal direction. In the 57s, the speed drops to 0 and the sliding stops, The final sliding distance is 420.3m. The concept of the comprehensive friction coefficient() of the contact surface of the submarine landslide was put forward, and the phenomenon of soil softening and hydroplaning caused by seawater mixing during the sliding process of the submarine landslide was characterized by , and applied to the submarine landslide movement.
In this paper, the material point software(Anura 3D) is used to set up the contact algorithm and fluid-solid coupling. Based on the M-C strength criterion, the whole process of the true submarine landslide in the South Mediterranean is simulated and back-analyzed. The coefficient of friction is 0.052. The landslide starts at the foot of the slope and gradually develops to the interior to form a whole landslide body. The whole body of the landslide accelerates and slides along the slope. At the 15th second, the maximum speed is 14.52ms-1,after which the friction is due to friction. ResistanceSlide force, the landslide body begins to decelerate. At the 21st second, the landslide body slides into a gentle section(slope is 1.1),the sliding force is close to 0, and the speeds of different particles are different, so the diffusion occurs in the horizontal direction. In the 57s, the speed drops to 0 and the sliding stops, The final sliding distance is 420.3m. The concept of the comprehensive friction coefficient() of the contact surface of the submarine landslide was put forward, and the phenomenon of soil softening and hydroplaning caused by seawater mixing during the sliding process of the submarine landslide was characterized by , and applied to the submarine landslide movement.
2018, 26(s1): 120-127.
Continental slope of deep ocean is a prone area of happening geological hazards. With the development of oil and gas resources in deepwater worldwide, the construction of submarine pipeline and the experimental exploitation of natural gas hydrate are increasing, the deep-water geologic disaster, such as submarine landslide, is paid more and more attention. Multi-national scientists have carried out a lot of research on submarine landslide surveying, in-situ monitoring, laboratory experiments, model construction and numerical simulation, and achieved a series of results. South China Sea is rich in energy resources, but the seabed geological conditions are complex and the stability is poor. The seabed stability is an important restricting factor of oil and gas resources exploitation, and the submarine landslide research becomes a key scientific issues of engineering geology environment research in the South China Sea. This paper systematically introduces the research progress and development trend of the international submarine landslide and expounds the current research status of the submarine landslide in the South China Sea. The paper finally summarizes and forecasts the key scientific issues and research hotspots related to the submarine stability, which can provide reference for the evaluation of seabed stability in the process of exploration and development.
Continental slope of deep ocean is a prone area of happening geological hazards. With the development of oil and gas resources in deepwater worldwide, the construction of submarine pipeline and the experimental exploitation of natural gas hydrate are increasing, the deep-water geologic disaster, such as submarine landslide, is paid more and more attention. Multi-national scientists have carried out a lot of research on submarine landslide surveying, in-situ monitoring, laboratory experiments, model construction and numerical simulation, and achieved a series of results. South China Sea is rich in energy resources, but the seabed geological conditions are complex and the stability is poor. The seabed stability is an important restricting factor of oil and gas resources exploitation, and the submarine landslide research becomes a key scientific issues of engineering geology environment research in the South China Sea. This paper systematically introduces the research progress and development trend of the international submarine landslide and expounds the current research status of the submarine landslide in the South China Sea. The paper finally summarizes and forecasts the key scientific issues and research hotspots related to the submarine stability, which can provide reference for the evaluation of seabed stability in the process of exploration and development.
2018, 26(s1): 128-134.
Tensile strength is an important index to describe the mechanical properties of loess and the basis for studying the characteristics of loess tensile failure. In this paper, using tensile instrument developed independently for intact loess with large section, several uniaxial tensile tests were conducted on L5 loess in Jingyang County, Shaanxi Province. The tensile stress-strain characteristics and tensile strength of the samples under different water contents were measured, and compared with the result obtained by the conventional triaxial shear test. The results show that the strength of loess at low water content is high, the tensile stress increases linearly with the increment of tensile strain and the failure exhibits brittle. The tensile strength of loess at high water content is low, the tensile stress increases nonlinearly with the increment of tensile strain, and the failure shows some plasticity. The relationship between the tensile strength and the water content shows exponential decline. Compared with the conventional triaxial test results, the tensile test results are smaller and closer to the actual situation, and a certain linear relationship between the two.
Tensile strength is an important index to describe the mechanical properties of loess and the basis for studying the characteristics of loess tensile failure. In this paper, using tensile instrument developed independently for intact loess with large section, several uniaxial tensile tests were conducted on L5 loess in Jingyang County, Shaanxi Province. The tensile stress-strain characteristics and tensile strength of the samples under different water contents were measured, and compared with the result obtained by the conventional triaxial shear test. The results show that the strength of loess at low water content is high, the tensile stress increases linearly with the increment of tensile strain and the failure exhibits brittle. The tensile strength of loess at high water content is low, the tensile stress increases nonlinearly with the increment of tensile strain, and the failure shows some plasticity. The relationship between the tensile strength and the water content shows exponential decline. Compared with the conventional triaxial test results, the tensile test results are smaller and closer to the actual situation, and a certain linear relationship between the two.
2018, 26(s1): 135-141.
The loess-paleosol layer is interphase with large thickness as well as long deposition age. Because of compacted and cemented effects, the shear strength of soil increases with the buried depth. And the stratigraphic division and their parameters are difficult to be decided. The variation regularity of the shear strength parameters of the loess and paleosol with the buried depth are explored, and it is found that the cohesion of loess increases linearly with buried depth and the intercept is 0. The cohesion of paleosol increases linearly with buried depth, with a intercept of 50.5kPa and a slope close to that of loess. As for the internal friction angles of loess and paleosol, neither of them significantly changes with the buried depth. Based on the results of absolute sedimentation dating of loess-paleosol, the linear equations of cohesion and depositional age are further established. Using the advantage of FEM division, the cohesive linear increasing model and elastic-plastic FEM are combined to establish a FEM model of cohesive linear increasing with deposition age. Meanwhile, the strength parameters of loess and paleosol layers are assigned differently, and the strength reduction method is used to calculate the slope safety factor. The model is validated by the case of the Jijia landslide in Shanxi province, and the model rationality is proved.
The loess-paleosol layer is interphase with large thickness as well as long deposition age. Because of compacted and cemented effects, the shear strength of soil increases with the buried depth. And the stratigraphic division and their parameters are difficult to be decided. The variation regularity of the shear strength parameters of the loess and paleosol with the buried depth are explored, and it is found that the cohesion of loess increases linearly with buried depth and the intercept is 0. The cohesion of paleosol increases linearly with buried depth, with a intercept of 50.5kPa and a slope close to that of loess. As for the internal friction angles of loess and paleosol, neither of them significantly changes with the buried depth. Based on the results of absolute sedimentation dating of loess-paleosol, the linear equations of cohesion and depositional age are further established. Using the advantage of FEM division, the cohesive linear increasing model and elastic-plastic FEM are combined to establish a FEM model of cohesive linear increasing with deposition age. Meanwhile, the strength parameters of loess and paleosol layers are assigned differently, and the strength reduction method is used to calculate the slope safety factor. The model is validated by the case of the Jijia landslide in Shanxi province, and the model rationality is proved.
2018, 26(s1): 142-148.
Loess plateau is one of the most serious geo-hazard areas in China. Frequent hazard brings large damage to the local human life and property and impedes the progress of county urbanization. In this paper, in the case of Rouyuan Township in Huachi County, Gansu Province, research findings that the best unite size of average relief is 65m65m in loess area in large scale, using the curve fitting and the mean change point method. The hazard assessment model of Rouyuan was established by the factors of history hazard intensity and potential hazard, including hazard surface density, formation lithology, the thickness of the loess, elevation, slope, aspect, relief, the distance to gully, NDVI,the distance to road, the distance to building, the weight of factors above were obtained by AHP. The vulnerability assessment was completed according to the difference between landcover after field survey and remote sensing interpretation. The risk assessment map was got from hazard assessment and vulnerability assessment by raster overlaying tool in ArcGIS. The study area was divided into high risk, middle risk, low risk, very low risk area, which covers 4.6%, 11.7%, 30.2%, 53.5% of total area, the result identifies with disaster and vulnerability of hazard-affected body, it can provide suitable suggestion to Rouyuan urbanization.
Loess plateau is one of the most serious geo-hazard areas in China. Frequent hazard brings large damage to the local human life and property and impedes the progress of county urbanization. In this paper, in the case of Rouyuan Township in Huachi County, Gansu Province, research findings that the best unite size of average relief is 65m65m in loess area in large scale, using the curve fitting and the mean change point method. The hazard assessment model of Rouyuan was established by the factors of history hazard intensity and potential hazard, including hazard surface density, formation lithology, the thickness of the loess, elevation, slope, aspect, relief, the distance to gully, NDVI,the distance to road, the distance to building, the weight of factors above were obtained by AHP. The vulnerability assessment was completed according to the difference between landcover after field survey and remote sensing interpretation. The risk assessment map was got from hazard assessment and vulnerability assessment by raster overlaying tool in ArcGIS. The study area was divided into high risk, middle risk, low risk, very low risk area, which covers 4.6%, 11.7%, 30.2%, 53.5% of total area, the result identifies with disaster and vulnerability of hazard-affected body, it can provide suitable suggestion to Rouyuan urbanization.
2018, 26(s1): 149-154.
In Northwest China, the rainfall is low and the climate is dry, but the groundwater is shallow, the wind resources are abundant. It has social and environmental benefits to take wind power as the driving force, extracting groundwater to irrigate and rehabilitating degraded natural ecosystems. This paper briefly describes the development history of wind water pumping in China, analyzes the problems existing in the selected wind water pumping machines, and makes some improvements. Taking the Hailiutu ranch in the Middle Banner of Inner Mongolia as an experimental site, the groundwater reserves are estimated by drilling data, and the geological conditions of the site are determined. According to the annual rainfall, sunshine, daily mean wind speed, groundwater migration and evaporation, the energy of the available wind energy is calculated and the quantity of the water pumping unit is determined according to the annual water requirement of the site. According to the location of the experimental site, a reasonable overview scheme has been worked out, and a set of irrigation system has been designed, and its feasibility has been analyzed. The test of a single set of equipment shows that the scheme is feasible. The system uses natural energy, one investment and permanent income, so it has good prospects for popularization and application.
In Northwest China, the rainfall is low and the climate is dry, but the groundwater is shallow, the wind resources are abundant. It has social and environmental benefits to take wind power as the driving force, extracting groundwater to irrigate and rehabilitating degraded natural ecosystems. This paper briefly describes the development history of wind water pumping in China, analyzes the problems existing in the selected wind water pumping machines, and makes some improvements. Taking the Hailiutu ranch in the Middle Banner of Inner Mongolia as an experimental site, the groundwater reserves are estimated by drilling data, and the geological conditions of the site are determined. According to the annual rainfall, sunshine, daily mean wind speed, groundwater migration and evaporation, the energy of the available wind energy is calculated and the quantity of the water pumping unit is determined according to the annual water requirement of the site. According to the location of the experimental site, a reasonable overview scheme has been worked out, and a set of irrigation system has been designed, and its feasibility has been analyzed. The test of a single set of equipment shows that the scheme is feasible. The system uses natural energy, one investment and permanent income, so it has good prospects for popularization and application.
2018, 26(s1): 155-161.
It is very problem that strength decreases and deformation heightened of loess with special structure under seasonal rainfall and evaporation. Uniaxial compressive strength test is used to obtain uniaxial compressive strength of loess by dry-wet cycle. The relationship among the compressive strength, water content and dry-wet circle number is discussed. The micromechanism of intensity change is analysised by SEM image. The results show that the compressive strength nonlinear increases with decreasing water content. The compressive strength of loess decreases with increasing number of cycles and finally reaches stable. The contact style of coarse particle was changed and the quantity of colloidal substances and humus was decreased when water content increases and dry-wet cycles increases. Meanwhile, the pore diameter was increases, and the percentages of big pore and medium pore. The change law of macroscopic strength was described by microstructure of microstructure.
It is very problem that strength decreases and deformation heightened of loess with special structure under seasonal rainfall and evaporation. Uniaxial compressive strength test is used to obtain uniaxial compressive strength of loess by dry-wet cycle. The relationship among the compressive strength, water content and dry-wet circle number is discussed. The micromechanism of intensity change is analysised by SEM image. The results show that the compressive strength nonlinear increases with decreasing water content. The compressive strength of loess decreases with increasing number of cycles and finally reaches stable. The contact style of coarse particle was changed and the quantity of colloidal substances and humus was decreased when water content increases and dry-wet cycles increases. Meanwhile, the pore diameter was increases, and the percentages of big pore and medium pore. The change law of macroscopic strength was described by microstructure of microstructure.
2018, 26(s1): 162-166.
Aiming at energy-saving and environment-friendly roads, many low embankment design schemes have been adopted, resulting in some loess roadbeds being within the influence of traffic loads, and the status of roadbed subsidence deformation is apt to occur. Starting from the perspective of dynamic triaxial tests, this paper investigates the response of dry density, confining pressure and frequency to the dynamic properties of subgrade soil under dynamic load. The study shows that the dynamic elastic modulus of subgrade soil increases with the increase of dry density, confining pressure, and loading frequency. The greater the dynamic elastic modulus of soil, the smaller the corresponding damping ratio. In the design scheme of low embankment, the settlement caused by vehicle load during operation can be reduced by appropriately increasing the dry density of the loess subgrade. At the same time, the lower limit of the frequency range of the vehicle dynamic load should be used in the subgrade design.
Aiming at energy-saving and environment-friendly roads, many low embankment design schemes have been adopted, resulting in some loess roadbeds being within the influence of traffic loads, and the status of roadbed subsidence deformation is apt to occur. Starting from the perspective of dynamic triaxial tests, this paper investigates the response of dry density, confining pressure and frequency to the dynamic properties of subgrade soil under dynamic load. The study shows that the dynamic elastic modulus of subgrade soil increases with the increase of dry density, confining pressure, and loading frequency. The greater the dynamic elastic modulus of soil, the smaller the corresponding damping ratio. In the design scheme of low embankment, the settlement caused by vehicle load during operation can be reduced by appropriately increasing the dry density of the loess subgrade. At the same time, the lower limit of the frequency range of the vehicle dynamic load should be used in the subgrade design.
2018, 26(s1): 167-173.
This paper presents a stability analysis of Sliding Mass I at riverside of Huangtupo Landslide, in which both rainfall and reservoir water level fluctuation in one hydrological year are explicitly considered. Based upon the properties of the sliding mass obtained from laboratory tests such as ring shear test, a GeoStudio numerical model is built to study the stability and deformation of Sliding Mass I at riverside. The comparison between the monitored deformation and the numerical analysis indicates that the use of the residual strength obtained from ring shear tests can yield a better prediction of the landslide deformation. The monitored deformation together with the numerical results illustrates that the deformation at the front edge of the sliding mass is mainly affected by the reservoir water level undulation; whereas, the deformation at the tailing edge of the sliding mass is mainly influenced by the rainfall. The stability analysis also indicates both rainfall and reservoir water level fluctuation could influence the stability of the sliding mass, and,the most unfavorable scenario could be under the combined influence of the rainfall and the decrease of reservoir water level. In other words, the stability of this sliding mass is relatively low in July and August each year, and in that period essential caution should be paid.
This paper presents a stability analysis of Sliding Mass I at riverside of Huangtupo Landslide, in which both rainfall and reservoir water level fluctuation in one hydrological year are explicitly considered. Based upon the properties of the sliding mass obtained from laboratory tests such as ring shear test, a GeoStudio numerical model is built to study the stability and deformation of Sliding Mass I at riverside. The comparison between the monitored deformation and the numerical analysis indicates that the use of the residual strength obtained from ring shear tests can yield a better prediction of the landslide deformation. The monitored deformation together with the numerical results illustrates that the deformation at the front edge of the sliding mass is mainly affected by the reservoir water level undulation; whereas, the deformation at the tailing edge of the sliding mass is mainly influenced by the rainfall. The stability analysis also indicates both rainfall and reservoir water level fluctuation could influence the stability of the sliding mass, and,the most unfavorable scenario could be under the combined influence of the rainfall and the decrease of reservoir water level. In other words, the stability of this sliding mass is relatively low in July and August each year, and in that period essential caution should be paid.
2018, 26(s1): 174-180.
When the mountain tunnel pass through the mountain and valley, the tunnel will inevitably be located on the slopes of different heights. Different hole elevation of the tunnel, the dynamic response under seismic load is bound to be different. Taking the loess tunnel of Western region as the engineering background, using the method of three-dimensional finite element numerical simulation, five different hole elevation model were set up(The pole elevation were h=0m, h=5m, h=10m, h=15m, and h=30m). In this paper, we explored the dynamic responses of the slope and the tunnel portal section under the influence of hole elevation. The results showed that:The change of the hole elevation has an important effect on the dynamic response of tunnel and slope. The displacement peak and peak stress of slope decreased with increasing hole elevation. The amplification effect is very obvious at the tunnel portal section, and the amplification effect is different by the affection of hole elevation. Obvious stress concentration phenomenon occurred on the slope near the entrance of the tunnel, and the dynamic response of acceleration and displacement of the tunnel invert showed that the hole elevation was larger, the length of amplification effect section was short. Therefore, the tunnel elevation effect should be considered in the seismic design of the crossing tunnel. According to the change of hole elevation of the tunnel, the anti-seismic fortified length and the key reinforcement area of the slope should be changed accordingly.
When the mountain tunnel pass through the mountain and valley, the tunnel will inevitably be located on the slopes of different heights. Different hole elevation of the tunnel, the dynamic response under seismic load is bound to be different. Taking the loess tunnel of Western region as the engineering background, using the method of three-dimensional finite element numerical simulation, five different hole elevation model were set up(The pole elevation were h=0m, h=5m, h=10m, h=15m, and h=30m). In this paper, we explored the dynamic responses of the slope and the tunnel portal section under the influence of hole elevation. The results showed that:The change of the hole elevation has an important effect on the dynamic response of tunnel and slope. The displacement peak and peak stress of slope decreased with increasing hole elevation. The amplification effect is very obvious at the tunnel portal section, and the amplification effect is different by the affection of hole elevation. Obvious stress concentration phenomenon occurred on the slope near the entrance of the tunnel, and the dynamic response of acceleration and displacement of the tunnel invert showed that the hole elevation was larger, the length of amplification effect section was short. Therefore, the tunnel elevation effect should be considered in the seismic design of the crossing tunnel. According to the change of hole elevation of the tunnel, the anti-seismic fortified length and the key reinforcement area of the slope should be changed accordingly.
2018, 26(s1): 181-188.
The stability of overlying land embankment was often influenced when a tunnel underpass the existing highway, which induced deformation of strata and highway. Based on the Dafang tunnel of Chengdu-Guiyang railway beneath expressway, the geological model of tunnel beneath highway was built based on the characteristics of the local layers. At the same time, according to the importance of the surface structure, the danger level was divided into the field monitoring area. According to the special geological conditions of karst, the damage mechanism of the road under karst tunnel was revealed. The corresponding construction key technology was given in combination with practical engineering cases. Finally, Settlement deformation characteristics of surface subsidence, road surface subsidence and subgrade layered settlement were analyzed. Research results show that subsidence curve has the characteristics of inverse parabola,the settlement value of the upward projection area of the tunnel boundary was larger, the deformation away from the boundary of the tunnel was smaller. At the same time, the subsidence curve characteristics of tunnel underpass the highway was divided into three stages:the initial stage of small deformation, medium-term accelerated deformation stage and late deformation stable stage. On the whole, settlement deformation was within the allowable range, demonstration of tunnel support parameters was reasonable. The research results can provide similar reference for the construction of the project below in the future.
The stability of overlying land embankment was often influenced when a tunnel underpass the existing highway, which induced deformation of strata and highway. Based on the Dafang tunnel of Chengdu-Guiyang railway beneath expressway, the geological model of tunnel beneath highway was built based on the characteristics of the local layers. At the same time, according to the importance of the surface structure, the danger level was divided into the field monitoring area. According to the special geological conditions of karst, the damage mechanism of the road under karst tunnel was revealed. The corresponding construction key technology was given in combination with practical engineering cases. Finally, Settlement deformation characteristics of surface subsidence, road surface subsidence and subgrade layered settlement were analyzed. Research results show that subsidence curve has the characteristics of inverse parabola,the settlement value of the upward projection area of the tunnel boundary was larger, the deformation away from the boundary of the tunnel was smaller. At the same time, the subsidence curve characteristics of tunnel underpass the highway was divided into three stages:the initial stage of small deformation, medium-term accelerated deformation stage and late deformation stable stage. On the whole, settlement deformation was within the allowable range, demonstration of tunnel support parameters was reasonable. The research results can provide similar reference for the construction of the project below in the future.
2018, 26(s1): 189-195.
The excavation of the deep foundation pit adjacent to the subway line has an impact on existing subway tunnels. We take a deep foundation pit project in Beijing central area as an example. In the paper, We simulate the influence of adjacent subway tunnel caused by excavation of deep foundation pit with FLAC3D.We also evaluate the deformation control of subway tunnel and puts forward relevant monitoring suggestions. The maximum deformation value of the tunnel structure is less than 3.00mm. And the early warning value of tunnel structural deformation is 2.10mm, and the alarm value is 2.40mm during construction.
The excavation of the deep foundation pit adjacent to the subway line has an impact on existing subway tunnels. We take a deep foundation pit project in Beijing central area as an example. In the paper, We simulate the influence of adjacent subway tunnel caused by excavation of deep foundation pit with FLAC3D.We also evaluate the deformation control of subway tunnel and puts forward relevant monitoring suggestions. The maximum deformation value of the tunnel structure is less than 3.00mm. And the early warning value of tunnel structural deformation is 2.10mm, and the alarm value is 2.40mm during construction.
2018, 26(s1): 196-201.
The infrastructure construction in China has been increasing in recent years and the working conditions encountered in the construction of line projects are becoming more and more complex. Mine goaf is a common problem in highway construction. When the highway tunnel project passes through the goaf, it will disturb the rock stratum in the goaf, which may cause the deformation and collapse of the surrounding rock, and hence influence the safety of the tunnel construction and the quality of the project. To address this problem, the Yudushan tunnel of Yan-Chong highway is studied in this paper. The existing condition of the goaf in the mined area was investigated with geophysical prospecting method of High-density Resistivity Method. The influence of the goaf on the construction of Yudushan tunnel of the Yan-Chong highway was studied with numerical simulation software. The results show that mining has a certain degree of disturbance to surrounding rock mass, but the overall stability of surrounding rock can basically be guaranteed. But when the tunnel is excavated to the goaf area, it will cause great disturbance to the surrounding rock, which may cause larger ground settlement. Therefore, it is necessary to adopt early grouting method to reinforce goaf and reduce surrounding rock deformation.
The infrastructure construction in China has been increasing in recent years and the working conditions encountered in the construction of line projects are becoming more and more complex. Mine goaf is a common problem in highway construction. When the highway tunnel project passes through the goaf, it will disturb the rock stratum in the goaf, which may cause the deformation and collapse of the surrounding rock, and hence influence the safety of the tunnel construction and the quality of the project. To address this problem, the Yudushan tunnel of Yan-Chong highway is studied in this paper. The existing condition of the goaf in the mined area was investigated with geophysical prospecting method of High-density Resistivity Method. The influence of the goaf on the construction of Yudushan tunnel of the Yan-Chong highway was studied with numerical simulation software. The results show that mining has a certain degree of disturbance to surrounding rock mass, but the overall stability of surrounding rock can basically be guaranteed. But when the tunnel is excavated to the goaf area, it will cause great disturbance to the surrounding rock, which may cause larger ground settlement. Therefore, it is necessary to adopt early grouting method to reinforce goaf and reduce surrounding rock deformation.
2018, 26(s1): 202-207.
The geological conditions of Dianchi Basin are complex, and soluble rocks are distributed in many parts of the basin and the edge of the basin. The Karst problem is prominent and has a great influence on metro. The investigation of Karst in metro needs to be carried out through multiple stages using comprehensive survey technology to find out its characteristics, properties and hazards. After investigation and analysis, the Karst weak development of the Dahegeng Station of Kunming metro Line 4~Datangzi Station Section, Chenggong East Station(including)~Kunming South Railway Station Section, Liandajie Station~Chenggong East Station Section, Bailongtan parking lot and the Karst middle development of the entrance and exit section line, The Karst section of Jindingshan Station~Xiaocaiyuan Station developed strongly. Line 4 is covered Karst. Karst mainly develops in the 15m range below the base rock surface, and is dominated by filled caves with a height of 0.5~3.0m. The average hole rate of boreholes is 21%, and the average line Karst rate is 3.29%.The Karst area is divided into stable area, sub-unstable area and unstable area. Karst management should adopt corresponding treatment principles and engineering measures for different engineering types and Karst characteristics. Karst treatment generally adopts grouting reinforcement measures. For Karst with a small buried depth, excavation to expose backfill grouting can be used for reinforcement treatment. The pile foundation needs to pass through the Karst and be placed in the lower stable strata. This paper has some guidance for the Karst survey and treatment of metro in Kunming.
The geological conditions of Dianchi Basin are complex, and soluble rocks are distributed in many parts of the basin and the edge of the basin. The Karst problem is prominent and has a great influence on metro. The investigation of Karst in metro needs to be carried out through multiple stages using comprehensive survey technology to find out its characteristics, properties and hazards. After investigation and analysis, the Karst weak development of the Dahegeng Station of Kunming metro Line 4~Datangzi Station Section, Chenggong East Station(including)~Kunming South Railway Station Section, Liandajie Station~Chenggong East Station Section, Bailongtan parking lot and the Karst middle development of the entrance and exit section line, The Karst section of Jindingshan Station~Xiaocaiyuan Station developed strongly. Line 4 is covered Karst. Karst mainly develops in the 15m range below the base rock surface, and is dominated by filled caves with a height of 0.5~3.0m. The average hole rate of boreholes is 21%, and the average line Karst rate is 3.29%.The Karst area is divided into stable area, sub-unstable area and unstable area. Karst management should adopt corresponding treatment principles and engineering measures for different engineering types and Karst characteristics. Karst treatment generally adopts grouting reinforcement measures. For Karst with a small buried depth, excavation to expose backfill grouting can be used for reinforcement treatment. The pile foundation needs to pass through the Karst and be placed in the lower stable strata. This paper has some guidance for the Karst survey and treatment of metro in Kunming.
2018, 26(s1): 208-213.
Down-hole dynamic compaction(abbreviated as DDC pile) is a ground treatment method that the filling is dynamically compacted from the bottom upby several times in the hole bored to the desired depth, in order to form the high bearing capacity dense pile and make soil strongly compacted. When the filling is gravel, DDC pile is not only an effective method of compacting and replacing soil but provide a verticaldrain path to consolidate soil more quickly. Vibrating sinking-tube gravel pile is a widely applied ground treatment method. There is a great difference between the two methods, but mechanical principle and improving soil principle are similar when dealing with cohesive soil. DDC pile can be viewed as large diameter vibrating sinking-tube gravel pile, which is arranged sparsely. Meanwhile, vibrating sinking-tube gravel pile can be viewed as small diameter DDC pile, which is arranged densely. Based on the ground treatment of airport in southwestern mountainous area, the theoretical derivation or quantitative analysis of the four aspects of consolidation effect, shear strength index, cost and efficiency and quality control are analyzed and compared in this paper. It is hoped that the theoretical basis and engineering experience in this paper will help geotechnical engineers in the choice of methods in airport ground treatment in mountainous area.
Down-hole dynamic compaction(abbreviated as DDC pile) is a ground treatment method that the filling is dynamically compacted from the bottom upby several times in the hole bored to the desired depth, in order to form the high bearing capacity dense pile and make soil strongly compacted. When the filling is gravel, DDC pile is not only an effective method of compacting and replacing soil but provide a verticaldrain path to consolidate soil more quickly. Vibrating sinking-tube gravel pile is a widely applied ground treatment method. There is a great difference between the two methods, but mechanical principle and improving soil principle are similar when dealing with cohesive soil. DDC pile can be viewed as large diameter vibrating sinking-tube gravel pile, which is arranged sparsely. Meanwhile, vibrating sinking-tube gravel pile can be viewed as small diameter DDC pile, which is arranged densely. Based on the ground treatment of airport in southwestern mountainous area, the theoretical derivation or quantitative analysis of the four aspects of consolidation effect, shear strength index, cost and efficiency and quality control are analyzed and compared in this paper. It is hoped that the theoretical basis and engineering experience in this paper will help geotechnical engineers in the choice of methods in airport ground treatment in mountainous area.
2018, 26(s1): 214-218.
The study on the bearing behavior of tunnel-type anchorage is the one of the basic scientific questions in the design and application of this type anchorage. Tunnel-type anchorages look like inverted-shape structures with bigger bottom and smaller top. This geometrical characteristic may be the main reason that the additional stress could initiate on the interface of anchor and rock under the main cable load. In order to study the difference of bearing capacity of tunnel-type anchorage in different load stage, the formulas of bearing capacities of anchorage are built with the analysis of the change law of additional stress. And these formulas are verified by the results of field model test. We find that:the load stages of tunnel-type anchorage can be classified as original stage, elastic stage and plastic stage. And the value of initial bearing capacity of tunnel-type anchorage relies on the gravity of the anchor while the ultimate capacity depending on the failure modes and additional stress. Besides, the failure surface of the object anchorage happens on the interface of the anchor and rock. And the initial bearing capacity of the support project is 1540MN,seven times higher than design load. The ultimate bearing capacity reaches to 3080MN,fourteen times higher than design load. While the results obtained from the field model test are 9 and 13 times higher than design load respectively. The results tell us that the bearing position, the range of rock taking part in the different stage and the degree of rock holding the anchor are different in different load stage. Moreover, the stage characteristics of tunnel-type anchorage capacity are closely relevant to the additional stress. And the geological characteristic of tunnel-type anchorage improves the bearing capacity tremendously. Last but not least, the estimation formulas for the bearing capacity is agree with the results of model test and can be applied to guide the design of tunnel-type anchorage.
The study on the bearing behavior of tunnel-type anchorage is the one of the basic scientific questions in the design and application of this type anchorage. Tunnel-type anchorages look like inverted-shape structures with bigger bottom and smaller top. This geometrical characteristic may be the main reason that the additional stress could initiate on the interface of anchor and rock under the main cable load. In order to study the difference of bearing capacity of tunnel-type anchorage in different load stage, the formulas of bearing capacities of anchorage are built with the analysis of the change law of additional stress. And these formulas are verified by the results of field model test. We find that:the load stages of tunnel-type anchorage can be classified as original stage, elastic stage and plastic stage. And the value of initial bearing capacity of tunnel-type anchorage relies on the gravity of the anchor while the ultimate capacity depending on the failure modes and additional stress. Besides, the failure surface of the object anchorage happens on the interface of the anchor and rock. And the initial bearing capacity of the support project is 1540MN,seven times higher than design load. The ultimate bearing capacity reaches to 3080MN,fourteen times higher than design load. While the results obtained from the field model test are 9 and 13 times higher than design load respectively. The results tell us that the bearing position, the range of rock taking part in the different stage and the degree of rock holding the anchor are different in different load stage. Moreover, the stage characteristics of tunnel-type anchorage capacity are closely relevant to the additional stress. And the geological characteristic of tunnel-type anchorage improves the bearing capacity tremendously. Last but not least, the estimation formulas for the bearing capacity is agree with the results of model test and can be applied to guide the design of tunnel-type anchorage.
2018, 26(s1): 219-226.
With the construction of western engineering facilities, the problems of bridge structure diseases in complex geological landslides are often encountered, and the most complicated one is the most unfavorable combination of coupling deep landslide bodies and bridge construction through the sliding surface of landslides, which poses a serious threat to land transportation safety operations. In this paper, the Zaoshugou bridge is paralleled by the old landslide with a thickness of 40m, and the conventional model test is established to simulate the rainfall condition by water injection. The deformation of the bridge pier and anti-slide pile coordination problem under the landslide deformation of this kind of bridge-landslide system exploratory analysis of mechanism and dynamic response. The results of the study show that:(1)The landslide body slides many times, the rock and soil structure is destroyed, the strength is significantly reduced, some landslide bodies are thicker, it is difficult to find a suitable bearing layer, and the original design and treatment plan for the pier played a very good role in protection. (2)The deformation of the sliding body may not be obvious in the case of small deformation, and the stability of the landslide is not significant. The pier is a sensitive structure. The small deformation of the landslide may have a great effect on the pier and even cause the pier to break, thus forming the microscopic progressiveness of the slope-the dynamic response mode of the macroscopic deformation of the pier. (3)The effect of slope deformation on the second row of piles is more obvious, forcing the deformation of the pile top, and the horizontal displacement of x is larger than that of the bridge pier and the first row of piles; the section of the pier is larger than the section of the pile, and the load sharing coordination ratio is renewed. The adjustment is greatly affected by the upper sliding body, so the variation of the pier is more significant than that of the first row. The analysis of the interaction between the bridge and the landslide body is reasonable. The successful treatment of this project can provide constructive reference for similar projects.
With the construction of western engineering facilities, the problems of bridge structure diseases in complex geological landslides are often encountered, and the most complicated one is the most unfavorable combination of coupling deep landslide bodies and bridge construction through the sliding surface of landslides, which poses a serious threat to land transportation safety operations. In this paper, the Zaoshugou bridge is paralleled by the old landslide with a thickness of 40m, and the conventional model test is established to simulate the rainfall condition by water injection. The deformation of the bridge pier and anti-slide pile coordination problem under the landslide deformation of this kind of bridge-landslide system exploratory analysis of mechanism and dynamic response. The results of the study show that:(1)The landslide body slides many times, the rock and soil structure is destroyed, the strength is significantly reduced, some landslide bodies are thicker, it is difficult to find a suitable bearing layer, and the original design and treatment plan for the pier played a very good role in protection. (2)The deformation of the sliding body may not be obvious in the case of small deformation, and the stability of the landslide is not significant. The pier is a sensitive structure. The small deformation of the landslide may have a great effect on the pier and even cause the pier to break, thus forming the microscopic progressiveness of the slope-the dynamic response mode of the macroscopic deformation of the pier. (3)The effect of slope deformation on the second row of piles is more obvious, forcing the deformation of the pile top, and the horizontal displacement of x is larger than that of the bridge pier and the first row of piles; the section of the pier is larger than the section of the pile, and the load sharing coordination ratio is renewed. The adjustment is greatly affected by the upper sliding body, so the variation of the pier is more significant than that of the first row. The analysis of the interaction between the bridge and the landslide body is reasonable. The successful treatment of this project can provide constructive reference for similar projects.
2018, 26(s1): 227-233.
To study the safety influence of a newly built water supply tunnel on the existing railway subgrade, a three dimensional numerical model was established by Midas NX to simulate the shield construction, based on the Damaowu-Renhe water supply tunnel shield underneath the Xuan-Hang railway located in Hangzhou. The displacement of the existing railway subgrade was calculated and the effectivity of the sub-regional reinforcement(splitting grouting reinforcement area, high pressure jet grouting pile reinforcement area and compaction grouting reinforcement area) was studied. Results show that due to the reinforcement measures, the lateral displacement induced by the tunnel shield construction is small enough to be neglected. In the reinforced area, the deformation is mainly vertical settlement with the maximum value of 8.6mm; and the uplift is the main deformation outside the reinforced area which the maximum value is 17.0mm. The maximum displacement location changes with the shield excavation. The sub-regional reinforcement measures can reduce the existing railway subgrade deformation induced by the tunnel shield construction effectively, which insures the safety operation of the existing railway.
To study the safety influence of a newly built water supply tunnel on the existing railway subgrade, a three dimensional numerical model was established by Midas NX to simulate the shield construction, based on the Damaowu-Renhe water supply tunnel shield underneath the Xuan-Hang railway located in Hangzhou. The displacement of the existing railway subgrade was calculated and the effectivity of the sub-regional reinforcement(splitting grouting reinforcement area, high pressure jet grouting pile reinforcement area and compaction grouting reinforcement area) was studied. Results show that due to the reinforcement measures, the lateral displacement induced by the tunnel shield construction is small enough to be neglected. In the reinforced area, the deformation is mainly vertical settlement with the maximum value of 8.6mm; and the uplift is the main deformation outside the reinforced area which the maximum value is 17.0mm. The maximum displacement location changes with the shield excavation. The sub-regional reinforcement measures can reduce the existing railway subgrade deformation induced by the tunnel shield construction effectively, which insures the safety operation of the existing railway.
2018, 26(s1): 234-240.
Anti-seepage reinforcement measures such as underground continuous wall+sleeve valve tube grouting were adopted in one cross-passage of subway tunnel in Nanning, whose structure located in water-rich round gravel stratum, but they failed to achieve the expected treatment purpose. In view of the characteristics and difficulties of the cross-passage, such as large thickness, strong permeability, and poor self-stability of the gravel layer, the comprehensive grouting of cement-paste slurry combined with stable slurry reinforcement+AC-MS acrylate chemical grouting is proposed. The problem of anti-seepage reinforcement of the water-rich round gravel stratum was solved successfully. The excavation and monitoring results showed that the water-rich round gravel was well cemented. The cemented body was hard and dense. The stability and permeability was improved significantly after comprehensive grouting. No collapse, instability, and mud flow occurred during excavation. The anti-seepage reinforcement effect is remarkable which can take a reference for the similar engineering.
Anti-seepage reinforcement measures such as underground continuous wall+sleeve valve tube grouting were adopted in one cross-passage of subway tunnel in Nanning, whose structure located in water-rich round gravel stratum, but they failed to achieve the expected treatment purpose. In view of the characteristics and difficulties of the cross-passage, such as large thickness, strong permeability, and poor self-stability of the gravel layer, the comprehensive grouting of cement-paste slurry combined with stable slurry reinforcement+AC-MS acrylate chemical grouting is proposed. The problem of anti-seepage reinforcement of the water-rich round gravel stratum was solved successfully. The excavation and monitoring results showed that the water-rich round gravel was well cemented. The cemented body was hard and dense. The stability and permeability was improved significantly after comprehensive grouting. No collapse, instability, and mud flow occurred during excavation. The anti-seepage reinforcement effect is remarkable which can take a reference for the similar engineering.
2018, 26(s1): 241-247.
In order to deeply study the main engineering geological problems existing in the resettlement area of Gushan Navigation and Hydropower Project, Using systematic geological survey studies, combined with the necessary exploration arrangements, The major geological problems in the resettlement areas have been identified. That is environmental geological problems, landslide stability problems, artificial slope stability problems, foundation settlement deformation problems. Finally, different engineering treatment measures are proposed for different geological problems, and the conclusions that the resettlement areas after the project treatment measures meet the overall planning and design requirements are obtained.
In order to deeply study the main engineering geological problems existing in the resettlement area of Gushan Navigation and Hydropower Project, Using systematic geological survey studies, combined with the necessary exploration arrangements, The major geological problems in the resettlement areas have been identified. That is environmental geological problems, landslide stability problems, artificial slope stability problems, foundation settlement deformation problems. Finally, different engineering treatment measures are proposed for different geological problems, and the conclusions that the resettlement areas after the project treatment measures meet the overall planning and design requirements are obtained.
2018, 26(s1): 248-253.
Due to complex geological, topographical and clearance conditions, a lot of high-fill airports with the characteristics of large volume of earthwork, complex filling materials, bad construction conditions, and toughly technical difficulty have appeared in mountainous area of southwest China. The purpose of this study is to analyze and summarize a typical case of a complex high-fill airport to provide references to other similar projects. In this paper, the reasons of tension cracks of filling slope in a high-fill airport in southwest China is analyzed, theoretical analysis is performed, and comprehensive treatment measures including construction of toe back pressure, geotextile material, anti-sliding pile, drainage system and draining holes are carried out. Monitoring data for more than 1.5 years after the treatment revealed that the deformation rate has reduled considerably, and that the treatment measures are reliable and effective. The study on deformation of slope, the method of theoretical calculation, and the treatment measures taken in the project will provide good reference for similar projects.
Due to complex geological, topographical and clearance conditions, a lot of high-fill airports with the characteristics of large volume of earthwork, complex filling materials, bad construction conditions, and toughly technical difficulty have appeared in mountainous area of southwest China. The purpose of this study is to analyze and summarize a typical case of a complex high-fill airport to provide references to other similar projects. In this paper, the reasons of tension cracks of filling slope in a high-fill airport in southwest China is analyzed, theoretical analysis is performed, and comprehensive treatment measures including construction of toe back pressure, geotextile material, anti-sliding pile, drainage system and draining holes are carried out. Monitoring data for more than 1.5 years after the treatment revealed that the deformation rate has reduled considerably, and that the treatment measures are reliable and effective. The study on deformation of slope, the method of theoretical calculation, and the treatment measures taken in the project will provide good reference for similar projects.
2018, 26(s1): 254-259.
The part of Xi'an Metro Line 3 in Xiaozhai which is parallel to ground fissure is taken as the research engineering. The dynamic response of subway tunnels during the coupled load of earthquake and ground fissure sedimentation was studied by the FLAC3D numerical simulation which is based on the finite difference principle. The results show that the peak acceleration of ground reaches maximum near the ground fissure. And the magnification coefficient of PGA gradually decays from the ground fissure to both sides. In ground fissure tunnel horizontal earth pressure increases with PGA.The increase of horizontal earth pressure on the hanging wall is obviously larger than that on the footwall and the curve has a peak at the tunnel. The horizontal earth pressure at the left arch waist is greater than that at the right arch waist and the top in the tunnel. The horizontal earth pressure at the bottom is consistent with that at the left arch waist. It obviously shows that the horizontal earth pressure increases at top. Horizontal earth pressure increases with PGA at the tunnel. The horizontal earth pressure at the left arch waist is greater than that at the right arch waist, but the increase is smaller than that at the right arch waist.
The part of Xi'an Metro Line 3 in Xiaozhai which is parallel to ground fissure is taken as the research engineering. The dynamic response of subway tunnels during the coupled load of earthquake and ground fissure sedimentation was studied by the FLAC3D numerical simulation which is based on the finite difference principle. The results show that the peak acceleration of ground reaches maximum near the ground fissure. And the magnification coefficient of PGA gradually decays from the ground fissure to both sides. In ground fissure tunnel horizontal earth pressure increases with PGA.The increase of horizontal earth pressure on the hanging wall is obviously larger than that on the footwall and the curve has a peak at the tunnel. The horizontal earth pressure at the left arch waist is greater than that at the right arch waist and the top in the tunnel. The horizontal earth pressure at the bottom is consistent with that at the left arch waist. It obviously shows that the horizontal earth pressure increases at top. Horizontal earth pressure increases with PGA at the tunnel. The horizontal earth pressure at the left arch waist is greater than that at the right arch waist, but the increase is smaller than that at the right arch waist.
2018, 26(s1): 260-273.
The Loess Plateau area of China, with an area 62.46104km2 and characterized by high tectonic activities, is an area with a large number of and prone of landslides and debris flows. It has a rich historical earthquakes and triggered landslides in the area. This study summarizes the earthquakes and triggered landslides in Loess Plateau and its adjacent areas(100-km-buffer zone). The results show that there are 395 earthquake records of magnitude M5 in the Loess Plateau and its adjacent areas. Among them, there were 6 earthquakes of magnitude M8 or larger, 20 earthquakes between M7 and M8, 74 of 6 M 7, and 295 events of 5 M 6. Among the 395 earthquakes, there are 98 earthquakes have coseismic landslide records or detailed information. The information of landslides triggered by these earthquake is briefly introduced. This study also briefly introduces the landslides triggered by four earthquakes, such as the 2013 Minxian M6.7, 1920 Haiyuan M8.5, 1927 Gulang M8, and 1995 Yongdeng M5.8 events. Finally, the research prospects of earthquake-triggered landslide in Loess Plateau and its adjacent areas is proposed. This study can provide important basic information for scientific research and prevention and reduction of earthquakes and associated landslides in the Loess Plateau and adjacent areas.
The Loess Plateau area of China, with an area 62.46104km2 and characterized by high tectonic activities, is an area with a large number of and prone of landslides and debris flows. It has a rich historical earthquakes and triggered landslides in the area. This study summarizes the earthquakes and triggered landslides in Loess Plateau and its adjacent areas(100-km-buffer zone). The results show that there are 395 earthquake records of magnitude M5 in the Loess Plateau and its adjacent areas. Among them, there were 6 earthquakes of magnitude M8 or larger, 20 earthquakes between M7 and M8, 74 of 6 M 7, and 295 events of 5 M 6. Among the 395 earthquakes, there are 98 earthquakes have coseismic landslide records or detailed information. The information of landslides triggered by these earthquake is briefly introduced. This study also briefly introduces the landslides triggered by four earthquakes, such as the 2013 Minxian M6.7, 1920 Haiyuan M8.5, 1927 Gulang M8, and 1995 Yongdeng M5.8 events. Finally, the research prospects of earthquake-triggered landslide in Loess Plateau and its adjacent areas is proposed. This study can provide important basic information for scientific research and prevention and reduction of earthquakes and associated landslides in the Loess Plateau and adjacent areas.
2018, 26(s1): 274-279.
Deep mixing(DM)method has become one of the most commonly-used techniques to improve soft soils under embankments, which can be used to reduce settlement, increase bearing capacity and enhance stability of foundation. However, the assessment of factor of safety against slope stability of DM column-supported embankment over soft soil is still a concern in practice, owing to a lack of well understanding of its failure modes. The existing method only considers the contribution of shear strength of DM column against the slope failure, which would overestimate the factor of safety of embankment stability. Accordingly, this paper presents a model test to investigate the failure modes of slope stability of deep mixed column-supported embankment. 3-D numerical model corresponding to the model test was simulated to investigate the evolution of plastic zone in the process of slope failure. The results indicated that the DM columns under different locations under the embankment had different failure modes. In the process of slope instability, the DM columns located under the embankment crest were mainly subjected to the vertical load, firstly resulting in a compression and shear failure. After that the horizontal earth thrust carried by the columns under the slope of embankment increased, resulting in these DM columns having a bending failure.
Deep mixing(DM)method has become one of the most commonly-used techniques to improve soft soils under embankments, which can be used to reduce settlement, increase bearing capacity and enhance stability of foundation. However, the assessment of factor of safety against slope stability of DM column-supported embankment over soft soil is still a concern in practice, owing to a lack of well understanding of its failure modes. The existing method only considers the contribution of shear strength of DM column against the slope failure, which would overestimate the factor of safety of embankment stability. Accordingly, this paper presents a model test to investigate the failure modes of slope stability of deep mixed column-supported embankment. 3-D numerical model corresponding to the model test was simulated to investigate the evolution of plastic zone in the process of slope failure. The results indicated that the DM columns under different locations under the embankment had different failure modes. In the process of slope instability, the DM columns located under the embankment crest were mainly subjected to the vertical load, firstly resulting in a compression and shear failure. After that the horizontal earth thrust carried by the columns under the slope of embankment increased, resulting in these DM columns having a bending failure.
2018, 26(s1): 280-288.
Railway tunnel secondary lining insufficient thickness caused by varies factors during construction need reinforce according to current relate regulations when the in-fact thickness less than 70%compare to the design value. We need to define the one time remove area of secondary tunnel lining to ensure the safety construction, and not affect the stability of existing structure. Right and reasonable implementation plan can be determined by calculation, analysis and engineering analogy, et al. For tunnel lining on the poor self-stability Ⅳ and Ⅴ grade surrounding no-layer rock-mass, using analytic calculation and numerical simulation method with 2D GTS(geotechnical and tunnel finite element analytic software),we can obtain the stress characteristics and structure safety factor of tunnel lining under the condition of different removed range on the vault of tunnel lining. The analysis and calculation results imply that the tunnel lining stress is relative large in the vault, side wall and bottom corner and tensile stress appears in the vault zone. The tunnel lining structure is safety when the cut open-window construction of the tunneling vault within 2m2 area for the Ⅳ grade surrounding rock-mass need not consider the reinforcing steel bar effect, but for the V grade surrounding rock-mass, must consider the reinforcing steel bar role.
Railway tunnel secondary lining insufficient thickness caused by varies factors during construction need reinforce according to current relate regulations when the in-fact thickness less than 70%compare to the design value. We need to define the one time remove area of secondary tunnel lining to ensure the safety construction, and not affect the stability of existing structure. Right and reasonable implementation plan can be determined by calculation, analysis and engineering analogy, et al. For tunnel lining on the poor self-stability Ⅳ and Ⅴ grade surrounding no-layer rock-mass, using analytic calculation and numerical simulation method with 2D GTS(geotechnical and tunnel finite element analytic software),we can obtain the stress characteristics and structure safety factor of tunnel lining under the condition of different removed range on the vault of tunnel lining. The analysis and calculation results imply that the tunnel lining stress is relative large in the vault, side wall and bottom corner and tensile stress appears in the vault zone. The tunnel lining structure is safety when the cut open-window construction of the tunneling vault within 2m2 area for the Ⅳ grade surrounding rock-mass need not consider the reinforcing steel bar effect, but for the V grade surrounding rock-mass, must consider the reinforcing steel bar role.
2018, 26(s1): 289-294.
The influence factors of external water pressure of lining and water inflow are important issues in the design of diversion tunnel in complex karst region, which are of great significance to tunnel drainage and environmental protection. In view of the Dali section Ⅱ diversion tunnel of the water diversion project for the central area of Yunnan Province, the formulas of external water pressure reduction coefficient and tunnel water inflow were derived from theory of circular tunnel seepage flow. The influence of lining and grouting ring parameters on external pressure and water inflow of tunnel lining was studied respectively. The results show that the increasing thickness and the decreasing permeability coefficient of lining both can lead to the decrease of external water pressure, but the tunnel water inflow will increase significantly, which is unfavorable for environmental protection around the tunnel. However, increasing the thickness of the grouting circle or reducing its permeability coefficient can effectively control the water inflow of tunnel while reducing the external water pressure of the lining. The research results can provide references for the design of waterproof and drainage system of tunnel engineering in complex karst area of Southwest China.
The influence factors of external water pressure of lining and water inflow are important issues in the design of diversion tunnel in complex karst region, which are of great significance to tunnel drainage and environmental protection. In view of the Dali section Ⅱ diversion tunnel of the water diversion project for the central area of Yunnan Province, the formulas of external water pressure reduction coefficient and tunnel water inflow were derived from theory of circular tunnel seepage flow. The influence of lining and grouting ring parameters on external pressure and water inflow of tunnel lining was studied respectively. The results show that the increasing thickness and the decreasing permeability coefficient of lining both can lead to the decrease of external water pressure, but the tunnel water inflow will increase significantly, which is unfavorable for environmental protection around the tunnel. However, increasing the thickness of the grouting circle or reducing its permeability coefficient can effectively control the water inflow of tunnel while reducing the external water pressure of the lining. The research results can provide references for the design of waterproof and drainage system of tunnel engineering in complex karst area of Southwest China.
2018, 26(s1): 295-300.
In this paper, micro-vibration tests at a display driver chips production workshop in Hefei were carried out lasting 24 hours. Vibration accelerations of each testing point on three directions were simultaneously recorded by a high-sensitivity type accelerometer. Internationally accepted one-third octave band analysis method was adopted to process the field test data. The variation of vibration over time was analyzed, and the attenuation characteristics of vibrations induced by traffic loads with distance were also studied by one-third octave band spectra. Results show that, vibration accelerations alter smoothly within 24 hours, and it should be noted that the peak acceleration in the daytime is slightly higher than that at night. Vibration amplitudes swing between 10-5 gal and 10-2 gal. In the low frequency ranges(2~8 Hz),the peak of vibration acceleration is 0.015gal. In the medium-high frequency ranges(8~250 Hz),the maximum value of vertical velocity reaches 0.5013ms-1,while the velocity touches higher to 0.6636ms-1 in horizontal direction. One-third octave band spectra of testing vibrations locate below the VC-B curve totally indicating that design requirements are satisfied. Besides, ground vibrations caused by traffic loads decay apparently with distance in the frequency from 15 to 60 Hz, which are regarded that ground layers play a role in the attenuation of vibration caused by traffic load.
In this paper, micro-vibration tests at a display driver chips production workshop in Hefei were carried out lasting 24 hours. Vibration accelerations of each testing point on three directions were simultaneously recorded by a high-sensitivity type accelerometer. Internationally accepted one-third octave band analysis method was adopted to process the field test data. The variation of vibration over time was analyzed, and the attenuation characteristics of vibrations induced by traffic loads with distance were also studied by one-third octave band spectra. Results show that, vibration accelerations alter smoothly within 24 hours, and it should be noted that the peak acceleration in the daytime is slightly higher than that at night. Vibration amplitudes swing between 10-5 gal and 10-2 gal. In the low frequency ranges(2~8 Hz),the peak of vibration acceleration is 0.015gal. In the medium-high frequency ranges(8~250 Hz),the maximum value of vertical velocity reaches 0.5013ms-1,while the velocity touches higher to 0.6636ms-1 in horizontal direction. One-third octave band spectra of testing vibrations locate below the VC-B curve totally indicating that design requirements are satisfied. Besides, ground vibrations caused by traffic loads decay apparently with distance in the frequency from 15 to 60 Hz, which are regarded that ground layers play a role in the attenuation of vibration caused by traffic load.
2018, 26(s1): 301-309.
There are lots of theories about the causation of ground fissures inXi'an,such as the tectonics theory, the excessive groundwater exploitation theory and the compositive theory. Based on the construction of the geologic environment monitoring network in Guanzhong urban agglomeration, the latest survey of Yuhuazhai ground fissures and land subsidence in Xi'an suggests that the extensive piping and quick sand in self-supply wells is a factor to induce ground fissures and the land subsidence. The paper works out the higher hydraulic gradient seepage deformation which can lead to sand gushing and the part of aquifer deformation into the composite aquifer is the main factor to induce ground fissures and the land subsidence. The paper also makes a systematic summarization of development characteristics of ground fissures and land subsidence by seepage deformation. The results will supply new schemes and methods for the causation of the land subsidence and ground fissure sin Xi'an and laid out a clear roadmap of control measures to the land subsidence and ground fissures.
There are lots of theories about the causation of ground fissures inXi'an,such as the tectonics theory, the excessive groundwater exploitation theory and the compositive theory. Based on the construction of the geologic environment monitoring network in Guanzhong urban agglomeration, the latest survey of Yuhuazhai ground fissures and land subsidence in Xi'an suggests that the extensive piping and quick sand in self-supply wells is a factor to induce ground fissures and the land subsidence. The paper works out the higher hydraulic gradient seepage deformation which can lead to sand gushing and the part of aquifer deformation into the composite aquifer is the main factor to induce ground fissures and the land subsidence. The paper also makes a systematic summarization of development characteristics of ground fissures and land subsidence by seepage deformation. The results will supply new schemes and methods for the causation of the land subsidence and ground fissure sin Xi'an and laid out a clear roadmap of control measures to the land subsidence and ground fissures.
2018, 26(s1): 310-315.
Deep foundation pit engineering plays an important role in urban construction. To implement deep foundation pit engineering in a densely populated city center, not only ensures the safety and stability of the foundation pit itself, but also ensures the stability of the adjacent building foundation. Taking a deep foundation pit support as an example, combined with the finite element software-Midas GTS NX,the modified-molar Coulomb constitutive model is used to establish a three-dimensional finite element model using two support forms to analyze the deep foundation pit excavation and support, including the self-supporting structure, the soil surrounding the foundation pit and the deformation law of the adjacent building foundation. The results show:(1)During the excavation of the foundation pit, the two types of support forms has little difference to the adjacent building's raft foundation, but there are significant differences in the internal forces of the two supporting structures. (2)The maximum surface settlement during the excavation of the foundation pit is not at the edge of the foundation pit, but occurs at a position about 2m from the edge of the pit. (3)The surface settlement during foundation excavation is approximately linear with the distance from the edge of the foundation pit.
Deep foundation pit engineering plays an important role in urban construction. To implement deep foundation pit engineering in a densely populated city center, not only ensures the safety and stability of the foundation pit itself, but also ensures the stability of the adjacent building foundation. Taking a deep foundation pit support as an example, combined with the finite element software-Midas GTS NX,the modified-molar Coulomb constitutive model is used to establish a three-dimensional finite element model using two support forms to analyze the deep foundation pit excavation and support, including the self-supporting structure, the soil surrounding the foundation pit and the deformation law of the adjacent building foundation. The results show:(1)During the excavation of the foundation pit, the two types of support forms has little difference to the adjacent building's raft foundation, but there are significant differences in the internal forces of the two supporting structures. (2)The maximum surface settlement during the excavation of the foundation pit is not at the edge of the foundation pit, but occurs at a position about 2m from the edge of the pit. (3)The surface settlement during foundation excavation is approximately linear with the distance from the edge of the foundation pit.
2018, 26(s1): 316-323.
Shanghai is located in the alluvial plain of the Yangtze River Delta. The Huangpu River and the Suzhou River flow through the central urban area. The unique geographical environment and sedimentary environment have formed the shallow sand layers in Shanghai. Due to the large-scale development of urban construction, in addition to aging underground pipelines in the urban center, the risk of quicksand sharpens, which further results in the ground collapse. Based on the identification of key elements of ground collapse, in this paper, a risk assessment system on ground collapse was established, in which both hazard and vulnerability were introduced. Further analysis was made on the characteristics of ②3 silty soil, the structural defects of underground pipelines and the scale of underground space. In this paper, the evaluation of hazard and vulnerability factors were quantified by a fuzzy evaluation model and the risk of ground collapse was studied in Shanghai city center. This study aims to provide technical support for the establishment of surveillance network to monitor an area of interest in time, offer basis for decision making in land resources management, city construction, municipal engineering, and environmental protection. Study findings also makes sense in providing demonstration of ground collapse prevention and risk management.
Shanghai is located in the alluvial plain of the Yangtze River Delta. The Huangpu River and the Suzhou River flow through the central urban area. The unique geographical environment and sedimentary environment have formed the shallow sand layers in Shanghai. Due to the large-scale development of urban construction, in addition to aging underground pipelines in the urban center, the risk of quicksand sharpens, which further results in the ground collapse. Based on the identification of key elements of ground collapse, in this paper, a risk assessment system on ground collapse was established, in which both hazard and vulnerability were introduced. Further analysis was made on the characteristics of ②3 silty soil, the structural defects of underground pipelines and the scale of underground space. In this paper, the evaluation of hazard and vulnerability factors were quantified by a fuzzy evaluation model and the risk of ground collapse was studied in Shanghai city center. This study aims to provide technical support for the establishment of surveillance network to monitor an area of interest in time, offer basis for decision making in land resources management, city construction, municipal engineering, and environmental protection. Study findings also makes sense in providing demonstration of ground collapse prevention and risk management.
2018, 26(s1): 324-330.
Tunnel construction ventilation is an important factor affecting the efficiency and safety of shield tunnel construction. The paper proposes a new ventilation system for the large diameter and long distance tunnel construction at Sutong GIL utility tunnel engineering. The tunnel is a single line tunnel without shaft and parallel guide hole, which is crossing gas stratum of Yangtze river bed. Moreover, the tunnel internal structure constructs when the tunnel bores, which causes a huge challenge for ventilation. Firstly, it chose the best ventilation-the forced and relay ventilation, according to the relevant specifications and engineering experience of similar projects. Next, it calculated the required air volume and wind pressure in the restriction of the trackless transport and equipment performance. The effects of harmful gases such as stratigraphic gas and automobile exhaust is fully considered in the calculation. At last, it put forward reasonable improvement measures for the field ventilation and the technical parameters of a safe and effective ventilation system. The measures improved the field construction conditions. The 5466m distance and large diameter tunnel successfully uses the single-head forced ventilation, which is of significance of the similar tunnel ventilation.
Tunnel construction ventilation is an important factor affecting the efficiency and safety of shield tunnel construction. The paper proposes a new ventilation system for the large diameter and long distance tunnel construction at Sutong GIL utility tunnel engineering. The tunnel is a single line tunnel without shaft and parallel guide hole, which is crossing gas stratum of Yangtze river bed. Moreover, the tunnel internal structure constructs when the tunnel bores, which causes a huge challenge for ventilation. Firstly, it chose the best ventilation-the forced and relay ventilation, according to the relevant specifications and engineering experience of similar projects. Next, it calculated the required air volume and wind pressure in the restriction of the trackless transport and equipment performance. The effects of harmful gases such as stratigraphic gas and automobile exhaust is fully considered in the calculation. At last, it put forward reasonable improvement measures for the field ventilation and the technical parameters of a safe and effective ventilation system. The measures improved the field construction conditions. The 5466m distance and large diameter tunnel successfully uses the single-head forced ventilation, which is of significance of the similar tunnel ventilation.
2018, 26(s1): 331-336.
Geosynthetic Reinforced Soil-Integrated Bridge System(GRS-IBS) is a new technology proposed by the United States for the rapid replacement of single-span bridges with medium and small size. It is an optimization and enhancement of the original GRS abutment technology. So far, the GRS-IBS structures have been designed and constructed for more than 250 bridges in 44states in US and engineering experiences have been accumulated for more than 10 years. This paper performed a literature review of more than 40 GRS-IBS structures in the US. The performance of the GRS-IBS structures has been investigated from field monitoring data, vehicle loading tests, and numerical analysis. Research results showed that the differential settlement between the bridge slab and the approaching embankment was minimized in the GRS-IBS structures. The change of temperature had little effect on the performance of the structures. The lateral earth pressure behind the facing was low and uniformly distributed along the height, which was not consistent with Rankine lateral earth pressure theory. Small tensile force developed in the geosynthetic reinforcement. The failure surface behind the wall facing matched well with the active Rankine failure surface at the lower portion of the wall. At the top of the wall, the failure surface deviated from the active Rankine failure surface. In addition, parametric study using numerical analysis showed that proper compaction of backfill soil and small spacing between reinforcement material were two key factors to ensure good performance of the GRS-IBS structures after construction. The increase of the friction angle of the backfill soil resulted in the increase of the interface friction angle between the geosynthetic reinforcement and the backfill soil, hence the smaller settlement and lateral deformation.
Geosynthetic Reinforced Soil-Integrated Bridge System(GRS-IBS) is a new technology proposed by the United States for the rapid replacement of single-span bridges with medium and small size. It is an optimization and enhancement of the original GRS abutment technology. So far, the GRS-IBS structures have been designed and constructed for more than 250 bridges in 44states in US and engineering experiences have been accumulated for more than 10 years. This paper performed a literature review of more than 40 GRS-IBS structures in the US. The performance of the GRS-IBS structures has been investigated from field monitoring data, vehicle loading tests, and numerical analysis. Research results showed that the differential settlement between the bridge slab and the approaching embankment was minimized in the GRS-IBS structures. The change of temperature had little effect on the performance of the structures. The lateral earth pressure behind the facing was low and uniformly distributed along the height, which was not consistent with Rankine lateral earth pressure theory. Small tensile force developed in the geosynthetic reinforcement. The failure surface behind the wall facing matched well with the active Rankine failure surface at the lower portion of the wall. At the top of the wall, the failure surface deviated from the active Rankine failure surface. In addition, parametric study using numerical analysis showed that proper compaction of backfill soil and small spacing between reinforcement material were two key factors to ensure good performance of the GRS-IBS structures after construction. The increase of the friction angle of the backfill soil resulted in the increase of the interface friction angle between the geosynthetic reinforcement and the backfill soil, hence the smaller settlement and lateral deformation.
2018, 26(s1): 337-341.
With development of informatization in engineering investigation, it completes the digitization stage, and gradually advances to informatization and intellectualization, and gradually realize the function of assistance, support and promotion of engineering investigation work. Combined with the requirements of the 13th five-year project survey informatization development, the engineering investigation will focus on the Internet, Internet of things, big data, cloud computing and BIM technology, whose integrated development trend of whole system, entire process and all element is realized. In addition, the informatization development of the engineering investigation will provide a firm and effective foundation for the national infrastructure construction, regional geo-science promotion and industrial technological innovation.
With development of informatization in engineering investigation, it completes the digitization stage, and gradually advances to informatization and intellectualization, and gradually realize the function of assistance, support and promotion of engineering investigation work. Combined with the requirements of the 13th five-year project survey informatization development, the engineering investigation will focus on the Internet, Internet of things, big data, cloud computing and BIM technology, whose integrated development trend of whole system, entire process and all element is realized. In addition, the informatization development of the engineering investigation will provide a firm and effective foundation for the national infrastructure construction, regional geo-science promotion and industrial technological innovation.
2018, 26(s1): 342-348.
In order to study the influence of engineering construction especially deep foundation excavation and dewatering on key transportation infrastructures in Shanghai, we analyzed relevant engineering monitoring data to investigatethe deformation characteristics of metro tunnels and elevated roads after dewatering of the foundation pits. Also, we combined the change of water level of confined aquifers and layered deformation of soil layers to reveal the influence of dewatering of deep foundation on key transportation infrastructures. The conclusions are as followed:(1)Dewatering of deep foundations contributions to the severe settlement of metro tunnels and elevated roads. The scope of influence can reach 30 times the excavation depth. The settlement rate of metro tunnels and elevated roads decreases greatly after the completion of dewatering, and the rebound of metro tunnels can even be observed. (2)The water level of confined aquifers will undergo significant decrease because of the considerable pumping water volumes. The recharge will also efficiently mitigate the decrease of the water level after dewatering ends. (3)The dewatering of deep foundation will lead to the compression of aquifers and aquitards above. The water release of aquitards is comparatively slow due to their soil characteristics, but the settlement of aquitards is larger than that of the aquifers. The rebound caused by recharge mainly takes place in the aquifers.
In order to study the influence of engineering construction especially deep foundation excavation and dewatering on key transportation infrastructures in Shanghai, we analyzed relevant engineering monitoring data to investigatethe deformation characteristics of metro tunnels and elevated roads after dewatering of the foundation pits. Also, we combined the change of water level of confined aquifers and layered deformation of soil layers to reveal the influence of dewatering of deep foundation on key transportation infrastructures. The conclusions are as followed:(1)Dewatering of deep foundations contributions to the severe settlement of metro tunnels and elevated roads. The scope of influence can reach 30 times the excavation depth. The settlement rate of metro tunnels and elevated roads decreases greatly after the completion of dewatering, and the rebound of metro tunnels can even be observed. (2)The water level of confined aquifers will undergo significant decrease because of the considerable pumping water volumes. The recharge will also efficiently mitigate the decrease of the water level after dewatering ends. (3)The dewatering of deep foundation will lead to the compression of aquifers and aquitards above. The water release of aquitards is comparatively slow due to their soil characteristics, but the settlement of aquitards is larger than that of the aquifers. The rebound caused by recharge mainly takes place in the aquifers.
2018, 26(s1): 349-361.
The excavation of underground engineering will inevitably form the damage zone in the surrounding rock mass. It is of great importance to understand the distribution and evolution of the damage zone for the stability and safe operation of the project. This paper reviews the research course of excavation damage zone from the concept, experiment, theory,hot topic and engineering applications and summarizes the results of predecessors' work. on the basis of this I thought:(1)The excavation damage zone will continue to be one of the hot issues in the future. To form a unified quantitative definition helps to research. (2)Under complex conditions, it is still impossible to judge the range and distribution of excavation damage zone by theory, and the existing prediction methods of excavation damage zone need to be improved constantly. (3)The formation and evolution mechanism of excavation damage zone under coupling conditions and the excavation response under real boundary conditions still need to be studied. (4)The influence of the evolution process of the damage zone on the mechanical parameters of rock mass is not clear, and multi-scale and multi-level studies can be carried out by means of numerical simulation. (5)It is necessary to strengthen the research on the deep excavation damage zone and the aging deformation effect.
The excavation of underground engineering will inevitably form the damage zone in the surrounding rock mass. It is of great importance to understand the distribution and evolution of the damage zone for the stability and safe operation of the project. This paper reviews the research course of excavation damage zone from the concept, experiment, theory,hot topic and engineering applications and summarizes the results of predecessors' work. on the basis of this I thought:(1)The excavation damage zone will continue to be one of the hot issues in the future. To form a unified quantitative definition helps to research. (2)Under complex conditions, it is still impossible to judge the range and distribution of excavation damage zone by theory, and the existing prediction methods of excavation damage zone need to be improved constantly. (3)The formation and evolution mechanism of excavation damage zone under coupling conditions and the excavation response under real boundary conditions still need to be studied. (4)The influence of the evolution process of the damage zone on the mechanical parameters of rock mass is not clear, and multi-scale and multi-level studies can be carried out by means of numerical simulation. (5)It is necessary to strengthen the research on the deep excavation damage zone and the aging deformation effect.
2018, 26(s1): 362-369.
A deep foundation pit of a subway in Tianjin is located in the center of the city. There are residential quarters, high-rise residential buildings, schools, research institutes and so on. The foundation pit is about 17.72m deep. The excavation area is large. The depth of foundation pit is deep. The groundwater level is high, and the soil layer is mainly composed of soft clay, such as silty clay. The foundation pit enclosure structure adopts the joint support type of underground continuous wall and inner support. In this paper, the characteristics of the stress and deformation of the continuous wall of underground continuous wall and the law of the surrounding ground settlement are studied by the control variable method. The law of settlement and deformation of underground continuous wall and surrounding surface is obtained, so as to determine the optimal supporting scheme of retaining structure. The research results can provide reference for similar foundation pit design.
A deep foundation pit of a subway in Tianjin is located in the center of the city. There are residential quarters, high-rise residential buildings, schools, research institutes and so on. The foundation pit is about 17.72m deep. The excavation area is large. The depth of foundation pit is deep. The groundwater level is high, and the soil layer is mainly composed of soft clay, such as silty clay. The foundation pit enclosure structure adopts the joint support type of underground continuous wall and inner support. In this paper, the characteristics of the stress and deformation of the continuous wall of underground continuous wall and the law of the surrounding ground settlement are studied by the control variable method. The law of settlement and deformation of underground continuous wall and surrounding surface is obtained, so as to determine the optimal supporting scheme of retaining structure. The research results can provide reference for similar foundation pit design.
2018, 26(s1): 370-375.
Underground excavation of the subway tunnels through is the normal operation of five railway box culverts. According to the control standard of railway deformation in safe operation, a special design was made for the tunnels excavation under railway box culverts. The big pipes shed+pre-grouting small tubes were used in advance support. The initial support of the tunnel was made of steel grille+shotcrete, and the temporary inverted arch was set. In order to facilitate the construction and operation of the big pipe shed, the operation room support of the pipe shed was designed. According to the positioning and guiding design of the large pipe shed, the positioning and guiding scheme were compared and reinforced concrete guide wall was adopted. The construction technology and grouting parameters of large pipe shed and pre-grouting small tubes were designed. The steel grille+shotcrete and the temporary reverse arch were used to support surrounding rocks in tunnels. The emergency plan was designed for the construction. At present, the project was safely completed, this paper will provide reference for those subway tunnels excavation under railway box culverts.
Underground excavation of the subway tunnels through is the normal operation of five railway box culverts. According to the control standard of railway deformation in safe operation, a special design was made for the tunnels excavation under railway box culverts. The big pipes shed+pre-grouting small tubes were used in advance support. The initial support of the tunnel was made of steel grille+shotcrete, and the temporary inverted arch was set. In order to facilitate the construction and operation of the big pipe shed, the operation room support of the pipe shed was designed. According to the positioning and guiding design of the large pipe shed, the positioning and guiding scheme were compared and reinforced concrete guide wall was adopted. The construction technology and grouting parameters of large pipe shed and pre-grouting small tubes were designed. The steel grille+shotcrete and the temporary reverse arch were used to support surrounding rocks in tunnels. The emergency plan was designed for the construction. At present, the project was safely completed, this paper will provide reference for those subway tunnels excavation under railway box culverts.
2018, 26(s1): 376-383.
Using 3D laser scanning technology in Wuxi Guangming Village, obtained the point cloud data and build a model. We used geomagic distinguish the characteristics of groung fissure, then evaluated itself and its influence on the surrounding construction. Using statistical principle and numerical calculation, we adopted the method of selecting feature points and feature lines to obtain ground fissure's tendency, direction, length, depth and dispersion. In addiction, we studied the influence of the number of feature points on the accuracy of the result. Besides, using the eigenvector of the fitting plane, obtained the tilt degree of the wall caused by the ground fissure through geometric transformation and calculation. Finally we obtianed qualitative and quantitative analysis of the effects of ground fissure. Through the analysis of the characteristics of the ground cracks and the influence of the surrounding walls, we can offer renovation suggestiond on this fissure, guide analysis of subsequent geological conditions. We can also provide a method of using geomagic to get the feature information of the monitored objects.
Using 3D laser scanning technology in Wuxi Guangming Village, obtained the point cloud data and build a model. We used geomagic distinguish the characteristics of groung fissure, then evaluated itself and its influence on the surrounding construction. Using statistical principle and numerical calculation, we adopted the method of selecting feature points and feature lines to obtain ground fissure's tendency, direction, length, depth and dispersion. In addiction, we studied the influence of the number of feature points on the accuracy of the result. Besides, using the eigenvector of the fitting plane, obtained the tilt degree of the wall caused by the ground fissure through geometric transformation and calculation. Finally we obtianed qualitative and quantitative analysis of the effects of ground fissure. Through the analysis of the characteristics of the ground cracks and the influence of the surrounding walls, we can offer renovation suggestiond on this fissure, guide analysis of subsequent geological conditions. We can also provide a method of using geomagic to get the feature information of the monitored objects.
2018, 26(s1): 384-387.
Equotip(Leeb hardness tester) is invented by Dietmai Leeb in the 1970s. At first, it was designed for detecting the hardness of metal materials. For it has the characteristics of small impact energy, undemanding impact direction, more sensitive to rock strength changes, it can be applied to non-destructive measurement of rocks. The authors used it to measure flake weathered rock surface of Yungang Grottoes, Datong, Shanxi province. The average hardness values of three chosen measurement regions were 224.8, 225.8 and 236.4,respectively. However, the average Leeb hardness value of unweathered rock with the same lithology was 661.4. According to the above measured values, the authors define the weathering degree, that is the ratio of the hardness values of weathered rock to that of fresh rock. Accordingly, the weathering degrees of the three measurement regions were 0.34, 0.34 and 0.36 respectively. According to the formula of Leeb hardness value and uniaxial compressive strength summarized in the literature, it also obtained that the uniaxial compressive strength of the three measurement regions were 6.06MPa, 6.13MPa and 6.87MPa, respectively.
Equotip(Leeb hardness tester) is invented by Dietmai Leeb in the 1970s. At first, it was designed for detecting the hardness of metal materials. For it has the characteristics of small impact energy, undemanding impact direction, more sensitive to rock strength changes, it can be applied to non-destructive measurement of rocks. The authors used it to measure flake weathered rock surface of Yungang Grottoes, Datong, Shanxi province. The average hardness values of three chosen measurement regions were 224.8, 225.8 and 236.4,respectively. However, the average Leeb hardness value of unweathered rock with the same lithology was 661.4. According to the above measured values, the authors define the weathering degree, that is the ratio of the hardness values of weathered rock to that of fresh rock. Accordingly, the weathering degrees of the three measurement regions were 0.34, 0.34 and 0.36 respectively. According to the formula of Leeb hardness value and uniaxial compressive strength summarized in the literature, it also obtained that the uniaxial compressive strength of the three measurement regions were 6.06MPa, 6.13MPa and 6.87MPa, respectively.
2018, 26(s1): 388-391.
The high density resistivity method has the advantages of high efficiency, high observation precision etc. The method is used in engineering geology and hydrogeology exploration widely. In this paper high density resistivity method was used in geothermal exploration in certain work area. By delineating the geothermal heating channel fault, the results proved high density resistivity method is feasible in geothermal exploration. The apparent resistivity data are collected by using Wenner device, the inversion results clearly inflect the resistivity distribution underground. It provides the geophysical basis for geothermal exploration.
The high density resistivity method has the advantages of high efficiency, high observation precision etc. The method is used in engineering geology and hydrogeology exploration widely. In this paper high density resistivity method was used in geothermal exploration in certain work area. By delineating the geothermal heating channel fault, the results proved high density resistivity method is feasible in geothermal exploration. The apparent resistivity data are collected by using Wenner device, the inversion results clearly inflect the resistivity distribution underground. It provides the geophysical basis for geothermal exploration.
2018, 26(s1): 392-396.
The gravity-type anchor block, one of the main important anchorage types of suspension bridge, has advantages of wide range of application and low demand for the bearing capacity of foundations. In the calculation of bearing capacity of gravity-type anchor block, the gravity and frictional resistance are taken into account while the resistances generated by the interaction of substruction and foundation as well as the gravity of backfill soil are neglected. It cannot be denied that the omission causes great error on the estimation of bearing capacity and the anti-sliding coefficient of gravity-type anchor block. Through analyzing the difference of the bearing behavior between the conventional anchor blocks and the rugged ones, the estimation method of the bearing capacity of gravity-type anchor block was studied in this paper. And the bearing capacity estimation formula and the using condition as well as the parameter estimation method are provided as well. Conclusions are draw as follows. Firstly, the bearing capacity generated from the base friction, the rugged surface pressure and the gravity of backfill soil. Secondly, comparing with the conventional estimation method, capacity obtained from the modified formula is improved tremendously. This phenomenon tells us that the gravity-anchorage can be optimized immensely. Taking the project of Xiang-Li Tiger Leaping Gorge, the volume of anchorage can be decreased 2.7%~75.6%. And the anti-sliding coefficient calculated from the conventional method is 2.42,while the modified one is 3.69.
The gravity-type anchor block, one of the main important anchorage types of suspension bridge, has advantages of wide range of application and low demand for the bearing capacity of foundations. In the calculation of bearing capacity of gravity-type anchor block, the gravity and frictional resistance are taken into account while the resistances generated by the interaction of substruction and foundation as well as the gravity of backfill soil are neglected. It cannot be denied that the omission causes great error on the estimation of bearing capacity and the anti-sliding coefficient of gravity-type anchor block. Through analyzing the difference of the bearing behavior between the conventional anchor blocks and the rugged ones, the estimation method of the bearing capacity of gravity-type anchor block was studied in this paper. And the bearing capacity estimation formula and the using condition as well as the parameter estimation method are provided as well. Conclusions are draw as follows. Firstly, the bearing capacity generated from the base friction, the rugged surface pressure and the gravity of backfill soil. Secondly, comparing with the conventional estimation method, capacity obtained from the modified formula is improved tremendously. This phenomenon tells us that the gravity-anchorage can be optimized immensely. Taking the project of Xiang-Li Tiger Leaping Gorge, the volume of anchorage can be decreased 2.7%~75.6%. And the anti-sliding coefficient calculated from the conventional method is 2.42,while the modified one is 3.69.
2018, 26(s1): 397-408.
In the past three decades, along with the acceleration of infrastructure construction and urbanization, a series of disasters related to ground deformation have emerged in various parts of China, resulting in a series of economic losses and casualties. Ground deformation monitoring plays an important role in preventing ground subsidence, ground subsidence and foundation instability. The conventional monitoring technologies is more and more difficult to meet the requirements of engineering practices in terms of real-time performance, coverage and accuracy. Therefore, a reliable monitoring system with high sensitivity, large dynamic range, stable performance and economic consideration is urgently needed. This paper introduces the working principle of distributed fiber optic sensing(DFOS)technologies and their unique advantages in ground deformation monitoring. This paper lists several common distributed optical fiber sensing technology, and summarized the research progress of the technology and its application in ground deformation mechanism study and engineering practice, the different monitoring scheme and the laying process comparative analysis. At last, the current bottleneck of ground deformation monitoring technology based on DFOS is summarized, and the development trend of this research is pointed out in the future.
In the past three decades, along with the acceleration of infrastructure construction and urbanization, a series of disasters related to ground deformation have emerged in various parts of China, resulting in a series of economic losses and casualties. Ground deformation monitoring plays an important role in preventing ground subsidence, ground subsidence and foundation instability. The conventional monitoring technologies is more and more difficult to meet the requirements of engineering practices in terms of real-time performance, coverage and accuracy. Therefore, a reliable monitoring system with high sensitivity, large dynamic range, stable performance and economic consideration is urgently needed. This paper introduces the working principle of distributed fiber optic sensing(DFOS)technologies and their unique advantages in ground deformation monitoring. This paper lists several common distributed optical fiber sensing technology, and summarized the research progress of the technology and its application in ground deformation mechanism study and engineering practice, the different monitoring scheme and the laying process comparative analysis. At last, the current bottleneck of ground deformation monitoring technology based on DFOS is summarized, and the development trend of this research is pointed out in the future.
2018, 26(s1): 409-413.
Simulation of some biological behaviors and physical processes is always helpful to establish new algorithms in conducting complicated optimization problems. In this paper, we propose a new optimization algorithm based on analogy of slope erosion which involves growth and development of slope rills induced by rain. This algorithm uses a new function with periodic variation to evaluate the fitness of individuals and to keep the diversity of the population. By incorporating the invasive weed optimization algorithm and the biogeography-based optimization algorithm, the new algorithm has satisfactory performance both in global search and in local search. Example shows that its computational efficiency and accuracy are better than the invasive weed optimization algorithm and the biogeography-based optimization algorithm. It is thought that the optimization ideology in this new algorithm may also has a certain enlightenment to the study of slope erosion.
Simulation of some biological behaviors and physical processes is always helpful to establish new algorithms in conducting complicated optimization problems. In this paper, we propose a new optimization algorithm based on analogy of slope erosion which involves growth and development of slope rills induced by rain. This algorithm uses a new function with periodic variation to evaluate the fitness of individuals and to keep the diversity of the population. By incorporating the invasive weed optimization algorithm and the biogeography-based optimization algorithm, the new algorithm has satisfactory performance both in global search and in local search. Example shows that its computational efficiency and accuracy are better than the invasive weed optimization algorithm and the biogeography-based optimization algorithm. It is thought that the optimization ideology in this new algorithm may also has a certain enlightenment to the study of slope erosion.
2018, 26(s1): 414-422.
When the proposed tunnel passes through the bottom of the surface water body, the influence of the surface water drainage and the leakage of the surface water body on the tunnel construction and operation is a special concern for the builders. In the tunnel hydrogeological investigation, hydrogeological survey, hydrogeological drilling, pumping test, water pressure test, field multi parameter water quality analyzer test, indoor water quality analysis test, drilling wave speed test were applied. The hydrogeological conditions of Qingcaoao reservoir and Qingshuigou reservoir in the tunnel area were identified through various exploration and testing methods. The hydraulic connection between the surface water of Qingcao'ao reservoir and Qingshuigou reservoir is not obvious. Tunnel excavation has little influence on Qingcao'ao reservoir and Qingshuigou reservoir, and surface water had little influence on tunnel water inflow. A variety of exploration methods can better identify the interaction between underground works and surface water bodies. It has great popularization and application value in the study of groundwater aquifer media and related investigation in the similar projects.
When the proposed tunnel passes through the bottom of the surface water body, the influence of the surface water drainage and the leakage of the surface water body on the tunnel construction and operation is a special concern for the builders. In the tunnel hydrogeological investigation, hydrogeological survey, hydrogeological drilling, pumping test, water pressure test, field multi parameter water quality analyzer test, indoor water quality analysis test, drilling wave speed test were applied. The hydrogeological conditions of Qingcaoao reservoir and Qingshuigou reservoir in the tunnel area were identified through various exploration and testing methods. The hydraulic connection between the surface water of Qingcao'ao reservoir and Qingshuigou reservoir is not obvious. Tunnel excavation has little influence on Qingcao'ao reservoir and Qingshuigou reservoir, and surface water had little influence on tunnel water inflow. A variety of exploration methods can better identify the interaction between underground works and surface water bodies. It has great popularization and application value in the study of groundwater aquifer media and related investigation in the similar projects.
2018, 26(s1): 423-429.
In order to evaluate the application effect of water-preserved technology with narrow strip in the coal mining area of northern Shaanxi, through the analysis of the geological structure in Yubojie coal mine and Xuemiaotan coal mine of Yu-Shen mine area. The strip mining method of mining 12 remining 8 was determined by numerical simulation and physical simulation. The monitoring system of coal pillar stress, displacement monitoring and loose ring of strip mining face were established in Yubojie coal mine. The observation hole for water table have been set up respectively in Yubojie coal mine and Xuemiaotan coal mine. To comparative analysis the development height of diversion fissure zone and the thickness of aquiclude with before and after mining, using the method of goaf submerged depth detection in Yubojie coal mine and Xuemiaotan coal mine of Yu-Shen mine area, and then systematic understanding of the variation characteristics of diving position before and after mining. The research shows that the development height of the guide water fracture zone in the coal working face is not through the aquifer. The coal pillar is relatively stable. The maximum depth of diving was 1.25m. The vegetation on the surface is good. It shows that the method of narrow strip mining effectively guarantees the stability of rock stratum and coal pillar, maintaining the reasonable depth of ecological water level, and achieving water-preserved mining.
In order to evaluate the application effect of water-preserved technology with narrow strip in the coal mining area of northern Shaanxi, through the analysis of the geological structure in Yubojie coal mine and Xuemiaotan coal mine of Yu-Shen mine area. The strip mining method of mining 12 remining 8 was determined by numerical simulation and physical simulation. The monitoring system of coal pillar stress, displacement monitoring and loose ring of strip mining face were established in Yubojie coal mine. The observation hole for water table have been set up respectively in Yubojie coal mine and Xuemiaotan coal mine. To comparative analysis the development height of diversion fissure zone and the thickness of aquiclude with before and after mining, using the method of goaf submerged depth detection in Yubojie coal mine and Xuemiaotan coal mine of Yu-Shen mine area, and then systematic understanding of the variation characteristics of diving position before and after mining. The research shows that the development height of the guide water fracture zone in the coal working face is not through the aquifer. The coal pillar is relatively stable. The maximum depth of diving was 1.25m. The vegetation on the surface is good. It shows that the method of narrow strip mining effectively guarantees the stability of rock stratum and coal pillar, maintaining the reasonable depth of ecological water level, and achieving water-preserved mining.
2018, 26(s1): 430-434.
The tensile strength of coal is one of the most important indexes in the calculation of the width of coal pillar. To achieve tensile strength parameters of coal, the 3# coal seam of Yuanzhuang coal mine was taken as research target. Based on elasticity theory and wave test, sleeve fracturing method was used for testing tensile strength. The results show the wave velocity of coal has an obvious anisotropy and wave velocity in vertical layers level direction is less than the parallel layers level direction. Tensile strength of coal rock by sleeve fracturing is 1.10MPa to 1.70MPa and average value is 1.35MPa. Integrity coefficient of coal was 0.47 and average value of tensile strength of coal seam is 0.63MPa. The research results can provide scientific basis for underground engineering application of tensile strength of coal seam and other low strength rock mass.
The tensile strength of coal is one of the most important indexes in the calculation of the width of coal pillar. To achieve tensile strength parameters of coal, the 3# coal seam of Yuanzhuang coal mine was taken as research target. Based on elasticity theory and wave test, sleeve fracturing method was used for testing tensile strength. The results show the wave velocity of coal has an obvious anisotropy and wave velocity in vertical layers level direction is less than the parallel layers level direction. Tensile strength of coal rock by sleeve fracturing is 1.10MPa to 1.70MPa and average value is 1.35MPa. Integrity coefficient of coal was 0.47 and average value of tensile strength of coal seam is 0.63MPa. The research results can provide scientific basis for underground engineering application of tensile strength of coal seam and other low strength rock mass.
2018, 26(s1): 435-441.
The cross section of anti-slide pile mainly has two forms, rectangle and circle respectively. These two forms play important roles in slide resistance, while they have their own strengths and weaknesses. In view of bringing out the utmost strengths of them and choosing the optimal type of cross section economically and reasonably, this article, through multi-attribute decision making, takes the construction site requirements, construction difficulty, construction period, manpower and machinery, engineering cost and construction risk into consideration. Then it also makes use of the weight of the decision attributes to implement the optimization of anti-slide pile's cross section in construction. It demonstrates that, the optimization model, based on the AOWEA operator, can find out the optimization result S1 S2 finally. With the requirement of management, reasonable construction technology and safety of landslide control and under the circumstance of the good construction site conditions and the urgent time requirement, the construction scheme of circular cross section of anti-slide pile is much better than that of rectangle. Eventually illustrating by the specific construction projects, this optimization can serve as the reference and guidance for construction application in anti-slide cross section.
The cross section of anti-slide pile mainly has two forms, rectangle and circle respectively. These two forms play important roles in slide resistance, while they have their own strengths and weaknesses. In view of bringing out the utmost strengths of them and choosing the optimal type of cross section economically and reasonably, this article, through multi-attribute decision making, takes the construction site requirements, construction difficulty, construction period, manpower and machinery, engineering cost and construction risk into consideration. Then it also makes use of the weight of the decision attributes to implement the optimization of anti-slide pile's cross section in construction. It demonstrates that, the optimization model, based on the AOWEA operator, can find out the optimization result S1 S2 finally. With the requirement of management, reasonable construction technology and safety of landslide control and under the circumstance of the good construction site conditions and the urgent time requirement, the construction scheme of circular cross section of anti-slide pile is much better than that of rectangle. Eventually illustrating by the specific construction projects, this optimization can serve as the reference and guidance for construction application in anti-slide cross section.
2018, 26(s1): 442-445.
On account of observation data of a large-fixed loop, a data processing software was designed and developed by C++language in the Microsoft Visual 2008 platform. The conversion of measured data was completed to achieve attenuation curves of the single-channel induced electromotive force and apparent resistivity and sectional drawing of the multi-channel induced electromotive force and the apparent resistivity. That is beneficial to deduce the direction of attenuation of the induced electromotive force and the apparent resistivity of the subsurface geology and to reflect the abnormal position and shape and trend of the geological body. To some extent complement the qualitative interpretation of date of the large-fixed loop.
On account of observation data of a large-fixed loop, a data processing software was designed and developed by C++language in the Microsoft Visual 2008 platform. The conversion of measured data was completed to achieve attenuation curves of the single-channel induced electromotive force and apparent resistivity and sectional drawing of the multi-channel induced electromotive force and the apparent resistivity. That is beneficial to deduce the direction of attenuation of the induced electromotive force and the apparent resistivity of the subsurface geology and to reflect the abnormal position and shape and trend of the geological body. To some extent complement the qualitative interpretation of date of the large-fixed loop.
2018, 26(s1): 446-456.
The strength parameters of rock mechanics test are mostly discrete because most rocks have various structural planes/interfaces, therefore the parameters obtained by the rock mechanics tests have the properties of estimation. For a uniaxial compression test the normal stress on failure surface, i.e. failure surface parallel to the axial stress, of the Mohr circle is zero, hence the tensile strength formula is derived for the compression splitting circle. The formula is then used to calculate tensile strength from 14 tests of rock and soil. And the results are compared with those of geotechnical Brazil splitting test and direct tensile test usually with a relative error within 20%.From the perspective of the discrete geotechnical parameters the compression splitting failure circle formula has its practical value. In fact, there is no lateral tension failure with zero compression stress under the uniaxial compression in the negative axial direction of the Mohr-Coulomb criterion, namely no circumferential tensile failure mode happening for a cylindrical specimen. Therefore, the ISRM suggested sigma t=f(3) plotting regression method, and a variety of Mohr stress circle based on geometric relations always have errors for calculating tensile strength. The stress cycle and its stress range of three kinds of failure modes with uniaxial compression are further analyzed.
The strength parameters of rock mechanics test are mostly discrete because most rocks have various structural planes/interfaces, therefore the parameters obtained by the rock mechanics tests have the properties of estimation. For a uniaxial compression test the normal stress on failure surface, i.e. failure surface parallel to the axial stress, of the Mohr circle is zero, hence the tensile strength formula is derived for the compression splitting circle. The formula is then used to calculate tensile strength from 14 tests of rock and soil. And the results are compared with those of geotechnical Brazil splitting test and direct tensile test usually with a relative error within 20%.From the perspective of the discrete geotechnical parameters the compression splitting failure circle formula has its practical value. In fact, there is no lateral tension failure with zero compression stress under the uniaxial compression in the negative axial direction of the Mohr-Coulomb criterion, namely no circumferential tensile failure mode happening for a cylindrical specimen. Therefore, the ISRM suggested sigma t=f(3) plotting regression method, and a variety of Mohr stress circle based on geometric relations always have errors for calculating tensile strength. The stress cycle and its stress range of three kinds of failure modes with uniaxial compression are further analyzed.
2018, 26(s1): 457-463.
It is very important to use the measured data to obtain the regional groundwater level distribution in groundwater flow modeling, which can provide the initial flow field or boundary condition for modeling, and can be used as the verification basis for the simulation results. Traditional methods are usually interpolated using existing water level data, and the accuracy of the results is greatly influenced by the number of boreholes and the rationality of distribution, so it is not applicable in ungauged region of northwest China. Actually, the flow of groundwater in most areas is affected by the topography at the regional scale, and the terrain and groundwater flow path are correlated. In this paper, a method based on digital elevation model to simulate the regional groundwater level distribution is presented. The selection of the trend surface equation and parameter calibration are the key points and difficulties, because low order polynomial may lead the trend surface equation cannot fit the measured data well, and high order polynomial maybe lead the instability of the solution to the equation. Therefore, this paper established the high order polynomial as the initial trend surface equation. The correlation between each parameter in the trend surface equation and the elevation of the measured groundwater level was analyzed, and the parameters with obvious correlation with the elevation of groundwater level compose the trend surface equation. And then using the measured data realized the optimal estimation of the average trend level of groundwater, to ensure the best trend surface equation. Finally, according to Lanczos singular value decomposition theory, the trend surface equation solution were obtained, and an unbiased and optimal estimation of the residual using the method of universal kriging interpolation was presented. This method was applied in a certain area of northwest China, and the error of the calculation results was much less than that of the kriging interpolation method, which was more consistent with the measured values and could be used to extrapolate. This method has a good prospect in the simulation of groundwater flow field in ungauged region of northwest China.
It is very important to use the measured data to obtain the regional groundwater level distribution in groundwater flow modeling, which can provide the initial flow field or boundary condition for modeling, and can be used as the verification basis for the simulation results. Traditional methods are usually interpolated using existing water level data, and the accuracy of the results is greatly influenced by the number of boreholes and the rationality of distribution, so it is not applicable in ungauged region of northwest China. Actually, the flow of groundwater in most areas is affected by the topography at the regional scale, and the terrain and groundwater flow path are correlated. In this paper, a method based on digital elevation model to simulate the regional groundwater level distribution is presented. The selection of the trend surface equation and parameter calibration are the key points and difficulties, because low order polynomial may lead the trend surface equation cannot fit the measured data well, and high order polynomial maybe lead the instability of the solution to the equation. Therefore, this paper established the high order polynomial as the initial trend surface equation. The correlation between each parameter in the trend surface equation and the elevation of the measured groundwater level was analyzed, and the parameters with obvious correlation with the elevation of groundwater level compose the trend surface equation. And then using the measured data realized the optimal estimation of the average trend level of groundwater, to ensure the best trend surface equation. Finally, according to Lanczos singular value decomposition theory, the trend surface equation solution were obtained, and an unbiased and optimal estimation of the residual using the method of universal kriging interpolation was presented. This method was applied in a certain area of northwest China, and the error of the calculation results was much less than that of the kriging interpolation method, which was more consistent with the measured values and could be used to extrapolate. This method has a good prospect in the simulation of groundwater flow field in ungauged region of northwest China.
2018, 26(s1): 464-472.
Accurate prediction or detection of Karst and groundwater is a difficult problem to be solved. It is great significant to study the mechanism of Karst and groundwater action for the problem solving. Further study on the hydro-chemical characteristics of Karst groundwater will help to better understand the runoff circulation conditions and geological environment. Based on the simplified hydro-geochemical model of Karst groundwater, the chemical composition of Karst tunnels and the hydrochemical kinetic parameters of Karst groundwater are analysized. On this basis, Ions of conventional hydro-chemical constituents are paired by borrowing the theory of complex reaction in analytical chemistry, the proportion relation of each ion pair are explored by changing the observation scales, self-similarity and scale invariance of the cumulative fraction of ion pairs are demonstrated. Thus the feasibility of applying fractal theory to study the chemical characteristics of Karst groundwater is proposed.
Accurate prediction or detection of Karst and groundwater is a difficult problem to be solved. It is great significant to study the mechanism of Karst and groundwater action for the problem solving. Further study on the hydro-chemical characteristics of Karst groundwater will help to better understand the runoff circulation conditions and geological environment. Based on the simplified hydro-geochemical model of Karst groundwater, the chemical composition of Karst tunnels and the hydrochemical kinetic parameters of Karst groundwater are analysized. On this basis, Ions of conventional hydro-chemical constituents are paired by borrowing the theory of complex reaction in analytical chemistry, the proportion relation of each ion pair are explored by changing the observation scales, self-similarity and scale invariance of the cumulative fraction of ion pairs are demonstrated. Thus the feasibility of applying fractal theory to study the chemical characteristics of Karst groundwater is proposed.
2018, 26(s1): 473-479.
Through the surface wave method to the exploration of the coal Rayleigh Surface, the characteristics and variation of wave velocity before and after rock fracture filling were analyzed and the grouting control results were determined. The pump-in test method and the core sampling method were used to verify the treatment of mine collapse. Surface wave metho dissuccess fully applied in Hezhou Guangxi Daling coal mine. The surface wave method was used to test the ground collapse coal mine before and after grouting, respectively adopt surface wave method to test, mainly through comparing the wave velocity and dispersion curve to determine the karst tunnel grouting effect. Results show that the drilling of the surface wave shape on the 0 to 20 v perpendicular is complete, and higher frequency, width is bigger, showing a full tilts traight line, show that in the same layer medium wave velocity feedback performance consistency, nodeficiency, after grouting hole, large cracks were better filling, forming a complete dielectric body
Through the surface wave method to the exploration of the coal Rayleigh Surface, the characteristics and variation of wave velocity before and after rock fracture filling were analyzed and the grouting control results were determined. The pump-in test method and the core sampling method were used to verify the treatment of mine collapse. Surface wave metho dissuccess fully applied in Hezhou Guangxi Daling coal mine. The surface wave method was used to test the ground collapse coal mine before and after grouting, respectively adopt surface wave method to test, mainly through comparing the wave velocity and dispersion curve to determine the karst tunnel grouting effect. Results show that the drilling of the surface wave shape on the 0 to 20 v perpendicular is complete, and higher frequency, width is bigger, showing a full tilts traight line, show that in the same layer medium wave velocity feedback performance consistency, nodeficiency, after grouting hole, large cracks were better filling, forming a complete dielectric body
2018, 26(s1): 480-487.
At present, the methods for obtaining information of rock mass discontinuity mainly include artificial field contact measurement, three-dimensional laser scanning and close-range photogrammetry. With the maturity of UAV photogrammetry technology, the use of a UAV to survey all-around, multi-angle photography for the rock slope and establish a three-dimensional model for the slope can more comprehensively, accurately and efficiently obtain the information of the discontinuities. In this paper, the slope in Changchun Jingyuedongsheng quarry is used as the object of study. The phantom 3 of Dajiang UAV is used to photograph the slope, and the prism less total station instrument is used for slope control measurement. The Pix4Dmapper is used to establish the three-dimensional model of the slope. After the model checking with control points not involved in modeling, and meeting the accuracy requirements, the coordinates of the feature points of the rock slope discontinuities are measured on the model. Furthermore, combined with the discontinuity trace line display model and the model for calculating the orientation based on the three-dimensional coordinates. The trace lines and orientations of discontinuities are obtained. Compared with orientations that are measured artificially with compass, the precision of the orientation acquisition of the discontinuities based on photogrammetry of the UAV is obtained. The research shows that the information acquisition of rock mass discontinuity by photogrammetry of UAV is low in cost, low in labor intensity, high in efficiency, reliable in accuracy, and has broad application prospect.
At present, the methods for obtaining information of rock mass discontinuity mainly include artificial field contact measurement, three-dimensional laser scanning and close-range photogrammetry. With the maturity of UAV photogrammetry technology, the use of a UAV to survey all-around, multi-angle photography for the rock slope and establish a three-dimensional model for the slope can more comprehensively, accurately and efficiently obtain the information of the discontinuities. In this paper, the slope in Changchun Jingyuedongsheng quarry is used as the object of study. The phantom 3 of Dajiang UAV is used to photograph the slope, and the prism less total station instrument is used for slope control measurement. The Pix4Dmapper is used to establish the three-dimensional model of the slope. After the model checking with control points not involved in modeling, and meeting the accuracy requirements, the coordinates of the feature points of the rock slope discontinuities are measured on the model. Furthermore, combined with the discontinuity trace line display model and the model for calculating the orientation based on the three-dimensional coordinates. The trace lines and orientations of discontinuities are obtained. Compared with orientations that are measured artificially with compass, the precision of the orientation acquisition of the discontinuities based on photogrammetry of the UAV is obtained. The research shows that the information acquisition of rock mass discontinuity by photogrammetry of UAV is low in cost, low in labor intensity, high in efficiency, reliable in accuracy, and has broad application prospect.
2018, 26(s1): 488-493.
Most of the oil and gas hydrate reservoirs discovered today are sandstone formations, and porosity as an important parameter of rock core is well worth studying. There are many methods to study rock porosity at present, but most of them have obvious defects. However, the low-field nuclear magnetic resonance(NMR) is applied to samples to explore the pore structure of rock without any damage to the sample. At the same time, low-field NMR can also be applied to undercompacted samples. The rock can be measured by LF NMR to obtain the corresponding pore size distribution and the porosity of the entire sample and the classification pore. Stratum structure will change with long-term temperature changes. Therefore, this experiment simulated the change of porosity of the whole rock and the classified pores under different temperature conditions when the sandstone freezes and thaws in the strata. The experimental results show that the overall porosity of rock is closely related to the porosity of macropores and mesopores. In a freeze-thaw process, there is an overcooling phenomenon in the pore water phase transition process, indicating that the supercooling phenomenon has a great influence on the porosity change of the rock.
Most of the oil and gas hydrate reservoirs discovered today are sandstone formations, and porosity as an important parameter of rock core is well worth studying. There are many methods to study rock porosity at present, but most of them have obvious defects. However, the low-field nuclear magnetic resonance(NMR) is applied to samples to explore the pore structure of rock without any damage to the sample. At the same time, low-field NMR can also be applied to undercompacted samples. The rock can be measured by LF NMR to obtain the corresponding pore size distribution and the porosity of the entire sample and the classification pore. Stratum structure will change with long-term temperature changes. Therefore, this experiment simulated the change of porosity of the whole rock and the classified pores under different temperature conditions when the sandstone freezes and thaws in the strata. The experimental results show that the overall porosity of rock is closely related to the porosity of macropores and mesopores. In a freeze-thaw process, there is an overcooling phenomenon in the pore water phase transition process, indicating that the supercooling phenomenon has a great influence on the porosity change of the rock.
2018, 26(s1): 494-498.
Based on Spude calculation principle of the mixed-layer pumping test, this paper has carried out a study on the permeability coefficient of aquifers by single-well mixed-layer pumping test in the No. 5 well in the south of Yanqi Basin, Xinjiang, under the condition of no observation holes and no stratified water stop. By means of graphical method, the static water level of confined aquifer in the lower part of the mixed-layer well is calculated to be 47.232m, and the Q-S curve of the aquifer is plotted. On this basis, the permeability coefficients of confined aquifer and phreatic aquifer are calculated by stratification, and the result is Kb=6.968md-1, Ka=4.979md-1 separately. By comparing with the actual pumping test results, the validity and accuracy of the method are verified. It can provide reference for the calculation of aquifer permeability coefficient in a single-well mixed-layer pumping experiment.
Based on Spude calculation principle of the mixed-layer pumping test, this paper has carried out a study on the permeability coefficient of aquifers by single-well mixed-layer pumping test in the No. 5 well in the south of Yanqi Basin, Xinjiang, under the condition of no observation holes and no stratified water stop. By means of graphical method, the static water level of confined aquifer in the lower part of the mixed-layer well is calculated to be 47.232m, and the Q-S curve of the aquifer is plotted. On this basis, the permeability coefficients of confined aquifer and phreatic aquifer are calculated by stratification, and the result is Kb=6.968md-1, Ka=4.979md-1 separately. By comparing with the actual pumping test results, the validity and accuracy of the method are verified. It can provide reference for the calculation of aquifer permeability coefficient in a single-well mixed-layer pumping experiment.
2018, 26(s1): 499-504.
In this paper, the measurement methods of soil volume change in triaxial tests are introduced in detail. Various methods are classified and summarized. For one of the typical methods outlined its basic principles, development history, advantages and disadvantages and so on. The paper not only introduces the development of more mature methods, such as:double-cell measurement system, a variety of strain sensor measurement methods. This paper also introduced the current more popular non-contact measurement methods, such as:digital image analysis, photogrammetry. Finally, several methods that can be used for reference are introduced, such as digital image correlation, particle image velocimetry. Each of these methods has its advantages. It is better to have a brief understanding of it, with a view to choose the appropriate method of specific research.
In this paper, the measurement methods of soil volume change in triaxial tests are introduced in detail. Various methods are classified and summarized. For one of the typical methods outlined its basic principles, development history, advantages and disadvantages and so on. The paper not only introduces the development of more mature methods, such as:double-cell measurement system, a variety of strain sensor measurement methods. This paper also introduced the current more popular non-contact measurement methods, such as:digital image analysis, photogrammetry. Finally, several methods that can be used for reference are introduced, such as digital image correlation, particle image velocimetry. Each of these methods has its advantages. It is better to have a brief understanding of it, with a view to choose the appropriate method of specific research.
2018, 26(s1): 505-512.
Fractal theory、neural network and other new methods have been widely applied in the current qualitative or quantitative evaluation of rock mass quality. Based on the fractal characteristics of the self similarity of the surface of the rock mass, We applied fractal theory to study the fractal dimension of the surface trace of rock slope structure based on digital close range photogrammetry technology. Taking one side slope of pure moon quarry in Changchun as an example, We used the grid covering method to calculate the fractal dimension of the structural plane traces, and verified the fractal characteristics of traces. In addition, we also improved the grid coverage method, and used the rectangular grid coverage method which was proportional to the research scope to calculate the fractal dimension. The latter is closer to fractal theory and easier to program. It is found that the results of the two methods are similar, the more the trace number, the larger the fractal dimension, the more broken rock mass and the worse the mass, and the quality classification of rock mass can be more accurately determined by the rectangular grid method. Finally, we analyzed the fractal dimension and the RQD to determine the relationship between the fractal dimension and the RQD, and selected the RQD under the reasonable threshold, and got the rock mass quality evaluation method with the fractal dimension as the index. The research shows that the fractal dimension of the slope trace is 1.22and the fitting degree is 0.98and the quality of the slope rock mass belongs to the Ⅱ level. In addition, the improved calculation of the fractal dimension of the rectangular grid coverage method is easy to do. The calculation process is simplified and the result is reliable. A quantitative evaluation method of rock mass quality based on fractal dimension of trace line of rock mass structure is obtained.
Fractal theory、neural network and other new methods have been widely applied in the current qualitative or quantitative evaluation of rock mass quality. Based on the fractal characteristics of the self similarity of the surface of the rock mass, We applied fractal theory to study the fractal dimension of the surface trace of rock slope structure based on digital close range photogrammetry technology. Taking one side slope of pure moon quarry in Changchun as an example, We used the grid covering method to calculate the fractal dimension of the structural plane traces, and verified the fractal characteristics of traces. In addition, we also improved the grid coverage method, and used the rectangular grid coverage method which was proportional to the research scope to calculate the fractal dimension. The latter is closer to fractal theory and easier to program. It is found that the results of the two methods are similar, the more the trace number, the larger the fractal dimension, the more broken rock mass and the worse the mass, and the quality classification of rock mass can be more accurately determined by the rectangular grid method. Finally, we analyzed the fractal dimension and the RQD to determine the relationship between the fractal dimension and the RQD, and selected the RQD under the reasonable threshold, and got the rock mass quality evaluation method with the fractal dimension as the index. The research shows that the fractal dimension of the slope trace is 1.22and the fitting degree is 0.98and the quality of the slope rock mass belongs to the Ⅱ level. In addition, the improved calculation of the fractal dimension of the rectangular grid coverage method is easy to do. The calculation process is simplified and the result is reliable. A quantitative evaluation method of rock mass quality based on fractal dimension of trace line of rock mass structure is obtained.
2018, 26(s1): 513-517.
Assuming that the soft soil strength obeys the Tresca rule, the influence of the depth of probe embedment on the resistance of T-bar penetration was studied by numerical simulation. It is found that, for the oval, rectangular and rhombus cross section probes with aspect ratio of 0.5,when the depth of the probe centre reaches 4~6 times the probe width, the penetration resistance tends to be fixed. The influence of probe embedment depth on the engineering practice results can be ignored. For oval and rhombus section probes and smooth surface rectangular probes, this value is consistent with the theoretical analysis in infinite soft clay. For the rectangular probe with rough surface, this value is larger than that in infinite soft clay. Analytical solution for penetration resistance of rectangular probe with rough surface is an approximate solution. The results of rectangular cross section probe need to be corrected appropriately.
Assuming that the soft soil strength obeys the Tresca rule, the influence of the depth of probe embedment on the resistance of T-bar penetration was studied by numerical simulation. It is found that, for the oval, rectangular and rhombus cross section probes with aspect ratio of 0.5,when the depth of the probe centre reaches 4~6 times the probe width, the penetration resistance tends to be fixed. The influence of probe embedment depth on the engineering practice results can be ignored. For oval and rhombus section probes and smooth surface rectangular probes, this value is consistent with the theoretical analysis in infinite soft clay. For the rectangular probe with rough surface, this value is larger than that in infinite soft clay. Analytical solution for penetration resistance of rectangular probe with rough surface is an approximate solution. The results of rectangular cross section probe need to be corrected appropriately.
2018, 26(s1): 518-524.
The microstructure of soil is the internal factor determining its engineering properties, especially the pore characteristics of soil. It is an important index reflecting the state and strength of soil. In order to further understand the engineering geological characteristics of the saline soil in Western Jilin Province, the pore characteristics and influencing factors of different depth saline soil in Nong'an area are studied by using the mercury intrusion method. The results show that:The porosity of the soil increases with the increase of depth, and the distribution of pores at different depths is different. According to the fractal theory, the distribution of pores has fractal characteristics, and the fractal dimension D of pores increases with the increase of depth. The pores of saline soil in the study area were divided into three grades:macropores(d30m),mesopores(7m d 30m), and small pores(d7m). The physicochemical properties of soil affect each other and decide their pore characteristics together, thus affecting their engineering geological properties. The results can provide a basis for exploring the strength mechanism of saline soil in Western Jilin Province.
The microstructure of soil is the internal factor determining its engineering properties, especially the pore characteristics of soil. It is an important index reflecting the state and strength of soil. In order to further understand the engineering geological characteristics of the saline soil in Western Jilin Province, the pore characteristics and influencing factors of different depth saline soil in Nong'an area are studied by using the mercury intrusion method. The results show that:The porosity of the soil increases with the increase of depth, and the distribution of pores at different depths is different. According to the fractal theory, the distribution of pores has fractal characteristics, and the fractal dimension D of pores increases with the increase of depth. The pores of saline soil in the study area were divided into three grades:macropores(d30m),mesopores(7m d 30m), and small pores(d7m). The physicochemical properties of soil affect each other and decide their pore characteristics together, thus affecting their engineering geological properties. The results can provide a basis for exploring the strength mechanism of saline soil in Western Jilin Province.
2018, 26(s1): 525-531.
As an important chemical raw material and clean energy, natural gas has more and more application prospects all over the world. Therefore, it is important to develop safe and efficient natural gas storage technology for using it reasonably and effectively. This article took Anhui Hengtai anhydrite mine as an engineering example, and we got the physical mechanical parameters of the anhydrite through laboratory tests. Used ABAQUS to establish a numerical model to simulate the cavern formation and natural gas storage processes, evaluated the overall stability of anhydrite wall rock. Focus on the changes in the plastic zone surrounding the cavern, the rock strain around the cavern, and the surface displacement of the cavern under different internal pressures during natural gas loading and unloading, thereby analyzing the overall and local stability of the anhydrite cavern group, providing reasonable advice for selecting a reasonable protection project to ensure the safety of the gas storage during construction and operation. The results show that after the excavation of the anhydrite cavern is completed, there is no plastic zone in the surrounding rock mass, indicating that the stability of the anhydrite cavern group is good, with the increase of the cavern pressure, the surrounding rock deformation and the stress in the cavern first decrease and then increase, it indicates that a certain high internal pressure environment is conducive to the stability of the surrounding rock of the cavern. And the cavern formed after the end of the anhydrite mine can be used as a natural gas storage tank.
As an important chemical raw material and clean energy, natural gas has more and more application prospects all over the world. Therefore, it is important to develop safe and efficient natural gas storage technology for using it reasonably and effectively. This article took Anhui Hengtai anhydrite mine as an engineering example, and we got the physical mechanical parameters of the anhydrite through laboratory tests. Used ABAQUS to establish a numerical model to simulate the cavern formation and natural gas storage processes, evaluated the overall stability of anhydrite wall rock. Focus on the changes in the plastic zone surrounding the cavern, the rock strain around the cavern, and the surface displacement of the cavern under different internal pressures during natural gas loading and unloading, thereby analyzing the overall and local stability of the anhydrite cavern group, providing reasonable advice for selecting a reasonable protection project to ensure the safety of the gas storage during construction and operation. The results show that after the excavation of the anhydrite cavern is completed, there is no plastic zone in the surrounding rock mass, indicating that the stability of the anhydrite cavern group is good, with the increase of the cavern pressure, the surrounding rock deformation and the stress in the cavern first decrease and then increase, it indicates that a certain high internal pressure environment is conducive to the stability of the surrounding rock of the cavern. And the cavern formed after the end of the anhydrite mine can be used as a natural gas storage tank.
2018, 26(s1): 532-538.
The deformating and damaging characteristics of the buildings and ground subsidence areas in a coal mine goaf is taken as a study case in this paper. The methods called investigation and mapping are applied, and the disease characteristics of the buildings and ground in the study area are exposed. Under the further study, the conclusion that the diseases are caused by disorderly coal mining, uneven foundation soil, incompact filling soil, rigid foundation and brick structure form of the upper-structure, rainfall as well as garden irrigation is drawn. Aaccording to the four indexes of building foundation and upper-structure, which are the bearing capacity, structure, settlement and cracks, the safety of the building is evaluated, and the targeted controlling and reinforcing measures are put forward. Under the study and analysis, the solid technical supporting is provided for the protecting and reinforcing existing buildings in the study area.
The deformating and damaging characteristics of the buildings and ground subsidence areas in a coal mine goaf is taken as a study case in this paper. The methods called investigation and mapping are applied, and the disease characteristics of the buildings and ground in the study area are exposed. Under the further study, the conclusion that the diseases are caused by disorderly coal mining, uneven foundation soil, incompact filling soil, rigid foundation and brick structure form of the upper-structure, rainfall as well as garden irrigation is drawn. Aaccording to the four indexes of building foundation and upper-structure, which are the bearing capacity, structure, settlement and cracks, the safety of the building is evaluated, and the targeted controlling and reinforcing measures are put forward. Under the study and analysis, the solid technical supporting is provided for the protecting and reinforcing existing buildings in the study area.
2018, 26(s1): 539-546.
To study influence of particle size distribution and shape on compressibility of sand, we used spherical quartz sand and laboratorial standard sand with irregular shape as materials to do confined compression test of specimens prepared by sand pluviation method, then used MatDEM,the 3D DEM software developed by our research group, to do numerical simulation. Specimens with various particle size distributions revealed influence of particle size, particle size range, relative size and content of fine grains on compressibility of sand, while control experiments between spherical quartz sand and laboratorial standard sand revealed the one of particle shape. On this basis, combined with numerical simulation, the results indicate that:There is a non-monotonic relation between particle size and compressibility. The wider the particle size range is,the greater compressibility the specimen prepared by sand pluviation method will show. The reduction of relative size and content of fine grains will both increase the compressibility. Particle shape will influence the specimen prepared by sand pluviation method, which makes laboratorial standard sand show greater compressibility under low stress and then converge with spherical quartz sand. The 3D DEM software MatDEM can simulate the process of sand confined compression test effectively, which provides a reference for future study of DEM numerical simulation in geotechnical engineering.
To study influence of particle size distribution and shape on compressibility of sand, we used spherical quartz sand and laboratorial standard sand with irregular shape as materials to do confined compression test of specimens prepared by sand pluviation method, then used MatDEM,the 3D DEM software developed by our research group, to do numerical simulation. Specimens with various particle size distributions revealed influence of particle size, particle size range, relative size and content of fine grains on compressibility of sand, while control experiments between spherical quartz sand and laboratorial standard sand revealed the one of particle shape. On this basis, combined with numerical simulation, the results indicate that:There is a non-monotonic relation between particle size and compressibility. The wider the particle size range is,the greater compressibility the specimen prepared by sand pluviation method will show. The reduction of relative size and content of fine grains will both increase the compressibility. Particle shape will influence the specimen prepared by sand pluviation method, which makes laboratorial standard sand show greater compressibility under low stress and then converge with spherical quartz sand. The 3D DEM software MatDEM can simulate the process of sand confined compression test effectively, which provides a reference for future study of DEM numerical simulation in geotechnical engineering.
2018, 26(s1): 547-553.
As a tool for studying the characteristics of bulk materials, granular discrete element method is widely used and has obvious advantages. This paper briefly introduces the basic principle of particle discrete element, an overview of the mesoscopic parameters calibration process, discusses the sandy soil and clayey soil, joint rock and the characteristics of natural gas hydrate, the research application and progress, and discussed the granular discrete element applied in study of slope deformation. When the discrete element simulation of rock and soil particles is carried out, the different parameters have certain influence on the macro parameters but there is no definite linear relation. Particle discrete element has the advantage in studying the mesoscopic properties of multiphase solid media, and can endow the material with various contact models and microscopic parameters. Therefore, the study of hydrate will promote the improvement of granular discrete element algorithm and further study on the characteristics of hydrate sediment. By coupling the particle discrete element with other methods, the research on complex engineering geological problems will be solved. In this paper, the further application of granular flow discrete element in Marine geotechnical engineering is prospected.
As a tool for studying the characteristics of bulk materials, granular discrete element method is widely used and has obvious advantages. This paper briefly introduces the basic principle of particle discrete element, an overview of the mesoscopic parameters calibration process, discusses the sandy soil and clayey soil, joint rock and the characteristics of natural gas hydrate, the research application and progress, and discussed the granular discrete element applied in study of slope deformation. When the discrete element simulation of rock and soil particles is carried out, the different parameters have certain influence on the macro parameters but there is no definite linear relation. Particle discrete element has the advantage in studying the mesoscopic properties of multiphase solid media, and can endow the material with various contact models and microscopic parameters. Therefore, the study of hydrate will promote the improvement of granular discrete element algorithm and further study on the characteristics of hydrate sediment. By coupling the particle discrete element with other methods, the research on complex engineering geological problems will be solved. In this paper, the further application of granular flow discrete element in Marine geotechnical engineering is prospected.
2018, 26(s1): 554-565.
Based on the engineering background of Jingning phosphate mine of Yunnan Phosphate Chemical Group Co.,LTD.,the displacement and stress response characteristics and dynamical evolution process of underground surrounding rock and overlying strata were studied after transformation from open-pit to underground mining of room and pillar method. And we carried similar material simulating experiment and digital photographic measurement technology to do target researching on these issues under the condition of two different ore body dips of twenty degrees and fifty degrees. The results showed that:(1) The evolution process of mining deformation of underground surrounding rock and overlying strata could be divided into three stages, which contained the stage of small deformation in originally small and local scale, linear continuous increase stage and the whole nonlinear violent collapse stage. (2)With the ore body dip increasing from twenty degrees to fifty degrees, the mining influence area narrowed down in a small range, the deformation slowed down of underground surrounding rock and overlying strata, and the geometric shape of settlement curve changed from asymmetric channel type to asymmetric bowl shape. (3) The abrupt occurrence of instability of underground surrounding rock occurred in the process of ore pillar recovery, and it presents the obvious The Domino Effect. The conclusions provide a theoretical reference for ground pressure management and slope maintenance in mine transition from open pit to underground mining.
Based on the engineering background of Jingning phosphate mine of Yunnan Phosphate Chemical Group Co.,LTD.,the displacement and stress response characteristics and dynamical evolution process of underground surrounding rock and overlying strata were studied after transformation from open-pit to underground mining of room and pillar method. And we carried similar material simulating experiment and digital photographic measurement technology to do target researching on these issues under the condition of two different ore body dips of twenty degrees and fifty degrees. The results showed that:(1) The evolution process of mining deformation of underground surrounding rock and overlying strata could be divided into three stages, which contained the stage of small deformation in originally small and local scale, linear continuous increase stage and the whole nonlinear violent collapse stage. (2)With the ore body dip increasing from twenty degrees to fifty degrees, the mining influence area narrowed down in a small range, the deformation slowed down of underground surrounding rock and overlying strata, and the geometric shape of settlement curve changed from asymmetric channel type to asymmetric bowl shape. (3) The abrupt occurrence of instability of underground surrounding rock occurred in the process of ore pillar recovery, and it presents the obvious The Domino Effect. The conclusions provide a theoretical reference for ground pressure management and slope maintenance in mine transition from open pit to underground mining.
2018, 26(s1): 566-571.
According to the well degree of grain composition and coarse grained content, four groups of grain composition were designed, and using triaxial tests, the strength and deformation characteristics of coal gangue with different grain composition were analyzed. The results reveal that, for coal gangue with different grain composition, the deviatoric stress is increasing with the increase of confining pressure and strain. The stress-strain curves have no peak and belong to strain hardening. When the grain composition is well, the distributions of peak strength with coefficient of curvature(Cc) and non-uniformity coefficient(Cu) are all parabolas, which are decreasing firstly then decreasing. While the grain composition becomes poor, the peak strength is decreasing gradually. The cohesive force is increasing with the decrease of coarse grained content, and its value is controlled by fine particles. The internal friction angle is not only affected by the content of coarse grain but also is associated with the well of grain composition.
According to the well degree of grain composition and coarse grained content, four groups of grain composition were designed, and using triaxial tests, the strength and deformation characteristics of coal gangue with different grain composition were analyzed. The results reveal that, for coal gangue with different grain composition, the deviatoric stress is increasing with the increase of confining pressure and strain. The stress-strain curves have no peak and belong to strain hardening. When the grain composition is well, the distributions of peak strength with coefficient of curvature(Cc) and non-uniformity coefficient(Cu) are all parabolas, which are decreasing firstly then decreasing. While the grain composition becomes poor, the peak strength is decreasing gradually. The cohesive force is increasing with the decrease of coarse grained content, and its value is controlled by fine particles. The internal friction angle is not only affected by the content of coarse grain but also is associated with the well of grain composition.
2018, 26(s1): 572-580.
Hongping pumped storage power station's engineering geological problems are complicated. (1)Hydrogeological conditions:Water conveyance system including underground powerhouse underground water acted strongly. Fault development of upper storage reservoir, hydraulic connection of basin and underground powerhouse, leakage problem. (2)Reservoir bank's stability:Stability of upper storage reservoir and its lower slope, et al. In allusion of above, we compared the former different stages of projects and studied the layout of main constructions, carried out test works specifically. Finally, we find out the water permeability of upper and bottom rock and earth mass, underground water and its dynamic regulation, leakage and stability of bank slopereservoir, knowing the engineering geology of lower storage reservoir and hydrogeologicalcondition, carring special work on measurement of geostress, high pressurepump-intest, and physical mechanics of rocks. Regarding to the problems like water burst on fault zone of long caving, the sharp fall of underground water in the south upper storage reservoir, we did some hydrogeological tracer connection tests and leakage calculation. During construction, we should work well not only on geological work but pay more attention to more scientific, more economic and more safety treatment as well as geological forecast. In conclusion of kinds of survey and the geology figures, we adopted effective engineering treatment on upper storage reservoir seepage-proofing, water conveyance systemlining type and underground caverns drainage design, which created a necessary condition for smoothly works for generate electricity in time. It can be used as a reference for similar projects.
Hongping pumped storage power station's engineering geological problems are complicated. (1)Hydrogeological conditions:Water conveyance system including underground powerhouse underground water acted strongly. Fault development of upper storage reservoir, hydraulic connection of basin and underground powerhouse, leakage problem. (2)Reservoir bank's stability:Stability of upper storage reservoir and its lower slope, et al. In allusion of above, we compared the former different stages of projects and studied the layout of main constructions, carried out test works specifically. Finally, we find out the water permeability of upper and bottom rock and earth mass, underground water and its dynamic regulation, leakage and stability of bank slopereservoir, knowing the engineering geology of lower storage reservoir and hydrogeologicalcondition, carring special work on measurement of geostress, high pressurepump-intest, and physical mechanics of rocks. Regarding to the problems like water burst on fault zone of long caving, the sharp fall of underground water in the south upper storage reservoir, we did some hydrogeological tracer connection tests and leakage calculation. During construction, we should work well not only on geological work but pay more attention to more scientific, more economic and more safety treatment as well as geological forecast. In conclusion of kinds of survey and the geology figures, we adopted effective engineering treatment on upper storage reservoir seepage-proofing, water conveyance systemlining type and underground caverns drainage design, which created a necessary condition for smoothly works for generate electricity in time. It can be used as a reference for similar projects.
2018, 26(s1): 581-586.
The special structure of lateritic clay has the characteristics of high water content, high porosity ratio, high liquid plastic limit but good mechanical properties. In this paper, the dynamic stress-dynamic strain relation curve of Guilin lateritic clay is obtained by kinetic test from Guilin lateritic clay, which is suitable for Hardin hyperbolic model. The conclusions are as follows:(1) The hyperbolic model parameters of Guilin lateritic clay are obtained by combining the conditions of different test factors. and obtain its peculiar strain softening characteristic. (2) The maximum dynamic shear modulus of Guilin lateritic clay in different test conditions is connected with the factors of confining pressure, consolidation stress ratio and structure, and the fitting parameters of the damping ratio of Guilin lateritic clay under different influence factors are obtained. By experiment, the fitting parameters can reflect the characteristics of lateritic clay well and be applied in engineering practice.
The special structure of lateritic clay has the characteristics of high water content, high porosity ratio, high liquid plastic limit but good mechanical properties. In this paper, the dynamic stress-dynamic strain relation curve of Guilin lateritic clay is obtained by kinetic test from Guilin lateritic clay, which is suitable for Hardin hyperbolic model. The conclusions are as follows:(1) The hyperbolic model parameters of Guilin lateritic clay are obtained by combining the conditions of different test factors. and obtain its peculiar strain softening characteristic. (2) The maximum dynamic shear modulus of Guilin lateritic clay in different test conditions is connected with the factors of confining pressure, consolidation stress ratio and structure, and the fitting parameters of the damping ratio of Guilin lateritic clay under different influence factors are obtained. By experiment, the fitting parameters can reflect the characteristics of lateritic clay well and be applied in engineering practice.
2018, 26(s1): 587-593.
Groundwater recharge is an important part of groundwater circulation, and it is important to study its source for understanding the groundwater circulation process. Controlled by geological structures, the distribution of groundwater in bedrock area is complicated, and therefore the study of its source is a difficult work in hydrogeology research. By analyzing the model of water-rich zone based on remote sensing information, and according to the groundwater dynamics, major ion concentration, velocity and direction of groundwater flow, pumping and water level data of water source site, this article studies the source of groundwater recharge of Barakan Water Source Site(BWSS)in front of Kuruktag, northwest of China, and analyses the reasons for the abnormal change of the total water yield and the drawdown of the well. The results show that the groundwater of the water source site comes from the Aggregate Reclaiming Plant(ARP)about 6.5 kilometers northwest of BWSS. The ARP water pumping is the main reason of the abnormal change of the total water yield and the drawdown of the well of BWSS. Based on this conclusions, the methods to protect the water source site safety are put forward.
Groundwater recharge is an important part of groundwater circulation, and it is important to study its source for understanding the groundwater circulation process. Controlled by geological structures, the distribution of groundwater in bedrock area is complicated, and therefore the study of its source is a difficult work in hydrogeology research. By analyzing the model of water-rich zone based on remote sensing information, and according to the groundwater dynamics, major ion concentration, velocity and direction of groundwater flow, pumping and water level data of water source site, this article studies the source of groundwater recharge of Barakan Water Source Site(BWSS)in front of Kuruktag, northwest of China, and analyses the reasons for the abnormal change of the total water yield and the drawdown of the well. The results show that the groundwater of the water source site comes from the Aggregate Reclaiming Plant(ARP)about 6.5 kilometers northwest of BWSS. The ARP water pumping is the main reason of the abnormal change of the total water yield and the drawdown of the well of BWSS. Based on this conclusions, the methods to protect the water source site safety are put forward.
2018, 26(s1): 594-600.
This paper mainly introduces natures of the Brazil White cardboard(abbr:White cardboard) and the Standard sand, including their physical and mechanical parameters. A model named the friction of Standard sand-White cardboard was made in regard to the friction performance of the White cardboard and the Standard sand. In the model, the stripped White cardboard simulated the reinforced body, and the Standard sand simulated the rock-soil body. We attempted to find out how the Standard sand's compactness and White cardboard's size or shape and other influence factors might change the friction of Standard sand-White cardboard. In the experiment, we adopted the Variable-controlling approach by Changing in turn the influence factors. Then we recorded values of the friction of Standard sand-White cardboard on different conditions, and drew corresponding line charts. Finally we got the conclusion:the friction of Standard sand-White cardboard grows with the Standard sand's compactness to a certain extent. It grows with the White cardboard's width and the White cardboard's length embedded in the Standard sand. It grows with the numbers of diamonds in the White cardboard, it but does not grows clearly when the number exceeds two. It decreases with the space between diamonds to a certain extent. It decreases with the crosswise diagonal line's width of the diamond, but in the middle it is independent of the width.
This paper mainly introduces natures of the Brazil White cardboard(abbr:White cardboard) and the Standard sand, including their physical and mechanical parameters. A model named the friction of Standard sand-White cardboard was made in regard to the friction performance of the White cardboard and the Standard sand. In the model, the stripped White cardboard simulated the reinforced body, and the Standard sand simulated the rock-soil body. We attempted to find out how the Standard sand's compactness and White cardboard's size or shape and other influence factors might change the friction of Standard sand-White cardboard. In the experiment, we adopted the Variable-controlling approach by Changing in turn the influence factors. Then we recorded values of the friction of Standard sand-White cardboard on different conditions, and drew corresponding line charts. Finally we got the conclusion:the friction of Standard sand-White cardboard grows with the Standard sand's compactness to a certain extent. It grows with the White cardboard's width and the White cardboard's length embedded in the Standard sand. It grows with the numbers of diamonds in the White cardboard, it but does not grows clearly when the number exceeds two. It decreases with the space between diamonds to a certain extent. It decreases with the crosswise diagonal line's width of the diamond, but in the middle it is independent of the width.
2018, 26(s1): 601-606.
Pressure solution plays an important role in the evolution of rock pores and fractures. The porosity and fissure of rock play a decisive role in CO2 storage and migration. In this paper, based on the multifield coupled numerical simulation program TOUGHREACT-FLAC3D,an additional module considering pressure solution is added. And the theoretical model of one-dimensional laboratory scale is established to explore the effect of pressure solution on CO2 sequestration. This paper is based on pressure-solubilization. The coupling model of limestone THCM is established. The study found that:In the presence of CO2,Pressure solubilization can promote the change of rock porosity, and the effect of pressure solution on porosity is about 20% of the total change of porosity. In mechanics, pressure solution increases the strain rate of rock by about 10%.In terms of mineral evolution, the concentration of calcium increases by about 1/1000,The mineral content is reduced by about 1/1000. The innovation of this paper is on the original coupling calculation module. The calculation module considering pressure solution is added. Based on the previous work, a reasonable and effective simulation experiment is carried out and a quantitative conclusion is drawn.
Pressure solution plays an important role in the evolution of rock pores and fractures. The porosity and fissure of rock play a decisive role in CO2 storage and migration. In this paper, based on the multifield coupled numerical simulation program TOUGHREACT-FLAC3D,an additional module considering pressure solution is added. And the theoretical model of one-dimensional laboratory scale is established to explore the effect of pressure solution on CO2 sequestration. This paper is based on pressure-solubilization. The coupling model of limestone THCM is established. The study found that:In the presence of CO2,Pressure solubilization can promote the change of rock porosity, and the effect of pressure solution on porosity is about 20% of the total change of porosity. In mechanics, pressure solution increases the strain rate of rock by about 10%.In terms of mineral evolution, the concentration of calcium increases by about 1/1000,The mineral content is reduced by about 1/1000. The innovation of this paper is on the original coupling calculation module. The calculation module considering pressure solution is added. Based on the previous work, a reasonable and effective simulation experiment is carried out and a quantitative conclusion is drawn.
2018, 26(s1): 607-611.
The deep fluvial soft soil is widely distributed in Anhui Province. It has a certain influence on the construction of regional engineering. In this paper, the soft soil in the Wuhu plain of Anhui Province is taken as the research object, including the alluvial soft soil of the Yangtze River and the alluvial soft soil of Qingyijiang River. The influence of different depositional environments on the mechanical properties of soft soil is explored. Geotechnical tests and field tests in deep soft soil area were carried out to evaluate their mechanical properties. The depositional environment of the quaternary system is analyzed in the deep soft soil area. The particle size test is used to establish the physical relation between the sedimentary environment and the mechanical properties. The results show that the alluvial soft soil of Qingyijiang River has higher compressive strength and lower compressibility than the alluvial soft soil of Yangtze River. The sedimentary environment of Yangtze River is volatile with strong water power and local existence of fine sand layer. However, in the alluvial plain area of Qingyijiang River, the hydrodynamic force is relatively stable, and the sedimentary environment is stable. Based on the analysis of engineering geology and Quaternary geology, the influence of fluvial facies sedimentary environment on the mechanical properties of soft soil is put forward. The physical relationship between mechanical properties and sedimentary environment is established. It provides the basis for the construction of the soft soil area in Anhui Province.
The deep fluvial soft soil is widely distributed in Anhui Province. It has a certain influence on the construction of regional engineering. In this paper, the soft soil in the Wuhu plain of Anhui Province is taken as the research object, including the alluvial soft soil of the Yangtze River and the alluvial soft soil of Qingyijiang River. The influence of different depositional environments on the mechanical properties of soft soil is explored. Geotechnical tests and field tests in deep soft soil area were carried out to evaluate their mechanical properties. The depositional environment of the quaternary system is analyzed in the deep soft soil area. The particle size test is used to establish the physical relation between the sedimentary environment and the mechanical properties. The results show that the alluvial soft soil of Qingyijiang River has higher compressive strength and lower compressibility than the alluvial soft soil of Yangtze River. The sedimentary environment of Yangtze River is volatile with strong water power and local existence of fine sand layer. However, in the alluvial plain area of Qingyijiang River, the hydrodynamic force is relatively stable, and the sedimentary environment is stable. Based on the analysis of engineering geology and Quaternary geology, the influence of fluvial facies sedimentary environment on the mechanical properties of soft soil is put forward. The physical relationship between mechanical properties and sedimentary environment is established. It provides the basis for the construction of the soft soil area in Anhui Province.
2018, 26(s1): 612-617.
Heavy metal pollution does not only influence the ecological environment, but also has great impact on the properties of the soil, which will result in great changes in the structure and mechanical properties of the soil, and ultimately affect the implementation of human engineering construction directly. The subsoil with severe heavy metal pollution in the surrounding area of HuiTeng Chemical Co.,Ltd. is selected for study in this paper, by comparing the nature of the soil, such as the microstructure, pore distribution, mineral composition, pH value, et al.,and the mechanical properties of the soil, i.e. the compression coefficient, cohesive force, internal friction angle and uniaxial shear strength of soil mass, et al.,before and after the heavy metal pollution, the impacts of heavy metal pollution on soil properties have been analyzed. The results of the study show that heavy metal pollution has resulted in the change of soil structure. There is no significant change in the mineral composition of the soil; the soil porosity is reduced, and the soil is denser; though the soil compactness increased, the uniaxial shear strength of the soil is significantly reduced after the pollution, and the shear strength is reduced by 10%~35%. The compression amount of soil before and after pollution is quite different, and the soil compressibility is reduced.
Heavy metal pollution does not only influence the ecological environment, but also has great impact on the properties of the soil, which will result in great changes in the structure and mechanical properties of the soil, and ultimately affect the implementation of human engineering construction directly. The subsoil with severe heavy metal pollution in the surrounding area of HuiTeng Chemical Co.,Ltd. is selected for study in this paper, by comparing the nature of the soil, such as the microstructure, pore distribution, mineral composition, pH value, et al.,and the mechanical properties of the soil, i.e. the compression coefficient, cohesive force, internal friction angle and uniaxial shear strength of soil mass, et al.,before and after the heavy metal pollution, the impacts of heavy metal pollution on soil properties have been analyzed. The results of the study show that heavy metal pollution has resulted in the change of soil structure. There is no significant change in the mineral composition of the soil; the soil porosity is reduced, and the soil is denser; though the soil compactness increased, the uniaxial shear strength of the soil is significantly reduced after the pollution, and the shear strength is reduced by 10%~35%. The compression amount of soil before and after pollution is quite different, and the soil compressibility is reduced.
2018, 26(s1): 618-622.
The cohesionless soils are of all types of sands, crushed-gravels and rock ballasts. The testing results of seepage deformation indicate that non-uniform factor discrimination method and gradation curve slope discrimination method are not general discrimination method for the seepage deformation type of cohesionless soil. In some cases, the testing results of the crushed-gravel and sand are even opposite under same conditions. The further study results indicate that prime cause is large difference of fine grain content. Thus, when the seepage deformation types of cohesionless soils are distinguished by discrimination methods of non-uniform factor and gradation curve slope, the fine grain content size of sampling shall be considered, or crushed-gravel and sand shall be studied separately.
The cohesionless soils are of all types of sands, crushed-gravels and rock ballasts. The testing results of seepage deformation indicate that non-uniform factor discrimination method and gradation curve slope discrimination method are not general discrimination method for the seepage deformation type of cohesionless soil. In some cases, the testing results of the crushed-gravel and sand are even opposite under same conditions. The further study results indicate that prime cause is large difference of fine grain content. Thus, when the seepage deformation types of cohesionless soils are distinguished by discrimination methods of non-uniform factor and gradation curve slope, the fine grain content size of sampling shall be considered, or crushed-gravel and sand shall be studied separately.
2018, 26(s1): 623-630.
Aiming at the sensitivity of modified red clay to many strength factors, the unconsolidated and undrained triaxial test of red clay with various gradients of nano-graphite powder under different moisture contents was designed, combining SPSS multiple regression analysis and MATLAB data fitting, which obtain the mathematical model between intensity and various factors. Analyzing the effect of nano-graphite content on the microstructure of regional red clay with SEM method. The results show that:The appropriate amount of nano-graphite powder has a significant effect on improving the mechanical strength of red clay, and its addition ratio is the most sensitive factor affecting the strength of regional red clay. The mathematical model established by the fitting curve of shear strength and cohesive force with the addition ratio shows that the shear strength and cohesive force c increase first and then decrease with the increase of nano graphite powder,while the internal friction angle is basically the same. The content of nano-graphite changed the microstructure of red clay to varying degrees, resulting in a gradual transition from a loose state to a dense state on the surface of the soil surface particles, which ultimately changed the strength properties of red clay.
Aiming at the sensitivity of modified red clay to many strength factors, the unconsolidated and undrained triaxial test of red clay with various gradients of nano-graphite powder under different moisture contents was designed, combining SPSS multiple regression analysis and MATLAB data fitting, which obtain the mathematical model between intensity and various factors. Analyzing the effect of nano-graphite content on the microstructure of regional red clay with SEM method. The results show that:The appropriate amount of nano-graphite powder has a significant effect on improving the mechanical strength of red clay, and its addition ratio is the most sensitive factor affecting the strength of regional red clay. The mathematical model established by the fitting curve of shear strength and cohesive force with the addition ratio shows that the shear strength and cohesive force c increase first and then decrease with the increase of nano graphite powder,while the internal friction angle is basically the same. The content of nano-graphite changed the microstructure of red clay to varying degrees, resulting in a gradual transition from a loose state to a dense state on the surface of the soil surface particles, which ultimately changed the strength properties of red clay.
2018, 26(s1): 631-638.
The mechanical properties of the dam material have an important influence on its stability. In this study, based on the discrete element method(DEM),direct shear tests were conducted on dam materials with different densities and particle grading(fine and coarse-grained materials). From the aspects of material stress-strain curve(macro) and internal stress(micro) information, the mechanical properties of the dam material were revealed. The results show that, from the macroscopic perspective, with the increase of the density of the dam material, the peak strength is enhanced, especially for the coarse-grained material. For different grain gradation materials, the stress-strain curve of the fine-grained material shows obvious strain hardening and shear properties, while coarse-grained materials exhibit strain softening and dilatancy characteristics. From the microscopic perspective, the direction of the internal principal stress of the material gradually shifts as the shear displacement increases, the internal force chains and the internal shear zone gradually concentrateand develops. The particle size distribution of materials determines the distribution of internal contact forces and the mode of transfer. The distribution of stress in coarse-grained materials is mainly distributed along the framework particles, and is evenly distributed in fine-grained materials. The density of the materials affects the contact patterns between the particles inside the material. The greater the degree of compaction, the more conducive to the transmission of occlusal forces between particles, so that the internal stress and the strength of the chain have different degrees of enhancement.
The mechanical properties of the dam material have an important influence on its stability. In this study, based on the discrete element method(DEM),direct shear tests were conducted on dam materials with different densities and particle grading(fine and coarse-grained materials). From the aspects of material stress-strain curve(macro) and internal stress(micro) information, the mechanical properties of the dam material were revealed. The results show that, from the macroscopic perspective, with the increase of the density of the dam material, the peak strength is enhanced, especially for the coarse-grained material. For different grain gradation materials, the stress-strain curve of the fine-grained material shows obvious strain hardening and shear properties, while coarse-grained materials exhibit strain softening and dilatancy characteristics. From the microscopic perspective, the direction of the internal principal stress of the material gradually shifts as the shear displacement increases, the internal force chains and the internal shear zone gradually concentrateand develops. The particle size distribution of materials determines the distribution of internal contact forces and the mode of transfer. The distribution of stress in coarse-grained materials is mainly distributed along the framework particles, and is evenly distributed in fine-grained materials. The density of the materials affects the contact patterns between the particles inside the material. The greater the degree of compaction, the more conducive to the transmission of occlusal forces between particles, so that the internal stress and the strength of the chain have different degrees of enhancement.
2018, 26(s1): 639-645.
During the process of hydraulic fracturing in shale gas reservoir, the fracturing parameters and reservoir protection will be affected by the interaction between fracturing fluid and shale due to the effects of ion adsorption, exchange and diffusion on the microstructure of shale. The changes of acoustic characteristics and microstructure of the siliceous shale of Lower Cambrian Niutitang Formation in northwestern Hunan were studied during static adsorption and diffusion of fracturing fluids with different ion concentrations and activities. And the response of macroscopic acoustic features and microstructures was revealed. The conclusions include the following. (1)Shale has the strongest adsorption capacity in a certain concentration of NaCl fracturing fluid, followed by SDBS fracturing fluid, and has the weakest adsorption ability in CTAB fracturing fluid. The higher the concentration of inorganic ions, the stronger the ability of diffusion and adsorption in shale. (2)Strong adsorption of ions and pore filling occurred in the static adsorption process, which resulted in the change of microporous structure and porosity. (3)As the ion concentration of the fracturing fluid with different surfactant, the number of shale micropores, the connectivity and the pore size distribution are all changed correspondingly. In the studied concentration range, when the concentration of NaCl salt ion is 15%,it is most beneficial to the protection of the reservoir, while a negative effect on the shale microscopic pore network occurs when it is combined with the surfactants.
During the process of hydraulic fracturing in shale gas reservoir, the fracturing parameters and reservoir protection will be affected by the interaction between fracturing fluid and shale due to the effects of ion adsorption, exchange and diffusion on the microstructure of shale. The changes of acoustic characteristics and microstructure of the siliceous shale of Lower Cambrian Niutitang Formation in northwestern Hunan were studied during static adsorption and diffusion of fracturing fluids with different ion concentrations and activities. And the response of macroscopic acoustic features and microstructures was revealed. The conclusions include the following. (1)Shale has the strongest adsorption capacity in a certain concentration of NaCl fracturing fluid, followed by SDBS fracturing fluid, and has the weakest adsorption ability in CTAB fracturing fluid. The higher the concentration of inorganic ions, the stronger the ability of diffusion and adsorption in shale. (2)Strong adsorption of ions and pore filling occurred in the static adsorption process, which resulted in the change of microporous structure and porosity. (3)As the ion concentration of the fracturing fluid with different surfactant, the number of shale micropores, the connectivity and the pore size distribution are all changed correspondingly. In the studied concentration range, when the concentration of NaCl salt ion is 15%,it is most beneficial to the protection of the reservoir, while a negative effect on the shale microscopic pore network occurs when it is combined with the surfactants.
2018, 26(s1): 646-651.
Because of its particularity, bentonite has been studied by many scholars. In the actual project, it causes many problems. Explores the expansive property of Nanning bentonite, through X-ray diffraction test to determine the mineral composition of Nanning bentonite, to determine the influence of montmorillonite on swelling. Combined with different cationic montmorillonite flocculation test, it was found that the concentration of sodium ions increased. The flocculation of Montmorillonite is enhanced and the critical value of magnesium ions for flocculation of Montmorillonite is rather than the critical concentration. The colloid is stabilized by the zeta potential, which is caused by the exclusive function, and the expansion mechanism is analyzed. The influence of cation on the swelling rate of Nanning Bentonite is studied based on the free expansion test. It was found that with the increase of (Mg) cation concentration, the swelling rate of Nanning bentonite decreased, and the time of stability experienced in the expansion experiment was increased with the increase of cationic valence. The results of low cation concentration and pure water test were similar. The ionic type had an effect on the volume expansion of Montmorillonite. At the same concentration increased, the order of volume expansion is NaClMgCl2.
Because of its particularity, bentonite has been studied by many scholars. In the actual project, it causes many problems. Explores the expansive property of Nanning bentonite, through X-ray diffraction test to determine the mineral composition of Nanning bentonite, to determine the influence of montmorillonite on swelling. Combined with different cationic montmorillonite flocculation test, it was found that the concentration of sodium ions increased. The flocculation of Montmorillonite is enhanced and the critical value of magnesium ions for flocculation of Montmorillonite is rather than the critical concentration. The colloid is stabilized by the zeta potential, which is caused by the exclusive function, and the expansion mechanism is analyzed. The influence of cation on the swelling rate of Nanning Bentonite is studied based on the free expansion test. It was found that with the increase of (Mg) cation concentration, the swelling rate of Nanning bentonite decreased, and the time of stability experienced in the expansion experiment was increased with the increase of cationic valence. The results of low cation concentration and pure water test were similar. The ionic type had an effect on the volume expansion of Montmorillonite. At the same concentration increased, the order of volume expansion is NaClMgCl2.
2018, 26(s1): 652-656.
In order to study the influence of soluble salt on the shear strength of loess, this paper takes the L1 of the original loess in Liulin County of Lliang as the research object. Take the salt content and water content as the variables, and analyze the influence of different moisture content and different salt content on the shear strength of loess. The results show that when the moisture content is low as 10%,the increase of the concentration of soluble salt ions makes the electromotive potential between the particles decrease, and make the cohesive force increases obviously with the increase of the salt content. When the moisture content is at 15%~25%,the concentration of soluble salt ions in the soil particles decreases with the increase of the moisture content. The electrochemical effect of soluble salt is weakened. As the same time, the softening effect of moisture on soil skeleton, the cohesion decreases with increasing moisture content. The internal friction angle increases slightly with the increase of salt content, and decreases with the increase of moisture content.
In order to study the influence of soluble salt on the shear strength of loess, this paper takes the L1 of the original loess in Liulin County of Lliang as the research object. Take the salt content and water content as the variables, and analyze the influence of different moisture content and different salt content on the shear strength of loess. The results show that when the moisture content is low as 10%,the increase of the concentration of soluble salt ions makes the electromotive potential between the particles decrease, and make the cohesive force increases obviously with the increase of the salt content. When the moisture content is at 15%~25%,the concentration of soluble salt ions in the soil particles decreases with the increase of the moisture content. The electrochemical effect of soluble salt is weakened. As the same time, the softening effect of moisture on soil skeleton, the cohesion decreases with increasing moisture content. The internal friction angle increases slightly with the increase of salt content, and decreases with the increase of moisture content.
2018, 26(s1): 657-664.
In view of the aeration zone of a future low and intermediate radioactive waste repository, variations on unsaturated permeability coefficient K() and dispersion coefficient D() of a clay with its volumetric water content were studied. The results indicate that the unsaturated clay is actually impermeable when 25%, and small change in will change the orders of magnitude of K() when 15%. The experiments show that dispersion coefficient of unsaturated clay tends to reduce with the decrease of . As =38%,the measured dispersion coefficient is 4.12m2a-1, and as =6%,the dispersion coefficient is 0.04m2a-1,which only about 1% of the former. The migration simulations show that as 25%,plutonium migrates very slowly in the clay barrier, whereas its migration rate will be enhanced obviously when 30%.
In view of the aeration zone of a future low and intermediate radioactive waste repository, variations on unsaturated permeability coefficient K() and dispersion coefficient D() of a clay with its volumetric water content were studied. The results indicate that the unsaturated clay is actually impermeable when 25%, and small change in will change the orders of magnitude of K() when 15%. The experiments show that dispersion coefficient of unsaturated clay tends to reduce with the decrease of . As =38%,the measured dispersion coefficient is 4.12m2a-1, and as =6%,the dispersion coefficient is 0.04m2a-1,which only about 1% of the former. The migration simulations show that as 25%,plutonium migrates very slowly in the clay barrier, whereas its migration rate will be enhanced obviously when 30%.
2018, 26(s1): 665-671.
Most of the failure occurred in the reservoir bank slope is related to the fluctuation of the reservoir water level. In order to effectively guide the slope design and prevent, regard the slope of the upper reservoir area of Shaanxi Zhen'an Pumped-storage Power Station as the object of the research. Using Rocscience Phase2 finite element software, simulate the seepage field-stress coupling field in the slope under drawdown conditions by transient flow and then calculate the stability of the upstream and the downstream slope by the method of SSR search area.It was found that when the water level rose at a constant speed, the safety factor of the downsteam slope continues to decrease with the water level rising, while the safety factor of the upsteam slope decreases first and then increases, but no damage occurs on both sides of the slope. When the water level falls, the downsteam slope safety factor also continued to decrease, but no damage occurred. The safety factor of the upsteam slope also continued to decrease. However, it dropped sharply when the water level dropped by 19m and eventually destroyed. Under the condition that the water fluctuation is constant, when the speed of the lift changes, the safety factor of the downsteam slope remains basically unchanged. When the water level rise speed increases, the safety factor of the upsteam slope gradually increases. When the water level decline speed increases, it gradually decreased. It is suggested that when the reservoir is operating, the decline of the reservoir water should not exceed 18m. In order to meet the demand of power generation and ensure the simulated slope, the normal water level should be lifted by 12m.
Most of the failure occurred in the reservoir bank slope is related to the fluctuation of the reservoir water level. In order to effectively guide the slope design and prevent, regard the slope of the upper reservoir area of Shaanxi Zhen'an Pumped-storage Power Station as the object of the research. Using Rocscience Phase2 finite element software, simulate the seepage field-stress coupling field in the slope under drawdown conditions by transient flow and then calculate the stability of the upstream and the downstream slope by the method of SSR search area.It was found that when the water level rose at a constant speed, the safety factor of the downsteam slope continues to decrease with the water level rising, while the safety factor of the upsteam slope decreases first and then increases, but no damage occurs on both sides of the slope. When the water level falls, the downsteam slope safety factor also continued to decrease, but no damage occurred. The safety factor of the upsteam slope also continued to decrease. However, it dropped sharply when the water level dropped by 19m and eventually destroyed. Under the condition that the water fluctuation is constant, when the speed of the lift changes, the safety factor of the downsteam slope remains basically unchanged. When the water level rise speed increases, the safety factor of the upsteam slope gradually increases. When the water level decline speed increases, it gradually decreased. It is suggested that when the reservoir is operating, the decline of the reservoir water should not exceed 18m. In order to meet the demand of power generation and ensure the simulated slope, the normal water level should be lifted by 12m.
2018, 26(s1): 672-676.
The experimental verification is conducted to verify the suitability of pore diameter method used to distinguish the seepage deformation types of various cohesionless coarse-gained soils. The statistical analysis is conducted based on seepage deformation testing results taken with 145sand samples from 27 projects. The results are as follows:(1)For the crushed gravels with continuous gradation, the coincidence rate is 80.0. (2)For the crushed gravels with discontinuous gradation, the coincidence rate is 55.0. (3)For the sands with different types, the coincidence rate is 22.0. Thus, the pore diameter method is applicable to the distinguishing of seepage deformation types of crushed gravels with continuous gradation. However, for the crushed gravels with discontinuous gradation and sands with different types, the suitability is poor.
The experimental verification is conducted to verify the suitability of pore diameter method used to distinguish the seepage deformation types of various cohesionless coarse-gained soils. The statistical analysis is conducted based on seepage deformation testing results taken with 145sand samples from 27 projects. The results are as follows:(1)For the crushed gravels with continuous gradation, the coincidence rate is 80.0. (2)For the crushed gravels with discontinuous gradation, the coincidence rate is 55.0. (3)For the sands with different types, the coincidence rate is 22.0. Thus, the pore diameter method is applicable to the distinguishing of seepage deformation types of crushed gravels with continuous gradation. However, for the crushed gravels with discontinuous gradation and sands with different types, the suitability is poor.
2018, 26(s1): 677-683.
From the acoustical exploring data of Sub-bottom profiler and Echo Sounder, it is found that fluid mud layer and partial disturbed strata existed in the subaqueous Yellow River Delta. The fluid mud is widely distributed in the study area, and the average thickness of the fluid mud is about 10cm. The distribution of fluid mud is relatively uniform and thicker in the flat area than terrain undulating area, and the fluid mud is in a spot distribution in low-lying areas. The disturbed strata is easy to identify according to the acoustical exploring data of superficial strata, due to difference from the ambient undisturbed strata in many aspects. The initial disturbed strata further expended in the space compared with the results of acoustical exploring data in 2003. This paper further illustrates the formation mechanism of disturbed strata under the storm waves based on the achievements of researches. The disturbed strata formed under the action of storm waves accompanied by negative topography. However, the long-time differential erosion under the hydrodynamic action of disturbed and undisturbed strata caused the disturbed negative topography switch to positive topography.
From the acoustical exploring data of Sub-bottom profiler and Echo Sounder, it is found that fluid mud layer and partial disturbed strata existed in the subaqueous Yellow River Delta. The fluid mud is widely distributed in the study area, and the average thickness of the fluid mud is about 10cm. The distribution of fluid mud is relatively uniform and thicker in the flat area than terrain undulating area, and the fluid mud is in a spot distribution in low-lying areas. The disturbed strata is easy to identify according to the acoustical exploring data of superficial strata, due to difference from the ambient undisturbed strata in many aspects. The initial disturbed strata further expended in the space compared with the results of acoustical exploring data in 2003. This paper further illustrates the formation mechanism of disturbed strata under the storm waves based on the achievements of researches. The disturbed strata formed under the action of storm waves accompanied by negative topography. However, the long-time differential erosion under the hydrodynamic action of disturbed and undisturbed strata caused the disturbed negative topography switch to positive topography.
2018, 26(s1): 684-690.
To obtain similar materials of soft rock, the experiment selects river sand as aggregate, lime and gypsum as cement, iron sand as densification agent, glycerol as plasticizer, and borax combined with water as the anchoring material. It establishes orthogonal test scheme with 4 factors and 4 levels, and conducts the physical and mechanical experiment of similar materials. Through the range analysis, variance analysis and damage analysis of the test results, the study summarizes the effect law of component changes in similar materials on the physical and mechanical properties of the specimen. The results show that the main factors, which affect the density and mechanical properties of similar materials, are the proportion of river sand to iron sand and the proportion of glycerol to lime and gypsum, respectively. Under the maximum load, the specimen is basically damaged, with its damage value between 0.85-0.97. Based on the physical and mechanical properties of similar materials obtained by the paper, the optimal proportion scheme of similar materials can be designed, to meet the requirements of similarity test related to soft rock material, with the fixed target strength and similarity ratio.
To obtain similar materials of soft rock, the experiment selects river sand as aggregate, lime and gypsum as cement, iron sand as densification agent, glycerol as plasticizer, and borax combined with water as the anchoring material. It establishes orthogonal test scheme with 4 factors and 4 levels, and conducts the physical and mechanical experiment of similar materials. Through the range analysis, variance analysis and damage analysis of the test results, the study summarizes the effect law of component changes in similar materials on the physical and mechanical properties of the specimen. The results show that the main factors, which affect the density and mechanical properties of similar materials, are the proportion of river sand to iron sand and the proportion of glycerol to lime and gypsum, respectively. Under the maximum load, the specimen is basically damaged, with its damage value between 0.85-0.97. Based on the physical and mechanical properties of similar materials obtained by the paper, the optimal proportion scheme of similar materials can be designed, to meet the requirements of similarity test related to soft rock material, with the fixed target strength and similarity ratio.
2018, 26(s1): 691-696.
The surrounding rock of a radioactive waste disposal site is granite. In order to evaluate the permeability of surrounding rock, the homogeneous zone was first divided into rock masses in the study area. In the homogenous area, based on numerous detailed joint geometry surveys, probability distribution functions of joint geometric parameters were analyzed. Based on Monte Carlo simulation and two-dimensional fractured rock mass hydraulics, a stochastic simulation and seepage calculation program for joint network was compiled based on Matlab. The statistical average of the principal permeability tensor, obtained by multiple sampling statistics. In order to make the value from the program more in line with the actual conditions of the project, the permeability tensor was revised by using the permeability coefficient obtained from the hydraulic pressure tests.
The surrounding rock of a radioactive waste disposal site is granite. In order to evaluate the permeability of surrounding rock, the homogeneous zone was first divided into rock masses in the study area. In the homogenous area, based on numerous detailed joint geometry surveys, probability distribution functions of joint geometric parameters were analyzed. Based on Monte Carlo simulation and two-dimensional fractured rock mass hydraulics, a stochastic simulation and seepage calculation program for joint network was compiled based on Matlab. The statistical average of the principal permeability tensor, obtained by multiple sampling statistics. In order to make the value from the program more in line with the actual conditions of the project, the permeability tensor was revised by using the permeability coefficient obtained from the hydraulic pressure tests.
2018, 26(s1): 697-703.
According to the influencing factors of red clay shear strength, I used the triaxial test method to unconsolidate the undrained test, and used the orthogonal test table to arrange the test plan. After the test, the microstructure of the sample after the test was tested. The comprehensive balance method was used to analyze the sensitivity of factors such as moisture content, mix ratio, and confining pressure to shear strength. The results show that the Nano-graphite powder content and water content are all significant factors affecting the shear strength parameters of red clay under certain dry density conditions. With the increase of the water content and the Nano-graphite powder incorporation ratio, the shear strength increases first and then decreases. The stress-strain curve of Nano graphite powder red clay has obvious peak stress, which is characterized by strain hardening. The micro-improved mechanism shows that the addition of Nano-graphite powder changes the adhesion of kaolinite and other clay minerals, resulting in re-agglomeration of graphite powder in the pores, reducing the porosity, and increasing the cementation of soil particles.
According to the influencing factors of red clay shear strength, I used the triaxial test method to unconsolidate the undrained test, and used the orthogonal test table to arrange the test plan. After the test, the microstructure of the sample after the test was tested. The comprehensive balance method was used to analyze the sensitivity of factors such as moisture content, mix ratio, and confining pressure to shear strength. The results show that the Nano-graphite powder content and water content are all significant factors affecting the shear strength parameters of red clay under certain dry density conditions. With the increase of the water content and the Nano-graphite powder incorporation ratio, the shear strength increases first and then decreases. The stress-strain curve of Nano graphite powder red clay has obvious peak stress, which is characterized by strain hardening. The micro-improved mechanism shows that the addition of Nano-graphite powder changes the adhesion of kaolinite and other clay minerals, resulting in re-agglomeration of graphite powder in the pores, reducing the porosity, and increasing the cementation of soil particles.
2018, 26(s1): 704-709.
The fault is the important boundary factor of the metallogenic structure. Fault stability influence the stability of overlying rock mass and ore-body. The study analyzed the mechanism of fault slip induced by mining in the No. 3 mine zone of the Jinchuan Mine. The fault slip led to the overlying rock mass deformation. This article also studied the process of fault slip based on the characteristics analysis of deformation of surface and underground. The results showed the evolution characteristics of the stress and displacement distribution. The fault slip process was divided into six stages, slowly growth stage, shocking stage, rapidly growth stage, peak value shocking stage, initially slip stage and rapidly slip stage. The evolution law of fault displacement showed the process of fault slide consist of displacement cumulative stage and sliding stage. And the displacement cumulative stage is divided into decelerate slide, stable slide and accelerate slide.
The fault is the important boundary factor of the metallogenic structure. Fault stability influence the stability of overlying rock mass and ore-body. The study analyzed the mechanism of fault slip induced by mining in the No. 3 mine zone of the Jinchuan Mine. The fault slip led to the overlying rock mass deformation. This article also studied the process of fault slip based on the characteristics analysis of deformation of surface and underground. The results showed the evolution characteristics of the stress and displacement distribution. The fault slip process was divided into six stages, slowly growth stage, shocking stage, rapidly growth stage, peak value shocking stage, initially slip stage and rapidly slip stage. The evolution law of fault displacement showed the process of fault slide consist of displacement cumulative stage and sliding stage. And the displacement cumulative stage is divided into decelerate slide, stable slide and accelerate slide.
2018, 26(s1): 710-715.
In recent years, the reduction of shallow resources has increased the demand for deep resources. The deep engineering exceeds 1 kilo-meters level has become more normal. The deep engineering of Jinchuan No. 2 Mine is deeper than 1000 m, facing the safe production issues of deep mining. The zonal disintegration phenomenon of the surrounding rock in deep roadway is a research hotspot of deep engineering research. In order to monitor the zonal disintegration phenomenon in the deep tunnel of metal mines, we selected six sections in the 700m horizontal roadway of Jinchuan No.2 Mine, and arranged two monitoring points in each section. By using the surrounding rock loosening zone test machine, we monitored the rupture zone of the surrounding rock and we found the phenomenon of zonal disintegration of surrounding rock in deep engineering. The monitoring results show that there are zonal disintegration parts in the monitored section. The thickness of the rupture zone decreases with the distance from the surface of the roadway, and the fragmentation degree decreases and the integrity increases. The rediscovery of the zonal disintegration is of great significance for the stability analysis of the surrounding rock in deep roadway and the improvement of support design.
In recent years, the reduction of shallow resources has increased the demand for deep resources. The deep engineering exceeds 1 kilo-meters level has become more normal. The deep engineering of Jinchuan No. 2 Mine is deeper than 1000 m, facing the safe production issues of deep mining. The zonal disintegration phenomenon of the surrounding rock in deep roadway is a research hotspot of deep engineering research. In order to monitor the zonal disintegration phenomenon in the deep tunnel of metal mines, we selected six sections in the 700m horizontal roadway of Jinchuan No.2 Mine, and arranged two monitoring points in each section. By using the surrounding rock loosening zone test machine, we monitored the rupture zone of the surrounding rock and we found the phenomenon of zonal disintegration of surrounding rock in deep engineering. The monitoring results show that there are zonal disintegration parts in the monitored section. The thickness of the rupture zone decreases with the distance from the surface of the roadway, and the fragmentation degree decreases and the integrity increases. The rediscovery of the zonal disintegration is of great significance for the stability analysis of the surrounding rock in deep roadway and the improvement of support design.
2018, 26(s1): 716-723.
Jinchuan Mine is the largest nickel-cobalt resource base in China. The deep rock mass in the mining area is characterized by crushing, creeping and expansion. The stability of roadway rock mass is the key issue of the sustainable development for the mining area. In this paper, the engineering geological investigation of the deformation and failure of deep rock mass, and the analysis of monitoring results of the deep experimental roadway convergence deformation are carried out. The results show that:(1) As the roadway rock body develops to the deep, the mining area expands and the ground pressure activity increases. Small fractures and other weak structural planes develop. The constrained deformation of the rock mass under the influence of the disturbing stress field is intensified, and there may be serious yield deformation and overall instability in the roadway. (2) Comprehensive site engineering geological survey and analysis of deformation and failure mechanism of roadway surrounding rock, complicated surrounding rock engineering geological conditions, aging characteristics, mining impact, high stress, crack shear creep, crack filling water-rock reaction and other unfavorable factors make the surrounding rock in the deep roadway exhibit obvious characteristics of creep and overall necking. (3) The analysis of monitoring data of roadway rock mass converging deformation shows that the deformation of broken rock mass in deep roadway is the overall deformation of the surrounding rock and the necking occurs. Convergence and deformation of roadway rock mass are mainly affected by high ground stress and rock mass structure. Mining influences the dynamic change of the boundary stress field of surrounding rock, causing the convergence curve to fluctuate.
Jinchuan Mine is the largest nickel-cobalt resource base in China. The deep rock mass in the mining area is characterized by crushing, creeping and expansion. The stability of roadway rock mass is the key issue of the sustainable development for the mining area. In this paper, the engineering geological investigation of the deformation and failure of deep rock mass, and the analysis of monitoring results of the deep experimental roadway convergence deformation are carried out. The results show that:(1) As the roadway rock body develops to the deep, the mining area expands and the ground pressure activity increases. Small fractures and other weak structural planes develop. The constrained deformation of the rock mass under the influence of the disturbing stress field is intensified, and there may be serious yield deformation and overall instability in the roadway. (2) Comprehensive site engineering geological survey and analysis of deformation and failure mechanism of roadway surrounding rock, complicated surrounding rock engineering geological conditions, aging characteristics, mining impact, high stress, crack shear creep, crack filling water-rock reaction and other unfavorable factors make the surrounding rock in the deep roadway exhibit obvious characteristics of creep and overall necking. (3) The analysis of monitoring data of roadway rock mass converging deformation shows that the deformation of broken rock mass in deep roadway is the overall deformation of the surrounding rock and the necking occurs. Convergence and deformation of roadway rock mass are mainly affected by high ground stress and rock mass structure. Mining influences the dynamic change of the boundary stress field of surrounding rock, causing the convergence curve to fluctuate.
2018, 26(s1): 724-729.
Underground mining leads to the overlying rock and surface movement, deformation and failure. Shaft failure always occurs caused by the surrounding rock movement. The dip of ore-body is 55-65. That is classified into steep inclined metal mine. Shallow-hole shrinkage mining method and underhand cut and filling method are used in different levels at the same time. The issue of rock mass stability is very important in this area because developed structures and broken rock mass. The method that used in mining area in past decades is open-stope. The mining engineering in these decades has leaded to the large scale mountain cracking and ground deformation. These cracks and deformations influence the underground mining. Therefore, this study analyzed three shafts stability influenced by mining based on the engineering geology condition. The analysis method is numerical simulation. And the results provided some further evidence to support mining safty.
Underground mining leads to the overlying rock and surface movement, deformation and failure. Shaft failure always occurs caused by the surrounding rock movement. The dip of ore-body is 55-65. That is classified into steep inclined metal mine. Shallow-hole shrinkage mining method and underhand cut and filling method are used in different levels at the same time. The issue of rock mass stability is very important in this area because developed structures and broken rock mass. The method that used in mining area in past decades is open-stope. The mining engineering in these decades has leaded to the large scale mountain cracking and ground deformation. These cracks and deformations influence the underground mining. Therefore, this study analyzed three shafts stability influenced by mining based on the engineering geology condition. The analysis method is numerical simulation. And the results provided some further evidence to support mining safty.
2018, 26(s1): 730-739.
A deep foundation pit in Zhengzhou is located in the alluvial plain of the Yellow River. The site soil is mainly composed of silt, silty clay and silty sand, and the geological environment is complex. The proposed building is residential, commercial and underground garage. The foundation pit is about 12.00m deep. The surrounding areas are residential, most of which are seven stories of brick and concrete structures, which are closest to 5.0m. The excavation area is large, the foundation pit is deep, and is close to the surrounding structures. In this paper, by analyzing the construction, surrounding environment and geological and hydrological conditions of the deep foundation pit, the combined support scheme of two row piles and anchor cables is adopted in the near side of the surrounding construction, and the comparison analysis is made in combination with the field monitoring data. The analysis results show that the settlement of the surrounding surface caused by the excavation of the deep foundation pit is small, and the influence radius of the soil excavation on the surrounding surface settlement is roughly in line with the principle of R=2H(H as the depth of the foundation pit). The location of the maximum settlement of the settlement is about 5meters from the top of the foundation pit, and is 0.4-0.5 times the depth of the foundation pit depth of H. The deformation monitoring results of the two rows of piles and the settlement monitoring data of the surrounding buildings are analyzed. The results meet the requirements of relevant design codes. The research in this paper will provide reference for similar projects.
A deep foundation pit in Zhengzhou is located in the alluvial plain of the Yellow River. The site soil is mainly composed of silt, silty clay and silty sand, and the geological environment is complex. The proposed building is residential, commercial and underground garage. The foundation pit is about 12.00m deep. The surrounding areas are residential, most of which are seven stories of brick and concrete structures, which are closest to 5.0m. The excavation area is large, the foundation pit is deep, and is close to the surrounding structures. In this paper, by analyzing the construction, surrounding environment and geological and hydrological conditions of the deep foundation pit, the combined support scheme of two row piles and anchor cables is adopted in the near side of the surrounding construction, and the comparison analysis is made in combination with the field monitoring data. The analysis results show that the settlement of the surrounding surface caused by the excavation of the deep foundation pit is small, and the influence radius of the soil excavation on the surrounding surface settlement is roughly in line with the principle of R=2H(H as the depth of the foundation pit). The location of the maximum settlement of the settlement is about 5meters from the top of the foundation pit, and is 0.4-0.5 times the depth of the foundation pit depth of H. The deformation monitoring results of the two rows of piles and the settlement monitoring data of the surrounding buildings are analyzed. The results meet the requirements of relevant design codes. The research in this paper will provide reference for similar projects.
2018, 26(s1): 740-744.
The influence factors analysis of backfill stability is complicated. This study focus on the dip of ore-body, geometrical morphology and mining method. The numerical simulation results showed:the dip of ore-body not only influence the maximum value of backfill footwall displacement, but influence its location. The relation of maximum displacement and the ore-body dip is linear. The geometrical morphology of ore-body has lager influence in the displacement distribution of backfill footwall. The mining operation in two sublevels at the same time could ease the stress concentration in mining void and make for the upper backfill stability. But this operation make the bottom backfill stress concentration more seriously.
The influence factors analysis of backfill stability is complicated. This study focus on the dip of ore-body, geometrical morphology and mining method. The numerical simulation results showed:the dip of ore-body not only influence the maximum value of backfill footwall displacement, but influence its location. The relation of maximum displacement and the ore-body dip is linear. The geometrical morphology of ore-body has lager influence in the displacement distribution of backfill footwall. The mining operation in two sublevels at the same time could ease the stress concentration in mining void and make for the upper backfill stability. But this operation make the bottom backfill stress concentration more seriously.
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