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Editor Work2015 Vol. 23, No. s1
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2015, 23(s1): 1-7.
Abstract
7298KB
To study the lining deformation characteristic of tunnel in cold region under the frost heaving force, a model test was designed, the model was made based on the surrounding rock and tunnel lining characteristic of the Balangshan Mountain, the low temperature environment in the tunnel of model was made by refrigeration equipment, the groundwater inside the model was frozen, the lining structure deformation characteristic under the frost heaving force was analyzed. The results show that the freezing temperature condition of model was satisfied after 5 day in the low temperature environment, the lining was distorted under the frost heaving force, the lining strain of the tunnel crown and side wall was greatly, the maximum strain is 122, and the lining strains of inverted arch and foot of wall was less, the minimum strain is 25.
To study the lining deformation characteristic of tunnel in cold region under the frost heaving force, a model test was designed, the model was made based on the surrounding rock and tunnel lining characteristic of the Balangshan Mountain, the low temperature environment in the tunnel of model was made by refrigeration equipment, the groundwater inside the model was frozen, the lining structure deformation characteristic under the frost heaving force was analyzed. The results show that the freezing temperature condition of model was satisfied after 5 day in the low temperature environment, the lining was distorted under the frost heaving force, the lining strain of the tunnel crown and side wall was greatly, the maximum strain is 122, and the lining strains of inverted arch and foot of wall was less, the minimum strain is 25.
2015, 23(s1): 8-15.
The eight key parametersof fuzzy setsplastic hardening model were used for the sensitivity analysis, which was based on the orthogonal test method. By using of the test data in U.S.CASE test database, such as seidsand, the expectation and variance of the parameters can be obtained after a lot of calculation and the adopting of mathematical statistics correlation theory. Through comparison, the key parameters have been sorted by sensitivity. The result shows that themethod provides necessary reference forthe selection of parameters of fuzzy setsplastic hardening model. Meanwhile, the method can be applied to the secondary development of the model in order to reduce workload in the process of parameters back analysis and screening.
The eight key parametersof fuzzy setsplastic hardening model were used for the sensitivity analysis, which was based on the orthogonal test method. By using of the test data in U.S.CASE test database, such as seidsand, the expectation and variance of the parameters can be obtained after a lot of calculation and the adopting of mathematical statistics correlation theory. Through comparison, the key parameters have been sorted by sensitivity. The result shows that themethod provides necessary reference forthe selection of parameters of fuzzy setsplastic hardening model. Meanwhile, the method can be applied to the secondary development of the model in order to reduce workload in the process of parameters back analysis and screening.
2015, 23(s1): 16-23.
Sodium montmorillonite is a layered clay mineral composed of hydrous aluminum silicate. The hydration and microscopic physical/mechanical properties of the mineral were investigated using a molecular dynamics simulation in the current study. After the model containing various water molecules of the sodium montmorillonite were developed, the crystal cell parameters and the various types of the energies before and after energy optimization were then analyzed. The changes in the volume and density with various water molecules and temperatures were also investigated. The hydration of the mineral was thereafter examined using the radial distribution function. The physical and mechanical properties of the mineral with various water molecules were further more explored. It shows that the shape of the unit cell of the sodium montmorillonite became much irregular after the energy optimization; the trosion energy increases, whereas other types of energies and the total energy decreased at different levels after the energy optimization; with the increase in water molecules, the volume and density of the mineral would increase and decrease respectively; as the surrounding temperature rose, the volume and density of the mineral would increase and decrease respectively; the hydration and mechanical properties of the mineral were much related to the number of water molecules.
Sodium montmorillonite is a layered clay mineral composed of hydrous aluminum silicate. The hydration and microscopic physical/mechanical properties of the mineral were investigated using a molecular dynamics simulation in the current study. After the model containing various water molecules of the sodium montmorillonite were developed, the crystal cell parameters and the various types of the energies before and after energy optimization were then analyzed. The changes in the volume and density with various water molecules and temperatures were also investigated. The hydration of the mineral was thereafter examined using the radial distribution function. The physical and mechanical properties of the mineral with various water molecules were further more explored. It shows that the shape of the unit cell of the sodium montmorillonite became much irregular after the energy optimization; the trosion energy increases, whereas other types of energies and the total energy decreased at different levels after the energy optimization; with the increase in water molecules, the volume and density of the mineral would increase and decrease respectively; as the surrounding temperature rose, the volume and density of the mineral would increase and decrease respectively; the hydration and mechanical properties of the mineral were much related to the number of water molecules.
2015, 23(s1): 24-30.
Based on the field measurement of the main fault of Longmenshan structral belt after the earthquake, the Radon concentration measurement's data is processed and analyzed, and three main faults' activities are compared. The result shows that the ratio of Radon viscosity's maximum and background value along the front fault is around 3.5～7.1, in which the ratio in the segment with surface rupture is 7.0～7.1, while the one without surface rupture ranges from 3.5 to 5.6; the ratio of central fracture and back range fracture are around 7.05～8.75 and 7.3 respectively. That means the central range fracture has the stronger activity than the others, which suggests that the seismic-fault of the earthquake is the central one and the other faults' movement were triggered by it. At the same time, the fault along the Tongji-Baishuihe bridge was stimulated by the central fracture, the ratio is 6.05.
Based on the field measurement of the main fault of Longmenshan structral belt after the earthquake, the Radon concentration measurement's data is processed and analyzed, and three main faults' activities are compared. The result shows that the ratio of Radon viscosity's maximum and background value along the front fault is around 3.5～7.1, in which the ratio in the segment with surface rupture is 7.0～7.1, while the one without surface rupture ranges from 3.5 to 5.6; the ratio of central fracture and back range fracture are around 7.05～8.75 and 7.3 respectively. That means the central range fracture has the stronger activity than the others, which suggests that the seismic-fault of the earthquake is the central one and the other faults' movement were triggered by it. At the same time, the fault along the Tongji-Baishuihe bridge was stimulated by the central fracture, the ratio is 6.05.
2015, 23(s1): 31-37.
Based on the data of ground temperature and deformation beneath embankment of the Qinghai-Tibet Railway in permafrost regions during the year 2006 to 2013, characteristics of thawed interlayer beneath the embankment and its effect on the embankment settlement deformation are studied. The results indicate that there is little thawed interlayer developed beneath natural field along the Qinghai-Tibet Railway, while beneath the embankment the thawed interlayer is developed widely, and it can be refrozen totally in the regions of lower mean annual ground temperature and developed further in the regions of higher mean annual ground temperature. The increasement of thickness of thawed interlayer in warm permafrost regions was duo to the decreasing of artificially permafrost table. Thawed interlayer is closely related to the embankment settlement deformation. The ice content of permafrost under the thawed interlayer controls the settlement deformation of embankment, the higher the ice content is, the bigger the settlement deformation is.
Based on the data of ground temperature and deformation beneath embankment of the Qinghai-Tibet Railway in permafrost regions during the year 2006 to 2013, characteristics of thawed interlayer beneath the embankment and its effect on the embankment settlement deformation are studied. The results indicate that there is little thawed interlayer developed beneath natural field along the Qinghai-Tibet Railway, while beneath the embankment the thawed interlayer is developed widely, and it can be refrozen totally in the regions of lower mean annual ground temperature and developed further in the regions of higher mean annual ground temperature. The increasement of thickness of thawed interlayer in warm permafrost regions was duo to the decreasing of artificially permafrost table. Thawed interlayer is closely related to the embankment settlement deformation. The ice content of permafrost under the thawed interlayer controls the settlement deformation of embankment, the higher the ice content is, the bigger the settlement deformation is.
2015, 23(s1): 38-43.
At-2.0℃and-5.0℃, a series of uniaxial compressive tests were conducted on frozen silty sand soil with different water contents on condition of various strain rates to analyze the influences of strain rate and water content on failure strain energy density of frozen soil. The testing results show that with strain rate increasing failure strain energy density increases nonlinearly at a slower rate and finally the affection becomes very little when strain rate is beyond 210-3s-1.However, the increase of water content makes failure strain energy density appear a decrease tendency in the late increase stage of strain rate. With moisture content increasing, firstly failure strain energy density increases sharply to a maximum and then decreases sharply to a minimum. Finally, the further increase of water content makes the failure strain energy density be basically equal to 0.05MPa. The mechanism of strength change is not totally coincident with the mechanism of failure strain energy density change.
At-2.0℃and-5.0℃, a series of uniaxial compressive tests were conducted on frozen silty sand soil with different water contents on condition of various strain rates to analyze the influences of strain rate and water content on failure strain energy density of frozen soil. The testing results show that with strain rate increasing failure strain energy density increases nonlinearly at a slower rate and finally the affection becomes very little when strain rate is beyond 210-3s-1.However, the increase of water content makes failure strain energy density appear a decrease tendency in the late increase stage of strain rate. With moisture content increasing, firstly failure strain energy density increases sharply to a maximum and then decreases sharply to a minimum. Finally, the further increase of water content makes the failure strain energy density be basically equal to 0.05MPa. The mechanism of strength change is not totally coincident with the mechanism of failure strain energy density change.
2015, 23(s1): 44-48.
Outwash deposits is located in the dagu station dam selection, the scale is huge, once the failure will directly affect the safety of dam construction. According to the field geological survey, analysis of Material composition and structure characteristics, the establishment of geological model, calculated its stability by limit equilibrium method, calculation results show that, outwash body as a whole is in a stable～basically stable state, the leading edge of the existence of local instability, to the dam site less affected, that can provide scientific basis to slope excavation and supporting.
Outwash deposits is located in the dagu station dam selection, the scale is huge, once the failure will directly affect the safety of dam construction. According to the field geological survey, analysis of Material composition and structure characteristics, the establishment of geological model, calculated its stability by limit equilibrium method, calculation results show that, outwash body as a whole is in a stable～basically stable state, the leading edge of the existence of local instability, to the dam site less affected, that can provide scientific basis to slope excavation and supporting.
2015, 23(s1): 49-56.
The Qinghai-Tibet Engineering Corridor(QTEC) is an important link between the inner China and Tibet, where several linear projects were located in. Since the fragility of ecology and warm, ice rich permafrost, the engineering geological conditions along QTEC are extremely sensitive to climate change and human activities. Based on the analysis of main influencing factors for engineering geological conditions of QTEC in permafrost regions, volumetric ice content, mean annual ground temperature, slope aspect, slope gradient and vegetation coverage were selected as assessment factors for evaluating engineering geological conditions along QTEC using Fuzzy C-means Clustering(FCM) and Analytic Hierarchy Process(AHP)methods. In this paper, Geographic Information System(GIS)was used to visualize the assessment results. According to the classification of FCM, the calculation results of AHP were classified into several grades. A comparison of the results from two methods showed that, in the permafrost regions with higher ice content, warmer ground temperature and higher slope gradient, engineering geological conditions are obviously poor. And these regions are mainly located at Kunlun Mountain, Chumar high plain, Wudaoliang Basin and Kaixinling Mountain. Evaluating results from the two methods showed a good agreement and the two methods can therefore effectively assess the engineering geological conditions of QTEC.
The Qinghai-Tibet Engineering Corridor(QTEC) is an important link between the inner China and Tibet, where several linear projects were located in. Since the fragility of ecology and warm, ice rich permafrost, the engineering geological conditions along QTEC are extremely sensitive to climate change and human activities. Based on the analysis of main influencing factors for engineering geological conditions of QTEC in permafrost regions, volumetric ice content, mean annual ground temperature, slope aspect, slope gradient and vegetation coverage were selected as assessment factors for evaluating engineering geological conditions along QTEC using Fuzzy C-means Clustering(FCM) and Analytic Hierarchy Process(AHP)methods. In this paper, Geographic Information System(GIS)was used to visualize the assessment results. According to the classification of FCM, the calculation results of AHP were classified into several grades. A comparison of the results from two methods showed that, in the permafrost regions with higher ice content, warmer ground temperature and higher slope gradient, engineering geological conditions are obviously poor. And these regions are mainly located at Kunlun Mountain, Chumar high plain, Wudaoliang Basin and Kaixinling Mountain. Evaluating results from the two methods showed a good agreement and the two methods can therefore effectively assess the engineering geological conditions of QTEC.
2015, 23(s1): 57-62.
With the development of the city, more and more projects go to the ground, to the underground space. There are more and more foundation pit projects, foundation pit engineering accidents also gradually appear. China's permafrost and seasonal frozen soil area is respectively 21.5% and 53.5% of the total land area. In theseareas, building foundation pits often damage by freezing and thawing cycle, causing great security hidden danger for foundation pit retaining structure safety in cold areas, putting forward a lot of new challenges to the research, design and construction units. Article based on the finite difference analysis software FLAC3D, using the flexibility of numerical simulation method, selecting of appropriate constitutive model, simulate the frost heave on the foundation pit.it is concluded that foundation pit temperature field variation law, law of supporting pile top displacement change with temperature, and puts forward several measures to reduce the displacement of pile body frost heave, to provide reference for design and construction of foundation pit supporting pile wintering in the future.
With the development of the city, more and more projects go to the ground, to the underground space. There are more and more foundation pit projects, foundation pit engineering accidents also gradually appear. China's permafrost and seasonal frozen soil area is respectively 21.5% and 53.5% of the total land area. In theseareas, building foundation pits often damage by freezing and thawing cycle, causing great security hidden danger for foundation pit retaining structure safety in cold areas, putting forward a lot of new challenges to the research, design and construction units. Article based on the finite difference analysis software FLAC3D, using the flexibility of numerical simulation method, selecting of appropriate constitutive model, simulate the frost heave on the foundation pit.it is concluded that foundation pit temperature field variation law, law of supporting pile top displacement change with temperature, and puts forward several measures to reduce the displacement of pile body frost heave, to provide reference for design and construction of foundation pit supporting pile wintering in the future.
2015, 23(s1): 63-69.
The year of 2010 is the extreme weather year when El Nio transferred into La Nia, and in this year most geological disasters happened extremely frequently in China. Statistics showed that the hazards concentrated in the southwest mountain areas of China, and the main hazards were the debris flows and landslides(including collapses).Drought happened in early 2010 and rainstorm occurred in rainy season, and the study about single case indicated that it was affected by the natural condition, the dominant factor of hazard was rarely quantitatively analyzed and indicated. In this paper, we coupled characteristic index of dry-wet cycle and the large-scale hazards in the southwest mountain areas of China and analyzed the influence factor of the disasters. Results indicated that 64 percent of the large-scale disasters in the research areas have a corresponding relationship with the drought in 2010, and the dry-wet cycle is one important factor to cause disasters. The influence of dry-wet cycle mainly reflects as follows: large numbers of cracks occurred with the happening of drought, then the rainfall infiltrated along the cracks which resulted in the decrease of resistance and the increase of both seepage pressure and sliding force.
The year of 2010 is the extreme weather year when El Nio transferred into La Nia, and in this year most geological disasters happened extremely frequently in China. Statistics showed that the hazards concentrated in the southwest mountain areas of China, and the main hazards were the debris flows and landslides(including collapses).Drought happened in early 2010 and rainstorm occurred in rainy season, and the study about single case indicated that it was affected by the natural condition, the dominant factor of hazard was rarely quantitatively analyzed and indicated. In this paper, we coupled characteristic index of dry-wet cycle and the large-scale hazards in the southwest mountain areas of China and analyzed the influence factor of the disasters. Results indicated that 64 percent of the large-scale disasters in the research areas have a corresponding relationship with the drought in 2010, and the dry-wet cycle is one important factor to cause disasters. The influence of dry-wet cycle mainly reflects as follows: large numbers of cracks occurred with the happening of drought, then the rainfall infiltrated along the cracks which resulted in the decrease of resistance and the increase of both seepage pressure and sliding force.
2015, 23(s1): 70-76.
Rock avalanche is characterized by complex kinematic process where drastic deformation and frequent collision with surrounding mountains of high-speed sliding rock mass may contribute to further dynamic fragmentation and progressive breakage of internal clastic rock fragments. It is of great significance to investigate the underlying mechanism of progressive breakage of rock fragments and its effects on macro deformation and mechanical behavior of sliding rock mass. This paper aims at the study of the progressive breakage failure of particle beds. Firstly, a series of confined compression tests were conducted on a type of spherical ceramic particle chosen to simulate quasi-brittle rock materials, and the comminution patterns and the mechanism behind were analyzed. Secondly, a three-dimensional numerical model was established which is capable of incorporating random deposition of spherical particles of prescribed size distribution and the frictional contact interaction between adjacent particles. The potential damage and fracture within a particle was simulated by a continuum damage material model. The test results demonstrate that tension splitting fracture dominates the size reduction performance of spherical particles under confined compression, and the variation of size distribution of the feed can mobilize different comminution patterns. The numerical results of particle breakage pattern compare favorably with the test results, and the numerical model can be extended for future applications in the progressive damage and disintegration behavior of particle assemblies made up of irregular rock fragments.
Rock avalanche is characterized by complex kinematic process where drastic deformation and frequent collision with surrounding mountains of high-speed sliding rock mass may contribute to further dynamic fragmentation and progressive breakage of internal clastic rock fragments. It is of great significance to investigate the underlying mechanism of progressive breakage of rock fragments and its effects on macro deformation and mechanical behavior of sliding rock mass. This paper aims at the study of the progressive breakage failure of particle beds. Firstly, a series of confined compression tests were conducted on a type of spherical ceramic particle chosen to simulate quasi-brittle rock materials, and the comminution patterns and the mechanism behind were analyzed. Secondly, a three-dimensional numerical model was established which is capable of incorporating random deposition of spherical particles of prescribed size distribution and the frictional contact interaction between adjacent particles. The potential damage and fracture within a particle was simulated by a continuum damage material model. The test results demonstrate that tension splitting fracture dominates the size reduction performance of spherical particles under confined compression, and the variation of size distribution of the feed can mobilize different comminution patterns. The numerical results of particle breakage pattern compare favorably with the test results, and the numerical model can be extended for future applications in the progressive damage and disintegration behavior of particle assemblies made up of irregular rock fragments.
2015, 23(s1): 77-83.
China is a big country of saline land, especially in the majority of the northern and western regions, the salinization of soil is much serious, which leads to significant deterioration in engineering properties of soil. To study the effect of soil salinity on shrinkage cracking, we prepare NaCl solution of concentration were 0, 1, 2, 3 moLL-1 respectively, then add the solution to soil stir saturated mud made the initial sample, the sample evaporation loss under simulated drought conditions, during the entire drying process measuring the moisture content of the sample timing change and use the camera to record the occurrence and evolution of fractures. The digital image processing system was used to quantitatively characterize the crack pattern, then the surface crack ratio, number of nodes, number of clods and fractal dimension is determined to describe surface cracking extent. The results show that the content of salt in the soil has an important impact on the dry shrinkage cracking process, with the increase of NaCl concentration, evaporation rate trends to decrease, and cracks appeared in the process of drying time delayed gradually, corresponding critical moisture content increases and the critical water content in the corresponding cracking rate increased. In addition, the development degree of fracture surface of specimen become lower with the increase of salt, as well as the crack width, length, fractal dimension, also with increasing salt concentration and decreasing. These phenomena related to the Interaction of salt-clay and the change of the electric double-layer.
China is a big country of saline land, especially in the majority of the northern and western regions, the salinization of soil is much serious, which leads to significant deterioration in engineering properties of soil. To study the effect of soil salinity on shrinkage cracking, we prepare NaCl solution of concentration were 0, 1, 2, 3 moLL-1 respectively, then add the solution to soil stir saturated mud made the initial sample, the sample evaporation loss under simulated drought conditions, during the entire drying process measuring the moisture content of the sample timing change and use the camera to record the occurrence and evolution of fractures. The digital image processing system was used to quantitatively characterize the crack pattern, then the surface crack ratio, number of nodes, number of clods and fractal dimension is determined to describe surface cracking extent. The results show that the content of salt in the soil has an important impact on the dry shrinkage cracking process, with the increase of NaCl concentration, evaporation rate trends to decrease, and cracks appeared in the process of drying time delayed gradually, corresponding critical moisture content increases and the critical water content in the corresponding cracking rate increased. In addition, the development degree of fracture surface of specimen become lower with the increase of salt, as well as the crack width, length, fractal dimension, also with increasing salt concentration and decreasing. These phenomena related to the Interaction of salt-clay and the change of the electric double-layer.
2015, 23(s1): 84-89.
The granite is a heterogeneous rock with the deformation and failure mechanism depending on the distributions and interactions of the meso compositions, including feldspar, quartz and biotite. The heterogeneity and macro-meso relation could be considered using the particle flow model in the current study. The test video images of the granite from Beishan were photographed during the uniaxial test. The conventional mineral recognition method and the grayscale threshold segmentation were then used together to get the actual distribution of each compositions in a frame extracted from the video images. The initial distributions were generated using the package FishTank of particle flow code in two-dimensions(PFC2D).The distribution of each composition was used to determine the types of particles in the initial locations. The interaction between compositions was characterized by the normal contact strengths between particles. The meso mechanical properties were determined by the macro mechanical properties. The particle flow model of granite based on the actual distributions was thereafter established. And the evolution of fissuring and force chain during the process of deformation and failure was discussed. It shows that the sum of squares of relative error between the simulated results and the actual ones is meet reliability requirements; the major fissuring generated in process of deformation and failure of granite was parallel to the direction of compressive stress; most of the fissuring was distributed in feldspar and was tensile fissuring; the evolvement of force chain network is in accordance with the process of deformation and failure of granite. The studied objects in the current study are the actual heterogeneous locations of the compositions in granite, it is reflect the substantive characteristics of petrographic composition and the presented results may be of great significance in investigating the macro-meso relations and forecast the process of deformation and failure for heterogeneous rock materials.
The granite is a heterogeneous rock with the deformation and failure mechanism depending on the distributions and interactions of the meso compositions, including feldspar, quartz and biotite. The heterogeneity and macro-meso relation could be considered using the particle flow model in the current study. The test video images of the granite from Beishan were photographed during the uniaxial test. The conventional mineral recognition method and the grayscale threshold segmentation were then used together to get the actual distribution of each compositions in a frame extracted from the video images. The initial distributions were generated using the package FishTank of particle flow code in two-dimensions(PFC2D).The distribution of each composition was used to determine the types of particles in the initial locations. The interaction between compositions was characterized by the normal contact strengths between particles. The meso mechanical properties were determined by the macro mechanical properties. The particle flow model of granite based on the actual distributions was thereafter established. And the evolution of fissuring and force chain during the process of deformation and failure was discussed. It shows that the sum of squares of relative error between the simulated results and the actual ones is meet reliability requirements; the major fissuring generated in process of deformation and failure of granite was parallel to the direction of compressive stress; most of the fissuring was distributed in feldspar and was tensile fissuring; the evolvement of force chain network is in accordance with the process of deformation and failure of granite. The studied objects in the current study are the actual heterogeneous locations of the compositions in granite, it is reflect the substantive characteristics of petrographic composition and the presented results may be of great significance in investigating the macro-meso relations and forecast the process of deformation and failure for heterogeneous rock materials.
STUDY ON THE ENGINEERING GEOLOGICAL CHARACTERISTICS AND GENESIS OF RED CLAY IN KARST AREA OF GUANGXI
2015, 23(s1): 90-96.
The geological genesis of red clay is the fundamental source of its special engineering characteristics. Based on analysis of Guangxi karst landscapes and distribution characteristics of the red clay, this paper chose 4 kinds of red clay in Guangxi karst area as the research objects to make an in-depth analysis of the engineering geological characteristics and genesis of red clay in karst area of Guangxi by field sampling, profile feature description, laboratory soil test and microscopic experiment. The research shows that:(1)The typical hot-humid climate and well-developed karst environment in Guangxi are beneficial to the formation of red clay.(2)Guangxi red clay has the general characteristics of red clay, such as the mineral component with kaolinte, illite, montmorillonite and thedouble pore structure with aggregate in the micro pore and particle mass pore.(3)It is the characteristics of Guangxi red clay from the surface to the bed rock that void ration, water content liquid limit, plasticity index, free swell and shrinkage increase gradually, while the density and dry density becomes smaller, and it shows obvious stratification.(4)Considering the geological genesis, the red clays from Guilin, Liuzhou and Wuming are residual red clays, and Laibin red clay is an alluvial red clay.
The geological genesis of red clay is the fundamental source of its special engineering characteristics. Based on analysis of Guangxi karst landscapes and distribution characteristics of the red clay, this paper chose 4 kinds of red clay in Guangxi karst area as the research objects to make an in-depth analysis of the engineering geological characteristics and genesis of red clay in karst area of Guangxi by field sampling, profile feature description, laboratory soil test and microscopic experiment. The research shows that:(1)The typical hot-humid climate and well-developed karst environment in Guangxi are beneficial to the formation of red clay.(2)Guangxi red clay has the general characteristics of red clay, such as the mineral component with kaolinte, illite, montmorillonite and thedouble pore structure with aggregate in the micro pore and particle mass pore.(3)It is the characteristics of Guangxi red clay from the surface to the bed rock that void ration, water content liquid limit, plasticity index, free swell and shrinkage increase gradually, while the density and dry density becomes smaller, and it shows obvious stratification.(4)Considering the geological genesis, the red clays from Guilin, Liuzhou and Wuming are residual red clays, and Laibin red clay is an alluvial red clay.
2015, 23(s1): 97-103.
Based on the statistical analysis of test values for the marine silt soil in the Hulushan bay at Changxing island, Dalian, the eigenvalues for all test indices were determined for this soil. By analyzing the depth-average values of the natural moisture content, 19 kinds of empirical relationships between the natural moisture content and test indices, were then established. This study revealed a regular relationship between the engineering properties indices and natural moisture content, and provided a theoretical basis for analysis and evaluation on engineering properties indices in this area.
Based on the statistical analysis of test values for the marine silt soil in the Hulushan bay at Changxing island, Dalian, the eigenvalues for all test indices were determined for this soil. By analyzing the depth-average values of the natural moisture content, 19 kinds of empirical relationships between the natural moisture content and test indices, were then established. This study revealed a regular relationship between the engineering properties indices and natural moisture content, and provided a theoretical basis for analysis and evaluation on engineering properties indices in this area.
2015, 23(s1): 104-109.
Based on the calcareous sand compaction experiments. Using glue after making the compaction of calcareous sand undisturbed samples. Using SEM to scan the sample and discuss the sample mesoscopic structure and the relationship between dry density. Results showed that the calcareous sand compaction curve can be divided into initial dry density drop zone, dry density increase and the decrease of the dry density of the secondary area three stages. Through the SEM images can be seen: The compaction of calcareous sand sample more than large particles formed after the skeletal structure, contact between particles of point-edge; the contact relationship between small particles for side-the side. The changes of the calcareous sand dry density of the compaction is the process of the changing process of pore between particles. Find out the control of the grain group was 0.1～0.25mm.
Based on the calcareous sand compaction experiments. Using glue after making the compaction of calcareous sand undisturbed samples. Using SEM to scan the sample and discuss the sample mesoscopic structure and the relationship between dry density. Results showed that the calcareous sand compaction curve can be divided into initial dry density drop zone, dry density increase and the decrease of the dry density of the secondary area three stages. Through the SEM images can be seen: The compaction of calcareous sand sample more than large particles formed after the skeletal structure, contact between particles of point-edge; the contact relationship between small particles for side-the side. The changes of the calcareous sand dry density of the compaction is the process of the changing process of pore between particles. Find out the control of the grain group was 0.1～0.25mm.
2015, 23(s1): 110-114.
The soil-water characteristic curve is one of the important curves describing unsaturated soil characteristics, measuring the curve precisely is one of the key to unsaturated soil mechanics. The influential factors and abnormal phenomenon in the test using GCTS-type soil-water characteristic curve(SWCC)device are investigated. The results show:(1)because the dry climate in lanzhou and long test time, the water loss caused by evaporation is dominant with the increasing of time, which affects the test results seriously. The evaporation for the instrument in Lanzhou city all the year round has been calibrated, which could be used to correct measurement results.(2)the ceramic plate is the core component of the instrument, directly affects the test time and test results, 5bar ceramic plate matches matrix suction of loess and shorten the test time; (3)the drying test could avoid pressure difference caused by the instrument structure, thus reduced experimental error. Based on the above conclusion, some suggestions and improving methods for SWCC test proposed.
The soil-water characteristic curve is one of the important curves describing unsaturated soil characteristics, measuring the curve precisely is one of the key to unsaturated soil mechanics. The influential factors and abnormal phenomenon in the test using GCTS-type soil-water characteristic curve(SWCC)device are investigated. The results show:(1)because the dry climate in lanzhou and long test time, the water loss caused by evaporation is dominant with the increasing of time, which affects the test results seriously. The evaporation for the instrument in Lanzhou city all the year round has been calibrated, which could be used to correct measurement results.(2)the ceramic plate is the core component of the instrument, directly affects the test time and test results, 5bar ceramic plate matches matrix suction of loess and shorten the test time; (3)the drying test could avoid pressure difference caused by the instrument structure, thus reduced experimental error. Based on the above conclusion, some suggestions and improving methods for SWCC test proposed.
2015, 23(s1): 115-120.
The interaction between pile and layered soil was investigated based on a project with pile foundations in Shanghai. The interaction between pile and soil was simulated using parallel-bonded model considering the layered distribution of the soils. The microscopic mechanical properties were characterized with seven parameters, including ball-ball contact modulus, ball stiffness ratio, frictional coefficient of the particles, parallel-bond modulus, parallel-bond stiffness ratio, parallel-bond normal strength, parallel-bond shear strength. The bond strength and stiffness ratio were determined based on the cohesion and compression modulus of the soils. The microscopic parameters were calibrated based on the in-situ load-displacement curve. The two-dimensional particle flow code in simulating the interaction between pile and soil was developed. The interaction between pile and soil particles and movement features of particles were thereafter explored. It shows that the moving features were different in different soil layers; the displacements of clay particles were greater than those of the sand ones; the contact force between pile and soil particles were different in different soil layers, and the contact forces in sand were greater because of its greater friction coefficient and stiffness; the force chain propagated mainly along the normal direction. These results are referable in investigating the load transfer mechanism of piles in layered soil under external loads.
The interaction between pile and layered soil was investigated based on a project with pile foundations in Shanghai. The interaction between pile and soil was simulated using parallel-bonded model considering the layered distribution of the soils. The microscopic mechanical properties were characterized with seven parameters, including ball-ball contact modulus, ball stiffness ratio, frictional coefficient of the particles, parallel-bond modulus, parallel-bond stiffness ratio, parallel-bond normal strength, parallel-bond shear strength. The bond strength and stiffness ratio were determined based on the cohesion and compression modulus of the soils. The microscopic parameters were calibrated based on the in-situ load-displacement curve. The two-dimensional particle flow code in simulating the interaction between pile and soil was developed. The interaction between pile and soil particles and movement features of particles were thereafter explored. It shows that the moving features were different in different soil layers; the displacements of clay particles were greater than those of the sand ones; the contact force between pile and soil particles were different in different soil layers, and the contact forces in sand were greater because of its greater friction coefficient and stiffness; the force chain propagated mainly along the normal direction. These results are referable in investigating the load transfer mechanism of piles in layered soil under external loads.
2015, 23(s1): 121-126.
About 292km of the passenger and cargo railway line from Changchun to Baicheng in northeastern China passes through the western region of Jilin Province, and special soil exists in this area. There are liquefaction soil, soft soil, saline soil, seasonally frozen soil and other special soil in this region. According to the investigation of the railway line, the soft soil and the seasonally frozen soil exist along the whole line, the saline soil exists along the line from Songyuan to Baicheng, and the liquefaction soil exists in this area from Songhua to Daan. The seasonally frozen soil is very sensitive to the change of temperature, and the liquefaction soil is prone to the phenomenon of sand liquefaction under the actions of dynamic loads and earthquake. The soft soil has features of high water content, large void ratio, high compressibility and poor permeability. The saline soil has moisture, leaching, subsidence, erosion, swelling and other features. These special soil will decrease the strength of the roadbed, resulting in roadbed subsidence, uneven settlement and other hazards, and they impact on the railway's design and construction. To service the engineering practice, combined with the actual of the engineering, the distribution and engineering characteristics of these special soil were analysised on basis of the requirements of railway project, then appropriate measures for the treatment of the ground and approaches of strengthening the foundation were proposed.
About 292km of the passenger and cargo railway line from Changchun to Baicheng in northeastern China passes through the western region of Jilin Province, and special soil exists in this area. There are liquefaction soil, soft soil, saline soil, seasonally frozen soil and other special soil in this region. According to the investigation of the railway line, the soft soil and the seasonally frozen soil exist along the whole line, the saline soil exists along the line from Songyuan to Baicheng, and the liquefaction soil exists in this area from Songhua to Daan. The seasonally frozen soil is very sensitive to the change of temperature, and the liquefaction soil is prone to the phenomenon of sand liquefaction under the actions of dynamic loads and earthquake. The soft soil has features of high water content, large void ratio, high compressibility and poor permeability. The saline soil has moisture, leaching, subsidence, erosion, swelling and other features. These special soil will decrease the strength of the roadbed, resulting in roadbed subsidence, uneven settlement and other hazards, and they impact on the railway's design and construction. To service the engineering practice, combined with the actual of the engineering, the distribution and engineering characteristics of these special soil were analysised on basis of the requirements of railway project, then appropriate measures for the treatment of the ground and approaches of strengthening the foundation were proposed.
2015, 23(s1): 127-131.
The collapsible loess has a large compressibility and a low strength. It often produces a larger settlement when the subgrade is built on it, and the rain often leads to subgrade subsidence and other subgrade diseases, which has seriously affected the construction of the railway. In order to prevent subgrade subsidence of loess, Hejin to Sanmenxia DK531+702.50～DK532+006.13 of one railway is taken as the test road section to study grain composition, physical-mechanical property and soluble salt composition analysis. It is concluded that the physical-mechanical property of the loess affccts the collapsible damage of loess roadbed deformation. Due to the high silt content in the loess, collapsibility may happen at a low moisture content; the subgrade subsidence of loess roadbed is mainly caused by tremendous variety of cohesion, while angle of internal friction has no distinct variety. Foundation treatment method and drainage measure are put forward combining with the engineering geological properties of the research section, which provides a basis for preventing and curing the subgrade diseases of loess roadbed.
The collapsible loess has a large compressibility and a low strength. It often produces a larger settlement when the subgrade is built on it, and the rain often leads to subgrade subsidence and other subgrade diseases, which has seriously affected the construction of the railway. In order to prevent subgrade subsidence of loess, Hejin to Sanmenxia DK531+702.50～DK532+006.13 of one railway is taken as the test road section to study grain composition, physical-mechanical property and soluble salt composition analysis. It is concluded that the physical-mechanical property of the loess affccts the collapsible damage of loess roadbed deformation. Due to the high silt content in the loess, collapsibility may happen at a low moisture content; the subgrade subsidence of loess roadbed is mainly caused by tremendous variety of cohesion, while angle of internal friction has no distinct variety. Foundation treatment method and drainage measure are put forward combining with the engineering geological properties of the research section, which provides a basis for preventing and curing the subgrade diseases of loess roadbed.
2015, 23(s1): 132-139.
In order to apply reliability theory in cutting loess slope design, 510 natural critical loess slope sections in the eight regions in loess plateau were investigated and the relationship between the slope heights and widths was regressed in each region. Considering the factor of safety as 1.0 with the profile of the regressed relation, comprehensive shear strength parameters c、 are reversed against different slope heights. Morgenstern-Price method was used to build limit state equation as well as Monte-Carlo method was used to simulate probability of failure against the reversed shearing strength and statistical results from 79groups of c、 coefficient of variations. Then the relations of the loess high slope probability of failure, factor of safety and coefficient of variations are showed systemically and the reliability criteria for loess cutting slope is proposed. The failure probability of cutting loess slopes should lower than 8.0%for express way and first grade highway as well as within 15.0% for second grade highway and lower ones. The factor of safety and the probability of failure have their own advantage respectively. Therefore, combining both of them is the better choice in assessment of slope stability in loess area where geo-hazards occur frequently.
In order to apply reliability theory in cutting loess slope design, 510 natural critical loess slope sections in the eight regions in loess plateau were investigated and the relationship between the slope heights and widths was regressed in each region. Considering the factor of safety as 1.0 with the profile of the regressed relation, comprehensive shear strength parameters c、 are reversed against different slope heights. Morgenstern-Price method was used to build limit state equation as well as Monte-Carlo method was used to simulate probability of failure against the reversed shearing strength and statistical results from 79groups of c、 coefficient of variations. Then the relations of the loess high slope probability of failure, factor of safety and coefficient of variations are showed systemically and the reliability criteria for loess cutting slope is proposed. The failure probability of cutting loess slopes should lower than 8.0%for express way and first grade highway as well as within 15.0% for second grade highway and lower ones. The factor of safety and the probability of failure have their own advantage respectively. Therefore, combining both of them is the better choice in assessment of slope stability in loess area where geo-hazards occur frequently.
2015, 23(s1): 140-144.
The earthquake engineering geological condition in the Suqian city is controlled by Tanlu faults. Three standard holes are drilled in the region to study Quaternary strata in the region. And the shear wave velocity is also tested in the borehole. Much related data are also formed in the procedure of Seismic Microzoning and seismic safety evaluation for important buildings. These data show that the shear wave velocity related to depth and deposited ages of sediments. The typical values of dynamic shear modulus ratio G/Gmax- and damping ratio - in the stratum are also list in the paper.
The earthquake engineering geological condition in the Suqian city is controlled by Tanlu faults. Three standard holes are drilled in the region to study Quaternary strata in the region. And the shear wave velocity is also tested in the borehole. Much related data are also formed in the procedure of Seismic Microzoning and seismic safety evaluation for important buildings. These data show that the shear wave velocity related to depth and deposited ages of sediments. The typical values of dynamic shear modulus ratio G/Gmax- and damping ratio - in the stratum are also list in the paper.
2015, 23(s1): 145-150.
Ground fissure and land subsidence are usually caused by soil mass deformation, which may occur in region of groundwater depression cone formed by overexploitation of groundwater. Soil deformation process is irreversible. It is extremely difficult for deformed soil to restore. Therefore, predicting soil deformation is one of the main researching contents for preventing and controlling ground fissure and land subsidence. In the north China plain, groundwater overexploitation is a very serious problem. A series of environmental geological problems(i.e, ground fissures, and land subsidence) have been caused by the overexploitation of groundwater in the North China Plain. It is very important for researchers to study soil deformation in region of groundwater depression cone in the north China plain. Soil mechanics experiments were carried out with different depths and different soils collected from Shijiazhuang and Hengshui in the north China plain where groundwater were overexploited heavily, and where groundwater depression cone have formed. The results show that the relationship among different soil deformations is clay soils silty clay soils sandy soils; the deeper buried soils are easier to occur deformation; Deformation of shallow clay is increasing with colloidal particles content increasing; Deformation process of deep silty clay is divided into fast and slow-steady two stages. This study of soil deformation has a guiding significance for land subsidence prediction in the North China plain.
Ground fissure and land subsidence are usually caused by soil mass deformation, which may occur in region of groundwater depression cone formed by overexploitation of groundwater. Soil deformation process is irreversible. It is extremely difficult for deformed soil to restore. Therefore, predicting soil deformation is one of the main researching contents for preventing and controlling ground fissure and land subsidence. In the north China plain, groundwater overexploitation is a very serious problem. A series of environmental geological problems(i.e, ground fissures, and land subsidence) have been caused by the overexploitation of groundwater in the North China Plain. It is very important for researchers to study soil deformation in region of groundwater depression cone in the north China plain. Soil mechanics experiments were carried out with different depths and different soils collected from Shijiazhuang and Hengshui in the north China plain where groundwater were overexploited heavily, and where groundwater depression cone have formed. The results show that the relationship among different soil deformations is clay soils silty clay soils sandy soils; the deeper buried soils are easier to occur deformation; Deformation of shallow clay is increasing with colloidal particles content increasing; Deformation process of deep silty clay is divided into fast and slow-steady two stages. This study of soil deformation has a guiding significance for land subsidence prediction in the North China plain.
2015, 23(s1): 151-158.
Jurassic formationand Cretaceous formation are widely distributed in Panxi region. The engineering geological property of red bed is bad and red bed is main sliding-prone stratum. Massive landslides develop in Panxi red bed region, its harm is serious. Large-scale landslides are easy to block rive, induce serious secondary damage. Based on the investigation of large-scale landslide, the paper systemically analyzed failure mode of large-scale landslides and it can supply theoretical support for landslide forecasting and prevention in Panxi red bed region. Through the research, we found that large-scale landslide development is significantly affected by geological structure. The favorable combination of structure planes and primarybedding surfaces lays a foundation for landslide, it controls failure mode of large-scale landslides. According to the characteristic of slope form, this paper divides failure mode of large-scale landslides in Panxi red bed region into three types, namely, consequent sliding, oblique sliding, cuneiform sliding.
Jurassic formationand Cretaceous formation are widely distributed in Panxi region. The engineering geological property of red bed is bad and red bed is main sliding-prone stratum. Massive landslides develop in Panxi red bed region, its harm is serious. Large-scale landslides are easy to block rive, induce serious secondary damage. Based on the investigation of large-scale landslide, the paper systemically analyzed failure mode of large-scale landslides and it can supply theoretical support for landslide forecasting and prevention in Panxi red bed region. Through the research, we found that large-scale landslide development is significantly affected by geological structure. The favorable combination of structure planes and primarybedding surfaces lays a foundation for landslide, it controls failure mode of large-scale landslides. According to the characteristic of slope form, this paper divides failure mode of large-scale landslides in Panxi red bed region into three types, namely, consequent sliding, oblique sliding, cuneiform sliding.
2015, 23(s1): 159-165.
Soft soil foundation is characterized mainly for low bearing capacity, large deformation, especially non-uniform deformation. The deformation stability can last for a few years or even decades. After the bridge foundation built in soft soil is completed, the place such as bridge foundation, subgrade, et al.appear significant differential settlement, and cause structural crack damage and tilt. Therefore, one overpass bridge foundation for soft soil was chosen in southwest China as the research object. The detailed geological investigation was conducted in study area. Physical and mechanical properties of the soil and the mineral and chemical composition in soft soil areas were measured and analyzed to obtain the soft foundation engineering characteristics and provide valuable reference for practical engineering. The conclusions and suggestions are expected to be applied to other road construction in soft soil district in southwest China.
Soft soil foundation is characterized mainly for low bearing capacity, large deformation, especially non-uniform deformation. The deformation stability can last for a few years or even decades. After the bridge foundation built in soft soil is completed, the place such as bridge foundation, subgrade, et al.appear significant differential settlement, and cause structural crack damage and tilt. Therefore, one overpass bridge foundation for soft soil was chosen in southwest China as the research object. The detailed geological investigation was conducted in study area. Physical and mechanical properties of the soil and the mineral and chemical composition in soft soil areas were measured and analyzed to obtain the soft foundation engineering characteristics and provide valuable reference for practical engineering. The conclusions and suggestions are expected to be applied to other road construction in soft soil district in southwest China.
2015, 23(s1): 166-166.
In mountainous areas, rockfall happens suddenly and occurs frequently, with the diverse kinematic characteristics such as free fall, sliding, rolling and projectile motion and the stochastic characteristics. Due to the diversity of factors, random motion and uncertainty in the study, it is still a big problem that how to predicate rockfall characteristics accurately. The problem leads to the truth that calculated results could not match the actual characteristics, and further leads to the phenomenon that countermeasures failed to prevent rockfall and rockfall disaster occurred often. Based on the summary of rockfall run-out calculation approaches in the past, we analyzed the applicability of different methods. Combing with case analysis, we found much uncertainty in rockfall study including cognitive uncertainty and random uncertainty. We proposed the idea that: the establishment of uncertainty view, theory and approaches in rockfall study is one of effective ways to promote the development of scientific prediction and prevention for rockfall. The study would provide reference for selection of appropriate rockfall calculation method and reasonable decision for rockfall prevention and mitigation.
In mountainous areas, rockfall happens suddenly and occurs frequently, with the diverse kinematic characteristics such as free fall, sliding, rolling and projectile motion and the stochastic characteristics. Due to the diversity of factors, random motion and uncertainty in the study, it is still a big problem that how to predicate rockfall characteristics accurately. The problem leads to the truth that calculated results could not match the actual characteristics, and further leads to the phenomenon that countermeasures failed to prevent rockfall and rockfall disaster occurred often. Based on the summary of rockfall run-out calculation approaches in the past, we analyzed the applicability of different methods. Combing with case analysis, we found much uncertainty in rockfall study including cognitive uncertainty and random uncertainty. We proposed the idea that: the establishment of uncertainty view, theory and approaches in rockfall study is one of effective ways to promote the development of scientific prediction and prevention for rockfall. The study would provide reference for selection of appropriate rockfall calculation method and reasonable decision for rockfall prevention and mitigation.
2015, 23(s1): 173-178.
The distribution of laggings' earth pressure between supporting piles is one of the key problems should be considered during design. Based on the loads transfer relationship in the pile and lagging system, this paper presents a compound retaining structure between two adjacent supporting piles which contains a flexible load reduction cushion between soil and laggings. A finite-difference model of the compound retaining structure is established by FLAC3D, by which both the load reduction effects and the influential factors of the flexible cushion were analyzed. The results show that the flexible cushion can effectively reduce the earth pressure acting on the laggings. The load reduction effect is more significant when the elastic modulus of the flexible cushion is smaller or the thickness of the flexible cushion is larger.
The distribution of laggings' earth pressure between supporting piles is one of the key problems should be considered during design. Based on the loads transfer relationship in the pile and lagging system, this paper presents a compound retaining structure between two adjacent supporting piles which contains a flexible load reduction cushion between soil and laggings. A finite-difference model of the compound retaining structure is established by FLAC3D, by which both the load reduction effects and the influential factors of the flexible cushion were analyzed. The results show that the flexible cushion can effectively reduce the earth pressure acting on the laggings. The load reduction effect is more significant when the elastic modulus of the flexible cushion is smaller or the thickness of the flexible cushion is larger.
2015, 23(s1): 179-183.
When vacuum preloading is performed on soft soil, changes in particle aggregates, void sizes and microstructure directly influence the consolidation process of the soft soil. In this paper, the marine soft soil sampling from south China coastal was adopted in the research.laboratory small-scale tests and scanning electron microscopy(SEM)tests were conducted to investigated the drainage mechanism of the soft soil. In addition, the fractal method was used to simulate evolution process of the drainage channels in the soft soil. In the initial stage of vacuum preloading, the drainage channels were developed and water was strongly attracted by vacuum suction. Therefore, the drainage channels could be deemed as straight pipes. In the subsequent stage, drainage channels shrank, enhancing the influence of soil particle adsorption. The water flow carrying tiny soil particles might be slowed down, leading to a higher adsorbed water content.the viscosity of adsorbed water and adsorb ability of fine particles gradually caused the blockage in drainage channels. At last, the drainage channels narrowed(even closed) and formed a mutually staggered grid. The soil showed obvious anisotropy and heterogeneity. Drainage process of the soft soil under vacuum preloading is essentially the process of the block up of the original drainage channels, followed by the formation of new drainage channels. A depth research in of microstructural change of soft soil in the reinforcement is advantageous for safe construction and operation of the engineering structure on the soft soil.
When vacuum preloading is performed on soft soil, changes in particle aggregates, void sizes and microstructure directly influence the consolidation process of the soft soil. In this paper, the marine soft soil sampling from south China coastal was adopted in the research.laboratory small-scale tests and scanning electron microscopy(SEM)tests were conducted to investigated the drainage mechanism of the soft soil. In addition, the fractal method was used to simulate evolution process of the drainage channels in the soft soil. In the initial stage of vacuum preloading, the drainage channels were developed and water was strongly attracted by vacuum suction. Therefore, the drainage channels could be deemed as straight pipes. In the subsequent stage, drainage channels shrank, enhancing the influence of soil particle adsorption. The water flow carrying tiny soil particles might be slowed down, leading to a higher adsorbed water content.the viscosity of adsorbed water and adsorb ability of fine particles gradually caused the blockage in drainage channels. At last, the drainage channels narrowed(even closed) and formed a mutually staggered grid. The soil showed obvious anisotropy and heterogeneity. Drainage process of the soft soil under vacuum preloading is essentially the process of the block up of the original drainage channels, followed by the formation of new drainage channels. A depth research in of microstructural change of soft soil in the reinforcement is advantageous for safe construction and operation of the engineering structure on the soft soil.
2015, 23(s1): 184-188.
Engineering characteristics of Dhaka soft clay in Bangladesh were summarized, by analyzing the a large number of experimental data. Meanwhile the main engineering geology problems of Dhaka soft clay were discussed. Aiming at the engineering characteristics of Dhaka soft clay and main engineering geological problems, finally introduced the suitable ground treatment method for dhaka alluvium soft clay.
Engineering characteristics of Dhaka soft clay in Bangladesh were summarized, by analyzing the a large number of experimental data. Meanwhile the main engineering geology problems of Dhaka soft clay were discussed. Aiming at the engineering characteristics of Dhaka soft clay and main engineering geological problems, finally introduced the suitable ground treatment method for dhaka alluvium soft clay.
2015, 23(s1): 189-192.
Most of the Bengal delta is composed of alluvium of various geological age, thickness of alluvial layer is bigger, the sedimentary environment is complex, geotechnical variety, uneven distribution. In order to find out the site engineering geological conditions, using the drilling, standard penetration test, static cone penetration test, loading test, water injection test and Laboratory test and so on.the basic geological conditions of Dasherkandi sewage treatment plant are introduced in this paper, foundation soil suggestion value is given on the basis of statistical analysis of test results, and detailed analysis and evaluation of the project the main geotechnical problems.
Most of the Bengal delta is composed of alluvium of various geological age, thickness of alluvial layer is bigger, the sedimentary environment is complex, geotechnical variety, uneven distribution. In order to find out the site engineering geological conditions, using the drilling, standard penetration test, static cone penetration test, loading test, water injection test and Laboratory test and so on.the basic geological conditions of Dasherkandi sewage treatment plant are introduced in this paper, foundation soil suggestion value is given on the basis of statistical analysis of test results, and detailed analysis and evaluation of the project the main geotechnical problems.
2015, 23(s1): 193-199.
On the basis of experiment measured hydrodynamic parameters on Guilin and Liuzhou lateritic soil, the solute transport process of the two lateritic soils are analyzed, for the purpose of indentifying the effect of hydrodynamic parameters. The results show that Guilin lateritic soil, which contains more quartz, exhibiting higher volume water content and lower hydraulic conductivity at the same suction, has better water holding capacity than Liuzhou lateritic soil. According to the solute transport theory, the 1-D concentration distributions in the two lateritic soils are simulated at four level of initial saturation 95%, 90%, 85%, 80%.With the initial saturation decreasing, solute diffusion depth of Liuzhou lateritic soil increases, while diffusion depth of Guilin lateritic soil become small at the 85%saturation, indicating the relationship between diffusion depth and initial saturation in Liuzhou lateritic soil is not applicable to Guilin lateritic soil. The process of seepage in unsaturated soil is controlled by the dual factors of suction and permeability. For Guilin lateritic soil, its low permeability becomes major governing factor as the saturation decreasing because the reduction of permeability surpasses the increases of suction gradient, resulting in the velocity of fluid. However, the hydraulic conductivity of Liuzhou lateritic soil has small change with the variation of initial saturation, indicating the unsaturated seepage dominated by suction gradient.
On the basis of experiment measured hydrodynamic parameters on Guilin and Liuzhou lateritic soil, the solute transport process of the two lateritic soils are analyzed, for the purpose of indentifying the effect of hydrodynamic parameters. The results show that Guilin lateritic soil, which contains more quartz, exhibiting higher volume water content and lower hydraulic conductivity at the same suction, has better water holding capacity than Liuzhou lateritic soil. According to the solute transport theory, the 1-D concentration distributions in the two lateritic soils are simulated at four level of initial saturation 95%, 90%, 85%, 80%.With the initial saturation decreasing, solute diffusion depth of Liuzhou lateritic soil increases, while diffusion depth of Guilin lateritic soil become small at the 85%saturation, indicating the relationship between diffusion depth and initial saturation in Liuzhou lateritic soil is not applicable to Guilin lateritic soil. The process of seepage in unsaturated soil is controlled by the dual factors of suction and permeability. For Guilin lateritic soil, its low permeability becomes major governing factor as the saturation decreasing because the reduction of permeability surpasses the increases of suction gradient, resulting in the velocity of fluid. However, the hydraulic conductivity of Liuzhou lateritic soil has small change with the variation of initial saturation, indicating the unsaturated seepage dominated by suction gradient.
2015, 23(s1): 200-204.
Waste rubber chips bring a lot of pressure to the environment. Some researches have been done for improving the properties of soil with rubber particles in engineering. Several specimens of rubber-sands mixtures with different sands percentage composition were made and consolidation tests were done to explore the compression properties of mixtures influenced by rubber particles. The tests results were that the density curves and the stress-strain curves of the specimens with different sands fraction were presented. It was found that the density of specimens increases with the sands fraction increases approximately linearly. The specimens with a lower sands fraction are more compressible and show a larger residual deformation. The Es of specimens develops with the sands fraction increases and it grows much faster when the sands fraction is higher than 60%.
Waste rubber chips bring a lot of pressure to the environment. Some researches have been done for improving the properties of soil with rubber particles in engineering. Several specimens of rubber-sands mixtures with different sands percentage composition were made and consolidation tests were done to explore the compression properties of mixtures influenced by rubber particles. The tests results were that the density curves and the stress-strain curves of the specimens with different sands fraction were presented. It was found that the density of specimens increases with the sands fraction increases approximately linearly. The specimens with a lower sands fraction are more compressible and show a larger residual deformation. The Es of specimens develops with the sands fraction increases and it grows much faster when the sands fraction is higher than 60%.
2015, 23(s1): 205-212.
Shear wave velocity is the important factor in seafloor acoustics, and the essential parameter in marine engineering geological exploration, which has close relationship with sediment physical properties. Samples were collected from Jiaozhou Bay to conduct shear wave velocity measurement by bender element system, and construct the correlation between shear wave velocity and frequency dispersion and physical parameters. Results present that shear wave velocity ranges from 26.5 to 103.5ms-1 at the frequency from 250Hz to 2000Hz; sandy sediment was characterized by the maximum shear wave velocity, silty sediment took second place, and clayed sediment and silty clay sediment has the low shear wave velocity; obvious frequency dispersion is found at the measuring frequency of shear wave velocity, and logarithmic growth function can describe the relationship between shear wave velocity and measuring frequency; dispersion factor ranges from 0.3 to 31.1, and PFE(percent frequency effect) ranges from 1.1%to 103.8%, which is affected by sediment types; hypo-two function can describe the relationship between shear wave velocity, dispersion factor, PFE and sediment physical parameters with different correlation degree but consistent variation trend; comparatively speaking, it is obvious low for the correlation degree between PFE and sediment physical parameters.
Shear wave velocity is the important factor in seafloor acoustics, and the essential parameter in marine engineering geological exploration, which has close relationship with sediment physical properties. Samples were collected from Jiaozhou Bay to conduct shear wave velocity measurement by bender element system, and construct the correlation between shear wave velocity and frequency dispersion and physical parameters. Results present that shear wave velocity ranges from 26.5 to 103.5ms-1 at the frequency from 250Hz to 2000Hz; sandy sediment was characterized by the maximum shear wave velocity, silty sediment took second place, and clayed sediment and silty clay sediment has the low shear wave velocity; obvious frequency dispersion is found at the measuring frequency of shear wave velocity, and logarithmic growth function can describe the relationship between shear wave velocity and measuring frequency; dispersion factor ranges from 0.3 to 31.1, and PFE(percent frequency effect) ranges from 1.1%to 103.8%, which is affected by sediment types; hypo-two function can describe the relationship between shear wave velocity, dispersion factor, PFE and sediment physical parameters with different correlation degree but consistent variation trend; comparatively speaking, it is obvious low for the correlation degree between PFE and sediment physical parameters.
2015, 23(s1): 213-217.
In this paper, we do it for the loess which come from a selected embankment of Shenhe highway. With the consolidation undrained triaxial tests of controlled suction, we do it to study the law of matric suction for the effective stress strength index c and .The deformation of the selected embankment is studied by finite element analysis under the certain suction. The results showed that: the change of strength index c is obvious with the increasing matric suction. The change of strength index is not obvious with the increasing matric suction. With the increasing of matric suction, the loess strength become greater, the vertical deformation reduced slightly under certain vehicle load. The stability of embankment will improve. The conclusion of the study have certain reference significance to the actual engineering.
In this paper, we do it for the loess which come from a selected embankment of Shenhe highway. With the consolidation undrained triaxial tests of controlled suction, we do it to study the law of matric suction for the effective stress strength index c and .The deformation of the selected embankment is studied by finite element analysis under the certain suction. The results showed that: the change of strength index c is obvious with the increasing matric suction. The change of strength index is not obvious with the increasing matric suction. With the increasing of matric suction, the loess strength become greater, the vertical deformation reduced slightly under certain vehicle load. The stability of embankment will improve. The conclusion of the study have certain reference significance to the actual engineering.
2015, 23(s1): 218-222.
By carrying out the laboratory shear tests of the different moisture content, in-situ shear and deformation tests. The results show that the sand stratum prones to disintegration and the shear strength is reducted along with the increase of the moisture content of specimens. Under the natural moisture content, the value of the laboratory shear strength is slightly higher than that of the in-situ test. The cohesive force are 0.160MPa and 0.157MPa individually. The internal friction angle are 37.8 and 36.4 individually. The in situ test results can be used to optimizing the design of the project. The uniformity of sand soil in working area is comparatively well and the deference of two modulus test values is small. The mean value of deformation modulus and Young's modulus are 122MPa and 242MPa individually.
By carrying out the laboratory shear tests of the different moisture content, in-situ shear and deformation tests. The results show that the sand stratum prones to disintegration and the shear strength is reducted along with the increase of the moisture content of specimens. Under the natural moisture content, the value of the laboratory shear strength is slightly higher than that of the in-situ test. The cohesive force are 0.160MPa and 0.157MPa individually. The internal friction angle are 37.8 and 36.4 individually. The in situ test results can be used to optimizing the design of the project. The uniformity of sand soil in working area is comparatively well and the deference of two modulus test values is small. The mean value of deformation modulus and Young's modulus are 122MPa and 242MPa individually.
2015, 23(s1): 223-228.
Loose sediments with a gentle-inclined impermeable base are widespread in nature. Therefore studies of seepage flows in this kind of sedimentary formation is of critical importance in many hydraulic engineering practices. The most famous analytical solution for this problem is Pavlovskii's method. However it is only applicable to the aquifer of a small slope angle and a small head difference between two boundaries because of its assumption that the divergence angle flow lines should be small. This paper presents a new analytical method for an aquifer with a downward-and counter-sloping base. An appropriate coordinate system was first chosen to divide the aquifer into two parts, one above and another below the x axis. A total differential equation was derived according to equivalent flux across the interface between two parts and the principle of mass conservation(continuity).Analytical solution was then obtained by solving the total differential equation with specified boundary conditions. The method was used in four examples taken from literatures. The results were compared with Pavlovskii's solutions. The discharge is almost identical, but the difference of phreatic surfaces between two methods increases as the slope angle rises and the head difference become larger(expressed as hydraulic slope, related to the divergence and convergence angles of streamlines).Based on analysis of hydraulic mechanisms, the new method presented in this paper provides higher accuracy for calculating phreatic surface than the Pavlovskii's method. It can also be applied to an aquifer with a higher slope angle of the base and greater head difference between boundaries(affecting convergence and divergence angles of streamlines).
Loose sediments with a gentle-inclined impermeable base are widespread in nature. Therefore studies of seepage flows in this kind of sedimentary formation is of critical importance in many hydraulic engineering practices. The most famous analytical solution for this problem is Pavlovskii's method. However it is only applicable to the aquifer of a small slope angle and a small head difference between two boundaries because of its assumption that the divergence angle flow lines should be small. This paper presents a new analytical method for an aquifer with a downward-and counter-sloping base. An appropriate coordinate system was first chosen to divide the aquifer into two parts, one above and another below the x axis. A total differential equation was derived according to equivalent flux across the interface between two parts and the principle of mass conservation(continuity).Analytical solution was then obtained by solving the total differential equation with specified boundary conditions. The method was used in four examples taken from literatures. The results were compared with Pavlovskii's solutions. The discharge is almost identical, but the difference of phreatic surfaces between two methods increases as the slope angle rises and the head difference become larger(expressed as hydraulic slope, related to the divergence and convergence angles of streamlines).Based on analysis of hydraulic mechanisms, the new method presented in this paper provides higher accuracy for calculating phreatic surface than the Pavlovskii's method. It can also be applied to an aquifer with a higher slope angle of the base and greater head difference between boundaries(affecting convergence and divergence angles of streamlines).
2015, 23(s1): 229-234.
There are regional faults in the Yanzi gully basin, adverse geological phenomena development, such as debris flow, landslides and collapse, which debris flow is more serious. There have been many serious debris flow disasters in history, inflicted major economic losses. On the basis of Engineering Surveying and mapping, analyzed the characteristics of debris flow source in the study area, to evaluate the loose material distribution and stability assessment of Yanzi gully, estimated the loose material total reserves. In order to predict the occurrence of debris flow when the maximum amount of the material may be out of there, Combined with the study area topography, hydrology and meteorology, lithology, geological structure and physical address phenomenon, qalitative assessment and investigation, egineering geological problems dangerous zoning were carried out of Yanzi gully.
There are regional faults in the Yanzi gully basin, adverse geological phenomena development, such as debris flow, landslides and collapse, which debris flow is more serious. There have been many serious debris flow disasters in history, inflicted major economic losses. On the basis of Engineering Surveying and mapping, analyzed the characteristics of debris flow source in the study area, to evaluate the loose material distribution and stability assessment of Yanzi gully, estimated the loose material total reserves. In order to predict the occurrence of debris flow when the maximum amount of the material may be out of there, Combined with the study area topography, hydrology and meteorology, lithology, geological structure and physical address phenomenon, qalitative assessment and investigation, egineering geological problems dangerous zoning were carried out of Yanzi gully.
2015, 23(s1): 235-241.
Enhanced geothermal system(EGS)could extract deep geothermal resource from low permeability hot rock through media circulation. Based on the real geological and logging data of one abandoned well YS 2, we first studied the conditions existing in the deep formation. A 3D fracturing model was created and various fracturing schemes have been numerically conducted. Subsequently, we performed the hydro-thermal simulations with different injection rates through the different fracture reservoirs generated by the hydraulic fracturing. Last, depending on the research results above, we obtained the optimal fracturing and operation strategies. The results indicate that in the optimal fracture reservoir, an electrical power of 0.60～1.23MW(10 fractures) over a 20 years period could be achieved when the 3 horizontal wells system was adopted and injection rate was 30kgs-1.
Enhanced geothermal system(EGS)could extract deep geothermal resource from low permeability hot rock through media circulation. Based on the real geological and logging data of one abandoned well YS 2, we first studied the conditions existing in the deep formation. A 3D fracturing model was created and various fracturing schemes have been numerically conducted. Subsequently, we performed the hydro-thermal simulations with different injection rates through the different fracture reservoirs generated by the hydraulic fracturing. Last, depending on the research results above, we obtained the optimal fracturing and operation strategies. The results indicate that in the optimal fracture reservoir, an electrical power of 0.60～1.23MW(10 fractures) over a 20 years period could be achieved when the 3 horizontal wells system was adopted and injection rate was 30kgs-1.
2015, 23(s1): 242-246.
Stability analysis of slopes is one of the classic problems in soil mechanics. Limit equilibrium method is the most commonly used method for slope stability analysis, and it is recommended by many specifications. Generally, the potential sliding surface corresponding to the minimum safety factor is thought to be the critical surface that are most likely to slip. Based on the analysis in this paper, an idea is proposed which considers the sliding surface corresponding to the maximum acceleration as the critical surface, and is called critical surface of acceleration. Examples show that the maximum acceleration is closely related to the minimum safety factor.
Stability analysis of slopes is one of the classic problems in soil mechanics. Limit equilibrium method is the most commonly used method for slope stability analysis, and it is recommended by many specifications. Generally, the potential sliding surface corresponding to the minimum safety factor is thought to be the critical surface that are most likely to slip. Based on the analysis in this paper, an idea is proposed which considers the sliding surface corresponding to the maximum acceleration as the critical surface, and is called critical surface of acceleration. Examples show that the maximum acceleration is closely related to the minimum safety factor.
2015, 23(s1): 247-251.
The impact of urban rail transit operating vibration of the building along with its rapid development has affected greatly valued. However, the current study is are mostly concentrated in the building structure. CFG pile composite foundation for less impact studies. This paper analyzed the two subway vibration on the impact of CFG pile composite foundation. And we also used FLAC-3D to analyze evaluation methods and speed of CFG pile deformation caused by the subway vibration changes. This result provides a basis for the evaluation of vibration impact on foundation.
The impact of urban rail transit operating vibration of the building along with its rapid development has affected greatly valued. However, the current study is are mostly concentrated in the building structure. CFG pile composite foundation for less impact studies. This paper analyzed the two subway vibration on the impact of CFG pile composite foundation. And we also used FLAC-3D to analyze evaluation methods and speed of CFG pile deformation caused by the subway vibration changes. This result provides a basis for the evaluation of vibration impact on foundation.
2015, 23(s1): 252-259.
The present research stage grade of surrounding rock sub classification in construction is a hot spot in surrounding rock, the purpose is to solve the current classification of surrounding rock of large span can not meet the actual needs of the construction difficulties. Subdivision scheme of surrounding rock during construction stage level tend to develop specific engineering geology based on the background, so there will be more limited in scope, but the segmentation mechanism is universal. In the city the rapid development today, the subway to alleviate traffic pressure, improve the city traffic mode of excellent radiation force in the construction of large and medium-sized city. In order to better guide the subway tunnel construction, fully consider the characteristics of city subway tunnel construction, typical granite strata in Qingdao subway construction of the engineering geology background, by using numerical simulation software FLAC3D, the simulation of surrounding rock in different surrounding rock mass surface in shallow strata of different depth under the settlement to evaluate the stability of surrounding rock, stability difference the surrounding rock based on Ⅲ, IV, V rock corresponding subdivided into 2, 3, and 3 sub classes.
The present research stage grade of surrounding rock sub classification in construction is a hot spot in surrounding rock, the purpose is to solve the current classification of surrounding rock of large span can not meet the actual needs of the construction difficulties. Subdivision scheme of surrounding rock during construction stage level tend to develop specific engineering geology based on the background, so there will be more limited in scope, but the segmentation mechanism is universal. In the city the rapid development today, the subway to alleviate traffic pressure, improve the city traffic mode of excellent radiation force in the construction of large and medium-sized city. In order to better guide the subway tunnel construction, fully consider the characteristics of city subway tunnel construction, typical granite strata in Qingdao subway construction of the engineering geology background, by using numerical simulation software FLAC3D, the simulation of surrounding rock in different surrounding rock mass surface in shallow strata of different depth under the settlement to evaluate the stability of surrounding rock, stability difference the surrounding rock based on Ⅲ, IV, V rock corresponding subdivided into 2, 3, and 3 sub classes.
2015, 23(s1): 260-265.
We take Ba-nan District of Chongqing as an example, constructed coordinated development index system of Mountain urbanization and Geological environment, divided the research area, calculated and analyzed the coordinated development coefficient of each region during Five-eleven period. Results show: the coordination of the urban comprehensive functional areas falls, the coordination of the functional areas of the eco-agriculture tourism rises, the coordination of eco industrial functional area and Industrial logistics functional area change little.
We take Ba-nan District of Chongqing as an example, constructed coordinated development index system of Mountain urbanization and Geological environment, divided the research area, calculated and analyzed the coordinated development coefficient of each region during Five-eleven period. Results show: the coordination of the urban comprehensive functional areas falls, the coordination of the functional areas of the eco-agriculture tourism rises, the coordination of eco industrial functional area and Industrial logistics functional area change little.
2015, 23(s1): 266-277.
A scientific and rational knowledge of geohazard susceptibility assessment is of vital importance to the warning of regional geohazard. Based on geohazard field investigation of Pinggu District at 1:50000 scale and geohazard database established subsequently, the development characteristics, spatial distribution and influence factors of geohazards were obtained. Factors such as engineering geological strata, slope gradient, tectonic fault, human engineering activities and vegetation coverage have a significant impact on the evolution of geohazard, they was comprehensively analyzed through the spatial tool in GIS.Using frequency ratio evaluation, geohazard susceptibility assessment of Pinggu District was carried out. Results showed the distribution of geohazard in Pinggu District had a close relationship to regional landform, faults and human engineering activities, which was consistent with actual conditions. According to the evaluation, the whole area can be divided into four areas: the high susceptibility of geohazards area, which covers 125.6km2, accounting for 27.3% of the total studied area the medium susceptibility of geohazards area, which is calculated 273.02km2, accounting for 13.3% the low susceptibility of geohazards area, which is measured 326.89km2, taking up 22.7% and the stable area covers 349.49km2, accounting for 36.7%.The results can provide a guideline for the mitigation and prevention of geohazard in Pinggu District.
A scientific and rational knowledge of geohazard susceptibility assessment is of vital importance to the warning of regional geohazard. Based on geohazard field investigation of Pinggu District at 1:50000 scale and geohazard database established subsequently, the development characteristics, spatial distribution and influence factors of geohazards were obtained. Factors such as engineering geological strata, slope gradient, tectonic fault, human engineering activities and vegetation coverage have a significant impact on the evolution of geohazard, they was comprehensively analyzed through the spatial tool in GIS.Using frequency ratio evaluation, geohazard susceptibility assessment of Pinggu District was carried out. Results showed the distribution of geohazard in Pinggu District had a close relationship to regional landform, faults and human engineering activities, which was consistent with actual conditions. According to the evaluation, the whole area can be divided into four areas: the high susceptibility of geohazards area, which covers 125.6km2, accounting for 27.3% of the total studied area the medium susceptibility of geohazards area, which is calculated 273.02km2, accounting for 13.3% the low susceptibility of geohazards area, which is measured 326.89km2, taking up 22.7% and the stable area covers 349.49km2, accounting for 36.7%.The results can provide a guideline for the mitigation and prevention of geohazard in Pinggu District.
2015, 23(s1): 278-283.
In the calculation of the settlement caused by exploiting the oil and gas, the previous calculation dosen't consider the effect of biot coefficient on the amount of compression and settlement, and defaults the biot coefficient is equal to 1. So the error that the theoretical calculation value deviate from the actual value increases. This may have some impact on the cost of the project investment and project design, in order to study the effect of the settlement amount of Biot coefficient and calculated true formation Settlement. The thesis uses two kinds of methods to obtain biot coefficient of granite samples, which one is acoustic test, another is three axial compression test. Biot coefficient measured by Acoustic test is 0.528. But biot coefficient calculated by that obtained by three axis test method through the drainage test and limit pressure and water pressure equal growth test is 0.665. And in all through establishing the FLAC3D model of land subsidence, Experimental research on effect of Biot coefficient on settlement formation, and writer finds the larger biot coefficient is, the larger ground settlement is .
In the calculation of the settlement caused by exploiting the oil and gas, the previous calculation dosen't consider the effect of biot coefficient on the amount of compression and settlement, and defaults the biot coefficient is equal to 1. So the error that the theoretical calculation value deviate from the actual value increases. This may have some impact on the cost of the project investment and project design, in order to study the effect of the settlement amount of Biot coefficient and calculated true formation Settlement. The thesis uses two kinds of methods to obtain biot coefficient of granite samples, which one is acoustic test, another is three axial compression test. Biot coefficient measured by Acoustic test is 0.528. But biot coefficient calculated by that obtained by three axis test method through the drainage test and limit pressure and water pressure equal growth test is 0.665. And in all through establishing the FLAC3D model of land subsidence, Experimental research on effect of Biot coefficient on settlement formation, and writer finds the larger biot coefficient is, the larger ground settlement is .
2015, 23(s1): 284-291.
Laboratory tests, field observations and engineering accidents have shown that sand exhibits long-term deformation like soft clay. These issues deserve our in-depth study. For further understanding of sand creep, the mechanism of creep is first discussed from macroscopic and microscopic viewpoints, results show that sand creep is caused mainly by the mechanism of particle reorganization and particle breakage. Then, creep characteristics are analyzed from internal and external factors, and the creep characteristics under both 1D and 3D creep tests are analyzed. Water content, pore water properties, stress history, stress path and size have a certain effect on sand creep. Finally, the creep models are analyzed from macroscopic and microscopic viewpoints, and a future prospect of sand creep is discussed. In the study of sand creep, discrete element method is an important way for future research. At the same time, experimental research, theoretical analysis and numerical analysis can be combined to carry out further research. Creep of sandy soil will be one of the major research directions for soil mechanics in the future.
Laboratory tests, field observations and engineering accidents have shown that sand exhibits long-term deformation like soft clay. These issues deserve our in-depth study. For further understanding of sand creep, the mechanism of creep is first discussed from macroscopic and microscopic viewpoints, results show that sand creep is caused mainly by the mechanism of particle reorganization and particle breakage. Then, creep characteristics are analyzed from internal and external factors, and the creep characteristics under both 1D and 3D creep tests are analyzed. Water content, pore water properties, stress history, stress path and size have a certain effect on sand creep. Finally, the creep models are analyzed from macroscopic and microscopic viewpoints, and a future prospect of sand creep is discussed. In the study of sand creep, discrete element method is an important way for future research. At the same time, experimental research, theoretical analysis and numerical analysis can be combined to carry out further research. Creep of sandy soil will be one of the major research directions for soil mechanics in the future.
2015, 23(s1): 292-297.
Stiffened Deep Mixed(SDM)column is a new kind of composite material column. It is formed by inserting a precast concrete core pile into the center of a Deep Mixed(DM)column immediately after the construction of deep mixing column. This new composite column is appropriate to reinforce the thick soft soil. However, previous studies have been mostly focused on the performance of SDM column under rigid foundation. There have been few studies regarding its mechanical behavior under flexible load at present. This paper presents a numerical study to investigate the behavior of SDM column-supported embankment over soft soil. Firstly, a comparison of results by the numerical model and field data was conducted to verify the reliability of the numerical model. Based on the calibrated numerical model, the study was conducted to investigate the influence factors of ratio of concrete core pile length to DM column length, area ratio of concrete core pile and column spacing on the behavior of SDM column-supported embankment over soft soil. The results showed that the settlement could be effectively reduced and the pile efficacy could be increased to some extent by increasing the ratio of core length to DM column length, and reducing column spacing. The results have the practical values to guide the application of SDM columns in practice.
Stiffened Deep Mixed(SDM)column is a new kind of composite material column. It is formed by inserting a precast concrete core pile into the center of a Deep Mixed(DM)column immediately after the construction of deep mixing column. This new composite column is appropriate to reinforce the thick soft soil. However, previous studies have been mostly focused on the performance of SDM column under rigid foundation. There have been few studies regarding its mechanical behavior under flexible load at present. This paper presents a numerical study to investigate the behavior of SDM column-supported embankment over soft soil. Firstly, a comparison of results by the numerical model and field data was conducted to verify the reliability of the numerical model. Based on the calibrated numerical model, the study was conducted to investigate the influence factors of ratio of concrete core pile length to DM column length, area ratio of concrete core pile and column spacing on the behavior of SDM column-supported embankment over soft soil. The results showed that the settlement could be effectively reduced and the pile efficacy could be increased to some extent by increasing the ratio of core length to DM column length, and reducing column spacing. The results have the practical values to guide the application of SDM columns in practice.
2015, 23(s1): 298-302.
Recently, with the development of aspect on foundation pit excavation. the accident of pipelines deformation and pipelines fracture happened frequently due to foundation pit excavation. Now, this research subject is becoming more and more attention. Based on the finite element software ABAQUS, using the method of numerical simulation. In this paper, the influence of excavation on adjust buried pipeline are studied by author. Also in this paper, the author analysis the buried pipelines under the different pipe diameter and different material, studied on displacement of excavation of buried pipelines, the authors conclude and sum up the influence of different diameters and different materials on the displacement of the pipelines during the excavation.
Recently, with the development of aspect on foundation pit excavation. the accident of pipelines deformation and pipelines fracture happened frequently due to foundation pit excavation. Now, this research subject is becoming more and more attention. Based on the finite element software ABAQUS, using the method of numerical simulation. In this paper, the influence of excavation on adjust buried pipeline are studied by author. Also in this paper, the author analysis the buried pipelines under the different pipe diameter and different material, studied on displacement of excavation of buried pipelines, the authors conclude and sum up the influence of different diameters and different materials on the displacement of the pipelines during the excavation.
2015, 23(s1): 303-312.
According to further study on geological characteristics, physical and mechanical properties, water physical properties and rheological property of the soft rock in the central area of Yunnan province. It is concluded that the red-bed soft rock shear strength, compressive strength is lower. with the increase of clay mineral and shale content, the physical and mechanical properties were gradually decreased.the muddy rock strength was reduced by 30%～40% when water-saturated, the fine sandstone and siltystone loss of it is 20%～30%.The disintegration and expansibility is controlled by the clay mineral and shale content. the test shows that the red-bed soft rock creep effect is obvious, the long-term compressive strength is 70% of the uniaxial compressive strength, Long-term shear strength values compared with the direct shear test of internal friction Angle decreased about 20%, cohesion was reduced by 60%. basis on many engineering experience and academic achievements, combined with the Engineering geological property and long-term strength of the soft rock in the central area of Yunnan province, this paper puts forward the evaluation methods of the soft rock tunnel extrusion and surrounding rock classification. To provide evidence for the discriminant of large deformation of soft rock in the tunnel.
According to further study on geological characteristics, physical and mechanical properties, water physical properties and rheological property of the soft rock in the central area of Yunnan province. It is concluded that the red-bed soft rock shear strength, compressive strength is lower. with the increase of clay mineral and shale content, the physical and mechanical properties were gradually decreased.the muddy rock strength was reduced by 30%～40% when water-saturated, the fine sandstone and siltystone loss of it is 20%～30%.The disintegration and expansibility is controlled by the clay mineral and shale content. the test shows that the red-bed soft rock creep effect is obvious, the long-term compressive strength is 70% of the uniaxial compressive strength, Long-term shear strength values compared with the direct shear test of internal friction Angle decreased about 20%, cohesion was reduced by 60%. basis on many engineering experience and academic achievements, combined with the Engineering geological property and long-term strength of the soft rock in the central area of Yunnan province, this paper puts forward the evaluation methods of the soft rock tunnel extrusion and surrounding rock classification. To provide evidence for the discriminant of large deformation of soft rock in the tunnel.
2015, 23(s1): 313-319.
Seabed sediments experienced consolidation, liquefaction and fluidization, erosion and deposition under cyclic loading of waves, together with the dynamic variation process of sediment composition, structure, physical-mechanical properties, and engineering geology properties. Single process can affect others, and in the dynamic process of coupling interaction, waves post-reformed the seabed sediments in cycles. This paper summarized the domestic and international research progress of sediment dynamic responses to waves systematically, and discussed the critical role and mechanism of waves in the post reformation of silty sediments from the aspects of pore water pressure responses of seabed sediments, variation of sediment strength, physical-mechanical properties, and sediment composition and structure. Taking silty sediment dynamics to waves in Yellow River delta as foothold, findings of physical modeling experiment, in situ observation, and mathematical calculation methods on wave-soil interaction was demonstrated in detail to provide guidance to further study estuarine and coastal sediment dynamics.
Seabed sediments experienced consolidation, liquefaction and fluidization, erosion and deposition under cyclic loading of waves, together with the dynamic variation process of sediment composition, structure, physical-mechanical properties, and engineering geology properties. Single process can affect others, and in the dynamic process of coupling interaction, waves post-reformed the seabed sediments in cycles. This paper summarized the domestic and international research progress of sediment dynamic responses to waves systematically, and discussed the critical role and mechanism of waves in the post reformation of silty sediments from the aspects of pore water pressure responses of seabed sediments, variation of sediment strength, physical-mechanical properties, and sediment composition and structure. Taking silty sediment dynamics to waves in Yellow River delta as foothold, findings of physical modeling experiment, in situ observation, and mathematical calculation methods on wave-soil interaction was demonstrated in detail to provide guidance to further study estuarine and coastal sediment dynamics.
2015, 23(s1): 320-326.
Take in Salah field in Algeria for example, numerical model has been established with the use of CGS-THCM coupled simulation program to simulate the changes of surface displacement caused by injected CO2 in different way. A method of combining Numerical simulation with monitoring data has been put forward to make comprehensive assessment of the CO2 escape problems during CO2 geological storage project. And the CO2 escape-surface displacement evaluation system has been established to assess whether CO2 escape and quantity size of the escaped CO2 during the CGS project. It is can be seen through simulation results: by the initial phase, smaller surface displacement be caused. And as time increased the surface displacement is more and more obvious. In addition, injection volume, injection pressure correspondingly cause large surface displacements.
Take in Salah field in Algeria for example, numerical model has been established with the use of CGS-THCM coupled simulation program to simulate the changes of surface displacement caused by injected CO2 in different way. A method of combining Numerical simulation with monitoring data has been put forward to make comprehensive assessment of the CO2 escape problems during CO2 geological storage project. And the CO2 escape-surface displacement evaluation system has been established to assess whether CO2 escape and quantity size of the escaped CO2 during the CGS project. It is can be seen through simulation results: by the initial phase, smaller surface displacement be caused. And as time increased the surface displacement is more and more obvious. In addition, injection volume, injection pressure correspondingly cause large surface displacements.
2015, 23(s1): 327-332.
When the new railway tunnel undercrosses the existing highway, the crossing interaction becomes inevitable between different lines, it not only affects deformation of the tunnel and the pavement, but also affects the safety of the line. Therefore, it is vital to analyze the changes of tunnel structures and patterns of construction settlement. Based on the engineering that a new open-cut railway tunnel undercrossed the existing highway, for the intersection part, the soil deformations, deformations and the mechanical conditions of supporting structure and existing highway were studied by using MIDAS/GTS finite element software under the self-weight load and the lane load after the completion of the tunnel construction. The results showed that the maximum settlement took place in crown. The cross-range size and angle had a striking impact on the lining settlement, the probability of tensile failure occurred in hance on the inside of supporting structure is higher than that of the crown. It was found that the settlement of the intersection part of existing highway and crossing railway tunnel was less than the pavement on both sides for the shallow tunnel with the ratio of cover and span below 0.5. The tensile failure may occur at the junction of C30 reinforced concrete pavement and C20 plain concrete pavement and the structures should be strengthened.
When the new railway tunnel undercrosses the existing highway, the crossing interaction becomes inevitable between different lines, it not only affects deformation of the tunnel and the pavement, but also affects the safety of the line. Therefore, it is vital to analyze the changes of tunnel structures and patterns of construction settlement. Based on the engineering that a new open-cut railway tunnel undercrossed the existing highway, for the intersection part, the soil deformations, deformations and the mechanical conditions of supporting structure and existing highway were studied by using MIDAS/GTS finite element software under the self-weight load and the lane load after the completion of the tunnel construction. The results showed that the maximum settlement took place in crown. The cross-range size and angle had a striking impact on the lining settlement, the probability of tensile failure occurred in hance on the inside of supporting structure is higher than that of the crown. It was found that the settlement of the intersection part of existing highway and crossing railway tunnel was less than the pavement on both sides for the shallow tunnel with the ratio of cover and span below 0.5. The tensile failure may occur at the junction of C30 reinforced concrete pavement and C20 plain concrete pavement and the structures should be strengthened.
2015, 23(s1): 333-340.
During the construction of hydropower project, slope instability will affect the construction safety and progress. In order to ensure the long-term security and stability of high steep slope, it is necessary to take reasonable construction measures for its comprehensive treatment. For the engineering characteristics of the Changheba hydropower's high steep environmental slope: the complex geological conditions, the decentralized management areas and the more fractured and jointed rock mass fissure development, the slope problems of the different depth can take the corresponding control measures by using of unique material transport and construction channel. Aiming at the slope covering and dangerous rock mass, the supporting technologies are often clearing the slope slag, active and passive protective net, retaining wall and anchor tendon bundle and so on; Aiming at the slope shallow support aiming at the slope surface stability problem, the used supporting means are anchor spray concrete, frame Beams, anchor and others; Aiming at the broken rock mass of the slope deep layer, consolidation grouting and anchor cable technique can be used to deep supporting. The long-term field monitoring data shows that the high steep environment slope is stable and safe after comprehensive treatment.
During the construction of hydropower project, slope instability will affect the construction safety and progress. In order to ensure the long-term security and stability of high steep slope, it is necessary to take reasonable construction measures for its comprehensive treatment. For the engineering characteristics of the Changheba hydropower's high steep environmental slope: the complex geological conditions, the decentralized management areas and the more fractured and jointed rock mass fissure development, the slope problems of the different depth can take the corresponding control measures by using of unique material transport and construction channel. Aiming at the slope covering and dangerous rock mass, the supporting technologies are often clearing the slope slag, active and passive protective net, retaining wall and anchor tendon bundle and so on; Aiming at the slope shallow support aiming at the slope surface stability problem, the used supporting means are anchor spray concrete, frame Beams, anchor and others; Aiming at the broken rock mass of the slope deep layer, consolidation grouting and anchor cable technique can be used to deep supporting. The long-term field monitoring data shows that the high steep environment slope is stable and safe after comprehensive treatment.
2015, 23(s1): 341-348.
Bias tunnel easily caused collapse accident during construction. For Reducing the risk of collapse and the maximum risk loss, the research established the accident tree risk assessment of bias tunnel construction collapse mainly caused by terrain. On the basis of the definition of the risk of bias on tunnel construction, this article studied the basic method of risk assessment using the accident tree Analysis, and built the accident tree chart of bias tunnel construction collapse. This article also made an analysis of the main events causing bias tunnel construction collapse, finally, identified the key events sets. Through the risk loss estimation model by bias tunnel construction, this article estimated loss results and made a real case study at last. The accident tree method provided the effective method for risk assessment of the bias tunnel collapse.this way made risk assessment more accurate.
Bias tunnel easily caused collapse accident during construction. For Reducing the risk of collapse and the maximum risk loss, the research established the accident tree risk assessment of bias tunnel construction collapse mainly caused by terrain. On the basis of the definition of the risk of bias on tunnel construction, this article studied the basic method of risk assessment using the accident tree Analysis, and built the accident tree chart of bias tunnel construction collapse. This article also made an analysis of the main events causing bias tunnel construction collapse, finally, identified the key events sets. Through the risk loss estimation model by bias tunnel construction, this article estimated loss results and made a real case study at last. The accident tree method provided the effective method for risk assessment of the bias tunnel collapse.this way made risk assessment more accurate.
2015, 23(s1): 349-354.
Throughstatistical analysis ofdebrisprovenancereserves, effective catchment area, rainfalland otherdata in Beijing, critical rainfallinducing debris flowis proposed in the calculation formula. In the formula, critical rainfall is proportionalto effective provenancereserves in the ditch, and is inversely proportional tothe effective catchment area. After applying the formula to the cases which happened previously, the critical rainfall is calculated using back analysis method according to the record the amount of accumulation of debris. At last, the critical rainfall is compared with the actual rain records. The results are showed that the critical rainfall can predict correctly the debris flow in different geological conditions. It is a good technical support for prevention of debris flow to reduce the property loss in the Beijing Area.
Throughstatistical analysis ofdebrisprovenancereserves, effective catchment area, rainfalland otherdata in Beijing, critical rainfallinducing debris flowis proposed in the calculation formula. In the formula, critical rainfall is proportionalto effective provenancereserves in the ditch, and is inversely proportional tothe effective catchment area. After applying the formula to the cases which happened previously, the critical rainfall is calculated using back analysis method according to the record the amount of accumulation of debris. At last, the critical rainfall is compared with the actual rain records. The results are showed that the critical rainfall can predict correctly the debris flow in different geological conditions. It is a good technical support for prevention of debris flow to reduce the property loss in the Beijing Area.
2015, 23(s1): 355-361.
Geological disaster emergency monitoring refers to one part of emergency action that monitoring geological body and risk factors, in order to emergency decision making. Major geological disaster emergency practices had showed that emergency monitoring is the key measure for risk mitigation. Because geological disaster emergency technical studies are just beginning, now its basic problem still was described in different. Therefore there were not operating plans, its emergency function was reduced. Based on emergency practices, through comparative with non-emergency conditions, this paper constructed two types of emergency monitoring scenarios: disaster and danger. Initially emergency monitoring technical requirements are proposed. General technical conditions: focus on monitoring, random design, comprehensive judgments, dynamic warning and response classification. The basic schemes of emergency monitoring for single landslide and debris flow are proposed, consists of tasks, content, design, methods, and monitoring frequency. Hope to useful for emergency plans.
Geological disaster emergency monitoring refers to one part of emergency action that monitoring geological body and risk factors, in order to emergency decision making. Major geological disaster emergency practices had showed that emergency monitoring is the key measure for risk mitigation. Because geological disaster emergency technical studies are just beginning, now its basic problem still was described in different. Therefore there were not operating plans, its emergency function was reduced. Based on emergency practices, through comparative with non-emergency conditions, this paper constructed two types of emergency monitoring scenarios: disaster and danger. Initially emergency monitoring technical requirements are proposed. General technical conditions: focus on monitoring, random design, comprehensive judgments, dynamic warning and response classification. The basic schemes of emergency monitoring for single landslide and debris flow are proposed, consists of tasks, content, design, methods, and monitoring frequency. Hope to useful for emergency plans.
2015, 23(s1): 362-367.
According to the current situation that there are few research results about the mechanics regularity of prestressed anchor cable and lattice beam at the wall in tilted back, the tilted three-dimensional model of anchor cable and lattice beam at Beijing Mentougou are built using Midas/GTS.And the stress, bending moment, horizontal deformation and the variation of lateral earth pressure at the wall in tilted back which is upright or tilted with 80 and 70 are analyzed. The results shows that the axial force of anchor rope, bending moment and horizontal deformation are the largest in the section with the angle of 70, while those are the smallest in the vertical section. So we suggest that the upright section should be chosen for the prestressed anchor cable and lattice beam.
According to the current situation that there are few research results about the mechanics regularity of prestressed anchor cable and lattice beam at the wall in tilted back, the tilted three-dimensional model of anchor cable and lattice beam at Beijing Mentougou are built using Midas/GTS.And the stress, bending moment, horizontal deformation and the variation of lateral earth pressure at the wall in tilted back which is upright or tilted with 80 and 70 are analyzed. The results shows that the axial force of anchor rope, bending moment and horizontal deformation are the largest in the section with the angle of 70, while those are the smallest in the vertical section. So we suggest that the upright section should be chosen for the prestressed anchor cable and lattice beam.
2015, 23(s1): 368-371.
To promote the development of public transport tunnel in Chongqing at the same time, also caused a series of geological environment problems. This paper selected 28 tunnel has been built through the geological environment in Chongqing, the special investigation of the tunnel site, in-depth analysis of the distribution of geological environment problems caused by the tunnel engineering in time and space, to provide a reference for future research to tunnel engineering geological environmental protection technology.
To promote the development of public transport tunnel in Chongqing at the same time, also caused a series of geological environment problems. This paper selected 28 tunnel has been built through the geological environment in Chongqing, the special investigation of the tunnel site, in-depth analysis of the distribution of geological environment problems caused by the tunnel engineering in time and space, to provide a reference for future research to tunnel engineering geological environmental protection technology.
2015, 23(s1): 372-377.
Slope stability analysis and evaluation is the one of the main engineering geological problems in Lancang river a power plant, this article through the carding of slope failure mode, it is concluded that the main failure mode of slope as sliding cracking, stepwise slip cracking, brittle dump deformation and compression deformation, the results obtained for the slope stability calculation and provide geological basis for excavation support design.
Slope stability analysis and evaluation is the one of the main engineering geological problems in Lancang river a power plant, this article through the carding of slope failure mode, it is concluded that the main failure mode of slope as sliding cracking, stepwise slip cracking, brittle dump deformation and compression deformation, the results obtained for the slope stability calculation and provide geological basis for excavation support design.
2015, 23(s1): 378-384.
Through the comprehensive analysis of hot spring distribution and its formation conditions, combined with regional geology, compared with the differences in the distribution of historical earthquake epicenter, the mechanism formation and tectonic background of hot spring were investigated in Changle-Nan'ao Faults Zone, SE China. the reason, differences distribution of hot spring, is the differences of tectonic-thermal, suggested different activity mode appeared in the same tectonic belt. A fault zone, developed hot springs, is active, but in different mode. The segment exposed hot springs(Fuzhou, Zhangzhou)creep, with more tectonic-thermal, but the part without hot spring(Quanzhou)stick-slip, with more devastating earthquake.
Through the comprehensive analysis of hot spring distribution and its formation conditions, combined with regional geology, compared with the differences in the distribution of historical earthquake epicenter, the mechanism formation and tectonic background of hot spring were investigated in Changle-Nan'ao Faults Zone, SE China. the reason, differences distribution of hot spring, is the differences of tectonic-thermal, suggested different activity mode appeared in the same tectonic belt. A fault zone, developed hot springs, is active, but in different mode. The segment exposed hot springs(Fuzhou, Zhangzhou)creep, with more tectonic-thermal, but the part without hot spring(Quanzhou)stick-slip, with more devastating earthquake.
2015, 23(s1): 385-391.
A Changchun No.1 Metro Line station tunnel was constructed by CRD method with the character of large cross-section, shallow-buried. It's necessary to study the deformation of the stratum and the tunnel structure. Therefore, the numerical model founded by FLAC3D based on the geological conditions and construction conditions is contrasted with the monitoring data to study the deformation regularity. The result shows, the settlement curves of cross section and vertical section are fitted in Gauss formula well. The settlement of the ground surface is approximate to be elliptical funneled in three dimensional space, and the location of the largest ground settlement is near to the horsehead in the projection of the tunnel. During the excavation, the upmost pilot tunnels have made great influence to the final settlement, and it accounts about the half of the final settlement. Due to the median lamella reduces the tunnel convergence, monitoring the settlement of the ground surface and the vault is the predominant way to judge the stability of the tunnel. The above analysis conclusions have practical guiding significance for the construction of metro tunnel with large cross-section in the future.
A Changchun No.1 Metro Line station tunnel was constructed by CRD method with the character of large cross-section, shallow-buried. It's necessary to study the deformation of the stratum and the tunnel structure. Therefore, the numerical model founded by FLAC3D based on the geological conditions and construction conditions is contrasted with the monitoring data to study the deformation regularity. The result shows, the settlement curves of cross section and vertical section are fitted in Gauss formula well. The settlement of the ground surface is approximate to be elliptical funneled in three dimensional space, and the location of the largest ground settlement is near to the horsehead in the projection of the tunnel. During the excavation, the upmost pilot tunnels have made great influence to the final settlement, and it accounts about the half of the final settlement. Due to the median lamella reduces the tunnel convergence, monitoring the settlement of the ground surface and the vault is the predominant way to judge the stability of the tunnel. The above analysis conclusions have practical guiding significance for the construction of metro tunnel with large cross-section in the future.
2015, 23(s1): 392-397.
The landslide hazards area is an important basis for division of the danger zone, also is basic to carry out landslide disaster prediction and prevention work. The large discrete element numerical 3DEC model was carried out, which researches Mawo landslide hazards area. The results shows: The hazards area after Mawo landslide damaging and deformation is 105m at left of landslide(facing slope), 65m at the right of landslide, and is 345m away from landslide vertical horizontal distance. The speed monitoring data show, after the landslide sliding out, the speed of the lateral movement is small, general trend movement of landslide is downward and forward. And it shows that central of landslide have the greater speed than other parts, which make it more likely to be long-range slide. The research results would provide a theoretical basis for local disaster prevention and mitigation decisions, therefore, we should recommend that Mawodang village would relocate or construct stopped stone walls retaining measures, which locates 248～345m from gentle segment landslide downstream.
The landslide hazards area is an important basis for division of the danger zone, also is basic to carry out landslide disaster prediction and prevention work. The large discrete element numerical 3DEC model was carried out, which researches Mawo landslide hazards area. The results shows: The hazards area after Mawo landslide damaging and deformation is 105m at left of landslide(facing slope), 65m at the right of landslide, and is 345m away from landslide vertical horizontal distance. The speed monitoring data show, after the landslide sliding out, the speed of the lateral movement is small, general trend movement of landslide is downward and forward. And it shows that central of landslide have the greater speed than other parts, which make it more likely to be long-range slide. The research results would provide a theoretical basis for local disaster prevention and mitigation decisions, therefore, we should recommend that Mawodang village would relocate or construct stopped stone walls retaining measures, which locates 248～345m from gentle segment landslide downstream.
2015, 23(s1): 398-404.
Land subsidence is a typical environment geological problem. It seriously affects the development of social economy and the process of urbanization. This article based on the key construction project of Golden International in Zibo, Shandong Province. To evaluate the impact of land subsidence on the project, the Quaternary formation, which is about 40meters thick and located at the 0.6km2 proposed project area, was taken as the research object. According to the engineering geological characteristics, the formation was divided into four compression layers. Considering respectively groundwater exploiting in ZhangXi water source field and different building loads, the amounts of land subsidence in the area of the construction project were calculated and the trends were predicted based on one-dimensional consolidation theory and geotechnical consolidation approach. The result showed that land subsidence due to groundwater withdrawal and building load had less impact on the construction project. The study helps making a basis decision for the construction project, and also provides a reference for constructions where are affected by land subsidence. Besides, the study of land subsidence due to groundwater withdrawal and building load in Zibo city of Shandong provice will guide the planning and construction of the city, it can benefit it sciencely, rapidly, sustainable developing.
Land subsidence is a typical environment geological problem. It seriously affects the development of social economy and the process of urbanization. This article based on the key construction project of Golden International in Zibo, Shandong Province. To evaluate the impact of land subsidence on the project, the Quaternary formation, which is about 40meters thick and located at the 0.6km2 proposed project area, was taken as the research object. According to the engineering geological characteristics, the formation was divided into four compression layers. Considering respectively groundwater exploiting in ZhangXi water source field and different building loads, the amounts of land subsidence in the area of the construction project were calculated and the trends were predicted based on one-dimensional consolidation theory and geotechnical consolidation approach. The result showed that land subsidence due to groundwater withdrawal and building load had less impact on the construction project. The study helps making a basis decision for the construction project, and also provides a reference for constructions where are affected by land subsidence. Besides, the study of land subsidence due to groundwater withdrawal and building load in Zibo city of Shandong provice will guide the planning and construction of the city, it can benefit it sciencely, rapidly, sustainable developing.
2015, 23(s1): 412-417.
This paper built four kinds of numerical analysis models of slope, inputting Ban Shen seismic waves. Summarizes the dynamic response of the law. Calculated result shows that: 1 the hardness-upward slope demonstrates larger amplification effect of acceleration than the softness-upward slope basically according to acceleration dynamic responses. Forthermore, vertical excitation concentrate than those in horizontal excitation, the largest amplification of horizontal acceleration is 1.5 to 2.0 times than the vertical acceleration.2 Soft rock is more sensitive to seismic waves than hard rock, under the strong earthquake, the hardness-upward slope is apt to fail according to the displacement.3 Rock slope with soft foundation demonstrates larger amplification effect of acceleration than the rock slope with no soft foundation according to acceleration and displacement dynamic responses. However, evolution of stress field shows that before the failure of the slope, the existence of soft foundation can reduce the role of earthquake dynamic effect to a certain extent, which is positive to slope stability.
This paper built four kinds of numerical analysis models of slope, inputting Ban Shen seismic waves. Summarizes the dynamic response of the law. Calculated result shows that: 1 the hardness-upward slope demonstrates larger amplification effect of acceleration than the softness-upward slope basically according to acceleration dynamic responses. Forthermore, vertical excitation concentrate than those in horizontal excitation, the largest amplification of horizontal acceleration is 1.5 to 2.0 times than the vertical acceleration.2 Soft rock is more sensitive to seismic waves than hard rock, under the strong earthquake, the hardness-upward slope is apt to fail according to the displacement.3 Rock slope with soft foundation demonstrates larger amplification effect of acceleration than the rock slope with no soft foundation according to acceleration and displacement dynamic responses. However, evolution of stress field shows that before the failure of the slope, the existence of soft foundation can reduce the role of earthquake dynamic effect to a certain extent, which is positive to slope stability.
2015, 23(s1): 418-426.
on August 31, 2014, Yunyang Foreign Languages School in Chongqing encountered a once-in-a-century torrential rainstorm which gave rise to obvious slide evidences of the slide mass. The aim is to evaluate the stability of the slide mass in consideration of the effect of hydrodynamic pressure after the rainstorm infiltration, the theoretical basis is the saturated-unsaturated seepage theory.this paper uses SEEP and SLOPE of software Geo-Studio to analyze. Further more, it analyzes the displacement and seepage characteristics under heavy rainfall condition comprehensively. The main results as follows: Firstly, the failure form and mechanism of the single landslide caused by heavy rainfall are interpreted; secondly, the evolvement rules of the displacement and seepage fields are obtained by analyzing the change characteristics during the whole failure process, it is able to provide theoretical basics for regulation project.
on August 31, 2014, Yunyang Foreign Languages School in Chongqing encountered a once-in-a-century torrential rainstorm which gave rise to obvious slide evidences of the slide mass. The aim is to evaluate the stability of the slide mass in consideration of the effect of hydrodynamic pressure after the rainstorm infiltration, the theoretical basis is the saturated-unsaturated seepage theory.this paper uses SEEP and SLOPE of software Geo-Studio to analyze. Further more, it analyzes the displacement and seepage characteristics under heavy rainfall condition comprehensively. The main results as follows: Firstly, the failure form and mechanism of the single landslide caused by heavy rainfall are interpreted; secondly, the evolvement rules of the displacement and seepage fields are obtained by analyzing the change characteristics during the whole failure process, it is able to provide theoretical basics for regulation project.
2015, 23(s1): 427-432.
According to Wuhu Zhongshan North Road underground passage foundation pit reconnaissance report, we raise foundation pit enclosure structure schemes of pile supporting and bracing as the foremost, taking mix-filled soil outside foundation pit with rather thick into consideration, setting grouting of water-stop curtain outside foundation pit support structures. Finally checking overall stability, the stability against overturning and uplift resistance of foundation pit by using the method of Sweden slice, Prandtl and Terzaghi theory. The research results show that the stability and uplift calculation meet security requirements and the foundation pit supporting scheme is feasible, the supporting method and the calculation method provide reference for the design and checking of the similar engineering.
According to Wuhu Zhongshan North Road underground passage foundation pit reconnaissance report, we raise foundation pit enclosure structure schemes of pile supporting and bracing as the foremost, taking mix-filled soil outside foundation pit with rather thick into consideration, setting grouting of water-stop curtain outside foundation pit support structures. Finally checking overall stability, the stability against overturning and uplift resistance of foundation pit by using the method of Sweden slice, Prandtl and Terzaghi theory. The research results show that the stability and uplift calculation meet security requirements and the foundation pit supporting scheme is feasible, the supporting method and the calculation method provide reference for the design and checking of the similar engineering.
2015, 23(s1): 433-440.
Jinzigou debris flow is a high-frequency prone gully debris flow in the high altitude area of the north-west Yunnan, its tributary more development, Channel longitudinal gradient big, source mainly in the upstream of the gully(active gully) on both sides of the landslides, avalanches, glacial till, and channel slope diluvium piled up slow early in the diluvium, debris.it has abundant loose sediment supply source, great catchment area, and might cause serious damage to it and the downstream villages. It is a high susceptibility to gully debris flow, on the basis of geology investigation, Scale and scope of the investigation disaster debris flow, and analyze their development characteristics and breaking strength, field investigation and simulation test, Determine the physical characteristics of debris flow and the corresponding value of the formula, debris flows were calculated flow rate, flow, a process and impact force of the total kinetic parameters, and then, the debris flow velocity, impact force, climbing height, and the total amount of a large viscous debris flow are the characteristics of the debris flow., According to its climate, the comprehensive engineering control measures of stable block based, sparse discharge auxiliary, bnding kinetics studies, without reducing the control effect of the premise, can effectively reduce the amount of control engineering and engineering investment, the reasonable prevention and control measures are put forward after further research. The achievements have some reference value for the similar mechanism debris flows.
Jinzigou debris flow is a high-frequency prone gully debris flow in the high altitude area of the north-west Yunnan, its tributary more development, Channel longitudinal gradient big, source mainly in the upstream of the gully(active gully) on both sides of the landslides, avalanches, glacial till, and channel slope diluvium piled up slow early in the diluvium, debris.it has abundant loose sediment supply source, great catchment area, and might cause serious damage to it and the downstream villages. It is a high susceptibility to gully debris flow, on the basis of geology investigation, Scale and scope of the investigation disaster debris flow, and analyze their development characteristics and breaking strength, field investigation and simulation test, Determine the physical characteristics of debris flow and the corresponding value of the formula, debris flows were calculated flow rate, flow, a process and impact force of the total kinetic parameters, and then, the debris flow velocity, impact force, climbing height, and the total amount of a large viscous debris flow are the characteristics of the debris flow., According to its climate, the comprehensive engineering control measures of stable block based, sparse discharge auxiliary, bnding kinetics studies, without reducing the control effect of the premise, can effectively reduce the amount of control engineering and engineering investment, the reasonable prevention and control measures are put forward after further research. The achievements have some reference value for the similar mechanism debris flows.
2015, 23(s1): 441-446.
Much attention has been paid to Lengmugou debris flows in Baoxing County after the Lushan earthquake. Affected by earthquakes superposition, the structure of the provenance is more wider and looser, and two large-scale debris flows are activated successively in August 18, 2010 and May 23, 2013 under the condition of triggering heavy rainfall. Combining with the provenance conditions, the paper makes the effects on the source provenance clear through the provenance response study under the action of earthquake, as well as the change characteristics of the source volume. Meanwhile, the paper also concludes inductively the causes of the provenance reserves increase through comparative analysis, and different types of source related transformation relationship between each other. Firstly, the Wenchuan earthquake is indirect contribution within the provenance in the watershed, and the Lushan earthquake induced directly, the same is likely to be indirect contribution to the next earthquake. Secondly, the provenance response of indirect contribution from the slope debris flows has been translated into collapse-type source and channel-type source. The paper obtains the preliminary understanding to the quantity change of the provenance the earthquake stacks effected, with more hope that the results provide certain enlightenment function on monitoring and warning research in debris flow disaster.
Much attention has been paid to Lengmugou debris flows in Baoxing County after the Lushan earthquake. Affected by earthquakes superposition, the structure of the provenance is more wider and looser, and two large-scale debris flows are activated successively in August 18, 2010 and May 23, 2013 under the condition of triggering heavy rainfall. Combining with the provenance conditions, the paper makes the effects on the source provenance clear through the provenance response study under the action of earthquake, as well as the change characteristics of the source volume. Meanwhile, the paper also concludes inductively the causes of the provenance reserves increase through comparative analysis, and different types of source related transformation relationship between each other. Firstly, the Wenchuan earthquake is indirect contribution within the provenance in the watershed, and the Lushan earthquake induced directly, the same is likely to be indirect contribution to the next earthquake. Secondly, the provenance response of indirect contribution from the slope debris flows has been translated into collapse-type source and channel-type source. The paper obtains the preliminary understanding to the quantity change of the provenance the earthquake stacks effected, with more hope that the results provide certain enlightenment function on monitoring and warning research in debris flow disaster.
2015, 23(s1): 447-451.
Site development a landslide in rural resettlement point on Muguagou village of Gushan Hydropower Station of Hanjiang river, the terrain of the site is slope terrain, Limited by scale of terrain and immigration, residents need to be placed on the landslide, this need to take the landslide to take measures for engineering control. A lot of work including surface mapping, exploration, geotechnical testing, etc, showed that: the landslide volume is about 11104m3, for middle scale rock mass shear landslide, status stability is better. By comparison, the engineering control of the way of cutting slope reduction and the foot in foot is put forward, the stability coefficient of landslide after engineering treatment meets the standard requirement. The results can provide technical support for the project construction and reference for the similar projects.
Site development a landslide in rural resettlement point on Muguagou village of Gushan Hydropower Station of Hanjiang river, the terrain of the site is slope terrain, Limited by scale of terrain and immigration, residents need to be placed on the landslide, this need to take the landslide to take measures for engineering control. A lot of work including surface mapping, exploration, geotechnical testing, etc, showed that: the landslide volume is about 11104m3, for middle scale rock mass shear landslide, status stability is better. By comparison, the engineering control of the way of cutting slope reduction and the foot in foot is put forward, the stability coefficient of landslide after engineering treatment meets the standard requirement. The results can provide technical support for the project construction and reference for the similar projects.
2015, 23(s1): 452-464.
Based on the research of landslide stability analyses, the new failure stability analyses of thrust-type landslide are established. Based on the mechanism of thrust-type landslide, critical stresses slice block(SB)(or element) and relative determinations are suggested. Two failure modes are proposed for the progressive movement landslide, the modeⅠ:the whole slope failure is occurred along the soft-weak layer, the modeⅡ:The landslide failure is occurred in the trailing's edges along the soft-weak layer, but its ahead shear failure is happened along the sliding body. The critical stress state moves from the behind zone to the front zone of landslide progressively. TheScurve property of time and deformation relationship is shown for the different points on the sliding surface during deformation period, and a parabolic curve is presented for the relationship of deformation of different points on the sliding suface and height of landslide by means of results of landslide mechanism. The two kinds of curve properties between time and deformation are proposed based on the mechanical behavior classification of rock-soil mass: unstable and stable time and deformation curve. The characteristics of current stability analyses is researched, the stability analysis method of comprehensive sliding force and anti-sliding force, main thrust force method and displacement method based on deformation are suggested. The movement of landslide is studied, the definition of main sliding direction of landslide is proposed. The cause of no convergence is analyzed for FEM, a new method to take the sliding face as a boundary condition of FEM is proposed for landslide stability analyses, the boundary condition of sliding surface can described not only as perfect elasto-plastic model(PEPM), but also the new constitutive theories(JCM).The results of stability analyses by PEPM can take the comparisons with the traditional slice method, the real stress and strain fields can obtained by other models for landslide. The determination of potential sliding surface is determinate by probability method, energy principle and in-situ exploration method.
Based on the research of landslide stability analyses, the new failure stability analyses of thrust-type landslide are established. Based on the mechanism of thrust-type landslide, critical stresses slice block(SB)(or element) and relative determinations are suggested. Two failure modes are proposed for the progressive movement landslide, the modeⅠ:the whole slope failure is occurred along the soft-weak layer, the modeⅡ:The landslide failure is occurred in the trailing's edges along the soft-weak layer, but its ahead shear failure is happened along the sliding body. The critical stress state moves from the behind zone to the front zone of landslide progressively. TheScurve property of time and deformation relationship is shown for the different points on the sliding surface during deformation period, and a parabolic curve is presented for the relationship of deformation of different points on the sliding suface and height of landslide by means of results of landslide mechanism. The two kinds of curve properties between time and deformation are proposed based on the mechanical behavior classification of rock-soil mass: unstable and stable time and deformation curve. The characteristics of current stability analyses is researched, the stability analysis method of comprehensive sliding force and anti-sliding force, main thrust force method and displacement method based on deformation are suggested. The movement of landslide is studied, the definition of main sliding direction of landslide is proposed. The cause of no convergence is analyzed for FEM, a new method to take the sliding face as a boundary condition of FEM is proposed for landslide stability analyses, the boundary condition of sliding surface can described not only as perfect elasto-plastic model(PEPM), but also the new constitutive theories(JCM).The results of stability analyses by PEPM can take the comparisons with the traditional slice method, the real stress and strain fields can obtained by other models for landslide. The determination of potential sliding surface is determinate by probability method, energy principle and in-situ exploration method.
2015, 23(s1): 465-471.
The slope of spillway of Wudongde Hydropower Station is a toppling rock slope with a height of 150m. The slope is composed of thin layered meta-dolomite rock mass from Mesoproterozoic YinMin Formation, cleavage develops between the layers and attach sericite film along bedding plane. Rock mass integrity is poor, and rock mass quality is mainly IV level. In view of this, this paper studies the rock mass from the view of engineering geology based on the combination of mineral chemical analysis and field physico-mechanical test, such as lithology characteristics, structure characteristics and mechanical property. This paper analyzes the deformation model and evaluates the stability of the slope according to the results, and provides a basis for the design. Monitoring results illustrate the effectiveness of the support measures and the importance of timely support. The research has important value to the stability analysis of slope composed of special geological body.
The slope of spillway of Wudongde Hydropower Station is a toppling rock slope with a height of 150m. The slope is composed of thin layered meta-dolomite rock mass from Mesoproterozoic YinMin Formation, cleavage develops between the layers and attach sericite film along bedding plane. Rock mass integrity is poor, and rock mass quality is mainly IV level. In view of this, this paper studies the rock mass from the view of engineering geology based on the combination of mineral chemical analysis and field physico-mechanical test, such as lithology characteristics, structure characteristics and mechanical property. This paper analyzes the deformation model and evaluates the stability of the slope according to the results, and provides a basis for the design. Monitoring results illustrate the effectiveness of the support measures and the importance of timely support. The research has important value to the stability analysis of slope composed of special geological body.
2015, 23(s1): 472-479.
Shield construction technology had been widely used in urban subway construction, ground subsidence or collapse problems caused by shield construction had been highly attentioned. Based on the research results at home and abroad, analysis of the main reasons of surface subsidence or collapse caused by shield construction, it was put forward to carry out detection technology studies for holes behind the shield. Chengdu Metro Line 3as an engineering example, combined with lessons of Metro Line 1 and Line 2, accorrding to a large number of field tests, the comprehensive detection technology suitable for detection holes behind the shield was got, for special Chengdu Metro across the sand and gravel formations with complex physical and mechanical properties. The comprehensive detection technology including pre-construction, construction and post-construction detection technologies, with inside and outside detection technologies, a system was initially formed, which was worthy of similar projects and in-depth study.
Shield construction technology had been widely used in urban subway construction, ground subsidence or collapse problems caused by shield construction had been highly attentioned. Based on the research results at home and abroad, analysis of the main reasons of surface subsidence or collapse caused by shield construction, it was put forward to carry out detection technology studies for holes behind the shield. Chengdu Metro Line 3as an engineering example, combined with lessons of Metro Line 1 and Line 2, accorrding to a large number of field tests, the comprehensive detection technology suitable for detection holes behind the shield was got, for special Chengdu Metro across the sand and gravel formations with complex physical and mechanical properties. The comprehensive detection technology including pre-construction, construction and post-construction detection technologies, with inside and outside detection technologies, a system was initially formed, which was worthy of similar projects and in-depth study.
2015, 23(s1): 480-484.
Engineering practice has proved that single geological prediction method in forecasting of tunnel occurrence of missed judgment, misjudgment phenomenon serious, extremely easy to cause the collapse, water bursting and burst mud geology disaster, it is difficult to ensure tunnel construction safety. In this paper, Using the method of TRT, transient electromagnetic method, ground penetrating radar method, advanced horizontal drilling method of comprehensive geological prediction technology to forecast the rich water area in tunnel. Practice has proved that the combination of geological prediction technology into full play the technical advantages of various geological forecast method, can from solid to plane, from speculation to the intuitive and constraints from the tunnel to the outside of the tunnel forecast the change of the surrounding rock and groundwater ahead, provides effective reference for decision-making for the tunnel construction. This approach can partly avoid the geological hazards, such as collapse tunnel water gushing and sudden mud.
Engineering practice has proved that single geological prediction method in forecasting of tunnel occurrence of missed judgment, misjudgment phenomenon serious, extremely easy to cause the collapse, water bursting and burst mud geology disaster, it is difficult to ensure tunnel construction safety. In this paper, Using the method of TRT, transient electromagnetic method, ground penetrating radar method, advanced horizontal drilling method of comprehensive geological prediction technology to forecast the rich water area in tunnel. Practice has proved that the combination of geological prediction technology into full play the technical advantages of various geological forecast method, can from solid to plane, from speculation to the intuitive and constraints from the tunnel to the outside of the tunnel forecast the change of the surrounding rock and groundwater ahead, provides effective reference for decision-making for the tunnel construction. This approach can partly avoid the geological hazards, such as collapse tunnel water gushing and sudden mud.
2015, 23(s1): 485-491.
Gezhouba Water Control Project is the first dam on the Yangtze River., which is the important part of the Three Gorges Project.week intercalation is the most impotant reason that lead to shut down the energine construction which was started in less than two yeaes. At the same time, it was the key problem of anti-erosion and anti-sliding stability of dam foundation. The Gezhouba Water Control Project has beening running for nearly 30 years, and insiders general concern about whether the properties of these weak intercalation(shear zone) may deteriorate under the long-term seepage pressure, which may reduce the value of mechanical parameters and then endanger the dam safety. This paper makes a conclusion that the weak intercalation(shear zone) stay stability basically and has no signs of deterioration by focusing on the two geological monitoring points of foundation gallery and through analyzing of geological observation and the result of sampling test, which thanks to the environment condition that the weak intercalation(shear zone) is stability and benefit from the previous investigation. The research result can be used for reference in similar problems.
Gezhouba Water Control Project is the first dam on the Yangtze River., which is the important part of the Three Gorges Project.week intercalation is the most impotant reason that lead to shut down the energine construction which was started in less than two yeaes. At the same time, it was the key problem of anti-erosion and anti-sliding stability of dam foundation. The Gezhouba Water Control Project has beening running for nearly 30 years, and insiders general concern about whether the properties of these weak intercalation(shear zone) may deteriorate under the long-term seepage pressure, which may reduce the value of mechanical parameters and then endanger the dam safety. This paper makes a conclusion that the weak intercalation(shear zone) stay stability basically and has no signs of deterioration by focusing on the two geological monitoring points of foundation gallery and through analyzing of geological observation and the result of sampling test, which thanks to the environment condition that the weak intercalation(shear zone) is stability and benefit from the previous investigation. The research result can be used for reference in similar problems.
2015, 23(s1): 492-498.
Human engineering activities have gradually become the key inducing factor of geo-hazards at the disturbance region under the process of large-scale and dense hydropower development in West China, which arouses extensive attention. The Shang Tianzhen gully is a typical debris flow gully where is born of disturbances. On the basis of the investigation and analysis on formation process, fluid property and activity features, trend of development and debris flow growth characteristics are revealed. Especially, comparison survey shows that engineering disturbances take an important role in the growth of debris flow. In addition, it is predicted that engineering influence of debris flows in accordance with the engineering capabilities. All the contents mentioned above are signification to solve the similar engineering problem.
Human engineering activities have gradually become the key inducing factor of geo-hazards at the disturbance region under the process of large-scale and dense hydropower development in West China, which arouses extensive attention. The Shang Tianzhen gully is a typical debris flow gully where is born of disturbances. On the basis of the investigation and analysis on formation process, fluid property and activity features, trend of development and debris flow growth characteristics are revealed. Especially, comparison survey shows that engineering disturbances take an important role in the growth of debris flow. In addition, it is predicted that engineering influence of debris flows in accordance with the engineering capabilities. All the contents mentioned above are signification to solve the similar engineering problem.
2015, 23(s1): 499-503.
Xiluodu hydropower station is located on the Jinshajiang River, with a 285.5m high arch dam. The bedrock of the dam foundation consists of basalt, which can be dominantly classified as Ⅲ-1 class with some local distribution of disturbed Ⅲ-2 class. The average acoustic velocity of the bedrock is originally 4652ms-1, with about 28% being slower than 4000ms-1.After consolidation grouting treatment, the average velocity is greater than 5200ms-1, with less than 5% being slower than 4000ms-1.After treatment, the average velocity of the Ⅲ-1 class bedrock has reached 5300～5500ms-1, being increased by 2%～5%; the Ⅲ-2 class 4200～4700ms-1, being increased by 12%～18%; the disturbed belt 3600～4200ms-1, being increased by 10%～28%, respectively. The rock permeability are less than 3 Lu and the average borehole deformation modulus is 10-15GPa. Consolidation grouting has dramatically improved the geological condition of the Ⅲ-2 class rock mass and the disturbed belt, which has effectively improved the integrity and homogeneity of the riverbed dam foundation.
Xiluodu hydropower station is located on the Jinshajiang River, with a 285.5m high arch dam. The bedrock of the dam foundation consists of basalt, which can be dominantly classified as Ⅲ-1 class with some local distribution of disturbed Ⅲ-2 class. The average acoustic velocity of the bedrock is originally 4652ms-1, with about 28% being slower than 4000ms-1.After consolidation grouting treatment, the average velocity is greater than 5200ms-1, with less than 5% being slower than 4000ms-1.After treatment, the average velocity of the Ⅲ-1 class bedrock has reached 5300～5500ms-1, being increased by 2%～5%; the Ⅲ-2 class 4200～4700ms-1, being increased by 12%～18%; the disturbed belt 3600～4200ms-1, being increased by 10%～28%, respectively. The rock permeability are less than 3 Lu and the average borehole deformation modulus is 10-15GPa. Consolidation grouting has dramatically improved the geological condition of the Ⅲ-2 class rock mass and the disturbed belt, which has effectively improved the integrity and homogeneity of the riverbed dam foundation.
2015, 23(s1): 504-508.
With high selectivity and low dilution, Cut- and -fill stoping plays an irreplaceable role in deposit mining projects, especially in which occurrence conditions of orebody are complicated, surface environmental protection needed and rockburst easily triggered. Cut- and -fill mining practices of past decades demonstrated that the main factors affecting fill mass stability include engineering geological condition, back-fill strength, stoping technology and surrounding-rock boundary condition and so on. The back-fill strength is the key factor for success or failure of the backfilling project. And the dimension of orebody-stoping drift is the critical factor affecting fill mass supporting layer stability. The irregular boundaries between fill mass and surrounding rock can transfer part of the former self-gravity into the latter, reduce the load on the supporting layers, and then advance the stability of the fill mass.
With high selectivity and low dilution, Cut- and -fill stoping plays an irreplaceable role in deposit mining projects, especially in which occurrence conditions of orebody are complicated, surface environmental protection needed and rockburst easily triggered. Cut- and -fill mining practices of past decades demonstrated that the main factors affecting fill mass stability include engineering geological condition, back-fill strength, stoping technology and surrounding-rock boundary condition and so on. The back-fill strength is the key factor for success or failure of the backfilling project. And the dimension of orebody-stoping drift is the critical factor affecting fill mass supporting layer stability. The irregular boundaries between fill mass and surrounding rock can transfer part of the former self-gravity into the latter, reduce the load on the supporting layers, and then advance the stability of the fill mass.
2015, 23(s1): 509-515.
The research on the engineering properties of the deep overburden layer is one of the long-term problems in the field of geotechnical engineering investigation. The overburden layer in the dam area of Wudongde Hydropower Station on Jinsha River is deep, and it has complex causes and uneven material composition and structure, which make it difficult to study on the mechanical characteristics, physical and water-physical properties. High cofferdam and deep foundation pit stability problems are serious. In order to determine the engineering properties of the overburden layer and propose the physical and mechanical parameters required for engineering design, some field tests and laboratory tests have been done, such as dynamic penetration test, lateral pressure test, pumping test, sonic wave test, borehole digital TV, routine soil test and simulated gradation sample The engineering problems of the deep overburden layer were solved by conducting comparison and discussion, a reliable basis for the engineering design of high cofferdam and deep foundation pit of Wudongde Hydropower Station was provided. Those methods can be used for similar engineering projects.
The research on the engineering properties of the deep overburden layer is one of the long-term problems in the field of geotechnical engineering investigation. The overburden layer in the dam area of Wudongde Hydropower Station on Jinsha River is deep, and it has complex causes and uneven material composition and structure, which make it difficult to study on the mechanical characteristics, physical and water-physical properties. High cofferdam and deep foundation pit stability problems are serious. In order to determine the engineering properties of the overburden layer and propose the physical and mechanical parameters required for engineering design, some field tests and laboratory tests have been done, such as dynamic penetration test, lateral pressure test, pumping test, sonic wave test, borehole digital TV, routine soil test and simulated gradation sample The engineering problems of the deep overburden layer were solved by conducting comparison and discussion, a reliable basis for the engineering design of high cofferdam and deep foundation pit of Wudongde Hydropower Station was provided. Those methods can be used for similar engineering projects.
2015, 23(s1): 516-523.
With rapid development of China national economy, the energy demand continues to increase in the central and southeast-coastal areas of China. China timely to start the west-east gas pipeline Ⅲ project to import the abundant natural gas in Central Asia.The west-east gas pipeline Ⅲ has a 5220km pipeline which obliquely across the western, central and south-east of the country. There is a variety of physiognomy in the areas along the gas pipeline and the seismogeological environment is so complex that prone to geological disasters.It is important for the feasibility studies of the project to have an intensive geological survey and study along the pipeline areas, including the study of active fault, the earthquake and geological disasters dangerous analysis, and local tectonic stability assessment, in order to ensure the pipeline safe in its lifecycle, neither in its design, construction nor operation.
With rapid development of China national economy, the energy demand continues to increase in the central and southeast-coastal areas of China. China timely to start the west-east gas pipeline Ⅲ project to import the abundant natural gas in Central Asia.The west-east gas pipeline Ⅲ has a 5220km pipeline which obliquely across the western, central and south-east of the country. There is a variety of physiognomy in the areas along the gas pipeline and the seismogeological environment is so complex that prone to geological disasters.It is important for the feasibility studies of the project to have an intensive geological survey and study along the pipeline areas, including the study of active fault, the earthquake and geological disasters dangerous analysis, and local tectonic stability assessment, in order to ensure the pipeline safe in its lifecycle, neither in its design, construction nor operation.
2015, 23(s1): 524-528.
Take the unstable rock masses of the altitude concrete system of Yangfanggou hydropower station as a background. Based on investigation on spot and geological analysis, the boundary characteristics of the unstable rock-masses are analyzed; and the unstable rock-masses may to be failure through three modes: shear-sliding, rip-ropple and shear-falling is proposed; the stability classification standards of the different failure modes are established; the stability of the unstable rock-masses is analyzed by qualitative geological analysis and quantitative calculation. The results show that the nine dangerious rock-masses are highly likely to be failure under the action of rainfall or earthquake. Some protective measures are put forward, and the facts prove that the measures are successful and useful.
Take the unstable rock masses of the altitude concrete system of Yangfanggou hydropower station as a background. Based on investigation on spot and geological analysis, the boundary characteristics of the unstable rock-masses are analyzed; and the unstable rock-masses may to be failure through three modes: shear-sliding, rip-ropple and shear-falling is proposed; the stability classification standards of the different failure modes are established; the stability of the unstable rock-masses is analyzed by qualitative geological analysis and quantitative calculation. The results show that the nine dangerious rock-masses are highly likely to be failure under the action of rainfall or earthquake. Some protective measures are put forward, and the facts prove that the measures are successful and useful.
2015, 23(s1): 529-534.
Exploiting Urban underground space has become the development trend of domestic and international city. China's exploitation and utilization of underground space has been more and more rapidly and Safety is more and more important. This paper evaluates the main geology environmental effect factors of underground space resources safety development.it has the important practical significance for city underground space science development security.
Exploiting Urban underground space has become the development trend of domestic and international city. China's exploitation and utilization of underground space has been more and more rapidly and Safety is more and more important. This paper evaluates the main geology environmental effect factors of underground space resources safety development.it has the important practical significance for city underground space science development security.
2015, 23(s1): 535-546.
Landslide is a common global geologic disaster, and also one of the major geologic disasters in China. Landslides often incur a lot of casualties and enormous economic loss. Model test is one of the most effective ways on studying landslide mechanisms, which has irreplaceable advantage: it can reproduce the whole process of landslide; it can be observed with the characteristics of the landslide deformation and failure process; the inputs and outputs of the tests can be quantitatively and precisely measured; it's easy to control the condition and factors of model test. In recent years, a lot of research results on landslides using model test have been achieved. However, the existing research are relatively scattered and have not be systematically summarized. This paper aims to review the development of landslide model test systematically with emphases on influence factors of landslide(loading, rainfall, reservoir water level and earthquake et al.) and the measurement technologies, and provide prospect for the study on landslide model test in the future. The study may lay the foundation for the subsequent related work.
Landslide is a common global geologic disaster, and also one of the major geologic disasters in China. Landslides often incur a lot of casualties and enormous economic loss. Model test is one of the most effective ways on studying landslide mechanisms, which has irreplaceable advantage: it can reproduce the whole process of landslide; it can be observed with the characteristics of the landslide deformation and failure process; the inputs and outputs of the tests can be quantitatively and precisely measured; it's easy to control the condition and factors of model test. In recent years, a lot of research results on landslides using model test have been achieved. However, the existing research are relatively scattered and have not be systematically summarized. This paper aims to review the development of landslide model test systematically with emphases on influence factors of landslide(loading, rainfall, reservoir water level and earthquake et al.) and the measurement technologies, and provide prospect for the study on landslide model test in the future. The study may lay the foundation for the subsequent related work.
2015, 23(s1): 547-552.
This paper, based on the test section of the culvert tunnel of Fushi road sand pit on the flood storage project of sandpit of the western suburbs of Beijing, do the field test of advanced small pipe grouting on the shallow hydraulic tunnel of gravel strata. Based on the test results, this paper gets the key parameters of the tunnel grouting mixture ratio, grouting volume ratio, the extent, et al. It provides a basis for the construction safety of tunnel excavation and schedule optimization. The method and conclusion of research will be valuable experience and for reference in design, construction, supervision and further theoretical research on tunnel engineering under similar condition.
This paper, based on the test section of the culvert tunnel of Fushi road sand pit on the flood storage project of sandpit of the western suburbs of Beijing, do the field test of advanced small pipe grouting on the shallow hydraulic tunnel of gravel strata. Based on the test results, this paper gets the key parameters of the tunnel grouting mixture ratio, grouting volume ratio, the extent, et al. It provides a basis for the construction safety of tunnel excavation and schedule optimization. The method and conclusion of research will be valuable experience and for reference in design, construction, supervision and further theoretical research on tunnel engineering under similar condition.
2015, 23(s1): 553-557.
The development of the city raised a high demand of traffic, which led to the rapid development of the subway. Subway stations as a water-tight structure, would cause barrier effect to steady groundwater flow. Therefore, it is necessary to study the influence of underground structures on groundwater flow. This paper studies the effect of underground structures on groundwater flow by numerical methods, based on cell-centered finite difference method software Visual MODFLOW.In order to clarify the factors affecting groundwater flow by underground structures, the calculation model was simplified. Model is used only for single layer soil in the underground structure's influence on the groundwater flow. Studies have shown that: underground structures not only can affect the stability time of groundwater flow, but also makes the upstream water level rises, and the downstream water level dropped, whereby, the upstream's degree of influence is bigger than downstream. Water level difference around underground structures between the upstream and downstream, is one of the factors affecting them.
The development of the city raised a high demand of traffic, which led to the rapid development of the subway. Subway stations as a water-tight structure, would cause barrier effect to steady groundwater flow. Therefore, it is necessary to study the influence of underground structures on groundwater flow. This paper studies the effect of underground structures on groundwater flow by numerical methods, based on cell-centered finite difference method software Visual MODFLOW.In order to clarify the factors affecting groundwater flow by underground structures, the calculation model was simplified. Model is used only for single layer soil in the underground structure's influence on the groundwater flow. Studies have shown that: underground structures not only can affect the stability time of groundwater flow, but also makes the upstream water level rises, and the downstream water level dropped, whereby, the upstream's degree of influence is bigger than downstream. Water level difference around underground structures between the upstream and downstream, is one of the factors affecting them.
2015, 23(s1): 558-558.
In this paper, the engineering geological conditions of one construction site in Beijing has been described in details based on the field investigations. As to the 6 typical slopes, stereographic projection method and limit equilibrium method have been used to analyzed the stability of them. For limit equilibrium method, complex plane sliding and three dimensional wedge analysis model were adopted. The analysis results show that the engineering geological conditions of the site is relatively simple, the rock mass is main of layered structure. The stability of the 6 slopes in the site is relatively well. However, there is a fault cut through the site, therefore, the stability of slope No.2 should be paid more attention to. Combining the slope stability and high availability of building sites, the protection method of slope excavation, retaining wall and slope surface protection were proposed.
In this paper, the engineering geological conditions of one construction site in Beijing has been described in details based on the field investigations. As to the 6 typical slopes, stereographic projection method and limit equilibrium method have been used to analyzed the stability of them. For limit equilibrium method, complex plane sliding and three dimensional wedge analysis model were adopted. The analysis results show that the engineering geological conditions of the site is relatively simple, the rock mass is main of layered structure. The stability of the 6 slopes in the site is relatively well. However, there is a fault cut through the site, therefore, the stability of slope No.2 should be paid more attention to. Combining the slope stability and high availability of building sites, the protection method of slope excavation, retaining wall and slope surface protection were proposed.
2015, 23(s1): 567-572.
The stabilization of loess can make the water physical properties of loess change, improve the structure of loess, and improve the compressive strength of loess. In this paper, the ratio of lime and soil is 7:1, water solid ratio is 0.38:1, the concentration of the proportion is 72.7%, after the mixed slurry of loess, solidifying powder and water curing, we can find the compressive strength of the age of 9 days has been more than 1MPa, the maximum com-pressive strength has reached 1.28MPa, the maximum compressive strength of the age of 28 days has reached 3.54MPa which were more than ten times than the old loess strength. In the comparison experimentthe of cement and solid powder of lime soil ratio 4:1, compare the age of 11 days with age of 20 days, the compressive strength is more than two times than the cement, the hydrophilic loess converts to hydrophobic material by solidifying powder curing, the disintegration will not occur when it encounters water and the intensity in the water increases with time..
The stabilization of loess can make the water physical properties of loess change, improve the structure of loess, and improve the compressive strength of loess. In this paper, the ratio of lime and soil is 7:1, water solid ratio is 0.38:1, the concentration of the proportion is 72.7%, after the mixed slurry of loess, solidifying powder and water curing, we can find the compressive strength of the age of 9 days has been more than 1MPa, the maximum com-pressive strength has reached 1.28MPa, the maximum compressive strength of the age of 28 days has reached 3.54MPa which were more than ten times than the old loess strength. In the comparison experimentthe of cement and solid powder of lime soil ratio 4:1, compare the age of 11 days with age of 20 days, the compressive strength is more than two times than the cement, the hydrophilic loess converts to hydrophobic material by solidifying powder curing, the disintegration will not occur when it encounters water and the intensity in the water increases with time..
2015, 23(s1): 573-577.
In high-fill airport engineering, it is important to ground treatment for building airport on karst foundation. The characteristics of airport engineering is analysed, and the hazards of airport engineering in karst is summarized. According to the airport road groove and the influence zone, the investigation of karst foundation detection, surface karst treatment, underground karst treatment, treatment of karst water are proposed principles and measures. In accordance with detailed study of treatment for the airport road groove and the influence zone, excavation rock foundation, excavation cover soil and filling karst foundation treatment are proposed treatment methods and the construction process. Through the application of karst ground treatment for an airport in the southwest, processing method has been proposed, the treatment effect is significant.
In high-fill airport engineering, it is important to ground treatment for building airport on karst foundation. The characteristics of airport engineering is analysed, and the hazards of airport engineering in karst is summarized. According to the airport road groove and the influence zone, the investigation of karst foundation detection, surface karst treatment, underground karst treatment, treatment of karst water are proposed principles and measures. In accordance with detailed study of treatment for the airport road groove and the influence zone, excavation rock foundation, excavation cover soil and filling karst foundation treatment are proposed treatment methods and the construction process. Through the application of karst ground treatment for an airport in the southwest, processing method has been proposed, the treatment effect is significant.
2015, 23(s1): 578-583.
The study area is Chengkou County in Chongqing. The main goal of this paper is to carry out study of geological hazard susceptibility on the basis of logistic regression model and geospatial database in mountain area. The process contains three major phases. Firstly, thirteen factors were selected as impact factor in total based on geospatial data.they were slope angle, slop aspect, curvature, micro-landform, slope position, distance from drainage, lithology, distance from faults, distance from highway, elevation, normalized difference vegetation index(NDVI), consequent-reverse slop and mean annual precipitation. Secondly, rasterizing every layer on the basis of GIS technology and establishing geospatial database. Thirdly, Sample training was accomplished by R software, the value of regression coefficients was determined as well as geological hazard susceptibility map could be obtained. Meanwhile, the susceptibility can be divided into five grades: very low, low, medium, high and very high. At last, the evaluation result was tested by ROC curve, the value of AUC is 0.901 which indicates logistic regression model is highly available to study of geological hazard susceptibility in Chengkou County.
The study area is Chengkou County in Chongqing. The main goal of this paper is to carry out study of geological hazard susceptibility on the basis of logistic regression model and geospatial database in mountain area. The process contains three major phases. Firstly, thirteen factors were selected as impact factor in total based on geospatial data.they were slope angle, slop aspect, curvature, micro-landform, slope position, distance from drainage, lithology, distance from faults, distance from highway, elevation, normalized difference vegetation index(NDVI), consequent-reverse slop and mean annual precipitation. Secondly, rasterizing every layer on the basis of GIS technology and establishing geospatial database. Thirdly, Sample training was accomplished by R software, the value of regression coefficients was determined as well as geological hazard susceptibility map could be obtained. Meanwhile, the susceptibility can be divided into five grades: very low, low, medium, high and very high. At last, the evaluation result was tested by ROC curve, the value of AUC is 0.901 which indicates logistic regression model is highly available to study of geological hazard susceptibility in Chengkou County.
2015, 23(s1): 584-589.
Abstruct Determined the probability distribution of coal floor rock mass mechanical parameters correctly is the premise of random uncertainty analysis of coal mining on the confined water barrier ability of bottom water.Based on the test results of lower group coal water-resisting floor rock mass(mudstone, siltstone and sandstone as representatives) mechanical parameters, the normal distribution, lognormal distribution and weibull distribution were used to fit the probability distribution, and k-s test was used to estimate the goodness of fit. On this basis, based on the thickness weight of three kinds of rocks in the water-resisting floor, the mean and variance of floor rock mechanics parameters were deduced. The results showed that: the best fit of water-resisting floor rock strength and deformation parameters is normal distribution, followed by lognormal and weibull distribution. The Poisson's ratio and elastic modulus of the overall floor are 0.35 and 36.46GPa, the variances are 0.01 and 1.15 respectively; the mean and variance of overall compressive strength are 37.82MPa and 583.41, of tensile strength are 2.62MPa and 2.23, of cohesion are 2.13MPa and 0.96, of friction angle are 32.93and 1.96.
Abstruct Determined the probability distribution of coal floor rock mass mechanical parameters correctly is the premise of random uncertainty analysis of coal mining on the confined water barrier ability of bottom water.Based on the test results of lower group coal water-resisting floor rock mass(mudstone, siltstone and sandstone as representatives) mechanical parameters, the normal distribution, lognormal distribution and weibull distribution were used to fit the probability distribution, and k-s test was used to estimate the goodness of fit. On this basis, based on the thickness weight of three kinds of rocks in the water-resisting floor, the mean and variance of floor rock mechanics parameters were deduced. The results showed that: the best fit of water-resisting floor rock strength and deformation parameters is normal distribution, followed by lognormal and weibull distribution. The Poisson's ratio and elastic modulus of the overall floor are 0.35 and 36.46GPa, the variances are 0.01 and 1.15 respectively; the mean and variance of overall compressive strength are 37.82MPa and 583.41, of tensile strength are 2.62MPa and 2.23, of cohesion are 2.13MPa and 0.96, of friction angle are 32.93and 1.96.
2015, 23(s1): 590-596.
The numerical simulation technique of three-phase non-isothermal flow in heterogeneous porous media was adopted to analyze the point source leakage, migration, and in situ air sparging(AS)process of Light Non-Aqueous Phase Liquids(LNAPLs) and Dense Non-Aqueous Phase Liquids(DNAPLs).The mass fraction distribution and removal rate of the contaminants were studied. The effects of sparging flow rate, well distance, and sparging depth on the contaminant removal rate were discussed. Theoretical analysis indicates that both the mass fraction distribution scope and concentration of dissolved benzene are larger than that of dissolved trichloroethylene(TCE).There exist peak concentration regions around 1～2m above the underground water level for both benzene and TCE.In addition, benzene mainly concentrates in the upper part of the aquifer as well as the vadose zone, while obvious distribution of the TCE can be found in the lower part of the aquifer. The largest migration depth of TCE is 5 times as much as that of benzene. The ratio of contaminant removal after a short period(1 day) of continuous AS remediation increases a little with the increase of sparging depth, decreases quickly with the increase of well spacing, but increases a lot with the air flow rate. To reach the required remediation standard given by standards, the operation periods for air sparging of benzene and TCE contaminated underground water need 60 and 30 days respectively, indicating a shorter period for TCE.In addition, experimental research achievements from different literature were referenced to verify the reasonability of above theoretical analysis.
The numerical simulation technique of three-phase non-isothermal flow in heterogeneous porous media was adopted to analyze the point source leakage, migration, and in situ air sparging(AS)process of Light Non-Aqueous Phase Liquids(LNAPLs) and Dense Non-Aqueous Phase Liquids(DNAPLs).The mass fraction distribution and removal rate of the contaminants were studied. The effects of sparging flow rate, well distance, and sparging depth on the contaminant removal rate were discussed. Theoretical analysis indicates that both the mass fraction distribution scope and concentration of dissolved benzene are larger than that of dissolved trichloroethylene(TCE).There exist peak concentration regions around 1～2m above the underground water level for both benzene and TCE.In addition, benzene mainly concentrates in the upper part of the aquifer as well as the vadose zone, while obvious distribution of the TCE can be found in the lower part of the aquifer. The largest migration depth of TCE is 5 times as much as that of benzene. The ratio of contaminant removal after a short period(1 day) of continuous AS remediation increases a little with the increase of sparging depth, decreases quickly with the increase of well spacing, but increases a lot with the air flow rate. To reach the required remediation standard given by standards, the operation periods for air sparging of benzene and TCE contaminated underground water need 60 and 30 days respectively, indicating a shorter period for TCE.In addition, experimental research achievements from different literature were referenced to verify the reasonability of above theoretical analysis.
2015, 23(s1): 597-602.
The mechanisms of contaminant transport in soil include advection, diffusion, dispersion, sorption, biological degradation, chemical reaction and so on. In engineering practice, deformation of consolidation will take place due to self-weight of soils and applied load. On the one hand, consolidation of contaminated soils will lead to advection of the contaminated pore fluid. On the other hand, the void ratio and consolidation coefficient of the soil as well as the hydrodynamic dispersion coefficient of the contaminant will also be changed with the development of deformation, which will comprehensively influence the transport behavior of the contaminants. At first, different types of consolidation-induced contaminant transport models including large strain and small strain consolidation models are summarized. Then, different kinds of test methods and equipment are listed and compared. Finally, related engineering application cases are presented.
The mechanisms of contaminant transport in soil include advection, diffusion, dispersion, sorption, biological degradation, chemical reaction and so on. In engineering practice, deformation of consolidation will take place due to self-weight of soils and applied load. On the one hand, consolidation of contaminated soils will lead to advection of the contaminated pore fluid. On the other hand, the void ratio and consolidation coefficient of the soil as well as the hydrodynamic dispersion coefficient of the contaminant will also be changed with the development of deformation, which will comprehensively influence the transport behavior of the contaminants. At first, different types of consolidation-induced contaminant transport models including large strain and small strain consolidation models are summarized. Then, different kinds of test methods and equipment are listed and compared. Finally, related engineering application cases are presented.
2015, 23(s1): 603-610.
For thick coal seam at mechanized caving mining conditions of coal project example, Analysis the perturbation failure law of overlying strata and explore the basic conditions for the formation of roof separation space. Discriminate cavity type separation location of the study area, obtained a total of 5 roof rock can develop the cavity type separation space. Draw the fitting curve of the relationship between mining height and the ratio of the height of the fractured zone to the mining height by the empirical formula for thick coal seam, then draw the maximum development highly evaluates 221.8m for water flowing fractured zone of overlying strata. Simulate the coal mining process by numerical simulation of FLAC3D, draw vertical displacement of roof rock changes, verify the correctness of the theory.
For thick coal seam at mechanized caving mining conditions of coal project example, Analysis the perturbation failure law of overlying strata and explore the basic conditions for the formation of roof separation space. Discriminate cavity type separation location of the study area, obtained a total of 5 roof rock can develop the cavity type separation space. Draw the fitting curve of the relationship between mining height and the ratio of the height of the fractured zone to the mining height by the empirical formula for thick coal seam, then draw the maximum development highly evaluates 221.8m for water flowing fractured zone of overlying strata. Simulate the coal mining process by numerical simulation of FLAC3D, draw vertical displacement of roof rock changes, verify the correctness of the theory.
2015, 23(s1): 611-616.
Taking Hefeng Waidongshan debris landslide in Huangshan Anhui Province as a case, the ralationship between the deformation-develop process and the critical water content of debris landslide was studied by the discrete element method. And the critical water content was proposed according to the results, providing evidence for the study of warning criterion of debris landslides. The simulation results indicate that, rainfall leads to the increase of water content of the debris landslide, which will reduce its physical and mechanical properties, induced landslide. When the water content of Waidongshan landslide is less than 26%, the landslide is stable. When the water content of Waidongshan landslide is greater than 29%, the landslide will make deformation. The results showen that the critical water content of Hefeng Waidongshan debris landslide is between 26%～29%. the study of warning criterion of debris landslides, can be studied the relationship between the rainfall and the warter content of debris landslide further. So the critical rainfall can be proposed, providing the basis for the study of warning criterion of debris landslides.
Taking Hefeng Waidongshan debris landslide in Huangshan Anhui Province as a case, the ralationship between the deformation-develop process and the critical water content of debris landslide was studied by the discrete element method. And the critical water content was proposed according to the results, providing evidence for the study of warning criterion of debris landslides. The simulation results indicate that, rainfall leads to the increase of water content of the debris landslide, which will reduce its physical and mechanical properties, induced landslide. When the water content of Waidongshan landslide is less than 26%, the landslide is stable. When the water content of Waidongshan landslide is greater than 29%, the landslide will make deformation. The results showen that the critical water content of Hefeng Waidongshan debris landslide is between 26%～29%. the study of warning criterion of debris landslides, can be studied the relationship between the rainfall and the warter content of debris landslide further. So the critical rainfall can be proposed, providing the basis for the study of warning criterion of debris landslides.
2015, 23(s1): 617-623.
The buried depth and geometry of potential sliding surface is the fundamental basis of estimating the evolution mechanism and performing administration of a landslide. The precision of engineering geological survey was closely related to the quality of landslide controlling engineering. Conventional techniques to obtain information about landslide structure were mainly drilling, pitting, trenching and so on, but they were time consuming, more labor and expense, especially a degree of damage on landslide body. These techniques were not conductive to do large scale surveying due to above limitations. In this study, we observed digital signals on the underlie bedrock gravel landslide using microtremor array, and extracted the shear wave velocity structure with Spatial Autocorrelation(SPAC)method. Compared to the boreholes, the results indicated that the depth of stratigraphic distribution and clear underlie bedrock interface basically coincided with drilling with high resolution and without limitation of terrains. MSM was superior to borehole in terms of surveying depth, scale and expense, and allowed a large scale and high density investigation of structure characteristics of underlie bedrock gravel landslide.
The buried depth and geometry of potential sliding surface is the fundamental basis of estimating the evolution mechanism and performing administration of a landslide. The precision of engineering geological survey was closely related to the quality of landslide controlling engineering. Conventional techniques to obtain information about landslide structure were mainly drilling, pitting, trenching and so on, but they were time consuming, more labor and expense, especially a degree of damage on landslide body. These techniques were not conductive to do large scale surveying due to above limitations. In this study, we observed digital signals on the underlie bedrock gravel landslide using microtremor array, and extracted the shear wave velocity structure with Spatial Autocorrelation(SPAC)method. Compared to the boreholes, the results indicated that the depth of stratigraphic distribution and clear underlie bedrock interface basically coincided with drilling with high resolution and without limitation of terrains. MSM was superior to borehole in terms of surveying depth, scale and expense, and allowed a large scale and high density investigation of structure characteristics of underlie bedrock gravel landslide.
2015, 23(s1): 624-630.
In order to solve exchange of qualitative and quantitative in the process of debris flow risk assessment, this paper establishes a model of debris flow risk assessment based on Cloud Model theory. First, we obtain the numerical characteristics of ten classified factors according to the classification standard method. Then we use the forward cloud generator to evaluate the measured data and calculate the certainty degrees of each gully belonging to the four grades. Second, combining the evaluation factor weights, we calculate the maximum comprehensive certainty degree of each gully. According to the four debris flow gully measured data in Miyun county of Beijing, this paper evaluates their risk assessment with Cloud Model. Compare the Cloud Model results with extension evaluation results, we find that the results are mostly the same. Therefore, we can make conclusion that the cloud model method is reasonable and accurate, which can evaluate the degrees of debris flow risk.
In order to solve exchange of qualitative and quantitative in the process of debris flow risk assessment, this paper establishes a model of debris flow risk assessment based on Cloud Model theory. First, we obtain the numerical characteristics of ten classified factors according to the classification standard method. Then we use the forward cloud generator to evaluate the measured data and calculate the certainty degrees of each gully belonging to the four grades. Second, combining the evaluation factor weights, we calculate the maximum comprehensive certainty degree of each gully. According to the four debris flow gully measured data in Miyun county of Beijing, this paper evaluates their risk assessment with Cloud Model. Compare the Cloud Model results with extension evaluation results, we find that the results are mostly the same. Therefore, we can make conclusion that the cloud model method is reasonable and accurate, which can evaluate the degrees of debris flow risk.
2015, 23(s1): 631-635.
Based on the study on the environmental geological problems such as deep rock's integrity of coal mining area, the change of shallow rock's bearing capacity, groundwater and surface water in Tai'an, this paper analyzes the geologic environmental effect in subsidence area. It shows that the present extracting technique of coal has great effect on geologic environment. And some area has been greatly influenced, unlikely recover any time soon. The surface subsidence caused by coal mining has little effect on agricultural production but great effect on landscapes, the ground stability, the surface water distribution area and the water level. The negative environmental effects above are bad for the economic development in coal mining subsidence area and they have significantly hindered the rational exploitation and utilization of groundwater. In response to these issues, this paper provides the reasonable plans of coal planning area in the countermeasures part which can reduce or even avoid the negative environmental effects and encourage the normal development of economy, realizing the consideration to environment and economy benefit.
Based on the study on the environmental geological problems such as deep rock's integrity of coal mining area, the change of shallow rock's bearing capacity, groundwater and surface water in Tai'an, this paper analyzes the geologic environmental effect in subsidence area. It shows that the present extracting technique of coal has great effect on geologic environment. And some area has been greatly influenced, unlikely recover any time soon. The surface subsidence caused by coal mining has little effect on agricultural production but great effect on landscapes, the ground stability, the surface water distribution area and the water level. The negative environmental effects above are bad for the economic development in coal mining subsidence area and they have significantly hindered the rational exploitation and utilization of groundwater. In response to these issues, this paper provides the reasonable plans of coal planning area in the countermeasures part which can reduce or even avoid the negative environmental effects and encourage the normal development of economy, realizing the consideration to environment and economy benefit.
2015, 23(s1): 636-636.
The method of using the stone-column in soft clay ground treatment has been applied widely in subgrade engineering. This study proposes a conversion method, using the unequal strain assumption theory, to obtain the equivalent plane-strain model of the unit cell. Firstly, the plane models of the pile-soil unit, based on equal strain assumption and unequal strain assumption theory, are established by ABAQUS.Secondly, the simulation results of these two models are compared with a reasonable axisymmetric result, and the results show that the unequal strain assumption theory is more suitable. Finally, a plateau wetland highway soft soil subgrade engineering is simulated using these two models, and the results further prove that the transformation model based on the unequal strain assumption theory is more reasonable.
The method of using the stone-column in soft clay ground treatment has been applied widely in subgrade engineering. This study proposes a conversion method, using the unequal strain assumption theory, to obtain the equivalent plane-strain model of the unit cell. Firstly, the plane models of the pile-soil unit, based on equal strain assumption and unequal strain assumption theory, are established by ABAQUS.Secondly, the simulation results of these two models are compared with a reasonable axisymmetric result, and the results show that the unequal strain assumption theory is more suitable. Finally, a plateau wetland highway soft soil subgrade engineering is simulated using these two models, and the results further prove that the transformation model based on the unequal strain assumption theory is more reasonable.
2015, 23(s1): 642-650.
Owing to its deficiency in considering influence factors of deep rock mass quality and determination of evaluation index values, the traditional RMR method has many limitations in the quality evaluation of deep mining rock mass. The marking indexes including uniaxial compressive strength of rock, rock quality designation, joint space and in-situ stress in traditional RMR method are firstly revised by calculation method of continuous thinning, regression curves and continuity equations between evaluation indexes and score values are obtained. Secondly, based on the analysis of bad geological factors and deep mining technology influence in rock mass quality, two new indexes including blasting vibration effect coefficient and stope exposed area are put forward; furthermore, M-IRMR evaluation system is established. Finally, the M-IRMR method is applied to the rock mass quality evaluation of Sanshandao gold mine which is a deep mining mine near coast. Achieved results will provide certain guiding significance to stability evaluation of rock engineering in deep mining mine.
Owing to its deficiency in considering influence factors of deep rock mass quality and determination of evaluation index values, the traditional RMR method has many limitations in the quality evaluation of deep mining rock mass. The marking indexes including uniaxial compressive strength of rock, rock quality designation, joint space and in-situ stress in traditional RMR method are firstly revised by calculation method of continuous thinning, regression curves and continuity equations between evaluation indexes and score values are obtained. Secondly, based on the analysis of bad geological factors and deep mining technology influence in rock mass quality, two new indexes including blasting vibration effect coefficient and stope exposed area are put forward; furthermore, M-IRMR evaluation system is established. Finally, the M-IRMR method is applied to the rock mass quality evaluation of Sanshandao gold mine which is a deep mining mine near coast. Achieved results will provide certain guiding significance to stability evaluation of rock engineering in deep mining mine.
2015, 23(s1): 651-653.
Load test is a major test method in deciding ground bearing capacity. And due to fast and convenience in test, dynamic penetration test is also considered to be a supplementary method. So far, relations between dynamic penetration test count and ground bearing capacity, discussed only in some industrial and regional code and construction, are based on massive original test data. Base on theory of dynamic load and take light dynamic penetration test for an example, this article takes similarity between light dynamic penetration test and load test into account, making a discussion over relations between light dynamic penetration test count and ground bearing capacity.
Load test is a major test method in deciding ground bearing capacity. And due to fast and convenience in test, dynamic penetration test is also considered to be a supplementary method. So far, relations between dynamic penetration test count and ground bearing capacity, discussed only in some industrial and regional code and construction, are based on massive original test data. Base on theory of dynamic load and take light dynamic penetration test for an example, this article takes similarity between light dynamic penetration test and load test into account, making a discussion over relations between light dynamic penetration test count and ground bearing capacity.
2015, 23(s1): 654-659.
Based on statistical analysis of standard penetration, vane shear and quick direct shear tests for marine facies clayed soil in the Hulushan bay at Changing island, Dalian, the eigenvalues for these tests were determined in this study. By analyzing the average test values by depth grouping, 15 kinds of empirical relationships between these tests were also built for this area.
Based on statistical analysis of standard penetration, vane shear and quick direct shear tests for marine facies clayed soil in the Hulushan bay at Changing island, Dalian, the eigenvalues for these tests were determined in this study. By analyzing the average test values by depth grouping, 15 kinds of empirical relationships between these tests were also built for this area.
2015, 23(s1): 660-667.
Slope instability under rainfall has a series of omens. In this paper, it is proved that rainfall infiltration play a very important rule in the process of the slope failure by the model test method. The mechanism of slope failure caused by rainfall infiltration is explained with numerical simulation method. Several monitoring methods were applied to the model test in this paper. In the model test, variation of soil water content is available by TDR-3 Sensors, and erosion situation of slope body can be observed before its unsteadiness, which show that the nature causes of the landslide are the variation of Soil water content and the water softening. To conclude time-strain relations as well as the evolution of slope-mass slide displacement through monitoring the slope strain variation with FBG Sensors. Then the potential damage position of week structural plane can be located. In addition, dial indicators were used to monitor the displacement of the slope. The slope failure is divided into three stages: initialization phase, creeping and sliding stage, acceleration phase and describe the characteristics of each stages. In the end, the forecast methods of slope failure are put forward with the histogram of the landslide speed.
Slope instability under rainfall has a series of omens. In this paper, it is proved that rainfall infiltration play a very important rule in the process of the slope failure by the model test method. The mechanism of slope failure caused by rainfall infiltration is explained with numerical simulation method. Several monitoring methods were applied to the model test in this paper. In the model test, variation of soil water content is available by TDR-3 Sensors, and erosion situation of slope body can be observed before its unsteadiness, which show that the nature causes of the landslide are the variation of Soil water content and the water softening. To conclude time-strain relations as well as the evolution of slope-mass slide displacement through monitoring the slope strain variation with FBG Sensors. Then the potential damage position of week structural plane can be located. In addition, dial indicators were used to monitor the displacement of the slope. The slope failure is divided into three stages: initialization phase, creeping and sliding stage, acceleration phase and describe the characteristics of each stages. In the end, the forecast methods of slope failure are put forward with the histogram of the landslide speed.
2015, 23(s1): 668-675.
The method of using the dielectric constant of the soil to determine the soil volumetric water content has been used widely by researchers. There exist a lot of works on TDR which can also measure the soil volumetric water content, but little research about the 5TM water content sensors. On one side, there almost has no research on 5TM in various soil; on the other side, the applicability evaluation of 5TM in sub-zero is unknown. In this study, three kinds of test materials were used, a Qinghai-Tibet red clay, a silt and a Micro silica. First, we analyzed the relationship between the dielectric constant and the soil volumetric water content, we revised the Topp(1980)formula and determined the value of a and b in Ledieu formula. Besides, a logarithmic formula to confirm the soil volumetric water content was proposed. By comparison, the fixed Topp formula can be used in all kind of test materials, this empirical formula gives a good response to the relationship between the dielectric constant and the soil volumetric water content. Second, by comparison the results with NMR, a new - empirical equation of saturated Qinghai-Tibetan red clay in freezing condition has been proposed, and the applicability evaluation of 5TM in heat and moisture of frozen soil has been researched.
The method of using the dielectric constant of the soil to determine the soil volumetric water content has been used widely by researchers. There exist a lot of works on TDR which can also measure the soil volumetric water content, but little research about the 5TM water content sensors. On one side, there almost has no research on 5TM in various soil; on the other side, the applicability evaluation of 5TM in sub-zero is unknown. In this study, three kinds of test materials were used, a Qinghai-Tibet red clay, a silt and a Micro silica. First, we analyzed the relationship between the dielectric constant and the soil volumetric water content, we revised the Topp(1980)formula and determined the value of a and b in Ledieu formula. Besides, a logarithmic formula to confirm the soil volumetric water content was proposed. By comparison, the fixed Topp formula can be used in all kind of test materials, this empirical formula gives a good response to the relationship between the dielectric constant and the soil volumetric water content. Second, by comparison the results with NMR, a new - empirical equation of saturated Qinghai-Tibetan red clay in freezing condition has been proposed, and the applicability evaluation of 5TM in heat and moisture of frozen soil has been researched.
2015, 23(s1): 676-682.
With the total area of 882km2, Xixian Area is the key construction projects for Xixian integration in Shaanxi province. Although the Xixian area has obvious advantages of location and economy in west of China, it also is subjected to some risks of geological problems due to complex topography and geological structure. Therefore, it is significant to carry out urban geological research in the study area. As a case study, the suitability evaluation of land for construction of Xixian Area was studied based on the methods of analytic hierarchy process(AHP) and MapGIS.The results show that suitable area for living and public facilities is mainly compose of the most suitable and suitable, accounts for 72.58% of the area, and the unsuitable area takes up 22.30%.The most suitable and suitable areas are mainly distributed on the terrace and loess tableland. While the unsuitable areas are mainly distributed on the flood plain and high flood plain, the contact zones between the Jinghe River and loess tableland. Because of the existing geological problems of active faults, landslide, sand liquefaction in these areas, and it is consistent with the practical survey results.
With the total area of 882km2, Xixian Area is the key construction projects for Xixian integration in Shaanxi province. Although the Xixian area has obvious advantages of location and economy in west of China, it also is subjected to some risks of geological problems due to complex topography and geological structure. Therefore, it is significant to carry out urban geological research in the study area. As a case study, the suitability evaluation of land for construction of Xixian Area was studied based on the methods of analytic hierarchy process(AHP) and MapGIS.The results show that suitable area for living and public facilities is mainly compose of the most suitable and suitable, accounts for 72.58% of the area, and the unsuitable area takes up 22.30%.The most suitable and suitable areas are mainly distributed on the terrace and loess tableland. While the unsuitable areas are mainly distributed on the flood plain and high flood plain, the contact zones between the Jinghe River and loess tableland. Because of the existing geological problems of active faults, landslide, sand liquefaction in these areas, and it is consistent with the practical survey results.
2015, 23(s1): 683-688.
According to the specific requirements of geological disaster prevention to geological exploration in the three gorges reservoir area, based on the database management system(DBMS), computer aided drawing system(CADS), geographic information system(GIS)technology and 3D modeling and spatial analysis technology(3DAS), discussed three key technical problems caused by scientific visualization: through the combination of geological interpolation and mathematical interpolation to improve the precision of the 3 d model, through the combination of 3 d model and database to enlarge the traditional CADS and through the double C(Center, data Center and application Center) model to process the system integration, Provide visual expression and analysis support from the area to the point, from the ground to the underground for disaster geological research and prevention.
According to the specific requirements of geological disaster prevention to geological exploration in the three gorges reservoir area, based on the database management system(DBMS), computer aided drawing system(CADS), geographic information system(GIS)technology and 3D modeling and spatial analysis technology(3DAS), discussed three key technical problems caused by scientific visualization: through the combination of geological interpolation and mathematical interpolation to improve the precision of the 3 d model, through the combination of 3 d model and database to enlarge the traditional CADS and through the double C(Center, data Center and application Center) model to process the system integration, Provide visual expression and analysis support from the area to the point, from the ground to the underground for disaster geological research and prevention.
2015, 23(s1): 689-694.
At present the hand-dug piles and micro piles of existing features and defects, we propose a fast, safe, environmentally friendly sliding retaining structures-trenchless pile, can play similar to the hand-dug piles role. Compared with tthe hand-dug piles can be fully mechanized construction, its biggest advantage is a fast, environmental protection, conservation, safety, with significant economic and social benefits. Suitable for rock and sandstone and mudstone landslide landslide, particularly suitable for rail, road or need to quickly get through life passage disaster emergency rescue work, the application prospect.
At present the hand-dug piles and micro piles of existing features and defects, we propose a fast, safe, environmentally friendly sliding retaining structures-trenchless pile, can play similar to the hand-dug piles role. Compared with tthe hand-dug piles can be fully mechanized construction, its biggest advantage is a fast, environmental protection, conservation, safety, with significant economic and social benefits. Suitable for rock and sandstone and mudstone landslide landslide, particularly suitable for rail, road or need to quickly get through life passage disaster emergency rescue work, the application prospect.
2015, 23(s1): 695-698.
On the east coast in our country, there are many Coastal liquefiable ground. This kind of groud compared with general liquefiable ground, there are more clay interlayer. The resonant compaction method with crisscross section vibratory probe as a new method of liquefiable ground treatment, whether in the processing of Coastal liquefiable ground has good processing effect, is a focus in the study of this article. Combining the use of resonant compaction method in highway of HuaiYan(Dafeng port section) project, I judge the treatment with methodsof SPT and CPT, both of before and after the treatment. Results show that the resonant compaction methodwith crisscross section vibratory probe can achieve good treatment effect in Coastal liquefiable ground. This method has good application prospect.
On the east coast in our country, there are many Coastal liquefiable ground. This kind of groud compared with general liquefiable ground, there are more clay interlayer. The resonant compaction method with crisscross section vibratory probe as a new method of liquefiable ground treatment, whether in the processing of Coastal liquefiable ground has good processing effect, is a focus in the study of this article. Combining the use of resonant compaction method in highway of HuaiYan(Dafeng port section) project, I judge the treatment with methodsof SPT and CPT, both of before and after the treatment. Results show that the resonant compaction methodwith crisscross section vibratory probe can achieve good treatment effect in Coastal liquefiable ground. This method has good application prospect.
2015, 23(s1): 699-705.
It is the important research direction to realize intelligent optimization design in underground mining.so, this paper present a method to optimize stope parameters based on the combining of evolutionary algorithm, orthogonal test and FLAC3D.Firstly, three dimension model of stope with different parameters are established by orthogonal-simulation, then, genetic programming is used to obtain the nonlinear relationship between displacement index and stope parameters, finally, the optimization parameters are gained by means of genetic algorithm. Engineering application shows that this method is a fast optimization of stope parameter, which has good practical value.
It is the important research direction to realize intelligent optimization design in underground mining.so, this paper present a method to optimize stope parameters based on the combining of evolutionary algorithm, orthogonal test and FLAC3D.Firstly, three dimension model of stope with different parameters are established by orthogonal-simulation, then, genetic programming is used to obtain the nonlinear relationship between displacement index and stope parameters, finally, the optimization parameters are gained by means of genetic algorithm. Engineering application shows that this method is a fast optimization of stope parameter, which has good practical value.
2015, 23(s1): 706-711.
Composite foundation with cement-fly ash-gravel piles had been widely applied to the average unit weight and soil of consolidation which had completed the grain filling soil foundation. Based on practical engineering, first of all, Use of cement fly ash gravel pile low-strain integrity test gauge in the nation, evaluate its effective length of pile within the scope of the pile integrity; in addition, through the static load test to verify the cement fly ash gravel pile composite foundation bearing capacity and bearing capacity of single pile composite foundation to enhance body whether meet the design requirements; at the same time, combined with the construction pile driving records, the geotechnical engineering investigation report, the design drawings of pile foundation and other information, come to the Objective comprehensive evaluation of the bearing capacity values and integrity of pile body, provide the basis for construction engineering design and construction.
Composite foundation with cement-fly ash-gravel piles had been widely applied to the average unit weight and soil of consolidation which had completed the grain filling soil foundation. Based on practical engineering, first of all, Use of cement fly ash gravel pile low-strain integrity test gauge in the nation, evaluate its effective length of pile within the scope of the pile integrity; in addition, through the static load test to verify the cement fly ash gravel pile composite foundation bearing capacity and bearing capacity of single pile composite foundation to enhance body whether meet the design requirements; at the same time, combined with the construction pile driving records, the geotechnical engineering investigation report, the design drawings of pile foundation and other information, come to the Objective comprehensive evaluation of the bearing capacity values and integrity of pile body, provide the basis for construction engineering design and construction.
2015, 23(s1): 712-720.
The paper describes a new method of failure depth of coal seam floor by using BOTDR(Brillouin Optical Time Domain Reflectometer) distributed optical fiber sensing technology. Taking a coal mine in Huainan as an example, a distributed fiber monitoring scheme of coal seam floor deformation was designed. By monitoring the deformation state and the strain distribution of the sensing optical cable buried in the floor of coal seam in the monitored space, combined with the consideration of coal seam floor strata structure, the distribution characteristic and the changes of deformation of coal seam floor during the process of the working face advancing are presented. The results show that, the BOTDR distributed optical fiber sensing technology can not only accurately reflect the deformation of coal seam floor but also monitor the whole process of progressive deformation and failure of the floor failure depth development. Thereafter, it's possible to determine the failure of the floor failure depth according to the strain distribution of sensing cables.
The paper describes a new method of failure depth of coal seam floor by using BOTDR(Brillouin Optical Time Domain Reflectometer) distributed optical fiber sensing technology. Taking a coal mine in Huainan as an example, a distributed fiber monitoring scheme of coal seam floor deformation was designed. By monitoring the deformation state and the strain distribution of the sensing optical cable buried in the floor of coal seam in the monitored space, combined with the consideration of coal seam floor strata structure, the distribution characteristic and the changes of deformation of coal seam floor during the process of the working face advancing are presented. The results show that, the BOTDR distributed optical fiber sensing technology can not only accurately reflect the deformation of coal seam floor but also monitor the whole process of progressive deformation and failure of the floor failure depth development. Thereafter, it's possible to determine the failure of the floor failure depth according to the strain distribution of sensing cables.
2015, 23(s1): 721-727.
The combined method with vacuum and surcharge preloading is an effective alternative to improve the thick soft soil. This paper introduced a field test of soft soil improved by the combined method with vacuum and surcharge preloading. The vacuum pressure under membrane, settlement of ground surface and pore water pressure in soil were monitored during the preloading period. The final settlement was predicted based on the field data. The average degrees of consolidation in terms of stress and strain were calculated respectively. The test results indicated that the differential settlement was mainly developed during the surcharge preloading period. The vacuum pressure decreased down the drain length. The computed average degrees of consolidation in terms of stress and strain were 90.2% and 91.8%, respectively, indicating that the most settlement occurred during the preloading period and a satisfactory improvement effect was achieved.
The combined method with vacuum and surcharge preloading is an effective alternative to improve the thick soft soil. This paper introduced a field test of soft soil improved by the combined method with vacuum and surcharge preloading. The vacuum pressure under membrane, settlement of ground surface and pore water pressure in soil were monitored during the preloading period. The final settlement was predicted based on the field data. The average degrees of consolidation in terms of stress and strain were calculated respectively. The test results indicated that the differential settlement was mainly developed during the surcharge preloading period. The vacuum pressure decreased down the drain length. The computed average degrees of consolidation in terms of stress and strain were 90.2% and 91.8%, respectively, indicating that the most settlement occurred during the preloading period and a satisfactory improvement effect was achieved.
2015, 23(s1): 728-728.
5.12 Wenchuan Earthquake led to large numbers of earthquake-induced deformation, and formed many potential hazards. The developing and evolving process of shatter crack of the mountains is the key element for the prevention and treatment of landslide. Shaking table test is a key mean of earthquake simulation in the lab, which can reproduce the deformation and destruction process of slope under earthquake action. GPR is a geophysical prospecting method by using reflection of high-frequency electromagnetic wave to detect target and geologic structure, which can be used to detect the position of sliding surface. By inputting sine wave of different frequency and same acceleration, the dynamic acceleration response characteristics of slope were researched on small scale shaking table. The development situation of slope cracks was detected by LTD-2100 GPR and radar antanna GC900MHz. The positions of the cracks were deduced on the basis of the interpretation results. The result showed that the location of the cracks detected by GPR were in accordance with dynamic acceleration response characteristics of slope. It is feasible to use GPR in shaking table test to analyses the cause and mechanism of earthquake landslide.
5.12 Wenchuan Earthquake led to large numbers of earthquake-induced deformation, and formed many potential hazards. The developing and evolving process of shatter crack of the mountains is the key element for the prevention and treatment of landslide. Shaking table test is a key mean of earthquake simulation in the lab, which can reproduce the deformation and destruction process of slope under earthquake action. GPR is a geophysical prospecting method by using reflection of high-frequency electromagnetic wave to detect target and geologic structure, which can be used to detect the position of sliding surface. By inputting sine wave of different frequency and same acceleration, the dynamic acceleration response characteristics of slope were researched on small scale shaking table. The development situation of slope cracks was detected by LTD-2100 GPR and radar antanna GC900MHz. The positions of the cracks were deduced on the basis of the interpretation results. The result showed that the location of the cracks detected by GPR were in accordance with dynamic acceleration response characteristics of slope. It is feasible to use GPR in shaking table test to analyses the cause and mechanism of earthquake landslide.
2015, 23(s1): 735-739.
This paper based on fuzzy mathematics selected five indicators, active fault, landforms, seism, neotectonic unit and geophysical field. On this basis, carry out quantitative evaluation of crustal stability in preselected area for low and intermediate-level radioactive waste disposal. Divided the studied region into eight areas with different crustal stability. Think the Low and intermediate-level radioactive waste disposal preselected area belong to stable region.
This paper based on fuzzy mathematics selected five indicators, active fault, landforms, seism, neotectonic unit and geophysical field. On this basis, carry out quantitative evaluation of crustal stability in preselected area for low and intermediate-level radioactive waste disposal. Divided the studied region into eight areas with different crustal stability. Think the Low and intermediate-level radioactive waste disposal preselected area belong to stable region.
2015, 23(s1): 740-744.
It's vital to acquire bearing capacity of soft rock foundation for large architecture such as high-rise buildings and nuclear power plants located on soft rock. Because engineering attribute of soft rock is special, it's not suitable to use saturated axial compressive strength to define bearing capacity of soft rock. And loading test is time-consuming and expensive. By means of pressuremeter test on Paleogene sandy soft rock foundation of Jiyang nuclear power plant in Anhui province and analysis of test data, this paper testifies the adaptability of pressuremeter test in obtaining bearing capacity of soft rock and acquires the formula of soft rock bearing capacity versus depth, i.e.fa=97.806H+882.39.
It's vital to acquire bearing capacity of soft rock foundation for large architecture such as high-rise buildings and nuclear power plants located on soft rock. Because engineering attribute of soft rock is special, it's not suitable to use saturated axial compressive strength to define bearing capacity of soft rock. And loading test is time-consuming and expensive. By means of pressuremeter test on Paleogene sandy soft rock foundation of Jiyang nuclear power plant in Anhui province and analysis of test data, this paper testifies the adaptability of pressuremeter test in obtaining bearing capacity of soft rock and acquires the formula of soft rock bearing capacity versus depth, i.e.fa=97.806H+882.39.
2015, 23(s1): 745-749.
The determination of strength parameters of rock and soil has always been the difficult problem in the geotechnical field, especially for soft rock. The relationship between stress and strain of soft rock is illustrated and reliable strength parameters is presented, by means of in-situ shear test in the soft rock foundation of Jiyang nuclear power plant and combined with laboratory three-axial test. The results show that: (1)Apparent stress yield and plastic deformation exist in the process of horizontal shear of Tertiary soft rock samples; (2)Each in-situ soft rock sample shows complete curves of stress-strain relationship, including linearly elastic part, elastic-plastic part, peak part and strain softening part; (3)Tertiary rock in Jiyang nuclear power plant, whose deformation characteristic is more similar to soil, is rock with plastic failure characteristic and the shear strength parameters can be determined by the yield strength of in-situ shear test, i.e.c=19.535kPa and =33.07; (4) obtained by in-situ shear test is equivalent to that obtained by three-axial test, while c obtained by in-situ shear test is a bit less than that obtained by three-axial test, and the former c and are more representative, considering that in-situ shear test reflects the actual situation better.
The determination of strength parameters of rock and soil has always been the difficult problem in the geotechnical field, especially for soft rock. The relationship between stress and strain of soft rock is illustrated and reliable strength parameters is presented, by means of in-situ shear test in the soft rock foundation of Jiyang nuclear power plant and combined with laboratory three-axial test. The results show that: (1)Apparent stress yield and plastic deformation exist in the process of horizontal shear of Tertiary soft rock samples; (2)Each in-situ soft rock sample shows complete curves of stress-strain relationship, including linearly elastic part, elastic-plastic part, peak part and strain softening part; (3)Tertiary rock in Jiyang nuclear power plant, whose deformation characteristic is more similar to soil, is rock with plastic failure characteristic and the shear strength parameters can be determined by the yield strength of in-situ shear test, i.e.c=19.535kPa and =33.07; (4) obtained by in-situ shear test is equivalent to that obtained by three-axial test, while c obtained by in-situ shear test is a bit less than that obtained by three-axial test, and the former c and are more representative, considering that in-situ shear test reflects the actual situation better.
2015, 23(s1): 750-756.
Wave velocity testing technology has been widely used in various engineering as a simple, quick test technology, and the Tertiary sandstone is one of the very representative soft rocks, so it has very important implications to research on Wave velocity testing of the Tertiary sandstone. This paper took the Tertiary sandstone in Jiyang nuclear power plant as an example, analysed the spatial distribution of the semi-formed Rock's wave velocity and searched the relationship of the wave velocity with depth, SPT and CPT though organizing the data of the wave velocity gain by cross-hole wave velocity measurement and single-hole wave velocity measurement. The results shows that the wave velocity increases with depth, above the depth of 5m, the rate of increase is very significantly, and the increase rate trend slow below the depth of 5m. The wave velocity for different holes are basically the same, which indicate that the Tertiary semi-formed sandstone is uniformitarian. Shear wave velocity and depth of buried linear regression fit well; there is no significant correlation between the shear wave velocity and SPT, and the shear wave velocity and CPT are uncorrelated.
Wave velocity testing technology has been widely used in various engineering as a simple, quick test technology, and the Tertiary sandstone is one of the very representative soft rocks, so it has very important implications to research on Wave velocity testing of the Tertiary sandstone. This paper took the Tertiary sandstone in Jiyang nuclear power plant as an example, analysed the spatial distribution of the semi-formed Rock's wave velocity and searched the relationship of the wave velocity with depth, SPT and CPT though organizing the data of the wave velocity gain by cross-hole wave velocity measurement and single-hole wave velocity measurement. The results shows that the wave velocity increases with depth, above the depth of 5m, the rate of increase is very significantly, and the increase rate trend slow below the depth of 5m. The wave velocity for different holes are basically the same, which indicate that the Tertiary semi-formed sandstone is uniformitarian. Shear wave velocity and depth of buried linear regression fit well; there is no significant correlation between the shear wave velocity and SPT, and the shear wave velocity and CPT are uncorrelated.
2015, 23(s1): 757-760.
Combination of vacuum preloading and surcharge preloading method is effective for reinforcing the soft clay foundation. However, the current relevant specifications estimated the soil strength increment as compared to the measured data. Considering the reinforcement mechanism of vacuum preloading and surcharge preloading, a calculation method of strength increment of soft soil under vacuum combined with surcharge preloading was proposed.A case history was adopted to verify the reliability of the proposed method and a good agreement was presented. The proposed method is applicable for the design in practice.
Combination of vacuum preloading and surcharge preloading method is effective for reinforcing the soft clay foundation. However, the current relevant specifications estimated the soil strength increment as compared to the measured data. Considering the reinforcement mechanism of vacuum preloading and surcharge preloading, a calculation method of strength increment of soft soil under vacuum combined with surcharge preloading was proposed.A case history was adopted to verify the reliability of the proposed method and a good agreement was presented. The proposed method is applicable for the design in practice.
2015, 23(s1): 761-766.
The extension engineering method is combined with rock quality evaluation, apply it to rock mass quality evaluation which data collected from an adit at Maji hydropower station dam. On the basis of the theory of extenics, Simultaneously, introducing precedence chart method to determine the weights of the evaluation indexes, and a matter-element model calculating procedure is proposed. Rock of each section in PD105 is evaluated by using the model, and the result consists with the law of site. Compared with the evaluation results by the former RMRmethod, the rock quality evaluation results obtained by the extenics method can more precisely reflect the engineering characteristics of tunnel rock.
The extension engineering method is combined with rock quality evaluation, apply it to rock mass quality evaluation which data collected from an adit at Maji hydropower station dam. On the basis of the theory of extenics, Simultaneously, introducing precedence chart method to determine the weights of the evaluation indexes, and a matter-element model calculating procedure is proposed. Rock of each section in PD105 is evaluated by using the model, and the result consists with the law of site. Compared with the evaluation results by the former RMRmethod, the rock quality evaluation results obtained by the extenics method can more precisely reflect the engineering characteristics of tunnel rock.
2015, 23(s1): 767-772.
Distributed optical fiber sensing technology, a new type of monitoring technology that emerges in our actual project several years ago, with many advantages for full distribution, real-time, anti-jamming and high durability, is becoming a hot spot in the field of geotechnical engineering. The optical fiber cable is buried in the soil, and the shear deformation of the soil is measured. Based on the correspondence between strain distribution of the optical fiber cable and the soil shear deformation, two strain-deformation conversion models based on arc curve and Logistic growth curve are proposed, and the applicability of the models are preliminarily considered. Then an interior shearing test of soil was designed to verify the accuracy of the models, and finally the models are used for the analysis of the distributed fiber monitoring data of Majiagou landslide in Three Gorges Reservoir. The results show that by using the conversion models, the shear deformation of soil can be figured out with strain distribution of the optical fiber cable.
Distributed optical fiber sensing technology, a new type of monitoring technology that emerges in our actual project several years ago, with many advantages for full distribution, real-time, anti-jamming and high durability, is becoming a hot spot in the field of geotechnical engineering. The optical fiber cable is buried in the soil, and the shear deformation of the soil is measured. Based on the correspondence between strain distribution of the optical fiber cable and the soil shear deformation, two strain-deformation conversion models based on arc curve and Logistic growth curve are proposed, and the applicability of the models are preliminarily considered. Then an interior shearing test of soil was designed to verify the accuracy of the models, and finally the models are used for the analysis of the distributed fiber monitoring data of Majiagou landslide in Three Gorges Reservoir. The results show that by using the conversion models, the shear deformation of soil can be figured out with strain distribution of the optical fiber cable.
2015, 23(s1): 773-777.
Using the seismic crosshole CT method for high precise detection of metro shield zone, Acquiring the information of formation and the distribution of adverse geological between test hole were acquired, so as to achieve the purpose of the shield advance geological prediction in tunnel construction. By introducing the size error and location error, the detection effect of location and size, which was detected by cross-hole seismic CT tomographic, were further compared and analyzed. And base on erroranalysis, the difference between each effects detected in different detecting target or different detecting area were analyzed. The results of error analysis show that the detection effect of the target location is superior to effect of the size, and, the detection accuracy for different object is mainly determined by the difference of the seismic wave velocity between object itsself and the surrounding. In addition, through the contrast of detection effect for different location on test section, can also be concluded that detection accuracy of areas in the middle of the test hole is higher than the areas adjacent test hole. According to the analysis result and the conclusions, the geological prediction method for shield tunnel which based on cross-hole seismic CT was formed.
Using the seismic crosshole CT method for high precise detection of metro shield zone, Acquiring the information of formation and the distribution of adverse geological between test hole were acquired, so as to achieve the purpose of the shield advance geological prediction in tunnel construction. By introducing the size error and location error, the detection effect of location and size, which was detected by cross-hole seismic CT tomographic, were further compared and analyzed. And base on erroranalysis, the difference between each effects detected in different detecting target or different detecting area were analyzed. The results of error analysis show that the detection effect of the target location is superior to effect of the size, and, the detection accuracy for different object is mainly determined by the difference of the seismic wave velocity between object itsself and the surrounding. In addition, through the contrast of detection effect for different location on test section, can also be concluded that detection accuracy of areas in the middle of the test hole is higher than the areas adjacent test hole. According to the analysis result and the conclusions, the geological prediction method for shield tunnel which based on cross-hole seismic CT was formed.
2015, 23(s1): 778-785.
In the valuation of engineering geological environmental quality, there is the weight dilemma problem in the traditional weighted composite index method, fuzzy comprehensive evaluation method, grey clustering method and etc., however, there is the dilemma problem of selecting training samples and testing samples in the artificial neural network method in this paper, sensitive unit, insensitive unit and similar-insensitive unit are firstly put forward according to the classification of the units of an engineering geological environmental system. An insensitive unit is defined as the unit whose quality category is constant while the maximum ratios of factor weights change from K=1～K=.Based on the concept of insensitive unit, the standard training set is defined as the input-output pairs of insensitive units. The paper has proposed a new artificial neural network method based on standard training set, trying to solve the weight dilemma problem in the traditional evaluation method and the dilemma problem of selecting training sample and testing sample in the artificial neural network method.
In the valuation of engineering geological environmental quality, there is the weight dilemma problem in the traditional weighted composite index method, fuzzy comprehensive evaluation method, grey clustering method and etc., however, there is the dilemma problem of selecting training samples and testing samples in the artificial neural network method in this paper, sensitive unit, insensitive unit and similar-insensitive unit are firstly put forward according to the classification of the units of an engineering geological environmental system. An insensitive unit is defined as the unit whose quality category is constant while the maximum ratios of factor weights change from K=1～K=.Based on the concept of insensitive unit, the standard training set is defined as the input-output pairs of insensitive units. The paper has proposed a new artificial neural network method based on standard training set, trying to solve the weight dilemma problem in the traditional evaluation method and the dilemma problem of selecting training sample and testing sample in the artificial neural network method.
2015, 23(s1): 786-792.
There are many ground collapses and other geological disasters due to leakages of urban underground water pipes. Through finite difference method for specific leak location and extend of the electromagnetic field leakage, the variation of electromagnetic wave field leakage are analyzed. The root mean square amplitude attribute analysis utilized severity can better identify pipeline leaks, especially for the pipe and a large area of the pipeline leaks better recognition. Combined with sweetness property, suppress multiple wave interference effects, to better identify the specific location and leakage extent in supply pipes or drainage. It is good method to distinguish large area leaking in supply pipes or drainage using divider attribute technology. By combination of three different properties, some effective methods to detect leakage disaster in urban underwater pipes using ground-penetrating radar are proposed.
There are many ground collapses and other geological disasters due to leakages of urban underground water pipes. Through finite difference method for specific leak location and extend of the electromagnetic field leakage, the variation of electromagnetic wave field leakage are analyzed. The root mean square amplitude attribute analysis utilized severity can better identify pipeline leaks, especially for the pipe and a large area of the pipeline leaks better recognition. Combined with sweetness property, suppress multiple wave interference effects, to better identify the specific location and leakage extent in supply pipes or drainage. It is good method to distinguish large area leaking in supply pipes or drainage using divider attribute technology. By combination of three different properties, some effective methods to detect leakage disaster in urban underwater pipes using ground-penetrating radar are proposed.
2015, 23(s1): 793-797.
The research on Geo-hazard emergency risk-elimination technologies is not only important research currently but also instantly demand. This paper proposed a 500kN pre-cast high strength concrete anchorage pier based on different types of structure design, numerical analysis and indoor test. Also production process and construction technology are introduced. The pre-cast high strength concrete anchorage pier has a wide field of application with reasonable structure and easy construction, which can strengthen landslide quickly and effectively.
The research on Geo-hazard emergency risk-elimination technologies is not only important research currently but also instantly demand. This paper proposed a 500kN pre-cast high strength concrete anchorage pier based on different types of structure design, numerical analysis and indoor test. Also production process and construction technology are introduced. The pre-cast high strength concrete anchorage pier has a wide field of application with reasonable structure and easy construction, which can strengthen landslide quickly and effectively.
2015, 23(s1): 798-806.
A Geology engineering geology is one of subject that the theories closely combine with practices. With the development and application of the new technologies, there are some limitations in the traditional teaching methods. Introducing the new technologies and teaching methods, during the teaching process of the traditional theories and methodologies, are the challenges facing the teaching links in current. In this paper, the author discusses the reforms and innovations in the teaching methods and teaching contents during the teaching process, and the results indicate that all of these methods have better teaching effect. At the same time, the author has constituted the first 3D information platform for the field practice of geology, which can provide an inclusive tool for the teaching of the geology practice, popular science education and online teaching. And for the current MOOC, the author exposes some key issues for discussion during the MOOC construction of the subjects of geology.
A Geology engineering geology is one of subject that the theories closely combine with practices. With the development and application of the new technologies, there are some limitations in the traditional teaching methods. Introducing the new technologies and teaching methods, during the teaching process of the traditional theories and methodologies, are the challenges facing the teaching links in current. In this paper, the author discusses the reforms and innovations in the teaching methods and teaching contents during the teaching process, and the results indicate that all of these methods have better teaching effect. At the same time, the author has constituted the first 3D information platform for the field practice of geology, which can provide an inclusive tool for the teaching of the geology practice, popular science education and online teaching. And for the current MOOC, the author exposes some key issues for discussion during the MOOC construction of the subjects of geology.
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