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Editor Work2007 Vol. 15, No. 5
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2007, 15(5): 577-584.
Abstract
Widely distributed on the surface of the Earth, soil mass is a kind of quite complex natural solid bodies. This paper identifies the soil mass to have seven scale-levels of structural hierarchies. Based on the functions of each scale-level structure, the paper further describes the dialectic relationships among the different scale-levels of soil structure system from the point of view of systems science. The examination includes the basic function form the lower scale-level to the higher scale-level, the influence of the higher scale-level on the lower scale-level, the synergism of the higher and lower scale-levels, interlacing, overlapping and evolvement of the different scale-levels. The structural system can simplify complicated problems if the soil mass is regarded as a system and then divided into reasonable hierarchies for analysis during scientific research and engineering practice related to soil mass. Thus the engineering properties and corresponding formation mechanisms of soil mass can be comprehensively and correctly understood.
Widely distributed on the surface of the Earth, soil mass is a kind of quite complex natural solid bodies. This paper identifies the soil mass to have seven scale-levels of structural hierarchies. Based on the functions of each scale-level structure, the paper further describes the dialectic relationships among the different scale-levels of soil structure system from the point of view of systems science. The examination includes the basic function form the lower scale-level to the higher scale-level, the influence of the higher scale-level on the lower scale-level, the synergism of the higher and lower scale-levels, interlacing, overlapping and evolvement of the different scale-levels. The structural system can simplify complicated problems if the soil mass is regarded as a system and then divided into reasonable hierarchies for analysis during scientific research and engineering practice related to soil mass. Thus the engineering properties and corresponding formation mechanisms of soil mass can be comprehensively and correctly understood.
2007, 15(5): 585-592.
Jietai temple landslide is located in the north wing slope of Maanshan mountain, Mentougou district of Beijing. The rock mass of the slope is weaker. Cracks is well developed. Rock mass of the slope is strongly unloaded and weathered severely after it had experienced several tectonic movements. The slope has daylighting bedding planes. Weak interlayers, weak structural surfaces and faults are well developed. All these discontinuities provided cutting and slipping surfaces for the landslide. Because the dip angle of the beddings is greater than that of the slope, the slope cant slide down along the bedding surface. Thus, the slope is a creep deformable body and controlled by specific discontinunity structures. Two coal mines locate in the middle of the mountain slopes. The mining activities such as excavation and blasting caused the slope rock mass to form and creep gradually and eventually to collapse locally. . Consequently, the slope creeped, relaxed and slipped along the weak planes. Rainfall water could infiltrate into the slope easily. Slope deformed and slipped more and more until its failure.
Jietai temple landslide is located in the north wing slope of Maanshan mountain, Mentougou district of Beijing. The rock mass of the slope is weaker. Cracks is well developed. Rock mass of the slope is strongly unloaded and weathered severely after it had experienced several tectonic movements. The slope has daylighting bedding planes. Weak interlayers, weak structural surfaces and faults are well developed. All these discontinuities provided cutting and slipping surfaces for the landslide. Because the dip angle of the beddings is greater than that of the slope, the slope cant slide down along the bedding surface. Thus, the slope is a creep deformable body and controlled by specific discontinunity structures. Two coal mines locate in the middle of the mountain slopes. The mining activities such as excavation and blasting caused the slope rock mass to form and creep gradually and eventually to collapse locally. . Consequently, the slope creeped, relaxed and slipped along the weak planes. Rainfall water could infiltrate into the slope easily. Slope deformed and slipped more and more until its failure.
2007, 15(5): 593-598.
Through on-site field investigation, a detailed study of the site environment and geological conditions are carried out at the landslide at the vegetable oil factory in Fuling District of Chongqing. According to the landslide feature and influential factors, three conclusions are reached as follow: the building of the State Road No. 319 above the landslide area caused the increased water flow and incomplete backfilling of the drainage channel. These two human activities are the crucial factors causing the landslide; the long-term rainfall is the controlling factor. FEM and limit equilibrium method were used to evaluate the stability of the slide. According to assessment results and influential factors, this paper discussed the treatment methods of the landslide.
Through on-site field investigation, a detailed study of the site environment and geological conditions are carried out at the landslide at the vegetable oil factory in Fuling District of Chongqing. According to the landslide feature and influential factors, three conclusions are reached as follow: the building of the State Road No. 319 above the landslide area caused the increased water flow and incomplete backfilling of the drainage channel. These two human activities are the crucial factors causing the landslide; the long-term rainfall is the controlling factor. FEM and limit equilibrium method were used to evaluate the stability of the slide. According to assessment results and influential factors, this paper discussed the treatment methods of the landslide.
2007, 15(5): 599-606.
Based on the saturated-unsaturated seepage theory and an extended Mohr-Coulomb failure criterion, combined with the results of saturated and unsaturated triaxial tests, a typical loess slope in the southern tableland of Jingyang County has been adopted for this parametric study. Transient seepage due to water level rise is computed using the finite element method. The computed transient pore water pressures are then used for subsequent limit equilibrium analyses of the slope. The results demonstrate that both transient pore water pressure distribution and slope stability are affected by groundwater level rise. The method involving unsaturated seepage and suction strength is more coincident with the factual data.
Based on the saturated-unsaturated seepage theory and an extended Mohr-Coulomb failure criterion, combined with the results of saturated and unsaturated triaxial tests, a typical loess slope in the southern tableland of Jingyang County has been adopted for this parametric study. Transient seepage due to water level rise is computed using the finite element method. The computed transient pore water pressures are then used for subsequent limit equilibrium analyses of the slope. The results demonstrate that both transient pore water pressure distribution and slope stability are affected by groundwater level rise. The method involving unsaturated seepage and suction strength is more coincident with the factual data.
2007, 15(5): 607-611.
The transmitting coefficient method for landslide stability analysis has an implicit and an explicit calculation equations for the solutions. It has some problems that need clarifications. The problems include the definition of safety coefficient, the types of the satisfactory statical equilibrium equations, the expression formulae of the safety coefficient calculation, the relationship between the coefficients of safety and the errors of safety coefficient calculation for the two solution approaches. In the paper, each of the problems is analyzed. On the basis of the above analyses, suggestions of solution approach selection for the transmitting coefficient method are presented.
The transmitting coefficient method for landslide stability analysis has an implicit and an explicit calculation equations for the solutions. It has some problems that need clarifications. The problems include the definition of safety coefficient, the types of the satisfactory statical equilibrium equations, the expression formulae of the safety coefficient calculation, the relationship between the coefficients of safety and the errors of safety coefficient calculation for the two solution approaches. In the paper, each of the problems is analyzed. On the basis of the above analyses, suggestions of solution approach selection for the transmitting coefficient method are presented.
2007, 15(5): 612-620.
The debris flows with low occurrence frequency are of more harmfulness than the debris flows of high occurrence frequency. This paper, on the basis of field investigation and material analysis about the typical low-frequency debris flows occurred in recent years, discusses the characteristics of low frequency debris flows. In order to further discuss the forecasting method of low frequency debris flows, the grey theory is applied and a grey catastrophe forecasting model was established. The Chayuan gully in Wenchuan county, Sichuan province is used as an example. The paper puts forward the corresponding prevention advices for low frequency debris flows according to the their characteristics. This discussion is of certain significance for debris flow subject in theory and for the hazard prevention and mitigation in mountain areas in practice.
The debris flows with low occurrence frequency are of more harmfulness than the debris flows of high occurrence frequency. This paper, on the basis of field investigation and material analysis about the typical low-frequency debris flows occurred in recent years, discusses the characteristics of low frequency debris flows. In order to further discuss the forecasting method of low frequency debris flows, the grey theory is applied and a grey catastrophe forecasting model was established. The Chayuan gully in Wenchuan county, Sichuan province is used as an example. The paper puts forward the corresponding prevention advices for low frequency debris flows according to the their characteristics. This discussion is of certain significance for debris flow subject in theory and for the hazard prevention and mitigation in mountain areas in practice.
2007, 15(5): 621-629.
Based on the data of GPS monitoring and the existing results of leveling, the evolutionary characteristics and regularity of the land subsidence in Jiangyin city were studied systematically and thoroughly. The reasons for the land subsidence were analyzed by integrating the observation data of groundwater activity and slice indicators of land subsidence. It was indicated that land subsidence took place mostly in the south of Jiangyin city, and the subsidence value decreased gradually from the south to the north and east. Land subsidence correlated with the exploitation of groundwater closely in Jiangyin city. It was retardant and irreversible. Land subsidence was controlled mainly by two factors in Jiangyin city. The geological environment with subsidence characteristics was the necessary intrinsic factor, including the discrepancies in the forms of bedrock. The aggradation structure of Quaternary period and hydro-geological conditions, and the super-pumping groundwater is the extrinsic factor. The land subsidence was caused by compression of aquiferous sand strata and concretion of clay soil of roof and bottom plate.
Based on the data of GPS monitoring and the existing results of leveling, the evolutionary characteristics and regularity of the land subsidence in Jiangyin city were studied systematically and thoroughly. The reasons for the land subsidence were analyzed by integrating the observation data of groundwater activity and slice indicators of land subsidence. It was indicated that land subsidence took place mostly in the south of Jiangyin city, and the subsidence value decreased gradually from the south to the north and east. Land subsidence correlated with the exploitation of groundwater closely in Jiangyin city. It was retardant and irreversible. Land subsidence was controlled mainly by two factors in Jiangyin city. The geological environment with subsidence characteristics was the necessary intrinsic factor, including the discrepancies in the forms of bedrock. The aggradation structure of Quaternary period and hydro-geological conditions, and the super-pumping groundwater is the extrinsic factor. The land subsidence was caused by compression of aquiferous sand strata and concretion of clay soil of roof and bottom plate.
2007, 15(5): 630-634.
Ground collapse is one of the major types of geological disasters and can have serious harm to the national economy and peoples lives and property and hamper the sustainable development in Guangzhou. The Information-value model and GIS are used for the fatalness appraisal study of ground collapse in downtown area of Guangzhou city. The appraisement indexes are conceived through choosing these factors such as fault, the stability of the earths crust, the quaternary sediment lithology and thickness, bedrock lithology, groundwater dynamics conditions, surface and underground intensity of human activities. ArcGIS software is applied involving in data collection, data management, data analysis and evaluation process, expressing. Finally, the fatalness classification chart of grade about ground collapse in Guangzhou is produced. The result tells us that there are five fatalness grades in main urban area, the most dangerous zone distribute in the south of Guang-hua basin, the more dangerous zone distribute the west-north of main urban, in Guang-cong fault or the intersection of subway, the basic stable grade zone distribute in the center of main urban area. The results show that the collapse hazard are caused by the interaction of the complicated nature environmental elements and the intense human activities.
Ground collapse is one of the major types of geological disasters and can have serious harm to the national economy and peoples lives and property and hamper the sustainable development in Guangzhou. The Information-value model and GIS are used for the fatalness appraisal study of ground collapse in downtown area of Guangzhou city. The appraisement indexes are conceived through choosing these factors such as fault, the stability of the earths crust, the quaternary sediment lithology and thickness, bedrock lithology, groundwater dynamics conditions, surface and underground intensity of human activities. ArcGIS software is applied involving in data collection, data management, data analysis and evaluation process, expressing. Finally, the fatalness classification chart of grade about ground collapse in Guangzhou is produced. The result tells us that there are five fatalness grades in main urban area, the most dangerous zone distribute in the south of Guang-hua basin, the more dangerous zone distribute the west-north of main urban, in Guang-cong fault or the intersection of subway, the basic stable grade zone distribute in the center of main urban area. The results show that the collapse hazard are caused by the interaction of the complicated nature environmental elements and the intense human activities.
2007, 15(5): 635-638.
By utilizing lots of highway loess cutting slopes mostly, this paper presents a forecast model of slope stability based on case-based reasoning. Slope examples are taken as slope base cases. Slopes that will study are taken as slope target cases in the model. Through calculating the similarity between slope base cases and slope target cases, the similar series are determined, and the most similar base case to the slope target case in the base cases of slope is found out. Finally,the slope stability of target cases is evaluated. It is shown from examples that the result of stability forecast of the slope is the same as the practical state, and the approach is simple and convenient to use.
By utilizing lots of highway loess cutting slopes mostly, this paper presents a forecast model of slope stability based on case-based reasoning. Slope examples are taken as slope base cases. Slopes that will study are taken as slope target cases in the model. Through calculating the similarity between slope base cases and slope target cases, the similar series are determined, and the most similar base case to the slope target case in the base cases of slope is found out. Finally,the slope stability of target cases is evaluated. It is shown from examples that the result of stability forecast of the slope is the same as the practical state, and the approach is simple and convenient to use.
2007, 15(5): 639-645.
At present, the subgrade soil of highway in seasonal frost region is not classified with frost heave in accordance with the soil classification standards. This paper presents the test results from a series of closed simulated frost heave tests with sand soil of different clay contents under different water contents, degree of saturations and compactness. Using statistics, the changes of frost heaving ratio of sand soil with different clay contents under different water contents are examined. The classification of frost heave on sand soil with the current standard is performed. The results are of reference value to survey, design, construct and maintain highway, and to provide the reliable materials for the establishment of the designing specification of highways in seasonal frost regions.
At present, the subgrade soil of highway in seasonal frost region is not classified with frost heave in accordance with the soil classification standards. This paper presents the test results from a series of closed simulated frost heave tests with sand soil of different clay contents under different water contents, degree of saturations and compactness. Using statistics, the changes of frost heaving ratio of sand soil with different clay contents under different water contents are examined. The classification of frost heave on sand soil with the current standard is performed. The results are of reference value to survey, design, construct and maintain highway, and to provide the reliable materials for the establishment of the designing specification of highways in seasonal frost regions.
2007, 15(5): 646-653.
Based on the scanning electron microscopy (SEM) of microstructure and collapsible test of undisturbed loess, the microstructure properties, the collapsible characteristics under different pressures and water contents, and the intrinsic mechanism between microstructure and collapsibility of loess were analyzed. The results indicated: (1) with the increasing of imbedding depth, the configuration of loess varying gradually from bracketed-macropore weak-cemented texture to inlaid-micropore half-cemented texture, the void properties from bracketed-macropore void to void among grains, then to micropore void; (2) the curves of coefficient of collapse-different pressures of loess under humidification can be divided into three phases, at the initial phase of compressive deformation was the course of loess compaction of structural strength, with a small settlement and microstructure no destroyed; (3) the second phase after the first turning point s=0.015 of the curves was the primary course of collapse deformation, the microstructure varying and particles redistributed with along the intrinsic texture of loess damaged , and ratio of collapsible settlement increased; and (4) the third, the new microstructure coming into being, the collapsible settlement decreased after the point of peak value. (5) the values of the initial collapsible pressure and the collapsible force of peak value increased, and the coefficient of collapse of peak value and the range values of pressures of collapsible settlement diminished as the increasing of imbedding depth; (6) the characteristics of framework grains and void of loess were the intrinsic influencing factors of collapsibility, and the amount and properties of cement were one of mainly contributing factors for the intensity of collapsibility of loess.
Based on the scanning electron microscopy (SEM) of microstructure and collapsible test of undisturbed loess, the microstructure properties, the collapsible characteristics under different pressures and water contents, and the intrinsic mechanism between microstructure and collapsibility of loess were analyzed. The results indicated: (1) with the increasing of imbedding depth, the configuration of loess varying gradually from bracketed-macropore weak-cemented texture to inlaid-micropore half-cemented texture, the void properties from bracketed-macropore void to void among grains, then to micropore void; (2) the curves of coefficient of collapse-different pressures of loess under humidification can be divided into three phases, at the initial phase of compressive deformation was the course of loess compaction of structural strength, with a small settlement and microstructure no destroyed; (3) the second phase after the first turning point s=0.015 of the curves was the primary course of collapse deformation, the microstructure varying and particles redistributed with along the intrinsic texture of loess damaged , and ratio of collapsible settlement increased; and (4) the third, the new microstructure coming into being, the collapsible settlement decreased after the point of peak value. (5) the values of the initial collapsible pressure and the collapsible force of peak value increased, and the coefficient of collapse of peak value and the range values of pressures of collapsible settlement diminished as the increasing of imbedding depth; (6) the characteristics of framework grains and void of loess were the intrinsic influencing factors of collapsibility, and the amount and properties of cement were one of mainly contributing factors for the intensity of collapsibility of loess.
2007, 15(5): 654-660.
Lime-treated expansive soil is of cluster structure . The micro-strcuture is made of particles, and the pole is made of micro-pole of inner of particle and the poles between particles , including a part of cementation materials poles. The test results show that the smaller of particle, more helpful for combining of lime and soil. Micro-structure is the chain structure; the quantity of lime mainly effect micro-structure of the surface of soil particle. Ca2+ can immerge to inner of the particle saturation, and there is a similar structure in out layer with its inner layer. The samples with the same quantity of lime, there are different distributions of weight relative contents of Ca for saturated and unsaturated conditions. At the unsaturated condition, the content of Ca2+ is relatively more on the surface and less in the inner. aeat. At the saturated condition, the mount of Ca on the surface is slightly more than that in the inner , and the particles can be larger.
Lime-treated expansive soil is of cluster structure . The micro-strcuture is made of particles, and the pole is made of micro-pole of inner of particle and the poles between particles , including a part of cementation materials poles. The test results show that the smaller of particle, more helpful for combining of lime and soil. Micro-structure is the chain structure; the quantity of lime mainly effect micro-structure of the surface of soil particle. Ca2+ can immerge to inner of the particle saturation, and there is a similar structure in out layer with its inner layer. The samples with the same quantity of lime, there are different distributions of weight relative contents of Ca for saturated and unsaturated conditions. At the unsaturated condition, the content of Ca2+ is relatively more on the surface and less in the inner. aeat. At the saturated condition, the mount of Ca on the surface is slightly more than that in the inner , and the particles can be larger.
2007, 15(5): 661-666.
Based on a large amount of dynamic tri-axial tests, dynamic properties of cement treated soft soils are examined thoroughly. The results show that the dynamic strain d is the most important factor affecting the dynamic modulus and the damping ratio . The dynamic modulus Ed decreases and the damping ratio increases very rapidly with the increase of the dynamic strain d. Both the dynamic modulus Ed and the damping ratio increase with the increase in the cement dosage ratio. The dynamic modulus increases while the damping ratio decreases as the confining pressure 3 increases, at the same strain level. It is further found that the maximum dynamic modulus Edmax increases as an exponential function of the confining pressure 3. The maximum damping ratio max varies from 7% to 30% and decreases as an exponential function of the confining pressure 3. The corresponding formulas are put forward.
Based on a large amount of dynamic tri-axial tests, dynamic properties of cement treated soft soils are examined thoroughly. The results show that the dynamic strain d is the most important factor affecting the dynamic modulus and the damping ratio . The dynamic modulus Ed decreases and the damping ratio increases very rapidly with the increase of the dynamic strain d. Both the dynamic modulus Ed and the damping ratio increase with the increase in the cement dosage ratio. The dynamic modulus increases while the damping ratio decreases as the confining pressure 3 increases, at the same strain level. It is further found that the maximum dynamic modulus Edmax increases as an exponential function of the confining pressure 3. The maximum damping ratio max varies from 7% to 30% and decreases as an exponential function of the confining pressure 3. The corresponding formulas are put forward.
2007, 15(5): 667-672.
Dugushan landslide situated on the YK128+630m~YK129+050m of the Quan-San expressway. The landslide located in a concave area, where the upper of stratum is quaternary deposit and the lower is weathered residual stratum. Base on the existing terrain and landform, also the drilling core, the existence of ancient landslide is deduced in this paper. Collapse in top area of the Dagushan Tunnel is due to the engineering construction. Under the influence of rainfall and surface water in slide area, the ancient landslide which lie in the middle and lower part of the slope could be re-activated, and it can be ascribed to the weak permeability of bedrock. In order to guarantee the stability and safe of tunnel entrance and the Lin-pan-keng bridge, the Morgenstern-Price method is adopted for the calculation and analysis. Based on the result of calculation along a section of the slope, the landslide treatment is proposed. Anchored anti-slide piles have been arranged in the middle and lower parts of the landslide. In order to prevent the deformation of the bridge pier, anchored piles have been arranged in front of the bridge pier. Also the engineering counter measures to rainfall and surface water are adopted to stabilize the landslide.
Dugushan landslide situated on the YK128+630m~YK129+050m of the Quan-San expressway. The landslide located in a concave area, where the upper of stratum is quaternary deposit and the lower is weathered residual stratum. Base on the existing terrain and landform, also the drilling core, the existence of ancient landslide is deduced in this paper. Collapse in top area of the Dagushan Tunnel is due to the engineering construction. Under the influence of rainfall and surface water in slide area, the ancient landslide which lie in the middle and lower part of the slope could be re-activated, and it can be ascribed to the weak permeability of bedrock. In order to guarantee the stability and safe of tunnel entrance and the Lin-pan-keng bridge, the Morgenstern-Price method is adopted for the calculation and analysis. Based on the result of calculation along a section of the slope, the landslide treatment is proposed. Anchored anti-slide piles have been arranged in the middle and lower parts of the landslide. In order to prevent the deformation of the bridge pier, anchored piles have been arranged in front of the bridge pier. Also the engineering counter measures to rainfall and surface water are adopted to stabilize the landslide.
2007, 15(5): 673-676.
Huanglongxicun landslide is located in Tianshui city of Gansu province. It belongs to loess landslide with high potential energy. With the volume capacity of 3.9105m3, its substratum is granodiorite. In order to improve the prediction accuracy of grey GM(1,1) model, center approach grey GM (1,1) model is used in the deformation prediction of Huanglongxicun landslide. It is indicated that the predicting values of center approach GM (1,1) model are well agreed with monitoring values for the landslide, and have much higher prediction accuracy than that of traditional grey GM(1,1) model because error sum of squares and error percent for center approach GM (1,1) model is lower than that of traditional grey GM(1,1) model. Moreover, the center approach GM (1,1) model can be improved by adjusting the value of the parameter m in the model. When m is equal to 6, prediction accuracy for center approach GM (1,1) model is over 5.34% than that of traditional grey GM(1,1) model.
Huanglongxicun landslide is located in Tianshui city of Gansu province. It belongs to loess landslide with high potential energy. With the volume capacity of 3.9105m3, its substratum is granodiorite. In order to improve the prediction accuracy of grey GM(1,1) model, center approach grey GM (1,1) model is used in the deformation prediction of Huanglongxicun landslide. It is indicated that the predicting values of center approach GM (1,1) model are well agreed with monitoring values for the landslide, and have much higher prediction accuracy than that of traditional grey GM(1,1) model because error sum of squares and error percent for center approach GM (1,1) model is lower than that of traditional grey GM(1,1) model. Moreover, the center approach GM (1,1) model can be improved by adjusting the value of the parameter m in the model. When m is equal to 6, prediction accuracy for center approach GM (1,1) model is over 5.34% than that of traditional grey GM(1,1) model.
2007, 15(5): 677-683.
This paper presents the remediation measures on a landslide in Lailong, a mountain near Hangzhou. The This paper analyzes the factors causing the landslide, carries out the slope stability analysis and adopts the treatment measures. The paper further analyzes the monitoring results of the slope after the remediation measures. The results show that the remediation measures are very good. The experiences from this study can also be used as a reference for landslide hazard remediation in this region.
This paper presents the remediation measures on a landslide in Lailong, a mountain near Hangzhou. The This paper analyzes the factors causing the landslide, carries out the slope stability analysis and adopts the treatment measures. The paper further analyzes the monitoring results of the slope after the remediation measures. The results show that the remediation measures are very good. The experiences from this study can also be used as a reference for landslide hazard remediation in this region.
2007, 15(5): 684-688.
The GM(2,1) model for safety inspection and forecasting of a landsliding site is set up based on Gray theory. The anisochronous displacement is changed to the isochronous serial with Lagrange function. This model is used to the Chuang-Kou landslide observation site in Tong-Huang expressway. The results show that the GM(2, 1) model has higher forecasting precision than the GM(1, 1). The study shows that the landslide is safe after completion of treatment. This result agrees well with the actual situation.
The GM(2,1) model for safety inspection and forecasting of a landsliding site is set up based on Gray theory. The anisochronous displacement is changed to the isochronous serial with Lagrange function. This model is used to the Chuang-Kou landslide observation site in Tong-Huang expressway. The results show that the GM(2, 1) model has higher forecasting precision than the GM(1, 1). The study shows that the landslide is safe after completion of treatment. This result agrees well with the actual situation.
2007, 15(5): 694-699.
Dynamic properties of intact loess are studied through laboratory dynamic triaxial tests; and variations with water contents are discussed of its dynamic shear strength and seismic subsidence. Test results show that water content has a major influence on the dynamic properties of intact loess. When taking plastic limit as a bound, variation of water content smaller than plastic limit has major influence on dynamic cohesion and seismic subsidence critical stress; while variation of water content greater than plastic limit has very minor influence on them. Little influence has variation of water content on dynamic friction angle. Through regression analysis of seismic subsidence curves, it is showed that seismic subsidence needs to be considered into loess classification.
Dynamic properties of intact loess are studied through laboratory dynamic triaxial tests; and variations with water contents are discussed of its dynamic shear strength and seismic subsidence. Test results show that water content has a major influence on the dynamic properties of intact loess. When taking plastic limit as a bound, variation of water content smaller than plastic limit has major influence on dynamic cohesion and seismic subsidence critical stress; while variation of water content greater than plastic limit has very minor influence on them. Little influence has variation of water content on dynamic friction angle. Through regression analysis of seismic subsidence curves, it is showed that seismic subsidence needs to be considered into loess classification.
2007, 15(5): 700-707.
Soil-water characteristic curve (SWCC) in unsaturated soil mechanics presents the relationship between water content and suction in the soil. The paper introduces six methods with their suitable application ranges. The volumetric pressure plate can measure the matric suction value of less than 1500kPa on wetting and drying SWCCs. The temple apparatus can measure matric suction range from 0 to 100kPa. Matric suction and total suction can be tested with filter paper. The dew-point potentiometer can be used to measure total suction, especially osmotic suction. The TDR probe is the same with matric suction less than 300kPa. The triaxial test system for GDS can be used to test SWCC. The test range lies on the air-entry value. It has a great significance for SWCC since it can be used in exact mathematic models to predict mechanics properties, coefficient of infiltration, shear strength and analysing stability of slope for unsaturated soil. It is very difficult to attain the curves accurately, which are affected by many additional factors . It is an alternative idea to predict SWCC with pore-size distribution and grain-size distribution.
Soil-water characteristic curve (SWCC) in unsaturated soil mechanics presents the relationship between water content and suction in the soil. The paper introduces six methods with their suitable application ranges. The volumetric pressure plate can measure the matric suction value of less than 1500kPa on wetting and drying SWCCs. The temple apparatus can measure matric suction range from 0 to 100kPa. Matric suction and total suction can be tested with filter paper. The dew-point potentiometer can be used to measure total suction, especially osmotic suction. The TDR probe is the same with matric suction less than 300kPa. The triaxial test system for GDS can be used to test SWCC. The test range lies on the air-entry value. It has a great significance for SWCC since it can be used in exact mathematic models to predict mechanics properties, coefficient of infiltration, shear strength and analysing stability of slope for unsaturated soil. It is very difficult to attain the curves accurately, which are affected by many additional factors . It is an alternative idea to predict SWCC with pore-size distribution and grain-size distribution.
2007, 15(5): 708-711.
Pingyao ancient city wall is a valuable cultural heritage of our country. Because of the old age of the city wall as well as the modern times artificial destroying, its inner structure has changed greatly, there are some horse faces and wall body appear rifts, even happen collapse at present. This paper uses the ground penetrating radar application technology as the foundation, examines the ground penetrating radar in Shanxi Pingyao ancient city wall restoration application and its basic principles briefly. The paper further discusses the goal body examination by the ground penetrating radar, the accurate surveying results of theancient city wall interior soft soil body, holes, cracks, and so on, gives the dangerous ranking, and provides the reliable basis for the scenic spot historical site restoration.
Pingyao ancient city wall is a valuable cultural heritage of our country. Because of the old age of the city wall as well as the modern times artificial destroying, its inner structure has changed greatly, there are some horse faces and wall body appear rifts, even happen collapse at present. This paper uses the ground penetrating radar application technology as the foundation, examines the ground penetrating radar in Shanxi Pingyao ancient city wall restoration application and its basic principles briefly. The paper further discusses the goal body examination by the ground penetrating radar, the accurate surveying results of theancient city wall interior soft soil body, holes, cracks, and so on, gives the dangerous ranking, and provides the reliable basis for the scenic spot historical site restoration.
2007, 15(5): 712-717.
With increasing extent and intensity of human activities, the rockfalls and their induced hazards have become more and more prominent, especially in mountainous regions. As a result, studies on rockfall hazards and relevant prevention and mitigation measures have been gaining extensive attentions. Generally speaking, methods for mitigating rockfall hazards can be classified two kinds. They are initiative measures and passive measures. They can be applied in various circumstances of rockfall hazards. After presenting a brief introduction to these measures, the paper analyzes applicable scopes and suitable conditions for each measure.
With increasing extent and intensity of human activities, the rockfalls and their induced hazards have become more and more prominent, especially in mountainous regions. As a result, studies on rockfall hazards and relevant prevention and mitigation measures have been gaining extensive attentions. Generally speaking, methods for mitigating rockfall hazards can be classified two kinds. They are initiative measures and passive measures. They can be applied in various circumstances of rockfall hazards. After presenting a brief introduction to these measures, the paper analyzes applicable scopes and suitable conditions for each measure.
2007, 15(5): 718-720.
Engineering geological research in weak ecological-environmental area is one of the important domains that engineering geology has faced. The author points out that the scientific basis of engineering geology should be strengthen. Engineering geology should assimilate the theories of other related objects, rebuild its theory and practice, present excellent projects, and think much of training of outstanding professionals.
Engineering geological research in weak ecological-environmental area is one of the important domains that engineering geology has faced. The author points out that the scientific basis of engineering geology should be strengthen. Engineering geology should assimilate the theories of other related objects, rebuild its theory and practice, present excellent projects, and think much of training of outstanding professionals.
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