Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at t...Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.展开更多
The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial ...The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial moisture content on the shear strength parameters of the soil-structure interfaces were analyzed.The results indicate that the cohesion of the interface initially increased and then decreased as the initial moisture content increased.In addition,the friction angle of the interface decreased as the initial moisture content increased.A constitutive model of the disturbed soil-structure interface,a rigid-plastic model based on the initial void ratio and saturability(VSRP) model,was established based on the results.In order to validate this model,a finite element analysis of DRS-1 direct shear tests was conducted.The finite element model calculations coincided with the results of the DRS-1 direct shear tests.The proposed model also reflected the nonlinear features of the soil-structure interface.展开更多
The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between c...The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.展开更多
基金Projects(50378097 50678177) supported by the National Natural Science Foundation of ChinaProject (01JJY3043) supported by the Natural Science Foundation of Hunan Province, China
文摘Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.
基金Project(51274192)supported by National Natural Science Foundation of China
文摘The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial moisture content on the shear strength parameters of the soil-structure interfaces were analyzed.The results indicate that the cohesion of the interface initially increased and then decreased as the initial moisture content increased.In addition,the friction angle of the interface decreased as the initial moisture content increased.A constitutive model of the disturbed soil-structure interface,a rigid-plastic model based on the initial void ratio and saturability(VSRP) model,was established based on the results.In order to validate this model,a finite element analysis of DRS-1 direct shear tests was conducted.The finite element model calculations coincided with the results of the DRS-1 direct shear tests.The proposed model also reflected the nonlinear features of the soil-structure interface.
基金Projects(51009053,51079039)supported by the National Natural Science Foundation of ChinaProject(20100094120004)supported by the Doctoral Program of Higher Education of China
文摘The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.
