The shear strength parameters for geotechnical designs are obtained mainly from consolidated drained （CD） or consolidated undrained （CU） triaxial tests. However, during construction, the excess pore-air pressure g...The shear strength parameters for geotechnical designs are obtained mainly from consolidated drained （CD） or consolidated undrained （CU） triaxial tests. However, during construction, the excess pore-air pressure generally dissipates instantaneously while the excess pore-water pressure dissipates with time. This condition needs to be simulated in a constant water content （CW） triaxial test. The study on Yunnan red clay is carried out to investigate the soil-water characteristics and the shear strength characteristics under the constant water content condition. Osmotic technique is used to obtain the soil-water characteristic curve. A series of CW triaxial tests are conducted on statically compacted specimens. The experimental results show that the soil-water characteristic curve has a low air entry value of 7 kPa due to large pores in non-uniform pore size distribution, and a high residual value exceeding 10 MPa. In addition, the initial degree of saturation and net confining stress play an important role in affecting the shear characteristics under the constant water content condition. Finally, a new semi-empirical shear strength model in terms of degree of saturation is proposed and then applied to Yuunan red clay. Simulation result shows that the model is capable of capturing some key features of soils. The model can be used in whole engineering practice range, covering both unsaturmed and saturated soils.展开更多
Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and str...Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and strain energy capacity of silty sands.The dissipated energy until liquefaction occurs was calculated by analyzing the results of three series of comprehensive cyclic direct simple shear and triaxial tests on Ottawa F65,Nevada,and Firoozkuh sands with varying silt content by weight and relative densities.Additionally,the shear wave velocity of each series was obtained using bender element or resonant column tests.Consequently,for the first time,a liquefaction triggering criterion,relating to effective overburden normalized liquefaction capacity energy(WL=s’c)to effective overburden stresscorrected shear wave velocity(eVs1)has been introduced.The accuracy of the proposed criteria was evaluated using in situ data.The results confirm the ability of shear wave velocity as a distinguishing parameter for separating liquefied and non-liquefied soils when it is calculated against liquefaction capacity energy(WL=s’c).However,the proposed WL=s’c-Vs1 curve,similar to previously proposed cyclic resistance ratio(CRR)-Vs1 relationships,should be used conservatively for fields vulnerable to liquefaction-induced lateral spreading.展开更多
The in situ shear test and in-lab triaxial shear test on compacted rockfill of Fuling safety embankment were carried out and their advantages and disadvantages were compared. The discreteness of cohesive force C and i...The in situ shear test and in-lab triaxial shear test on compacted rockfill of Fuling safety embankment were carried out and their advantages and disadvantages were compared. The discreteness of cohesive force C and internal frictional angle by in situ shear test is much severer than that by in-lab triaxial shear test. The consolidation of in-lab triaxial shear test is bigger than actual consolidation in rockfill engineerings, so the confining pressure should be reduced to a low level in-lab triaxial shear test.展开更多
基金Project(51068002) supported by the National Natural Science Foundation of ChinaProject(10-046-14-1) supported by Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering,China
文摘The shear strength parameters for geotechnical designs are obtained mainly from consolidated drained （CD） or consolidated undrained （CU） triaxial tests. However, during construction, the excess pore-air pressure generally dissipates instantaneously while the excess pore-water pressure dissipates with time. This condition needs to be simulated in a constant water content （CW） triaxial test. The study on Yunnan red clay is carried out to investigate the soil-water characteristics and the shear strength characteristics under the constant water content condition. Osmotic technique is used to obtain the soil-water characteristic curve. A series of CW triaxial tests are conducted on statically compacted specimens. The experimental results show that the soil-water characteristic curve has a low air entry value of 7 kPa due to large pores in non-uniform pore size distribution, and a high residual value exceeding 10 MPa. In addition, the initial degree of saturation and net confining stress play an important role in affecting the shear characteristics under the constant water content condition. Finally, a new semi-empirical shear strength model in terms of degree of saturation is proposed and then applied to Yuunan red clay. Simulation result shows that the model is capable of capturing some key features of soils. The model can be used in whole engineering practice range, covering both unsaturmed and saturated soils.
文摘Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and strain energy capacity of silty sands.The dissipated energy until liquefaction occurs was calculated by analyzing the results of three series of comprehensive cyclic direct simple shear and triaxial tests on Ottawa F65,Nevada,and Firoozkuh sands with varying silt content by weight and relative densities.Additionally,the shear wave velocity of each series was obtained using bender element or resonant column tests.Consequently,for the first time,a liquefaction triggering criterion,relating to effective overburden normalized liquefaction capacity energy(WL=s’c)to effective overburden stresscorrected shear wave velocity(eVs1)has been introduced.The accuracy of the proposed criteria was evaluated using in situ data.The results confirm the ability of shear wave velocity as a distinguishing parameter for separating liquefied and non-liquefied soils when it is calculated against liquefaction capacity energy(WL=s’c).However,the proposed WL=s’c-Vs1 curve,similar to previously proposed cyclic resistance ratio(CRR)-Vs1 relationships,should be used conservatively for fields vulnerable to liquefaction-induced lateral spreading.
基金SupportedbyChongqingScienceandTechnologyCommittee (No .2 0 0 1 74 2 9)andWesternCommunicationsProjectofMinistryofCommunications
文摘The in situ shear test and in-lab triaxial shear test on compacted rockfill of Fuling safety embankment were carried out and their advantages and disadvantages were compared. The discreteness of cohesive force C and internal frictional angle by in situ shear test is much severer than that by in-lab triaxial shear test. The consolidation of in-lab triaxial shear test is bigger than actual consolidation in rockfill engineerings, so the confining pressure should be reduced to a low level in-lab triaxial shear test.
