Soil-water characteristics and shear strength in constant water content triaxial tests on Yunnan red clay
来源期刊：中南大学学报(英文版)2013年第5期
论文作者：MA Shao-kun(马少坤) HUANG Mao-song(黄茂松) HU Ping(扈萍) 杨超
文章页码：1412 - 1419
Key words：Yunnan red clay; soil-water characteristic curve; shear strength; constant water triaxial test
Abstract: 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 Yunnan 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 unsaturated and saturated soils.
MA Shao-kun(马少坤)1, HUANG Mao-song(黄茂松)2, HU Ping(扈萍) 3, YANG Chao(杨超)2
(1. College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China;
2. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;
3. School o)
Abstract: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 Yunnan 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 unsaturated and saturated soils.
Key words:Yunnan red clay; soil-water characteristic curve; shear strength; constant water triaxial test
