中主应力对饱和松砂不排水单调剪切特性的影响

利用土工静力-动力液压-三轴扭转多功能剪切仪，针对相对密度为30 %的福建标准砂，在不排水条件下控制主应力方向、中主应力系数、平均主应力保持不变，进行了单调剪切试验。以此着重探讨了中主应力系数对相变有效内摩擦角、峰值有效内摩擦角及有效应力路径的影响。研究表明，中主应力系数对在不排水单调剪切条件下饱和松砂的强度参数具有显著的影响，而对有效应力路径及应力-应变关系发展模式影响较小。基于广义双剪强度准则，从理论上探讨了土的强度参数对于中主应力的依赖性，并与试验结果进行了对比。

Effect of intermediate principal stress on undrained behavior of saturated loose sands under monotonic shearing

The experimental tests of loose sands subjected undrained monotonic shearing with the relative density of 30 % are performed by using the soil static and dynamic universal triaxial and torsional shear apparatus which is newly developed in Dalian University of Technology.A series of tests are conducted for loose sand under complex stress conditions with different coefficient of intermediate principal stress,orientation of principal stress and mean principal stress.Based on the experimental results,the effects of coefficient of intermediate principal stresses on the friction angles at phase-transformation state(PTS) and peak stress state as well as effective stress paths are respectively examined.It is found that the coefficient of intermediate principal stress will play an important role in controlling the undrained shear strength parameters of loose sands while its effects on both effective stress paths and the variation patterns of the relation between stress and strain is relatively minor.The dependency of soil strength parameter on the coefficient of intermediate principal stress is illustrated theoretically by using the generalized double shear criterion and can agree well with the experimental data.