应力历史对饱和砂土力学性状影响的试验研究

三向应力历史条件的影响是准确预测地基变形的重要参考因素之一。针对相对密度为30 %的福建标准砂，利用土工静力-动力液压-三轴扭转多功能剪切仪，进行了复杂条件下应力路径变化的应力控制式单调排水剪切试验。通过控制试验过程的平均主应力保持不变，改变应力历史条件，着重探讨应力历史对饱和砂土剪切强度和应力-应变关系的影响。试验结果表明：当平均主应力一定时，在排水条件下应力历史的改变，对砂土的剪切强度几乎没有影响，但会影响应力-应变特性。弹性轨迹随着中主应力系数和主应力方向角历史的不同而发生变化。引入考虑应力历史同剪切过程之间条件变化的参数，结合试验数据，给出了三维空间中砂土受到应力历史作用后形成的弹性边界的关系表达式。

Experimental study of effect of stress history on mechanical properties of saturated sand under complex stress conditions

The effect of stress history under three dimensional stress conditions are one of the important phenomena which have to be evaluated for the accurate prediction of ground deformation. Various stress-controlled drained monotonic shear tests on the Chinese Fujian standard sand of relative density 30 % under complex stress conditions with different stress paths are conducted using the soil static and dynamic universal triaxial and torsional shear apparatus. The mean principal stress is controlled unchanged in the process of tests. The stress history conditions are varied so that their influences on shear strength and stress-strain relationship of saturated sand are explored. Test results show that under drained condition sand specimens with stress history of different type do not change their shear strength for a given mean principal stress. On the other hand, the stress-strain characteristics behaved differently with respect to the stress history. The elastic locus varied with stress history has directional and stress condition effects. Finally, introducing predominant parameters for the difference of the direction and the stress condition between stress history and shear process, as well as taking into account the experimental results, the elastic boundary space due to the stress history is expressed under three dimensional stress conditions.