考虑主应力轴旋转的砂土变形特性试验研究

采用空心圆柱扭剪仪(HCA)进行一系列排水试验，研究主应力轴旋转条件下砂土的变形特性。试验采用2种类型的加载路径，第一种保持偏应力不变旋转主应力轴，第二种在增加偏应力的同时旋转主应力轴。通过改变偏应力的应力水平，研究砂土的变形以及非共轴度的变化规律。同时，对同等试验条件、材料和加载路径下不同密实度试样的试验结果分析，研究密实度对于非共轴度的影响。另外，采用2种材料进行对比试验(Portaway砂与LB砂)，研究砂土初始各向异性与非共轴性之间的关系。试验研究结果表明：砂土的变形随着主应力轴的旋转而累加，并体现出显著的非共轴特性。砂土的非共轴度与材料所处的应力水平、密实度及初始各向异性均存在一定相关性。

EXPERIMENTAL STUDY OF DEFORMATION BEHAVIOUR OF SAND UNDER ROTATION OF PRINCIPAL STRESS AXES

A hollow cylinder apparatus(HCA) was used to study the deformation behaviour of sand under rotation of principal stress axes. A series of drained tests were carried out with two types of stress path. The first one was pure rotating stress axes without changing the deviator stress，while in the other one the deviator stress was increased with the rotation of principal stress axes. Various constant deviator stresses were used to study the effects of stress level on the deformation and non-coaxial behaviour of sand. Specimens with two relative densities were prepared to investigate the influence of density on non-coaxiality. Meanwhile，study was carried out to validate the previous viewpoint that non-coaxiality was induced by the initial fabric anisotropy of material by comparing results from two different materials，which were Portaway sand and Leighton Buzzard sand. The results show that the deformation would accumulate with the rotation of principal stress axes. And the non-coaxial behaviour of soil was found in the study. It was also indicated that the non-coaxiality would be affected by the stress level，density and the initial fabric anisotropy of material.