π平面上原状土的空心扭剪试验

为了通过空心扭剪试验获得原状土在π 平面上的屈服特性，在分析空心扭剪试验仪加载过程和加载特点的基础上，研究了空心圆柱试样可实现的应力状态，并设计了相应的加载路径．与重塑试样不同，原状土样的初始应力状态位于K0 固结线上而不是等倾线上，因此，其加载路径应从原点开始沿K0 固结线行至原始应力状态，然后再在π 平面上进行以初始应力为起点的等p 试验．在考虑原状土的初始应力状态和各项异性的基础上，针对具有不同主应力方向角的平行试样，给出了等p 条件下保持主应力方向角不变的加载路径实现方法，采用该方法可得到任意平均主应力时π 平面上六分之一范围内的屈服曲线，该范围对应于大主应力方向角从-45o~45o．本文设计的加载方案可完成真三轴试验的部分功能，但经济成本相对较低，操作方法简单易行．

Hollow Torsional Shear Test in π Plane for Undisturbed Soil

In order to obtain the yield characteristics of undisturbed soil on the π plane by hollow torsional shear test, based on the analysis of the loading process and loading characteristics of the hollow torsional shear tester, the stress state of the hollow cylindrical specimen was studied and the corresponding loading path was designed. Unlike the remolded specimen, the initial stress state of the undisturbed soil was on the K0 consolidation line rather than the equipotential line. Therefore, the loading path starts from the origin along the K0 consolidation line to the original stress state, and then follows an iso-p test starting from the initial stress on the π plane. Considering the initial stress state and anisotropy of the undisturbed soil, the loading path method for keeping the principal stress direction angle unchanged under equal-p conditions was given for the parallel specimens with different principal stress directions. The yield curve in the range of one-sixth of the π plane at any average principal stress can be obtained. This range corresponds to the direction of the large principal stress from -45o~45o. The loading scheme proposed in this paper can realize some characters of the true triaxial test, with relatively low economic cost, and simplified operation scheme.