宏细观结合考虑主应力轴旋转的砂土破坏特性

采用宏细观结合各向异性破坏准则对主应力轴旋转条件下砂土的破坏特性进行分析。该准则是加载应力、组构各向异性程度和应力与组构几何关系3个因素的函数，可描述细观特性对任意应力旋转角度条件下破坏特性的影响。根据空心圆柱扭剪试验的特点推导一般正交坐标系下主应力轴旋转条件下的破坏关系式，考虑应力与砂土细观组构的几何关系，推导的关系式即可分析该条件下破坏特性。材料为各向异性时，主应力轴旋转造成破坏特性发生变化，细观各向异性程度越小变化越小；材料为各向同性时，则不会造成砂土破坏特性的变化。该式表明主应力轴旋转条件下不同破坏特性存在的根本原因是砂土各向异性的存在。采用空心圆柱试验结果进行验证，结果表明建立的关系式能较好描述不同应力加载角度条件下砂土的破坏特性。初步验证了由于砂土各向异性的存在使得主应力轴旋转造成了不同的破坏规律。

Failure properties of sand considering rotation of principal stress axis with method of macro-meso incorporation

Based on anisotropy failure criterion with the method of macro-meso incorporation, failure properties of sand considering rotation of principal stress axis are analyzed. The criterion is a function of loading stress, degree of fabric anisotropy and geometric relationship between fabric and stress. So it can describe the effect of mesostructure on failure properties with any rotation angle of principal stress axis. According to the characteristics of hollow cylindrical torsional shear tests, the failure expression considering rotation of principal stress axis is derived in general orthogonal coordinate system. Considering the geometric relationship between loading stress and sand meso-fabric, the established expression can analyze failure properties under the condition of principal stress axis rotation. Rotations of principal stress axis cause the changes of failure properties when anisotropy exists. The greater degree of anisotropic causes the more change of failure. There isn’t any change when the material is isotropic. Therefore, it is indicated that the nature reasons of different failure properties under the condition of principal stress axis rotation is the exist of anisotropy. The verification with hollow cylindrical test results show that the established expression can describe the failure properties with different angles of loading stress. The different failure properties caused by sand anisotropy under the condition are verified preliminarily.