刘红 张吾渝 冯永珍 王鹏

摘 要：利用GDS空心圆柱扭剪仪，在不同平均主应力条件下对青海重塑黄土进行一系列定向剪切试验，研究平均主应力对青海重塑黄土应力应变特性的影响。试验保持中主应力系数b不变，在不同平均主应力条件下，将重塑黄土试样分别进行主应力轴未发生旋转和旋转45°两种剪切破坏应力路径的剪切试验。结果表明：平均主应力和主应力方向角对重塑黄土的强度和变形有着显著影响;重塑黄土在大主应力方向角等于45°剪切破坏时峰值八面体剪应力与平均主应力呈线性关系，重塑黄土破坏时所产生的八面体剪应变发展趋势基本相同;剪切过程中，重塑黄土的大主应变和小主应变成对称发展，破坏时中主应变只有小幅度增长。当八面体剪应力应变曲线没有出现峰值时，建议采用八面体剪应变为15%对应的八面体剪应力作为重塑黄土的破坏标准。

关键词：重塑黄土;主应力;主应变;破坏强度

中图分类号：TU411.7 文献标志码：A 文章编号：2096-6717（2021）06-0057-07

Abstract： A series of directional shear tests on Qinghai remolded loess under different conditions of average principal stress were performed using the British GDS Hollow Cylindrical Torsion Shear Apparatus. The influence of the average principal stress on the stress-strain characteristics of the Qinghai remolded loess was studied. In the test， the principal stress coefficient b remained unchanged. Under different conditions of the average principal stress， the remolded loess samples were subjected to two kinds of shear failure stress paths in which the principal stress axis did not rotate and rotates 45°， respectively. The experimental results show that the average principal stress and the principal stress direction angle have a significant effect on the strength and deformation of the remodeled loess; The octahedral peak shear stress of the remodeled loess has a linear relationship with the average principal stress of the remodeled loess when the major principal stress direction angle is equal to 45° shear failure. The development trend of the octahedral shear strain generated by the remodeled loess failure is basically the same; during the shearing process， the major and minor principal strains of the remodeled loess develop symmetrically， and the major principal strains increase only slightly during failure. When there is no peak in the octahedral shear stress-strain curve， it is recommended to use the octahedral shear stress corresponding to 15% of the octahedral shear strain as the destructive criterion for remodeled loess.

Keywords： remolded loess; principal stress; principal strain; failure strength

在交通、地震等荷载作用下，路基土体的应力路径复杂多变，尤其是主应力轴旋转这一应力路径普遍发生。应力路径影响着土体的强度和变形，只有在室内试验条件下还原土体所受应力状态，才能得出更可靠的试验结论。传统静三轴、动三轴等仪器不能实现主应力轴旋转，研究复杂应力路径下土体的力学特性有一定局限性，一些学者进行了主应力轴不发生旋转条件下围压对黄土应力应变规律影响的研究[1-3]。……