中主应力对散粒体材料强度和变形影响的数值模拟研究

NUMERICAL SIMULATION STUDY OF INFLUENCE OF INTERMEDIATE PRINCIPAL STRESS ON STRENGTH AND DEFORMATION OF GRANULAR MATERIALS

采用PFC3D数值模拟软件,研究散粒体材料在真三轴试验条件下中主应力对强度和变形的影响,并用统计方法从细观角度探讨中主应力的影响机制。数值模拟结果表明,中主应力比b增大,材料的有效内摩擦角、轴向应力峰值以及对应的轴向应变都呈现先增大然后减小的变化规律。b值的增大使中主应力方向应变由拉伸变为压缩,体应变由剪缩变为剪胀。b值对散粒体材料有效内摩擦角的影响规律和Lade-Duncan准则比较一致。从细观层面上,b值影响颗粒间法向接触力的分布。在b值增大过程中,当b值较小时中主应力方向的增强效应占主导使得材料强度增大,b值较大时小主应力方向的减弱效应占主导使得材料强度降低。

Using PFC3 D,the influence of intermediate principal stress on strength and deformation of granular materials was studied and microcosmic mechanism was probed using statistical method. Simulating results show that shearing resistance angle,axial peak stress and the corresponding axial strain firstly increase and subsequently decrease with the increase of intermediate principal stress ratio b. The strain in the intermediate principal stress direction is tensile train and becomes compressive strain with the increase of b,while volumetric strain transitions from shear contraction to shear dilatancy. Simulating results agree very well with Lade-Duncan criterion. In microscopic level,b affects the distribution of contact forces. As b increases,the increase effects in intermediate principal direction are more prominent for lower b values and strength has an initial increase. When b approaches 1,the decrease effects in minor principal direction are more prominent and lead to a lower strength.