初始组构各向异性对类砂土直剪试验影响的非圆颗粒组模拟

Intrinsic anisotropy effect to quasi-sand in direct shear test using non-circular particles group

针对圆形和单粒组颗粒模拟试验的缺陷,基于PFC2D的clump命令,开发了非圆形颗粒组,采用单向法、各向同法和沉积法生成不同初始组构特征的试验样品,模拟了砂土直接剪切试验过程.探讨了初始组构各向异性对砂土抗剪强度与剪胀性的影响规律,研究了剪切过程中力链的演化形式,分析了颗粒旋转以及剪切带内外颗粒长轴定向的变化特征.数值试验结果表明:颗粒初始组构的差异对抗剪强度的影响较大,对材料的剪胀性以及内摩擦角的影响较小;剪切过程应力主轴发生了偏转,颗粒接触角向主应力方向靠拢;颗粒旋转主要发生在8倍于平均颗粒半径的条带内,颗粒长轴定向也发生了偏转,偏转方向与主应力偏转方向相同,但滞后于主应力的偏转速度;初始组构的不同影响剪切带内颗粒的旋转速度.

Considered the defect of circular and the group of single-particle,a non-circular particle group has been developed,based on the order of clump in PFC2D.Different initial deposition and fabric characteristics of the test samples have been generated with one-way method,uniform method and deposited method.The direct shear test has been simulated.The shear strength and the dilatancy affected by initial fabric anisotropy have been studied,and how the force chain derived in shear process has been analyzed,and how the particle rotated inside or outside of the shear zone has also been studied.Numerical results show that： the original fabric has great impact on shear strength,but little on material dilatancy and internal friction angle;stress axis deflects during shear process,and the contact angle moves closely to the principal stress direction;grains rotate mainly in 8 times the average particle radius of the band,and the particle long axis orientation also deflects with the same direction of main stress;the particle rotation speed in the shear zone is also affected by the initial fabric of the group.