基于PFC~(3D)的砂土直剪模拟及宏细观分析

为能更好地分析砂土在剪切过程中的体积变化及力学行为,通过PFC~(3D)颗粒流程序,按照室内实际级配建立数值试样,进行了不同垂直压力下的砂土直剪试验模拟,并将模拟结果与室内试验结果进行了对比;研究了砂土在剪切过程中的体积变化,并用两种方法分析了砂土剪切带的演变过程;从细观角度对试样颗粒的速度场及力链网络的发展变化进行了分析研究。结果表明,数值模拟结果与室内试验结果基本一致,砂土的体积变化表现为先剪缩后剪胀,剪胀量与垂直压力成反比;剪切带厚度约为11～12倍d_(50),在剪切带内颗粒的位移和欧拉角变化较大;试样内部强力链的演变较为明显,力链网络对外荷载变化的敏感性很高;剪切过程中上盒颗粒速度场方向的变化能够较好地解释砂土产生的剪胀现象。

Shear simulation and macro meso analysis of sand based on PFC3D

In order to analyze the volume change and mechanical properties of sandy soil in the shear process,according to the PFC^3D particle flow program,a numerical sample was built according to the indoor gradation,and the direct shear test of sandy soil under different vertical pressures is simulated and compared with the indoor shear test.The volume change of sandy soil in the shear process is studied,and the evolution process of sandy soil shear zone is analyzed by two methods.The results show that the numerical simulation results are basically consistent with the actual test results.The volume change of sandy soil shows that the shear expansion rate is inversely proportional to the vertical pressure.The thickness of shear zone is about 11 to 12 times of d₅₀,and the displacement and Euler angle of particles in the shear zone vary greatly.The evolution of the strong chain is most obvious.The force chain network is highly sensitive to external loads.In the shear process,the direction change of particle velocity field can explain the dilatancy of sandy soil.