压-剪复合应力下非球形颗粒材料空心圆柱剪切试验的离散元模拟

DEM modelling of hollow cylinder shear test on granular materials under combined compression-shear stress using non-spherical particles

采用离散元模拟平台PFC3D构建空心圆柱型数值试样,分析了压-剪复合应力条件下非球形颗粒材料数值试样的宏细观力学响应,重点探讨了颗粒形状和围压对数值试样初始变形模量、抗剪强度、剪切带倾角和组构各向异性演化的影响。结果表明:在保持大主应力方向角α=30°不变的单调剪切条件下,数值试样的初始变形模量能够反映实际砂土的压硬性规律,也即初始变形模量随着围压的增大而增大。数值试样的峰值内摩擦角随着颗粒长短轴比Se的增大而增大,且随着围压的增大而减小。数值试样的剪切带倾角在16°~25°范围内,且随着Se的增大,剪切带倾角越大。无论接触法向初始各向异性分布如何,随着剪切荷载的施加,接触法向各向异性的主方向均逐渐接近大主应力方向,也即试样发现明显的应力诱发各向异性,且在低围压下这一规律更为显著。

In this study,hollow cylindrical specimens were prepared on a discrete element commercial plat form PFC3D using non-spherical particles.Both macro-and micro-mechanical behaviors of granular materials under combined compression-shear stress condition were comprehensively examined,with emphasis on the effects of particle shape and confining stress on initial deformation modulus,shear resistance,inclination of shear band and the evolution of fabric anisotropy of the numerical samples.The results show that under monotonic shear loading,with the major principal stress direction fixed at 30°,the numerical samples can well reflect the compression hardening behavior of laboratory sand samples,i.e.the initial deformation modu lus of the sample gradually increases as confining stress increases.The peak internal friction angle of the numerical sample increases with aspect ratio(Se)of the particles,but decreases with the increase of confin ing stress.The inclination angle of shear band of the numerical sample ranges between 16°~25°.It is also found that the inclination angle of shear band increases with particle shape index Se.Irrespective of the ini tial direction of contact normal anisotropy,the orientation of contact normal anisotropy of the sample gradu ally closes to the direction of major principal stress under shear loading,which means the notable stress-in duced anisotropy of the sample,and this phenomenon is more significant under low confining stress.