Effect of Particle Shape on Contact Network and Shear-Induced Anisotropy of Granular Assemblies: A DEM Perspective

The particle shape plays an important role in the macroscopic response of granular materials. Based on discrete element method (DEM) simulation results of triaxial tests on samples with different particle shapes, this study focuses on the microcharacteristics of contact network and anisotropy in granular media during shearing by a quad-partition method. Numerical results show that the interlocking is enhanced, and stronger contact force will be generated along the loading direction as the deviation of particle shape from a sphere, causing the increase of shear strength. Sliding mainly occurs in weak contacts, and the microscopic dissipative behavior in weak contact sliding plays a key role in the transformation from contraction to dilation. The samples with different particle shapes all reach the maximum proportion of sliding contacts at the phase transformation state that is the transition points of volumetric change. The anisotropy of samples increases as the deviation of particle shape from a sphere, and the contribution of the normal contact force anisotropy to the shear strength is the largest one. With the increase of the particle axial ratio, the mean coordination number and geometrical anisotropy increase due to the oriented alignment occurring at the critical state. Compared with superball particles, the ellipsoid particles have lower compressibility with a smaller axial strain and volumetric strain at the peak state.