The effects of rolling resistance and non-convex particle on the mechanics of the undrained granular assembles in 2D

To study their influences on the mechanics of granular assembles under undrained tests, a rolling resistance model for two-dimensional disks and three types of non-convex grains (i.e. disk, ellipse and triangle) without rolling resistance are introduced into discrete element methods. Both macroscopic and microscopic responses are analyzed by consideration of four aspects of the mechanical quantities of these systems at the steady state, i.e. shear strength, solid fraction, force anisotropies, and probability distribution of contact forces, to analyze the influences of rolling resistance at particle contacts and shape irregularity of particles. Our main findings are: 1) the rolling resistance is unable to achieve as large critical shear strength of granular systems, even when the rolling resistance coefficient artificially becomes very large. 2) the main weight of anisotropic parameters which dominate the macroscopic shear strength for the non-convex particles is contact normal anisotropy, for the rolling resistance assembles is contact normal force anisotropy, and 3) the average friction mobilization for the rolling resistance assembles is much lower than that for the non-convex packings.