New insights into the effect of interparticle friction on the critical state friction angle of granular materials
This letter examines the effect of interparticle friction (μ) on the critical state friction angle (φcs) of granular materials via the discrete element method. A series of drained triaxial tests are conducted on multisphere ellipsoids. The results indicate that φcs first increases with μ and then reaches a plateau when μ ≥ 0.3. Anisotropic analysis provides new insights into the underlying mechanisms of the φcs evolution from two perspectives. First, the initial increase of φcs results from the increases of contact normal anisotropy ac, normal contact force anisotropy an and tangential contact force anisotropy at; subsequently, the saturation of φcs is a consequence of the decrease of an being compensated by the increase of at. Second, the relationship between the stress ratio q/p and the contact normal anisotropy within the strong and nonsliding contacts is nearly linear for ellipsoids (i.e., q/p = ). Accordingly, the initial increase of φcs is related to the increase of k and at low μ. The plateau of φcs at high μ can be attributed to the decrease of being compensated by the increase of k.
Keywords: Interparticle friction, Critical state friction angle, Anisotropy, Microscopic mechanisms, DEM, Drained triaxial test,