OBSERVATIONS ON THE EFFECTS OF PARTICLE ROTATIONS ON THE FAILURE OF IDEALIZED GRANULAR-MATERIALS

Based on the computer simulations of biaxial tests, particle rotations are shown to have little influence on the elastic properties of ideal ized granular materials, but significant effects on their shear streng th. The overall peak and residual friction angles, phi(p) and phi(r), are smaller than the interparticle friction angle phi(mu) because of t he concentration of rotations in shear bands. When particle rotations are artificially prevented, phi(p) and phi(r) become larger than phi(m u), and the localized failure patterns become different from those obs erved experimentally in granular media. The average particle rotation remains small in the complete biaxial specimen, but increases in shear bands. The particle rotations follow an exponential distribution inde pendent of the axial strain. Particle rotations induce twice as many r olling contacts as sliding contacts. Compared to sliding contacts, rol ling contacts are oriented differently, generate different fabric tens ors, and are less capable of dissipating energy and supporting incline d contact forces.