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 idealized granular materials, but significant effects on their shear strength. The overall peak and residual friction angles, phi(p) and phi(r), are smaller than the interparticle friction angle phi(mu) because of the concentration of rotations in shear bands. When particle rotations are artificially prevented, phi(p) and phi(r) become larger than phi(mu), and the localized failure patterns become different from those observed 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 independent of the axial strain. Particle rotations induce twice as many rolling contacts as sliding contacts. Compared to sliding contacts, rolling contacts are oriented differently, generate different fabric tensors, and are less capable of dissipating energy and supporting inclined contact forces.