Plastic deformation and failure in granular media

Pre-failure plastic deformation is modelled as a process controlled by simultaneous plane strain hardening and plane strain softening associated with no-extension directions and maximum stress obliquity planes. The equality of rates of strain hardening and softening defines failure. Principal axes of stress and strain increment may or may not coincide depending on the constraints on a deforming soil element. The model defines the orientations of thin rupture layers which may form at failure and suggests the possible form of a hardening law and yield surface. Data in agreement with the model are presented from seven different shear apparatuses and a range of plane strain model tests. The shear apparatuses include those with entirely rigid boundaries, a mixture of rigid and flexible boundaries, and entirely flexible boundaries. The full variation of the intermediate principal stress is covered. La deformation plastique avant rupture est definie comme un processus regi simultanement par un durcissement de de...