ABSTRACT
The effect of principal stress rotation on the behaviour of granular media is known to induce plastic strains, despite the principal stresses, and hence stress invariants are kept constant as demonstrated on sand in simple shear tests. By contrast, classic plasticity flow rule predicts zero plastic deformations under such a particular but pertinent loading process. This is strongly linked to micro-structural changes in fabric as well as sliding characteristics during loading history, whereas continuum plasticity theories are devoid of any micro-scale information. This study describes a systematic micro-mechanical investigation of granular media deformations under a rotation of principal stresses so that findings can be incorporated into a micro-structurally enriched flow rule which accounts for such effects.
