A constitutive platform for sand modeling

This paper addresses the issue of sand dilatancy and the impact of fabric anisotropy. A platform model based on the concept of state-dependent dilatancy is introduced first, and a joint invariant, A, of the stress tensor and a second-order fabric tensor is developed afterwards. With this objective measure of the sand anisotropy state, the dilatancy and plastic hardening are formulated, and the critical-state line is assumed non-unique in the e-p-q space but unique in the e-p-q-A space. This simple approach is rigorous and correct within the fundamentals of anisotropic constitutive modeling and captures some of the most important features of stress-strain-strength responses of sand including the impact of inherent fabric anisotropy under proportional loading conditions.