A simple constitutive model for granular soils: Modified stress-dilatancy approach

The dependencies of granular soil behaviour on void ratio and stress are modelled within plasticity theory enriched by a modified stress-dilatancy law. Simplicity has been kept in the development of the constitutive law for easy future implementation in afinite element code. By using a void ratio dependent factor which measures the deviation of the current void ratio from the critical one, Rowe's stress dilatancy equation is modified. This modification indeed corresponds to a new energy dissipation equation for a granular assembly which sustains kinematical constraints under the action of stresses. The proposed constitutive law predicts in a very consistent manner the response of sands in monotonic loading conditions for a large range of initial void ratios and confining pressures without the need to make any adjustments to the material parameters. Well known published data for the drained triaxial compression of Sacramento River sand was successfully modelled.