Energy Approach Towards Stress-Dilatancy Formulation based on Double Slip-Rotation Rate Concept

This paper proposes a new approach for the analysis of shear-induced volume change of granular materials. Following a revisit to the micro-mechanical deformation mechanism and the findings from discrete element method simulations, it is concluded that the double slip-rotation rate mechanism is appropriate for the description of granular materials subjected to shear. The implementation of energy principle with the double slip-rotation rate mechanism provides a new method for the derivation of stress-dilatancy relation under general stress conditions without adopting Rowe's hypothesis of minimum energy ratio. This new approach can be easily extended to take into account the non-coaxility of granular material deformation. The dilatancy formulations proposed by Taylor, Rowe and Matsuoka-Nakai can all be recovered as special cases of the proposed approach. Comparisons with experimental data show that the new stress-dilatancy relation correctly captures the dilatancy behaviour of sand observed in both general 3D stress conditions and simple shear tests.