State dependent dilatancy relationship for sands

The stress dilatancy relation which accounts for the dependencies on stress level and density is proposed. The consideration of these aspects would give a significant implication on the modelling of granular materials behaviour since it is mostly dominated by the evolution of dilatancy and density history. Modified Cam clay dilatancy is modified through state index parameter I_s proposed by Verdugo (1992) which measures the ratio between the deviation of the current void ratio and its relative critical void ratio to a reference one. The proposed stress dilatancy relation is compared to the experimental result from undrained triaxial test for wide range density and stress level. It also indeed exhibits a special case of general anisotropic dissipation function introduced by Dafalias (1986).