A sand model with state-dependent dilatancy

A comprehensive bounding surface sand model has been formulated within a critical-state framework. This model differs from some existing models in that it incorporates the concept of state-dependent dilatancy in its formulation. The concept of state-dependent dilatancy states that the dilatancy of a granular soil depends not only on the stress ratio η = q/p, where q and p are the deviatoric and mean effective normal stresses respectively, but also on the current material internal state in reference to the critical state in e–p–η space, where e is the void ratio. By adopting such a state-dependent dilatancy, the present model simulates, with a single set of model constants, both the contractive and the dilative responses of granular soils over a wide range of variations in stress and material internal states. The model is formulated in general three-dimensional stress-strain space, and works for both monotonic and cyclic loading paths, and under either drained or undrained conditions. The formulations and the underlying concepts are presented in this paper.