A bounding surface plasticity model of sand for cyclic loading analysis

A bounding surface plasticity model for describing the stress-strain behavior of saturated sand subjected to drained cyclic loading is presented within a critical-state framework. A hardening rule depending on incremental deviatoric strain is adopted. During the initial loading, the stress state always locates on the bounding surface. During the unloading and reloading processes, the bounding surface is the historical maximum yielding surface. This hardening rule can describe the softening phenomena of dense sands and remember the stress history by the bounding surface. The shape of the bounding surface is a modified ellipse, which enables the model to describe the plastic strain during loading with constant stress ratio. This model incorporates state-dependent dilatancy and adopts the non-associated flow rule, so it can reasonably describe the volume change behavior of sandy soil. A mapping rule passing through stress reversal points is adopted. A single set of 10 model constants calibrated by conventional triaxial tests is needed for one type of sand under different initial void ratios and different confining pressures. The predicted results by the model for the monotonic and cyclic triaxial tests on Hostun sand, Nevada sand, Toyoura sand and Fuji River sand demonstrate that the model can reasonably describe the stress-strain characteristics of saturated sand.