Unified mechanics model for sand based on thermomechanics

The different deformation curves of loose sand and dense sand can be simulated by a unified way by which the dependence of dilatancy on material state is considered.A proper energy dissipation function based on modern ideas of thermomechanics is used to develop the families of models describing the elasto-plastic behavior of soils.A modified model combining the theory of state-dependent dilatancy with thermodynamics laws is proposed.In the model,state dependence is introduced into dilatancy function indirectly by establishing the relationship between initial state parameter and rotation hardening rule.The model takes the dependence of dilatancy on initial state of material into account and guarantees the consistence of dilatancy function with yield locus because of the thermodynamics basis involved.The simulation capability of the proposed modified model is shown by computing general features of soil in triaxial drained or undrained tests with a unified model set of model parameters and rotation hardening rule.The parameters can be determined by fitting a part of triaxial test data of Toyoura sand.According to the obtained parameters a group of triaxial test curves are computed and compared with the experimental data to verify the validity of the model.The results show that the differences are acceptable.