A Constitutive Model for Sands

In this paper, an elastoplastic constitutive model is presented for predicting sandy soil behavior under monotonic and cyclic loadings. The model is based on the CJS3 model that takes into account deviatoric and isotropic mechanisms of plasticity. The flow rule in deviatoric mechanism is non-associated and a kinematic hardening law controls the evolution of the yield surface. In the present study, the critical state surface and history surface separating the virgin and cyclic states in the stress space are defined. Hardening modulus and stress-dilatancy law for monotonic and cyclic loadings are effectively modified. Taking the hardening modulus as a function of deviatoric and volumetric plastic strain, the model will be capable of predicting sand behavior once the history surface and stress reversal are defined. All model parameters have clear physical meanings and can be determined simply from laboratory tests. The results of homogeneous tests on Hostun sand are used to validate the model. The results of validation indicate the capability of the proposed model.