A state-dependent non-orthogonal elastoplastic constitutive model for sand

Abstract

The state-dependent deformation behavior of sand is reinterpreted from the perspective of strain increment magnitude and direction by analyzing the existing test data. A state-dependent non-orthogonal elastoplastic constitutive model for sand is established by incorporating the state variable into plastic strain increment magnitude and direction, respectively. For the magnitude of plastic strain increment, an S-type isotropic compression hardening rule applicable in large stress ranges is proposed, which is extended into a new hardening parameter for general stress states. Furthermore, the state variable is introduced into the newly proposed hardening parameter to consider the state dependence. On the other hand, the non-orthogonal plastic flow rule is employed to determine the plastic strain increment direction. To consider its state dependence, the relationship between the state variable and the parameter controlling the plastic flow direction is established. The comparison with the test results of four types of sand demonstrates that the proposed model can reasonably capture the state-dependent deformation behaviors of plastic strain increment magnitude and direction of sand.