A unified elastoplastic model for clay and sand with the SMP criterion

In this paper, the modified Cam-clay model is revised to a unified elastoplastic model for clay and sand under three-dimensional stress conditions in the following two aspects. Firstly, the method for the transformation of the curved surface of the SMP (Spatially Mobilized Plane) criterion to a cone in the transformed principal stress space is proposed by introducing a transformed stress. The transformed stress is applied to the Cam-clay model. The revised model realizes the consistency from the shear yield to the shear failure and the combination of the Cam-clay model with the SMP criterion for clay. Secondly, in order to develop a unified constitutive model for clay and sand, a new hardening parameter is derived, which can not only describe the dilatancy of sand, but also be reduced to the plastic volumetric strain for normally consolidated clay.