A double yield surface constitutive model for sand based on state-dependent critical state theory

By analyzing shortages of the single yield surface model for sand, a double yield surface constitutive model is presented based on the critical state and state-dependent dilatancy theories which is suitable for different initial density sands. This double yield surface model reflects the mechanism of shear deformation and mechanism of compressive deformation simultaneously, and overcomes some shortages of the single yield surface model in describing test results of sand. One set of model constants can simulate well the stress-strain responses of sand under different confining pressures and densities. The proposed model can be employed to investigate properly the dilatancy behaviors of sand. It is verified by the one-dimensional and triaxial compression test results of Toyoura sand and Hostun sand, and good predictions show its rationality and validity. Key words: state-dependency; critical state; double yield surface constitutive model; dilatancy