An elastoplastic constitutive model for frozen sandy soil considering particle breakage

A series of triaxial compression tests of frozen sandy soil are carried out under five confining pressures (1 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa) at -6 degrees C. By comparing the grain size distribution curves of frozen sandy soil before and after shearing, it is found that significant particle breakage can occur during triaxial shearing. Particle breakage changes internal structure of geomaterials and has a significant effect on their stress-strain relationships. In order to accurately describe the effect of particle breakage of frozen sandy soil on the stress-strain relationships, an elastoplastic constitutive model for frozen sandy soil considering particle breakage is proposed. Based on the energy balance equation established by Indraratna and Salim, the constant critical state stress ratio (M-cr) in the energy balance equation is modified to the stress ratio (M) which changed with shear strain during the shearing process. A yield function, considering particle breakage, is proposed using the modified energy balance equation. The hardening law is determined based on the rebound test results of frozen sandy soil, and the associated flow rule is adopted in the model. Compared with experimental data, the model can well simulate the stress-strain relationships under different confining pressures for frozen sandy soil.