Post-Yield Properties of Rock Salt Using the Concept of Mobilized Strength Components and the Dilation Angle

Post-yield strength and deformation characteristics of rock salt are of great significance in the analysis of progressive failure and convergence of rock surrounding the deep underground storage areas. The post-yield stress state of rock salt is assumed to satisfy the Mohr–Coulomb strength criterion, and a dilation angle can be used to describe the volumetric deformation. The post-yield mobilized cohesion, internal friction angle, and dilation angle were obtained based on the complete stress–strain curves under different confining pressures. The post-yield evolution laws of strength components and the dilation angle of rock salt were studied. A nonlinear cohesion weakening–friction strengthening model and a dilation angle model with respect to the equivalent plastic strain and confining stress were proposed using nonlinear fitting methods. The new models were then implemented into the FLAC^3D software to verify that they could capture the post-yield strain hardening/softening and volumetric behaviors of rock salt reasonably.