Nonlinear Volumetric Deformation Behavior of Rock Salt Using the Concept of Mobilized Dilatancy Angle

Post-yield strength and deformation properties of rock salt are of great importance to the stability of rock surrounding deep underground storage caverns. Uniaxial and triaxial compression tests were performed to explore the volume change of Qianjiang rock salt under different confining stress states. The experimental results indicate that the dilatancy angle first increases rapidly then decreases gradually and drives to a constant with equivalent plastic strain. A higher confining stress results in a lower peak dilatancy angle. With the increase of confining pressure, the dilatancy angle decreases nonlinearly. Based on the volumetric-axial strain curves of rock salt, a mobilized dilatancy angle model taking into account the effects of confining pressure and the equivalent plastic strain was developed using nonlinear fitting. The new model was implemented in the software FLAC^3Dand verified effective to predict the volumetric dilatancy behavior of rock salt.