Abstract: To accurately depict energy evolution during rock deformation, we propose methodologies for computing rock cohesion and internal friction angle using elastic shear strain energy and the triple shear energy yield criterion. Additionally, we introduce a method for determining the dilatancy angle based on the triple shear energy plastic potential function. Leveraging these approaches alongside data from cyclic loading and unloading tests on rocks, we derive the elastic modulus, cohesion, internal friction angle, and dilatancy angle at various plastic accumulation stages under different confining pressures. Our findings reveal a negative exponential decrease in elastic modulus with increasing plastic deformation, linear increases in pre-peak cohesion, and negative exponential decreases in post-peak cohesion. The internal friction angle conforms to a Weibull function with proportional and shape parameters of 1 and 1.5, respectively, while the dilatancy angle decreases linearly. Furthermore, elevating confining pressure leads to linear increases in elastic modulus and cohesion, accompanied by a linear decrease in the dilatancy angle. We establish a triple shear energy elasto-plastic coupling mechanical model and integrate it into finite difference software, developing code to monitor energy evolution. Through simulated triaxial compression tests on rocks, our model accurately captures rock mechanical behaviors during subsequent yielding, encompassing phenomena such as hardening, softening, dilatancy, confining pressure effects, and energy evolution. These findings furnish both theoretical insights and practical tools for examining rock mass instability from an energy perspective.

Key words: rock mechanics, triple shear energy yield criterion, elasto-plastic coupling model, elastic shear strain energy, confining pressure effect, secondary development