Abstract: For the nonlinear fracture phenomena of rock, many numerical methods are carried out for study, but the numerical simulation methods for cracked rock are still being studied. Therefore, this paper combines the bilinear strain softening constitutive model with energy dissipation principle to establish damage constitutive equations; and through the strain energy density theory, energy failure criterion of mesoscopic element is established. When the strain energy of an element stored exceeds a fixed value, the element comes into damage situation and the damage degree increases with the increasing of energy dissipation. Simultaneously, the material properties of the damaged element change until it becomes the element with residual strength. As load increases, the element’s damage degree increases. When the strain energy of the element stored exceeds the established value of the energy criterion, the element gets into fracture. With the increasing of fractured elements, macro-crack generates. This method implements linear calculation instead of the process of nonlinear computation, avoids the singularity of the numerical calculation in element fracture, and simulates the post-peak fracture behaviour of rock. The algorithm can be used to develop a rock fracture process computer program by the FISH language in the fast Lagrangian analysis of continual (FLAC). This program is successfully applied to the simulation of Brazilian splitting and tensile test with cracks. The simulation results agree well with the experimental results. It indicates that the simulation method of rock failure process is correct and feasible.

Key words: strain energy density, energy dissipation, rock fracture, fast Lagrangian analysis of continua in 2D (FLAC2D)