Numerical Simulation Method Study of Rock Fracture Based on Strain Energy Density Theory

Many numerical methods are carried out to study the nonlinear failure behaviors of the rock; however, the numerical simulation methods for the failed rock are still in the research stage. This paper establishes the damage constitutive equation by combining the bilinear strain softening constitutive model with energy dissipation principles, as well as the energy failure criterion of mesoscopic elements based on the strain energy density theory. When the strain energy stored by an element exceeds a fixed value, the element enters the damage state and the damage degree increases with increasing energy dissipation. Simultaneously, the material properties of the damaged element change until it becomes an element with certain residual strength. As the load increases, the damage degree of an element increases. When the strain energy stored by an element exceeds the established value of the energy criterion, the element is defined to be failed. As the number of failed elements constantly increases, failed elements interconnect and form macrocracks. The rock fracture calculation program on the basis of the preceding algorithm is successfully applied to the fracture simulation process in Brazilian splitting and intermediate crack tensile tests. This method completes the nonlinear calculation process with linear calculation, avoids singularity of numerical calculation in element fracture, and simulates the rock post-peak fracture behaviors. The simulation results agree well with the test results, indicating the accuracy and feasibility of this method for simulating the rock fracture process.