The Microscopic Mechanism of Crack Evolution in Brittle Material Containing 3-D Embedded Flaw

In this paper, the microscopic mechanism of crack evolution in brittle material containing 3-D embedded flaw is investigated. The crack evolution mode of 3-D flaw is summarized by the uniaxial compression experiment first. Based on experiment results, the micro-parameters in the flat-joint model are calibrated and numerical models containing 3-D embedded flaw are established in PFC3D. Then, the numerical uniaxial compression experiment is carried out to validate the effectiveness of numerical model. The simulation results indicate that the flat-joint model is appropriate to model the cracking processes of 3-D flaw. The method of particle velocity vector field is introduced to analyze crack evolution mechanism, and four types of particle velocity vector field corresponding to typical cracks are proposed. Generally, the initiation of wing crack is tensile crack and the further propagation is mixed tensile and shear crack. However, the interaction between flaws has important impacts on the crack evolution mechanism and the specimen failure mode. In the rock bridge, wing crack may initiate as mixed tensile and shear crack. The failure mode turns from burst failure to splitting failure with the condition changing from single flaw to double flaws.