The modeling of crack propagation and coalescence in rocks under uniaxial compression using the novel conjugated bond-based peridynamics

In this paper, crack propagation and coalescence behaviors in rock specimens containing pre-existing open flaws under uniaxial compression are investigated using the novel conjugated bond-based peridynamics (BB-PD). The novel conjugated BB-PD is an extended BB-PD model, where interacting forces are not only related to normal stretch of bonds, but also related to rotation bond angles of a pair of conjugated bonds. Simple elastic-brittle bond rupture criteria, which are related to the uniaxial tensile strength and uniaxial compressive strength, are implemented into this novel conjugated BB-PD. The novel conjugated BB-PD model is found to be effective for simulating rock fracture problems under compression. Initiation and propagation of cracks in rock specimens with a single flaw are firstly studied. Then, crack initiation, propagation and coalescence of two parallel and un-parallel flaws under uniaxial compression are investigated. Meanwhile, effects of flaw inclination angles and rock bridge angles on crack propagation and coalescence behaviors are analyzed. Finally, characteristics of crack coalescence modes are discussed, which reveals the crack coalescence mechanism of pre-flawed rock specimens under uniaxial compression. Comparing the present numerical results with the previous experimental observations and other numerical results, it can be found that the present numerical results are in good agreement with the experimental observations.