Study on the failure process of rocks with closed fractures under compressive loading using improved bond-based peridynamics

Abstract

Since the consistency of the bond failure criterion in traditional bond-based peridynamics (BB-PD) theory, the crack-propagation pattern of rocks under tensile and compressive loads is almost the same, however in reality the mechanisms of fractures in tensile and compression state are totally different. To solve this problem, two extensions are conducted on the basis of the traditional BB-PD to form the improved bond-based peridynamics theory (iBB-PD). First, a novel fracture-modeling method considering the actual closed state of fractures in a rock mass is proposed, which can transfer stress or waves across closed fractures. Second, by introducing the elastic-brittle-plastic constitutive model, the traditional PMB model is extended to simulate bond failure under compressive conditions. Three benchmark examples are presented to illustrate the rationale of iBB-PD. The iBB-PD theory is used to simulate the crack initiation, propagation and coalescence in rock specimens with pre-existing closed fractures under uniaxial compression, and the numerical results are in good agreement with the experimental results. The iBB-PD method proposed in this paper could extend traditional peridynamics to capture the failure process of rocks under compressive-shear stress conditions.