Numerical Study on Strength and Failure Behavior of Rock with Composite Defects under Uniaxial Compression

TLDR

Cracks and holes in underground engineering critically destabilize surrounding rock. The study aims to assess how combined crack and hole defects affect surrounding rock stability. PFC 2D simulations of seven defect models—single circular holes with double cracks at 0°–90°—were calibrated against uniaxial compression experiments and used to study crack evolution, acoustic emission, failure modes, and stress states. Combined defects lower rock strength, change stress and displacement patterns, and generate three primary macro‑crack types.

Abstract

The cracks and holes in underground engineering are the critical factors that cause the instability of the surrounding rock. It is helpful to control the stability of surrounding rock to study the samples with combined defects of cracks and holes. In this study, PFC 2D is used to analyze the numerical models. Seven combined models of single circular hole and double cracks with different angles are established, and the fracture angle varies from 0° to 90° with an interval of 15°. First, uniaxial compression experiments and numerical simulations are carried out in the 0° defect combination model, and the microscopic parameters of PFC 2D are determined. Then, the numerical simulations of seven defect models under uniaxial compression are carried out, and the crack development law and acoustic emission characteristics of different defect combination models are studied. The failure modes, mechanical behavior, and stress states are studied. The displacement vector distributions of different defect combination models are analyzed; it is found that there are three main types of macro cracks in the defect combination samples. The results show that the combined defects reduce the strength of the model. Meanwhile, the distributions of the stress and displacement are changed by the cracks with different angles in the defective models.