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.
Highlights
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The rock mass in underground engineering is in an environment of high stress, high temperature, and seepage
These factors lead to the occurrence of rock mass fractures and holes, which bring difficulties to engineering constructions and personnel safety
Summary
A large number of defects in the natural rock masses, such as faults, cavities, and joints, are discontinuous, heterogeneous, and anisotropic. The existence of these defects will have a significant effect on the physical and mechanical behavior of rock. The rock mass in underground engineering is in an environment of high stress, high temperature, and seepage. The parallel bond model is usually used to simulate the discontinuous deformation of the rock sample. The parallel bond model is shown, where kn is normal contact stiffness and ks is tangential contact stiffness. If the maximum normal or tangential stress on the bond boundary exceeds the corresponding bond strength, the bond will break and produce a microcrack
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