Research on crack evolution law and mechanical analysis of three cracked rock masses subjected to compression load

Abstract

Rocks containing various types of cracks may undergo microcrack expansion and connection under compressive load, which leads to rock fracture under different loading conditions, posing a significant threat to the stability of underground tunneling. Therefore, studying the mechanical response of rocks with different types of cracks is of great importance for controlling the stability of underground mining projects. In this study, we conducted compression tests on three cracked rock samples with different crack types, using an electro-hydraulic servo universal testing machine. We investigated the effect of crack dip angle on the compressive strength, stress–strain curve, and failure pattern of the three cracked rocks, and examined the fracture morphology of the specimens using an industrial camera and the digital image correlation (DIC) technique. To verify the test results, we constructed a parallel bond model in the discrete element method PFC2D to describe the compression process, and compared the peak strength, damage results, and crack number curves. We also investigated the effect of in-situ stress on the mechanical characteristics of the rock by applying in-situ stress values based on the successful PFC2D model. Our research findings revealed that the weakening effect of cracks parallel to the loading direction on the strength of rock is smaller than that of cracks perpendicular to the loading direction. During the compression process, stress concentration phenomena appear first at the crack tip, and the specimen eventually undergoes tensile splitting-type damage. Furthermore, the compressive strength of the three cracked rock samples tends to increase first and then decrease with the application of in-situ stress. These results provide valuable insights into the behavior of cracked rocks and can be utilized to improve the stability of underground mining projects.