Failure characteristics and crack propagation process of coal-rock combinations under mine-induced stress

Understanding the failure characteristics and progressive failure mechanisms of coal-rock combinations under mining-induced stress is crucial for promoting safe and efficient underground mining operations. In this study, uniaxial compression tests were conducted on standard specimens with varying interface angles. Threedimensional (3D) laser scanning technology was employed to examine the macroscopic failure characteristics, while digital image correlation (DIC) was used to monitor surface displacement fields. Additionally, acoustic emission (AE) technology provided continuous monitoring throughout the testing process. Results show that the crack initiation sites largely correspond to the primary failure areas within the specimens. As the interface angle increases, crack initiation transitions progressively from the coal side to the coal-rock interface, and eventually to the rock side. Notably, the 0 degrees and 90 degrees specimens display distinct failure characteristics, particularly on the coal and concrete sides. Furthermore, the interfacial strength of the coal-rock composite influences the transinterfacial crack propagation, with low interfacial strength favouring crack extension along the interface and high inter-facial strength prompting crack extension through or halting at the interface. This study provides comprehensive insights into the fracture behavior of concrete composites.