Experimental study on the evolution of rock fractures induced by rolled static cracking agents in steeply inclined hard faults

Abstract

The static blasting method is the preferred approach for addressing hard faults within an inclined working face. The presence of shear stress within the inclined rock layers can significantly affect the cracking efficiency of the Rolled Static Cracking Agent(RSCA). To study the rupture damage characteristics of rocks under the expansion of RSCA with different shear stress magnitudes, a novel Compression Shear Coupling Test system (CSCT) was employed. Fracture tests were conducted on RSCA specimens at six different inclination angles (0°, 5°, 10°, 15°, 20°, and 25°) under constant pressure. Acoustic emission monitoring and full-field strain measurement were employed to analyze the dynamic fracture process and damage characteristics of the specimens. The results indicate that an increase in inclination accelerates the crack initiation efficiency of RSCA, causing cracks to propagate at lower expansion pressures. The magnitude of the shear stress component significantly affects the fracturing characteristics of the specimens; as the inclination increases, the proportion of shear cracks in the specimens increases significantly. Additionally, the AE energy, fractal dimension, and surface density of cracks initially decrease and then increase. The distribution of surface strain concentration areas is closely related to the inclination angle, with shear stress causing the maximum tensile stress point to shift towards the shear direction of the specimen, forming strip-shaped damage zones. As a key factor affecting rock fracturing, the shear stress component alters the crack propagation pattern during RSCA fracturing. The research results provide data support and theoretical reference for field applications.