Crack propagation mechanism in bedded rock with parallel flaws: Insights from moment tensor inversion

Abstract

Studying defects’ effect on bedded rock mechanical properties and failure mechanisms is essential for slope and underground excavation engineering. Acoustic emission helps analyze microcrack generation in rocks, shedding light on quasi-brittle material failure. However, previous studies have shown that the inhomogeneous geometry of defect-containing specimens complicates the localization of acoustic emission events, and some events may go undetected by sensors. This study uses discrete element modeling to examine bedded rock failure with parallel defects. We differentiate damage between acoustic emission events and macro fractures by assessing forces on failure sources. Our findings are as follows: (1) Bedding influences crack propagation direction but has limited impact on final failure. Cracks merging and penetrating in the bridge area are critical for catastrophic failure of samples. (2) Shear failure accumulates at the bridge area and defect tip, resulting in fragmented macroscopic failure. Tensile failure occurs during nucleation region development, leading to a more regular macroscopic failure. (3) High-magnitude events primarily arise from microcrack merging and connections, while crack propagation struggles to generate high-magnitude events. Most acoustic emission events involve 1∼4 microcracks, regardless of bedding angles or defects. The acoustic emission simulation method based on moment tensor inversion presents a novel approach for quantitatively determining the crack propagation law and failure mechanism of rocks with defects.