Study on Failure Characteristics and Fracture Susceptibility of Surrounding Rock Under True Triaxial Stress.

To investigate the failure behavior and cracking mechanisms in surrounding rock, a true triaxial experimental system and digital imaging were employed to perform compression tests on sandstone specimens containing preexisting flaws. Experimental results revealed the propagation characteristics of microfractures under stress concentration conditions and their correlation with failure patterns. Furthermore, a fracture propagation model was implemented to evaluate the susceptibility of surrounding rock to failure. Macroscopic analysis identified four distinct failure phases: quiescent, particle ejection, stable damage, and structural collapse. The load-bearing capacity demonstrated positive correlation with in situ stress magnitude, while deformation accommodation capacity followed a nonmonotonic trajectory characterized by initial enhancement followed by deterioration. Furthermore, the analysis of influencing factors on surrounding rock failure identified the order of sensitivity as in situ stress > crack angle > crack size > friction coefficient. Furthermore, the reason for V-shaped failure crater of surrounding rock was clarified through intermediate parameter of critical compressive strength. This research provides valuable insights that can be referenced for designing strategies to control roadway stability.