Influence of Joint Orientation on Rockburst Mechanism in Straight-Wall Arch-Shaped Roadways: A True Triaxial Experimental Study

To investigate the influence of joint spatial orientation on the rockburst mechanism of deep roadways, this study employs a true triaxial rockburst testing system to conduct physical simulation experiments on three types of limestone specimens from Yunnan: joint-free, parallel-jointed, and vertical-jointed. By integrating multi-source data acquisition techniques including high-speed imaging, acoustic emission (AE) monitoring, and fragments sieving, this research systematically analyzes the macroscopic failure process of rockburst, the evolutionary patterns of AE signals, and the characteristics of fragment generation under different fracture configurations. Joint orientation critically governs the rockburst failure mode, with parallel joints promoting extensive spalling and vertical joints localizing damage. Parallel joints act as guiding weak planes, resulting in a wider and more intense failure range, while vertical joints cause localized failure. The characteristics of acoustic emission signals reveal the regulatory mechanism of joints on the AE energy accumulation and release process. The parallel-jointed specimens exhibit a “step-like” increase, reflecting their phased damage and stress redistribution. Quantitative analysis of fragments indicates that the total mass of fragments in the parallel joint specimens is the largest, and the fractal dimension is the highest, indicating the most thorough fragmentation. This research provides crucial experimental evidence for the precise identification and differentiated prevention and control of rockburst risks in deep jointed rock mass engineering. It should be noted that these findings are derived from exploratory laboratory comparisons based on one specimen for each joint configuration, and further repeated tests are required to verify the generalizability of the observed patterns.