Mechanism of rock burst vertical damage induced by layered crack structures of the steeply inclined extremely thick coal seams

This study focuses on steeply inclined and extremely thick coal seams (SIETCS) characterized by immense thickness, a steep inclination of coal seams (87 degrees), and high horizontal stress. The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams, resulting in notable variations in roadway stress distributions. On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts, with limited emphasis on SIETCS roadways. This study employs comprehensive methods, integrating numerical simulations, theoretical analyses, and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage, subsequently validated in situ. The vertical stress in SIETCS is minimal, while horizontal stress is concentrated, leading to the formation of layered crack structures (LCS) that distribute above and below the roadways. Additionally, elastic energy significantly concentrates within the LCS. Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability, readily triggering failure. During the LCS failure process, the stored energy is released, converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy, ultimately leading to rock burst-induced vertical damage in roadways. On-site detection and analysis within SIETCS, along with historical rock burst data, confirm the existence of LCS and its role in inducing vertical rock burst damage. This research establishes essential foundations for preventing rock bursts within SIETCS.