Study on the mechanism and prevention techniques of dynamic disaster in nearly vertical extra-thick coal seams

To address the issues of complex rock mass movement and dynamic disasters during the mining of near-vertical extra-thick coal seams, this study takes the + 425 level B3 + 6 working face of Wudong Coal Mine as the research background, aiming to investigate the mechanism of dynamic disasters. By adopting theoretical analysis, on-site investigation, and physical simulation, the study established a mechanical model for rock pillar deformation and failure, analyzed the failure modes of rock pillar as well as roof and floor, and their impacts on coal seam stability, revealed the corresponding disaster-inducing mechanism, and proposed a pressure relief and rock burst prevention technology. The results show that the deformation and prying rotation of rock pillar are the main factors causing strain energy accumulation in coal-rock masses, while the fracture of rock pillar and the toppling-sliding of roof and floor are the primary forms of dynamic impact loading. Specifically, the large-scale fracture depth of rock pillar reaches 350 m, and the fracture step distance of the immediate roof exceeds 43 m. To prevent and control rock burst, a pressure relief and rock burst prevention technology was proposed, which achieves pressure relief through deep-shallow hole blasting on the roof and floor. Combined with the numerical simulation analysis of deep-shallow hole blasting, the significant reduction in electromagnetic intensity, the gradual decrease in the frequency of microseismic events, and the gradual reduction in energy have verified the pressure relief effect of this technology. This study provides an effective technical approach for the safe mining of coal seams.