Control of dynamic hazards induced by mining stress distortion in extremely steep and thick coal seams

Dynamic hazards being induced by mining stress always threaten safe mining in extremely steep and thick coal seams. Aimed at prevention and control of dynamic hazards in Wudong Coal Mine,Urumchi mine area,we applied a comprehensive methodology including in-situ investigation,theoretical analysis,numerical calculation and field moni- toring to reveal mechanism of dynamic hazards being induced by distorted mining stress. The relevant results indicate that mining stress transfer from top of the No. 43 coal seam to sandwiched coal-rock pillar in seams ( SCPS),and SCPS deformed largely towards mine-out-area due to self-gravity,which causes tensile stress in its upper position and compressive stress in the bottom. Furthermore,high stress concentration is formed in the roof of the +575 level of No. 45 coal seam,leading to substantial dynamic hazards. With fully considering existing mining scheme,coupled fracturing that we injected water firstly and then blasted rock masses have been put forward and applied as hazard-relieving measures. By means of micro-seismic monitoring and electromagnetic radiation intensity,the frequency of micro-seismic big events decrease to one time per minute from four time per time,and the peak intensity of electromagnetic radiation reduces to about 42. 8 mV below the precautious line. Dynamic hazards relief obviously.