Numerical Simulation And On-site Investigation Of The Influence Law Of Mining Pressure Relief In The Upper Protective Layer Of Puxi Mine

Coal and gas outburst is one of the main disasters affecting mine safety.The current mining protection layer is the most effective regional outbreak prevention measure.In this paper,the 5#coal seam of Puxijing,Hunan Jiahe Mining Co.,Ltd.as the upper protective layer is used as the research background.The theoretical analysis,numerical simulation,field test and other methods are used to analyze the protected layer during the mining process of the 2152 coal face of the upper protective layer 6#coal seam pressure relief effect law;and determine the protection scope and outburst elimination effect of Puxijing 5#coal seam of Hunan Jiahe Mining Co.,Ltd.(1)Through numerical simulation,the influence of pressure relief on the change of stress and displacement after mining of the upper protective layer was studied.Using the coal seam stress determination criterion,the coal seam deformation criterion and the numerical simulation calculation results to delimit the protection scope of the protection layer mining.According to the coal seam stress determination criterion combined with the numerical simulation results,it is concluded that the upper protective layer has a pressure relief angle of69.6°in the upper direction and 74°in the lower portion;and a pressure relief angle of59°along the strike.According to the coal seam deformation criterion,the upper pressure relief angle of the upper protective layer along the trend is 67.2°,the lower pressure relief angle of the lower protection layer is 71.8°,and the strike direction is 56.3°.(2)On-site inspection of the protected layer in the 21 mining area of Puxijing.The gas pressure,gas flow and permeability coefficient of the protected layer before and after the mining of the protective layer have been investigated.Combined with the results of the field investigation,the protective range of the protective layer on the 21 mining area of Puxijing was calculated:the pressure relief angles along the upper and lower directions were 69.1°and 72.8°,respectively;and the pressure relief angle along the strike direction was57.2°.(3)Through analysis and calculation of the measured data,it is concluded that the gas pressure in the protection range is reduced from the original 0.9MPa?1.40MPa to 0.24MPa?0.46MPa;the residual gas content is reduced to 4.607?6.486m~3/t;air permeability The coefficient has increased by 339 times;it is determined that the safety lead is 110m.The inspection results show that mining the upper protective layer 5#coal seam can effectively reduce the prominent danger of the protected layer 6#coal seam,and the outburst elimination effect is obviously effective.