Study On The Effect Of Pressure Relief Mining And Efficient Gas Extraction Method For Protective Layers On Coal Seams

The increasing mining depth of coal mines has led to an increase in the degree of coal and gas outburst disasters,which seriously affects the safe production of coal mines.As a commonly used method for controlling gas pressure relief in deep mining,protective layer mining is widely used,and is currently one of the most effective,safe,and economic measures for controlling coal and gas outburst.Aiming at the difficult problem of pressure relief mining in the upper protective layer of the Zhangji Coal Seam Group and in the complex situation of coal and gas outburst,this paper uses a combination of numerical simulation and on-site investigation to carry out a study on the impact of pressure relief on the underlying coal seam during the mining of Zhangji9 Coal,as well as a study on efficient gas extraction methods.The main conclusions are as follows:(1)The basic theory of protective layer is used to predict the protective range of the first mining coal seam 9 in Zhangji.The protective effect of protective layer decreases with the increase of layer spacing,and the protective effect will no longer be significant after reaching the critical distance.(2)The numerical simulation software is used to study the change rule of stress in the underlying protective layer during the mining of Zhangji 9 coal seam.During the advancing process of the working face,the underlying coal and rock body in the goaf undergoes upward expansion and deformation,and the distribution of the stress field in the underlying protective layer is basically the same as that of the protective coal seam.The failure of the surrounding rock in the stope is mainly manifested in the failure of the elastic-plastic zone,and extends to the deep part as the working face continues to move forward.(3)By analyzing the gas source and calculating the estimated gas emission amount,it is concluded that during the mining process of 11129 coal mining face,the relative gas emission amount is about 13.01m~3/t,the absolute gas emission amount when the daily output of the working face is 4000t/d is 36.14m~3/min,and the absolute gas emission amount when the daily output of the working face is 5000t/d is45.17m~3/min.(4)The pressure relief range of Coal 8 and Coal 6 in the underlying coal seam has been designed,and the pressure relief range of Coal 8 and Coal 6 has been observed based on on-site investigation.Based on the expansion deformation rate of each deformation hole,it is concluded that both Coal 8 and Coal 6 have achieved full pressure relief within the investigation range.(5)Conduct gas drainage analysis during mining,and comprehensively analyze the effect of gas drainage from high drainage roadway,upper corner buried pipe drainage,and bottom drainage roadway in Working Face 11129.During the recovery period,the total amount of gas extraction averaged 14.3m~3/min,with a maximum of33.3m~3/min.The total amount of gas extraction accumulated to 13.4061 million m~3,and the average amount of gas extraction per ton of coal was 9.85m~3/t,achieving efficient gas extraction.Figure[68]table[25]reference[53]...