| With the mining of coal mines in our country,the coal resources of shallow coal seams are gradually exhausted,and coal in deeper strata has been mined one after another.With the extension of mining level,the gas pressure as well as gas content in coal seams are gradually increasing.The threat of gas to coal seam mining is also increasing.Most mines are faced with the situation of mining in the case of high gas.In the driving work of high gas roadway,the driving speed is slow,and the gas concentration of the roadway frequently exceeds the limit,so it is difficult to reduce the gas concentration in the roadway only by the ventilation system.In many gas control technologies,gas pre-drainage is the best methods to reduce gas concentration as well as prevent gas disasters.Taking the Changcun Coal Mine in Lu'an mining area as the experimental background,this paper manly researchs the problem that the gas concentration often exceeds the limit in the driving process of 2302 return airway.Using the means of field measuremen,industrial test,parameter optimization,theoretical analysis,numerical simulation analysis and so on,through the optimization of ventilation parameters and ventilation equipment,as well as the design of gas pre-drainage drilling hole and drilling site,to solve the problem that the gas concentration frequently exceeds the limit in the process of 2302 return airway driving.The main research contents and results are as follows:(1)The content of gas in coal at different elevations is analyzed,and it is concluded that there is a linear correlation between gas content and depth.And the regression equation W=0.042H-10.76(R2~0.907)is obtained,the following conclusions are drawn through the relevant data:The lowest gas content of coal seam in No.23 mining area of Changcun Coal Mine is 9.86m~3/t,and the highest value is11.62m~3/t.According to the measurement and analysis of on-site gas parameters,the average gas emission characteristic coefficient of 2302 return air roadway is calculated,and C=4.1975.(2)According to the measurement and analysis of the field gas parameters,it is calculated that the gas emission limit time T of the 2302 return air roadway is 181days,and the maximum gas emission is 9.8m~3/min.According to the measured parameters,it is concluded that the ventilation equipment parameters needed in the heading process of the 2302 return air roadway are as follows:the minimum air volume is654.4m~3/min,and the required air pressure is 3896.97Pa.(3)Combined with the relevant parameters,the effective extraction radius of drilling is calculated and analyzed.And it is concluded that the effective extraction radius of Changcun Coal Mine is 2.41m.The drilling effect of 2302 return airway is numerically simulated by using COMSOL software.And by comparing and analyzing the extraction effects of different drilling diameter and negative pressure conditions,it is concluded that the drilling diameter 94mm negative pressure 15KPa is the best extraction scheme.(4)A drilling field for advanced gas pre-drainage is designed.A drilling field is set up every 60 meters on both sides of the roadway.The cross section of the drilling field is trapezoidal.The external width of the drilling field is 8 meters,the internal width is 4m,the depth is 4m,the height is 3.2 meters,and the height is 2 meters higher than that of the drivage roadway.(5)The parameters of pre-drainage drilling are as follows:the diameter of the drilling is 94mm,the drilling is divided into upper and lower layers,the distance between the same row of drilling is 0.6 meters,and the distance between the upper and lower rows of drilling is 0.5 meters.The distance between the innermost drilling of the drilling site is 0.3 m,the opening heights of the upper and lower layers are 2.7meters and 2.2 meters respectively,and the depth of the drilling is 140 meters.There are 46 pictures,18 tables and 65 references in this paper. |
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