Study On The Outburst Prevention Technology Of Upper Protective Layer Mining In Dawan Coal Mine

Dawan Coal Mine has typical regional characteristics such as complex coal seams,Coal seam group mining,high gas,highland stress and Complex geological structure,so the mine faces various problems.At present,the most effective and reliable regional outburst prevention measures are mining protection layer.Therefore,it has great significance for the mine safe and efficient mining to study the outburst prevention technology.Taking Dawan Coal Mine as engineering background,this paper use laboratory tests,theoretical analysis,FLAC numerical analysis and field measurement analysis method to study on the outburst prevention Technology of upper protective layer mining.Firstly,this paper study the protective layer theory,separately analyze the stress distribution law of surrounding rock after mining the protective layer,protective layer mining ways to apply the mechanism of coal and gas outburst prevention and expanding the protective layer;Secondly,through field research,observation,combined with coal and rock mechanical parameters,use FLAC3D software to build a numerical model of the protective layer in Dawan Coal mining,Results:relief angle to the left is 66°,right side is 66°,the relief region showed a symmetrical shape,tendency down side relief angle 76°,the relief angle of the hill side is 78°,the maximum of the bottom direction relief depth more than 80m;Then,use measured means to analyze the gas pressure,gas flow rate,coal seam permeability coefficient deformation of the top and bottom floor.The results show that the original gas pressure of No.11 coal seam decreases from 2.31 MPa to 0.12 MPa,the gas flow rate increases 35.8 times of the original value,the permeability coefficient increases 52 times of the original value,and the expansion deformation(relative deformation)of No.11 coal seam is 3.02‰.According to FLAC3D software numerical simulation and field measurement data analysis results,it is determined that the reasonable lead distance of no.2 coal seam face to no.11 coal seam face should be more than 120m,the pressure relief angle of the no.2 coal seam is 52°,and the coal pressure in the protection area eliminate the danger of coal and gas outburst.