Research On Gas Relief Drainage Technology Of The Under Protective Layer Mining In11515Mining Face

Faceing the current situation that our gas disasters severity of the consequences, in coal and gas outburst mines,if they meet the mining conditions of the protective layer, mining techniques are used in the protective layer,and protective layer mining as a regional conflict prevention measures draws more and more people’s attention. For this situation,it uses theoretical analysis, numerical simulation and field engineering practice and investigation research tools.It has more comprehensively studied overburden’s migration and fracture distribution, gas flow in coal formations, and pressure relief gas drainage technology and so on unde the protective layer mining conditions.By research of the law of mining overburden’s movement、fissures’s distribution and gas seepage characteristics,it has analzed the theory of cross "three areas" and vertical "three zones" after the coal seam mining、mining "o" crack distribution ring theory and the occurrence of gas flow characteristics in coal seams.And analzed protection scope along tendency and toward Trend,making11515mining face of PanYi coal mine as the research object.It has analyzed the gas flow and occurrence characteristics in the coal seam through the understanding of gas flow characteristics in the coal seam,and proposed three basic parameters of gas seepage. For specific location and coal mining conditions, it has proposed relief gas drainage techniques.Using numerical simulation calculation,it gas gotton the characteristics of overburden stress field migration expansion and deformation in each seam and seam relief range under15degrees coal mining conditions. After roof collapsed, vertical stress in central stope was more than a "V" superimposed distribution,and level stress was more than a "V" superimposed distribution in reverse. And the largest expansion and deformation capacity in6-1coal reaches to twenty-five thousandths in protected layer. Relief protect angle along trend in cut position is fifty-three degrees and is fifty-seven degrees in mining face,the height of mining fractured zone reaches to29.8meters. The relief protect angle is seventy-seven degrees and seventy-nine degrees on the left and right side position along tilt, with a height of thirty-two meters in mining fracture.It has proposed technology methods gas relief drainage in protectived layer combining specific mining engineering practice in11515mining face. Mainly in method of pumping and mining of internal vertical well drilling in high pumping roadway of seam group and drilling that up through the layer in bottom pumping roadway and drainage pipe layout in tail roadway buried pipe of "Y" type ventilation.The inspect results showed that: the largest coal swelling deformation reaches22.3‰in6-1coal above mining face.The8coal seam,which has a farther distance from5-2coal seam,its coal swelling deformation rate reaches14.2‰.The largest original gas content reduces from9.68m3/t to3.2m3/t in protected layer, the original gas pressure reduces from4.5Mpa to0.48Mpa, the coal seam gas extraction rate all reaches to62.5%in6-2、7-1and8coal, and the5-1coal seam gas extraction rate reaches up to82.6%by the highest.It has achieved a safety and fast mining excavation work and high efficient mining through protective layer mining.