The Technology Of Strike High Drainage Roadway Cooperate With Dip Drilling Holes Drainage Upper Adjcent Layers' Pressure Relief Methane

In the mining process of high methane coal seam group,due to the influence of mining on upper layers,methane was desorpted and flow into the working face and resulting methane overrun in working face,so the drainage of pressure relief methane in upper layers has been paid more and more attention.During the mining process of 8210 working face of 15# coal seam in Yangquan minmetals,gas emission from overlying strata is more than 90% and using one strike high drainage roadway can not prevent methane overrun in working face,So strike high drainage roadway cooperate with dip drilling holes is proposed to drainage pressure relief methane in overlying strata,that is arrange a strike high drainage roadway in fissure zone of air return side of working faceto drainage pressure relief methane,and using strike drainage roadway in fissure zone of adjcent spare face,then arrange dip drilling holes into working face overlying strata to drainage air inlet side fissure zone methane.This method can drainage the entire overlying strata methane.Based on the distribution of startas that containing methane and the geological condition of 8210 working face in Yangquan Minmetals,combined with theoretical research,numerical simulation and some other approachs to study stress redistribution in overburden,distribution of fissure in overburden,the flow law of pressure relief methane,drainage method of pressure relief methane and drainage effect after working face mining.Providing an important reference for the drainage of pressure relief methane in overburden fissure zone,the main contents are as follows:(1)Study the distribution of fissure in overburden after the mining of working face,so as to determine the enrichment area of pressure relief methane in overlying strata.First,using FLAC3 D software to establish the mining model of 8210 working face,through the analysis of plastic deformation,displacement varation and stress redistribution change of overlying strata,finally obtains the distribution of internal fissure and the location of gas migration channel in overburden after mining.The simulation result shows that tensile failure occurred within 40 m above the roof and shear failure occurred within 50-70 m above the roof;above 50 m of working face roof,the gradient of overburden stress has been significantly reduced and the displacement suddenly dropped;Theoverburden stress relief value above 70 m of working face roof is less than 20%and the displacement is close to zero;The horizontal displacement change and the horizontal stress change is the largest in the range of 25-35 m around the wind lane.which means this area is in the longitudinal fissure enrichment area.(2)According to the simulation results of fissure distribution in overlying strata after working face excavation,establish the model of pressure relief gas drainage to simulate drainage effect of strike high drainage roadway and dip drilling holes and its drainage area.First,using COMSOL software to establish the model of pressure relief gas drainage in 8210 working face overburden,And according to the fissure distribution and the source of gas emission to set up porosity and permeability and gas flux of the model,then compare methane pressure cloud picture of overburden before and after drainage.The cloud picture shows after 40 days' drainage,the gas pressure in vertical fissure channel reduced from 2MPa to 0.6MPa on strike high drainage roadway side,and reduced to 0.74 MPa in the horizontal direction within 26 m,Within 7.5m around dip drilling hole,the gas pressure reduced from 2MPa to 0.74 MPa.According to the definition of effective drainage radius,the effective radius of drainage borehole is 7.5m.(3)According to the drainage simulation effect of overburden pressure relief gas and the effective drainage area,designed the layout parameters of strike high drainage roadway and dip drilling boreholes in 8210 overlying strata of working face.The strike high drainage roadway is set up in the fissure zoneof the overburden which 55 m above working face roof and 30 m away from wind lane;Dip drilling field is arranged in high drainage roadway that arranged in adjacent spare face,and each drilling field is 30 m away,each drilling field have 9 drilling holes and each borehole is 0.5m away at the begining and 13 m away at the end,the drilling length is 100m-120 m through the enrichment area.(4)Combined with the simulation results and the design layout parameters of strike high drainage roadway cooperate with dip drilling boreholes in 8210 working face overburden,then calculate and predict the methane drainage effect of strike high drainage roadway and dip drilling boreholes.The result shows:The methane content decrease from 18.69m3/m3 to 3.37m3/m3 and reduced 82% in the effective drilling area;The methane drainage amount of strike high drainage roadway is 40.78m3/min and 27.58m3/min for dip drilling field,which means the drainage capacity of dip drilling boreholes is about 67.4% compared to strike high drainage roadway.According to the gas emission amount of 8210 working face,the gas drainage rate is 47.8% with one single strike high drainage roadway,after cooperate with dip drilling boreholes,the gas drainage rate increased from47.8% to 79.7% and the drainage rate reach the strandard.