Study On Gas Distribution Characteristics Of Mined-out Area On Three Sides Along Isolated Island Faces

As the depth of coal mining increases,continuous mining methods are sometimes adopted to avoid interference between working faces.When comprehensively considering the complexity of geological conditions,isolated island mining faces will be formed.The characteristics of such working faces are The overburden in the working face will move and deform,and the stress concentration will be obvious.The overburden cracks are fully developed and provide a direct channel for gas flow.As a result,the pressure-relief gas enters the working face during mining,which affects the safe and efficient mining of the working face.In order to solve the above problems,this paper takes the 120502 working face as the research background and uses the FLAC3D software to construct a three-sided goaf island working face model in accordance with the actual mining sequence in the stope.The stress,displacement,The deformation characteristics of the fractured area are studied,and it is concluded that during the advancement of the working face,the left,right and upper mined-out areas will disturb the working face,and the upper mined-out area will be the most significant.The column stress concentration is relatively high,and the vertical stress at the front of the working surface decreases first and then increases,and the stress concentration coefficient gradually increases;the vertical displacement direction shows a downward trend,and then an upward trend.The vertical displacement peak keeps increasing and the upward vertical displacement peak is basically stable.The fracture area is generally "saddle-shaped",gradually expanding and intersecting with the three adjacent goafs,and the rock mass above the roof is in the area of tension and compression stress.The development of surrounding rock fissures in the goaf of the working face is more fully developed;the height range of the caving zone and the fissure zone in the working face is obtained by means of the stress discrimination method.Using COMSOL software,combined with Naiver-Stoke equation,Brinkman equation,translation-diffusion equation and Fick's theorem,a gas-gas flow model for goaf was established based on the 120502 three-sided goaf island fully mechanized coal mining face,and the high extraction roadway extraction conditions were studied.The influence on the gas concentration in the goaf,the above corners,return air flow,and gas concentration in the working face are used as the basis for determination,and the reasonable layout parameters of the high pumping lane are obtained:the horizontal distance S from the return lane is about 15m,and it is perpendicular to the roof of the coal seam.The distance H is about 20m.The actual analysis of the upper corner,return air flow,and gas concentration of the working face during the normal mining face was compared with the numerical simulation results,and the results were basically consistent,and the numerical simulation process was verified.At the same time,the working face was normal.The actual measurement and analysis of the gas evacuated and absolute gas emission in the high pumping lane during the mining period,it is concluded that the gas evacuated and pure gas in the high pumping lane accounts for about 45%of the absolute gas emission.Can achieve safe and efficient mining.Figure[32]table[12]reference[91]...