Study On Distribution And Evolution Law Of "Three Fields" Along Goaf Side In Pingdingshan No.2 Coal Mine

The determination of safety width of pressure relief zone is one of the keys to prevent and control coal and gas outburst and ensure safe driving and mining of working face.Working face mining will have a severe impact on some adjacent working face coal,which will change the stress environment of coal along the goaf,resulting in the decrease of coal stress,gas migration,fracture development and so on.In order to determine the stability and safety of gob side coal mass of adjacent working face after mining,it is necessary to study the safety width of pressure relief zone on the side of solid coal after mining.In this thesis,theoretical calculation,field test and numerical simulation are combined to analyze the distribution and evolution law of"three fields",namely stress field,gas field and fracture field,in 31010 mining face and 31030 gob side heading face under the influence of mining.The safety width of pressure relief zone is determined(1)By arranging stress monitoring sensors in machine roadway of 31010experimental working face,the distribution characteristics and evolution law of mining stress in adjacent working face are analyzed when mining in one side working face.The results show that:the mining effect of working face is severe,the 5m deep coal body is under pressure sharply,and the stress is transferred to the deep,which makes the stress of 9m deep coal body gradually increase;The distribution of dip stress along the coal seam:the stress relief zone is about 0?5m beside the roadway;The stress concentration zone is about 5m?9m near the roadway.(2)Through the measurement of gas parameters in the air lane of 31030experimental working face,the distribution law of gas basic parameters in the air lane of working face with a slope of 15m is obtained.The coal gas content W is less than3.2 m~3/T within 15m away from 31030 air roadway,and it increases with the increase of the distance from roadway.In the strike direction,the gas content w increases first and then decreases slowly with the increase of the distance from the excavation head.(3)The gas-solid coupling model was established by COMSOL software,and the distribution and variation law of"three fields"near the roadway during mining and tunneling were simulated.The results show that the mining and tunneling of working face will increase the stress and transfer to the deep part of coal body,and the width of pressure relief zone increases significantly;During mining and driving,the variation of gas pressure and porosity is different.The lateral abutment pressure has great influence on the development of gas pressure and porosity;(4)According to the field test,theoretical calculation and numerical simulation,it is concluded that the width of the pressure relief zone is directly proportional to the mining distance and the time of gob placement,and that the size and distribution of the internal stress and gas parameters within 25m of the solid coal side of the gob conform to the"detailed rules for prevention and control of coal and gas outburst".This paper contains 50 figures,7 tables and 95 references.