Research On Pressure Relief And Permeability Enhancement And Gas Stereoscopic Extraction Technology For Close Range Coal Seam Mining In Zhongxing Coal Mine

There have been many research results on protective layer mining,tress relief and permeability improvement mechanism,due to the complex coal seam conditions in China,more research work is needed to do.In this thesis,the gas control under the condition of unequal length working face of thin coal seam protective layer is studied.Through the combination of theoretical analysis,numerical simulation and laboratory experiment,the stress relief and permeability enhancement mechanism,stress relief gas drainage method and gas control effect of protective layer mining are studied,he main results are as follows:(1)The permeability evolution law during the whole stress-strain process was tested in the laboratory.It is found that the coal has the characteristics of strain softening,the permeability of the coal increases with the damage,and the growth rate can reach 2-3 orders of magnitude in the strain softening stage.(2)Based on the experimental law,the constitutive model and permeability evolution model in line with the mechanical characteristics of coal body are constructed,and the Comsol numerical calculation software is used to simulate and solve the problem.The numerical analysis obtains the changes of vertical stress and volume stress of coal surrounding rock under the mining condition of thin coal seam protective layer.It is found that the permeability of coal seam under the working face of protective layer can increase by two orders of magnitude,but the stress concentration area will also reduce the permeability of coal below.(3)Different drainage boreholes are used to carry out three-dimensional drainage of stress relief gas in the coal seam,fracture zone and goaf,and the drainage parameters are investigated and analyzed.It is found that after the mining of the protective layer,the stress relief gas drainage effect is remarkable,and the fracture zone drilling and downward interception drilling have high drainage concentration and volume.(4)Under the condition of mining in the protective layer of thin coal seam,the gas outburst risk of the upper working face and the lower protected working face and the gas control effect during the mining of the working face were investigated.The results show that through the application of protective layer mining and comprehensive gas drainage,the outburst risk of the working face in the protected layer is eliminated and the problem of gas concentration in the flow is solved.The above research work shows that the mining of unequal length thin coal seam protective layer has played an effective role in gas disaster prevention and control,and provides a basis for gas control under similar conditions...