Study On Safe Mining Technology And Application Of Protective Layer Over Close Coal Seam In Shangliang Mine

The mining of protective layer is an effective technical means to prevent coal and gas outburst.It is the premise and foundation of the safe mining and application of protective layer to study the movement and deformation law of roof and floor strata and the effect of gas relief during the mining of protective layer in close distance coal seam.Taking the 3^-2#and 3^-3#short-distance coal seams of Shangliang Coal Mine of Xiangmine Group in Shanxi Province as the research object,this paper systematically studied the roof and floor failure deformation and the law of gas migration under the mining of the upper protective layer by using the research methods of field test,theoretical analysis,numerical simulation,engineering application and verification.The research results are as follows:（1）The gas content,pressure and other basic parameters of the 3^-2#and 3^-3#coal seams in Shangliang Coal Mine were measured on site,and the feasibility of mining the 3^-2#coal seam as the upper protective layer was analyzed in combination with the occurrence of coal seams;Taking 32206 fully-mechanized mining face as the research object,the gas source prediction was carried out to determine the main gas emission source of the face.（2）Establish the overlying rock space structure model of"three-hinged oblique arch"formed by roof breakage under the mining of upper protective layer,deduce the reasonable arch axis equation of three-hinged oblique arch,and further calculate the height of caving zone and fracture zone;The mechanical transfer model of floor was established,the failure depth of floor was theoretically calculated,the floor stress isoline map was drawn by Mathcad software,and the floor heave was calculated.（3）FLAC^3D numerical simulation software was used to study the stress distribution of roof and floor,plastic deformation and failure,expansion deformation and pressure relief and deformation law of protected layer under different mining distances;According to the governing equations of fluid mechanics and coal and rock mass,a fluid-solid coupling mathematical model of pressure relief gas was established.COMSOL numerical simulation software was used to compare and analyze the law of gas migration in goaf under the condition of bottomless drainage,as well as the drainage effect of bedding and drilling holes.（4）According to the above research results,the drainage design scheme of pressure relief gas was formulated,and drilling optimization was carried out according to the change of porosity of the protected layer,and the field application effect was good.The research results provide scientific theoretical guidance and reasonable design scheme for the safe mining of the protective layer on the close coal seam in Shangliang Mine,and guarantee the safe and efficient production of the mine.