Study On Gas Migration Law And Control Method Of Working Face Of First Mining Upper Protected Seam In Close Distance Coal Seam Group

In order to study the gas migration and gas control problems of close distance coal seam group first mining upper protected seam,taking the first mining upper protected seam 13125 working face of Tucheng Mine Coal Seams Group in Guizhou Panjiang Coal Limited by Share Ltd as the engineering background,using theoretical analysis,numerical simulation of FLAC3 D and FLUENT,field test to analyse the overburden stress distribution,deformation and failure law of first mining upper protected seam,study the distribution and migration law after gas the pressure relieved in first mining upper protected seam,on this basis,the corresponding technical scheme of gas extraction was put forward,and the following conclusions were drawn:(1)The protection scope of Tucheng Mine 13 mining area 16# coal seam was analyzed as the lower protective seam,including the protective vertical distance and the pressure relief angle.Stress variation of overlying strata and plastic area distribution were simulated with FLAC3 D,and the spatial form of overburden pressure relief zone was analyzed during 12# coal seam mining process after the lower protective seam was mined.(2)According to the theory of gas migration,the direction of gas migration in the process of 12# coal seam mining was obtained.Combined with the numerical simulation results of FLAC3 D,the migration path of pressure relief gas was analyzed.Numerical simulation of gas migration law in first mining upper protected seam stope was simulated by FLUENT,analyzed the U type ventilation,U ventilation + pipe goaf under the two conditions of stope gas concentration distribution,the distribution law of stope gas in three-dimensional space,inclined direction and longitudinal direction was obtained.The results showed that the extraction of goaf buried pipe could effectively reduce the gas concentration in the mined out area and upper corner of the coal seam,therefore,the gas concentration in the working face and return air way can be effectively controlled,but the gas concentration in the mining fracture zone is still high,so other measures should be taken to assist gas extraction in adjacent seams.(3)The fracture morphology in different areas of overlying strata and the possibility of gas storage were analyzed,and the gas enrichment area of the first mining upper protected seam in the close distance coal seam group is obtained.According to the characteristics of gas migration,the gas extraction technology suitable for first mining upper protected seam of close distance coal seam group was selected,and the main technical parameters and adaptation conditions were defined.(4)The gas drainage technology was put forward by combining the method of seam drilling,bedding hole drainage and goaf buried pipe drainage for design of gas drainage,gas drainage design in Tucheng Mine near distance coal seams by upper protective seam mining,at the same time,the ventilation and other gas control measures were put forward and applied in the 13125 working face.The monitoring data showed that the average gas concentration in the return air lane was 0.31%,and the gas extraction rate was 64.48%,a good gas control effect has been achieved.