Study On Ordinary Mechanized Longwall Mining Pressure And Control Beneath The Area Mined With Longwall-pillar Method In Close Seams

Coal pillar under close longwall goaf general mining refers to the two seams arecomparatively close, adopting downstriker mining sequence. Mining the upper coal use coalpillars to supporting the roof, and for the under coal seam is mined by way of ordinarymechanized mining technology. The process of mining the upper coal seam, the roof of coalseam will sufffer some damage, so that the integrity and continuity is destroyed, it will seriouslyaffect the normal production of coal seam. In this case, the characteristics of under coal seamworking face of mine pressure appearance, Control relationship of supporting structure andsurroundingrock,layoutfeatures ofroadway and supporting methodetc.areparticularity.In this paper as Xinjiang Changping Mining Co., Ltd. one hundred and four coal mine B4,B5seam as the research background. Firstly, it discusses the close distance coal seamsdetermination method and an overview of the coal pillar’s specific meaning and the currentdevelopment situation, then according to the actual situation of B4coal seam, using of materialmechanics related theory of mining pressure and strata control analyze B4coal seam miningafter the roof strata movement characteristics, goaf residual coal pillar in the steady state and inthefloorstress distribution.On this basis, discussed when mining the B5coal seam, immediate roof in located undergoaf and coal pillar thickness and risk falling in different situations, and on the theory ofmechanics of materials in the "beam" and "board" to calculate the roof first weighting andperiodic weighting step distance. Theoretical calculation the selection of supporting equipment,reasonable support density and reasonable layout position of the gateway in the B5coal seamminingface.Using FLAC3Dnumerical simulation software, to build coal mining model in the actualsituation of occurrence and the characteristics, then simulate B4coal mining residual coal pillarand the stress distribution in the floor. Based on this analysis the stope face take different length, working face and roadway stress condition, ultimately determine the stope facereasonablelengthand the technicalmeasuresin themining process.Finally, due to the influence of the stress concentration in the residual coal pillar underroadway layout,with the engineering geological analogy method as the main methoddetermined the reasonable parameters of roadway bolt,designing reasonable support scheme inminingroadway.Thefollowingconclusions:(1)B4coal seam in coal pillar support mining roof because of the residual coal pillarsupporting role can not be broken in the goaf, goaf residual coal pillar in the steady state, thefloorofcoal pillar5m isconcentrated stressthemain sphereofinfluence.(2) The initial pressure step of the old roof after the B5coal seam mining is in the range of47.5~64.4m, and the pressure step distance is19.45m. Pillar mining face row spacing of a at0.8m, b at0.6m. In the B5coal seam mining, the mining height adjustment, the adjustment ofthecoalmining andthequick coalextraction methodareadopted.(3) Determine the reasonable length of the coal seam working face in the B5coal seam is120m. The top corner of the mining roadway should adopt the grouting bolt on the surroundingrock reinforcement, in order to control the deformation of roadway. In the roadway, theunloading pressure hole is arranged, so that the concentrated stress can be transferred to theroadwayinorderto reducethepressureofthesupporting structure.