Optimal Layout Of Composite High Roadway And Analysis Of Secondary Disasters In Deep Mining

Gas disasters restrict the safety of coal-mine production severely, which becomesmore and more harmful and urgent with the increasing mining exploitation depth.Therefore, it gradually turns out to be a heated research topic that the gas control fordeep outburst-threat coal seams of high gas content, high geostress and lowpermeability. Additionally, as the economic condition in China is experiencing adownward trend, the gas control projects becomes more and more efficient, whichmeans a wonderful way to improve economic performance of the deep coal mines.Based on the conventional high shelter roadway, and by the optimal layout ofhigh roadway and the effective control on the goaf secondary disaster, the compositehigh roadway technique appears to realize two excellent functions: sheltering the coalroadway drivaging at the previous mining-preparation stage, and controlling the gasemitted from the goaf and neighboring coal seam at the subsequent mining stage. Thisnew composite technique is multi-functional, and it’s a beneficial and promisingattempt for gas control and economical production in the deep coal mines.Taking JI15-31040working face of the PingMei Group Four Mine as researchbackground, that is the three levels first working face, this thesis uses manycombination methods, such as theoretical analysis, physical simulation, numericalanalysis and the industrial applications, to study the reasonable height position anddislocation distance of the composite high roadway, gas control efficacy andsecondary disasters features of the goaf. Here come the major results, as follows:Firstly, this thesis theoretically analyzes the stope overburden rock fractureformation and the gas migration regularity in mining fissure. The researches show that:The stope fracture is composed of the abscission layer fissures and the cross crevice,and the former provides the gas accumulation space while the latter provides the gasmigration path. There are two ways for gas of the overlying rock to migrate, includingporous media seepage and buoyant diffusion. The abscission layer area close to returnair side of goaf is the best construction site for the high roadway drainage project.Secondly, by physical analog simulation experiment and FLAC3Dnumericalanalysis, the reasonable layout of composite high roadway is optimized. Theresearches show that: once working face advances21m, main roof periodicweightings take place, meanwhile structural instability of high roadway and main roofbreakage appear; According to calculation statistics formula, subsidence of main roof and fracture evolution of overlying rock;besides lithologic character of roof strata;itcan be sure that the composite high roadway is located in the16m height above JI-15coal seam;below the bottom of fine-sandstone;drivaging along Sandy mudstone roof;while composite high roadway shields coal roadway drivaging synchronously;horizontal stress becomes the main reason of roadway damage;meanwhile throughthe analysis of horizontal stress and roadway subsidence when the inward dislocationdistance is0m;5m;10m;20m between the high composite roadway and the coalroadway;the reasonable distance is20m for composite high roadway shielding coalroadway to drivage synchronously.Finally;U type and U+I type ventilation models is established to analysis goafgas extraction and secondary disasters after the composite high roadway using. Theresearches show that;Under high position extraction;the gas concentration reducingarea appears near the goaf bottom and gas zone move up;The gas concentration ofreturn air side reduces42%;meaning that the composite high roadway has a goodeffect on controlling the gas of the upper corner. The oxygen concentration distributeuniformly along the goaf inclination;the cooled zone and the spontaneous combustionzone become wider and move backward along the goaf strike;especially thespontaneous combustion near the wind inlet side;the width increases29.2%andmoves backward35m. Therefore composite high roadway can control the gasemission and at the same time also make secondary disasters exacerbate. improvingthe advance speed of working face becomes an important measure to prevent thesecondary disasters;enhancing27.8%of the speed the safety can be ensured. Whenthe working face advance speed is limited;the management of the goaf should bereinforced and measures to the secondary disasters should be taken.