Study On The Pressure-unloading Area And Effect For Far Distance Lower-protection Mining Of Xing Ji Coal Mine

Exploitation of the protective layer has been increasing attention as a regional anti-surprise measures, generally, if conditions permitting protective layer mining regarded as the preferred anti-sudden measures. C13-1 coal seam of xin-ji mine with coal and gas outburst danger, in this case, select the B11-2 coal seam as the first exploitation, through the mining-impact caused C13.1 Coal pressure relief to reduce the risk of its prominence.This paper based on the theoretical analysis of the protection layer exploitation against geological conditions of coal seam of xin-ji mine, through the similar simulation test researched the law of movement-destruction and stress distribution of overlying strata with the advancing of the working face; through numerical Computing researched the stress variation and the plastic zone distribution of the overlying strata in the under-protective B11-2 coal seam mining etc.; through measurement on locale-site reviewed the layer of gas pressure change of protected layer and variation of permeability and pressure relief gas drainage effects with the face of the advancing, and combined field measurement and numerical simulation and similar simulation results obtained the relief angle 55°of protective layer along the direction of advancing and the uphill relief angle 86°and downhill relief angle 69°of the inclined direction, after under-protection layer mining the stress drop in the scope of protection and the protected coal deformed and expanded, its maximum deformation ratio is 20.42%, fully seam permeability after stress-relief greatly enhanced,permeability coefficient of expansion of the nearly 1000 times,the protective-layer mining obtained well effects.