Study On The Mechanism And Application Of Pressure Relief Of Thin Coal Seam Mining As Upper Protective Seam In High Gas Coal Seams

According to the pressure relief of the upper protective seam mining in thecondition of low permeability, high gas, close-distance coal seam group, thin coalseam in Shaqu coal mine, and the stress distribution of coal floor, crack growth lawand pressure relief gas migration law of coal seam group were analyzed in protectiveseam mining of thin coal seam by using of theoretical analysis, numerical simulation,field test and other methods.The pressure relief protection range of protective seam ofthin coal seam mining was defined.The dynamic progressive process of rock stratacaused by mining of the upper protective seam was simulated by UDEC, the rockstrata failure and movement laws were got, the stress and deformation distributingcharacteristics of the protected strata along with the protect stratum mining wereobtained, and the mechanism of eliminate pressure relief blind area of thin coal seamas upper protective seam, and the scope of pressure relief blind area when leavingcoal pillar.Through comparative analysis the effect of kilometer gas drainage drillingfield the14301working face of south No.4coal seam and the24208working face ofnorth No.3+4coal seam to study the effect of the site industrial test of thin coal seammining as upper protective seam in Shaqu coal mine.The field of industrial test results show that the gas drainage concentration stayabove25%, the highest reached80%, gas drainage scalar stay above2.0m3/min, andthe max reached3.0m3/min of the14301working face of south No.4coal seamkilometer gas drainage drilling field in Shaqu coal mine. Relative to the north wing ofthe protective seam on the No.2thin seam coal mining, the kilometer gas drainagedrilling field effect of under the protective seam of No.3+4coal seam is obviouslyimproved, and gas extraction from scalar field and the concentration of every drillingwill progress experience: smooth, rising, falling and restore smooth. The extractiongas scalar scalar max reached18m3/min, the concentration of the largest about90%when the kilometer the unloading hole drilling into field of pressure relief region, to acertain extent, which shows that the pressure relief effect is obvious of thin coal seammining as upper protective seam.