Study on Seam Deformation and Permeability Improved Effect of Pressure Released Mining in Protective Seam

In order to study the pressure released and permeability improved effect of the high gas content seam and to reach the targets to improve the gas draina ge rate of the low permeability soft seam and to reduce the gas outburst danger of the coal mining face,the RFPA2D-Gasflow software was applied to analyze the minin g crack development and the stress distribution features of the overburden coal and rock and thus created pressure released and permeability effect after the pressure「 eleased mining in the underneath protective seam.The results showed that the permeability coefficient of the pressure released mining seam could be increased about 200 times and the permeability improved effect was obvious.The study results were applied to the layout of the inclined upward long and short boreholes in the gateway retained along goaf in Guqiao Mine to replace the layout of the inclined upward borehole in the conventional floor gateway for the gas drainage in the mining goaf and t he overburden pressure released seam.Thus the gas volume fractions of the air returning flow in the gateway retained and the gas in the upper corner both could be Co ntrolled below 0.5%,the average gas drainage rate could be 50%7 0% and the safety mining of the coal mining face could be ensured.