Protection Scope Research of Upper Protective Layer with Bow Pseudo-oblique Mining in Outburst Coal Seams

In order to study the problem of locating the protection scope of steep-inclined upper protective layer with bow pseudo-oblique mining, a practical test research on the protection scope and protective effect for exploiting upper-protective layer was carried out at the first coalface of 4-6 district in a coal mine. The results show that the pressure-relief angles of upper protective layer are 85.7°and 79.5°along inclined upper and downside boundary respectively, and 47.1°to 74.1°along strike with irregular distribution in different height. As a result, there is significant difference about the protection scope between practical test and reference value of Coal and Gas Outburst Prevention Regulation. And besides, the permeability coefficient of protected layer was increased from 53 to 360 times, the volume fraction of pressure-relief gas drainage reached up to 40% to 65% and the average drainage rate reached up to 79.1%. Therefore, the gas regional control effect is remarkable so that the risk of coal and gas outburst is effectively reduced.