Research on depressurized mining technology before developing floor strata tunnel in close coal-seam group

In order to reduce the mining dynamic pressure adverse effect on floor strata ventilation roadway in close coal-seam group of Qianjiaying mine, main roadway's reasonable layout, length and effectiveness of pressure relief mining are researched by theoretical analysis, numerical simulation, etc.The results indicate:the bottom roadway should be exploited after the depressurized face recovery and its floor strata stability; length of upward mining plane is twice of support pressure range at least, and roadway should be arranged out of the fracture's distribution of mining face's floor strata; applying depressurized mining technology with 180 m depressurized face in coal 9 and return-air roadway layout in coal 12-1 floor rock layer, the maintenance conditions of roadway are very effective, which could be explained by obviously reduced stress, roof-floor displacement reducing to 389 mm, side coal-walls displacement reducing to 324 mm.This kind of scheme is advantageous to maintain and use roadways safely.