Study on Floor Pressure Relief Law of Simultaneous Mining Working Faces in close Distance Seam Group of Dongsheng Coalfield

In order to research floor pressure relief law of shallowly buried descending coal-mining working face covered with thin soft bedrock in Dongsheng coalfield , taking Lijiahao coal mine for example, firstly, to calculate the impact depth was 18.86m by the theoretical formula, then analyzing coal and rock mass stress and displacement variation of the upper work surface to its floor during mining based on numerical simulation. Obtaining coal and rock pressure relief depth of the floor was 70m, with the working face advancing, the pressure relief depth and range became larger, to achieve stable at a certain number;affected by the mining of 2-2 coal, coal and rock mass strength of its floor was weak, the largest damage depth was about 18m,this result would provide a basis to the roadway of the 3-1 coal in different coal pitch; affected by the mining, the goaf overburden and floor of 2-2 coal working face appeared "O" shape fracture zone, the floor rock fissure of 2-2 coal got through to the roof of 3-1 coal,cracks formed transfixion,which made the pressure change of 3-1 coal working face, Mine pressure appearance tended to be ease, it would be easily control if the roadway of 3-1 coal was arranged in the area of pressure relief. The theoretical results would be useful to actual production.