关键词: 分层开采, 放顶煤, 水力压裂, 固体产气预裂, 放煤效果

Abstract: In order to solve the problems of low layer fully mechanized caving face and upper layer fully mechanized caving face of super-thick hard coal in compound area of Huojitu mine, there are some problems in the process of stoping, such as poor coal caving effect at the tail end of the working face and too much coal in goaf. According to the geological conditions of coal seam mining in composite area, the main factors affecting caving property of top coal caving working face are analyzed, and the technology of pre-weakening the top coal at both sides of working face by using high-pressure hydraulic pre-fracturing and high-pressure gas deep-hole pre-cracking is put forward. Through the implementation of the No.206 working face in the 12 lower coal seam, it is shown that the coal caving effect is improved after the use of high-pressure hydraulic pre-fracturing technology, but the effect is not good, the top coal recovery rate is only about 50-70%. The new technology of high pressure gas deep hole pre-cracking can weaken the top coal pre-cracking, produce a large number of cracks, and enhance the top coal caving property. The recovery rate of top coal can reach about 85%, at the same time, it can release the stress of the overburden coal, and prevent the sudden collapse of the roof of the tail section in the mining process, causing the support to die. The application of solid gas pre-cracking technology can weaken the hard top coal in advance, enhance the caving property of top coal, reduce the lump coal rate, improve the recovery rate, and reduce the apparent strength of periodic pressure, thus providing an effective guarantee for the safe production of top coal caving.