Study on high level gas drainage gateway layout along roof strike in high gassy mechanized coal mining face

In order to solve the gas overlimite problem of high gassy mechanized coal mining face, according to the actual geological condition and the mining tech nology level of No.1307 coal mining face in Zhaozhuang Mine, a high level gas drainage gateway layout along the roof strike of the coal mining face was provided. In 0 rder to make a rational layout of the high level gas drainage gateway, a correction of the experiential formula was applied to the theoretical calculation and the FLAC3D software was applied to simulate the roof strata movement. With the site observation of the borehole flow method, the highest height of the caving zone was 25.15 m, th e highest height of the cracking zone was 75 m and a vertical distance between the high level gas drainage gateway and the seam roof was 30 m. With a gateway stres s analysis conducted on the air return gateway and the high level gas drainage gateway and in consideration of the rock strata falling angle, a horizontal offset distance between the high level gas drainage gateway and the air return gateway selected was 25 m. The engineering practices showed that during the gas drainage period of th e high level gateway, the drained gas pure volume and concentration were kept in a high value and the fluctuation size was affected by the periodical strata pressure of the coal mining face and the geological condition. During the mining period of the coal mining face, the gas concentration in the top corner and the air return gateway w ere kept in a low value and thus the gas overlimite problem was avoided.