Abstract: Aiming at the problems of high gas concentration and difficult management in the upper corner of "U" ventilation face in high gas mine，Liyazhuang coal mine has carried out the optimization analysis of coal seam extraction and the research of fracture zone extraction。Through improving the sealing depth,joint hole technology,pipeline connection mode,etc，the concentration of borehole extraction decreased from 4 months to 9%,and increased to 19% after 10 months。By adjusting the layout of the holes in the fracture zone,optimizing the arrangement of the holes and adopting the technology of protecting the holes with the lower screen pipe，the maximum net flow of gas drainage in the drilling field of fracture zone is 13.6 m3/min,the average net flow of gas drainage is 8 m3/min,and the total net flow of gas drainage in the two drilling fields is more than 13 m3/min。The gas drainage in the fracture zone of high drainage roadway and high level drilling field is cancelled in the working face,and the average gas concentration in the upper corner and return air flow is controlled below 0.5% and 0.4% respectively.

Key words: extraction of this coal seam,lower sieve tube,process improvement,peep,trajectory control,horizon optimization