Abstract: In order to determination of normal distribution of "vertical three-zone" in coal seam overlying strata more accurate, improve the effect of high gas drainage drilling, normal distribution of "vertical three-zone" of coal seam is divided initially, choosing a resonable arrangement of layers drilling is the key factor which influence the effect of high gas drainage drilling is discussed, construction parameters of each drilling should quantitative designed based on the height of caving zone and fractured zone in goaf. Field observation and theoretical calculation method of height of caving zone and fractured zone are discussed, and construction parameter of each drainage hole of high level borehole on high gas working face could designed and optimized overall according to these two results.

Key words: High level borehole, Caving zone, Fractured zone, Determination, Gas drainage