Design Method and Application on Gas Pre- drainage Borehole to Expose Coal in Cross-cut

In order to expose coal and through the coal seam quickly and safely when drainage in cross-cut, according to four principles for arrangement of advanc e detect borehole, and three-point method for analysis on the boreholes data, as well as the technical points of back sight point and closure drainage, the five-step pre- drainage borehole design method contains was put forward.Practical results showed that the arrangement of advance detect borehole based on the four principles can be accurately ascertain the coal ocurrence in the case of proven regional. The five-step pre-drainage borehole design method could ensure the accuracy of the borehole construction, hole depth error could be controlled within +3 m, it could eliminate the gas blank zone caused by inaccurate borehole construction, and it was good for pre -drainage in uncovering coal area and roadway driving.