Abstract：In order to study difference of two effective drainage radius,taking the No. 11-2 coal seam of Zhujizi coal mine as object,the effective drainage radius of cross-measure borehole was measured by use pressure reducing method,and the effective drainage radius of in-seam borehole was determined in the same coal seam by combine SF6 gas trace method with numerical simulation in COMSOL software. The results show that the effective drainage radius of cross-measure borehole and in-seam borehole are 4. 5 m and 7. 8 m respectively under the condition of 13 k Pa drainage negative pressure and 90 d drainage period,and the effective drainage radius of cross-measure hole is less than the one of hole drilled along seam significantly. The result is enormously significant to choose drainage right borehole spacing in drainage design.

Keyword：cross-measure borehole;bedding borehole;effective drainage radius;SF6 trace method;gas drainage;