Study on borehole arrangement mode for eliminating the blank zone in blind area of drilling gas extraction

In order to eliminate the blank zone in blind area of gas extraction in coal seam caused by drilling gas extraction, this paper studies the existing mode of the blank zone among the typical crossing holes. The analysis shows there is no blank zone in blind area of gas extraction in the "triple eye" borehole arrangement mode, the optimized square borehole arrangement mode and the equilateral triangle borehole arrangement mode, and the utilization rate of the effective extraction area of the equilateral triangle mode is 1.9 times that of the "triple eye" mode and the optimized square method. Taking the 25031 open-off cut of Gaocheng Coal Mine in Zhengzhou mining area as the project research object, the field test and investigation are carried out on the quantity of drilling work and average gas extraction pure quantity of single borehole under different borehole arrangement mode. The results show the equilateral triangle mode requires the least quantity of drilling work, while the "triple eye" mode requires the most quantity of drilling work; the average gas extraction pure quantity of single borehole in optimized square method is slightly higher than that in equilateral triangle mode, and the average gas extraction pure quantity of single borehole is the lowest in the "triple eye" mode, combined with the analysis results of typical borehole arrangement mode, the equilateral triangle mode is considered as the optimal scheme, the research results can be used as a guide for the design of crossing holes.