Drilling Spacing Optimization Design Based on Relationship Between Pre-pumping Time and Extraction Radius

While ensuring gas extraction to meet the requirements before working face mining, to maximally save borehole engineering quantity, by establishing gas extraction radius and pre-pumping time model at working face, and field measurement of the drainage radius, this article analyzes and grasps the dynamic relation between the borehole spacing and pre-pumping time. On the basis of this, in Liyazhuang Mine 2-609 face, borehole spacing is designed for subregional combined with roadway construction speed and working face mining speed. Field application showed that drilling engineering quantity reduced by 27.8%, which still met the requirements of gas extraction.