Technology of large-diameter back reaming and screen pipe installation for gas extraction boreholes in coal mine working faces

ZHANG Kaijia; XU Cheng

doi:10.11799/ce202602010

Abstract：To address the difficulties in fully running screen pipes and the diameter limitations encountered during the drilling of bedding gas extraction boreholes in soft coal seams,a large-diameter back reaming combined with screen pipe installation technology for extraction boreholes in mining faces was proposed,drawing on the technical characteristics of raise boring in underground excavation engineering and considering the operational conditions of bedding drilling in working faces.Based on the technological features of large-diameter back reaming combined with screen pipe installation,a corresponding back reaming bit was developed.Field tests were conducted at the 20603 working face in Jinyan Coal Mine,where two Φ250 mm large-diameter extraction boreholes were successfully constructed,achieving full-length borehole protection with Φ180 mm PVC large-diameter screen pipes in bedding boreholes.Field practice demonstrates that the large-diameter back reaming combined with screen pipe installation technology for extraction boreholes in mining faces can achieve the goals of"large-diameter borehole formation and large-diameter screen pipe borehole protection,"effectively improving the extraction performance of bedding boreholes.This technology provides a new approach for large-diameter gas extraction borehole construction and borehole protection,offering an innovative solution for efficient gas extraction in soft coal seam working faces.