Extraction of Pressurized Gas in Low Air-Conductivity Coal Seam Using Drainage Roadway

A drainage roadway was constructed in the fractured zone beside an air-return roadway of a mining site. However, drainage roadways serve only one working face and are discarded after mining, thus weakening sustainable mining practices. To improve the sustainability at mining sites, this paper proposes a new drainage roadway that can serve two adjacent working faces. A schematic layout of the proposed lateral high drainage roadway (LHDR) is presented. The LHDR can be used to extract pressurized gas from two neighboring mining zones. A theoretical study, numerical simulation, and field observations were performed to identify the mining-induced fractures and stress distribution. The layout of the LHDR and the optimal position of the extraction boreholes were derived considering the geological conditions in the Liyazhuang Coal Mine in China. A borehole and LHDR were installed at the specified mining site and the rock displacement of the LHDR and gas concentration at branch pipelines, boreholes of the LHDR, and upper part of the working face were monitored during mining. The performance of the LHDR was validated.