Methane drainage with cross-measure boreholes on a retreat longwall face.
Thakur-PC; Lauer-SD; Cervik-J
Pre Soc min eng AIME Fall Mtg & Exhib Salt Lake City Utah, 1983 Oct; :13 pages
Methane drainage by cross-measure boreholes on retreat longwall faces can be a viable alternative to the vertical gob degas boreholes under favorable circumstances. This study, the first application of this technique in the Pittsburgh coal seam, was performed in a working mine in northern West Virginia. Fourteen small-diameter, inclined boreholes were drilled over a retreat longwall panel from gate roads, to intersect the overlying coal seams. All boreholes were manifolded to a pipeline and the gob gas was extracted by an exhaust fan on the surface. The methane capture ratio was poor at 7% to 18% at various stages of the longwall panel. A vertical gob degas borehole captured an additional 20% gas. Poor results were caused by premature failures of the cross-measure boreholes leading to air leakage. For better performance, the boreholes should be drilled from a point 30 to 45 m from the longwall pillar over the largest chain pillar, the standpipe should be grouted for at least 6 m, and the entry containing boreholes and the pipeline must be supported to ensure access for maintenance and the optimization of methane capture. Coursing the ventilation air around the longwall such that it forces methane-migration toward cross-measure boreholes can further improve methane capture. The optimum vertical inclination is 45 deg. to 10 deg.
Mining-industry; Longwall-mining; Methane-control; Methane-drainage; Methanes; Gases; Retreat-mining; Coal-gas; Coal-mining; Ventilation
Pre. Soc. Min. Eng. AIME Fall Mtg. & Exhib., Salt Lake City, Utah, Oct. 1983, Preprint 83-398, 13 Pp