Development of a model to predict longwall gas emissions resulting from overburden failure.
Trevits-MA; Garcia-E; McCall-FE
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado. Hustrulid WA, Johnson GA, eds., Brookfield, VT: A.A. Balkema, 1990 Jan; :187-194
The accumulation of methane gas is and will continue to be one of the most formidable problems facing the mining industry. Although several methane drainage alternatives are available to augment conventional ventilation, longwall mine operators typically rely on gob gas boreholes. Such boreholes are used because they cause minimum disruption to mining operations and provide instant relief to underground problem areas. In the deep, ultra gassy coalbeds (i.e., Pocahontas No. 3 and Mary Lee Coalbeds), mine operators are also using horizontal boreholes to supplement gob holes and mine ventilation. With the advent of high-extraction mining systems, particularly the longwall method, deeper yet highly productive mines are being developed in the major mining regions in the U.S. Such mines are traditionally more gassy. Summaries of U.S. mine gas emissions compiled from Mine Safety and Health Administration reports show that mine emissions have increased from 227 MM ft(3)/day in 1971 to 303.9 MM ft(3)/day in 1985 (Grau 1987, Trevits 1989). Also, the number of mines producing gas in excess of 10 MM ft(3)/day accounted for almost 30 pct of the 1985 total. The dimensions of longwall panels also continue to grow. From 1976 to 1989, the average longwall face width has grown by more than 200 ft (Merrit 1985, Sprouls 1986, 1989). Furthermore, panels are routinely developed that are in excess of 900 ft wide. The trend of the industry is to also extend panel length. In fact, some operators are considering longwall panel length in excess of 10,000 ft. The change in longwall panel size has serious implications on the amount of gas that may be emitted during mining. An increase from 600 to 900 ft in panel width increases the area disturbed by mining by 50 pct. A concomitant increase in mine emissions may be also expected from an extension of longwall panel length. Currently, U.S. mine operators must rely on European mine emission prediction techniques to estimate the amount of gas that may be emitted during mining. This study discusses the key concepts of longwall gas prediction and proposes a preliminary prediction model for U.S. mining conditions.
Rock-mechanics; Gases; Mining-industry; Mining-equipment; Underground-mining; Coal-mining; Coal-gas; Methanes; Ventilation; Ventilation-equipment; Ventilation-systems; Boreholes; Mining-engineering; Longwall-mining; Mines-excavations; Emission-sources
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado