The U.S. Bureau of Mines, in cooperation with a southwestern Pennsylvania coal mining company, recently assessed the feasibility of using predriven recovery rooms (open entry recovery) when longwall mining to increase the productivity of the coal extraction process. Four recovery entries, one 200 ft long and three 600 ft long, were supplementally supported with bolts, channels, and wire mesh, and either fly ash-cement piers, fiber cribs, or cement-sand piers, then mined into by the longwall face. The recovery entries showed little deterioration as the supports provided adequate resistance to the front abutment loading. As compared to conventional recovery methods, recovery rooms allowed for panel extraction to be completed an average 12.5 Days faster and reduced face equipment move time by 30 pct. The productivity increase accompanying recovery rooms was greater than the 2 to 4 times increased support costs. Recovery rooms provided over 22 additional production days and the opportunity to mine nearly 85,000 short tons of coal per year per panel mined.
Proc. 1989 Multinational Conf. on Mine Planning and Design, Univ. Kentucky, 1989, PP. 119-124