This report describes a study, conducted jointly by Bethenergy Mines, Inc., and the Bureau of Mines, to assess the effects of longwall front abutment loading on various supplemental support materials utilized in a predriven recovery room. The purpose of the predriven recovery room is to reduce longwall equipment transfer time by eliminating the premove preparation associated with conventional recovery methods. In addition, the room provides a large area in which face salvage equipment can maneuver. Results of four recovery-room study areas show the progression and influence of the front abutment on the longwall panel and supports and their subsequent behavior. The best performance (i.e., the support that most facilitated recovery) of support material was achieved through the use of a concrete mixture that had a sand content of 35 pct by volume. The longwall transfer time was reduced by 30 pct, which translates to a production advantage of 37,000 raw tons of coal per panel.
Proceeds of 1989 Longwall USA, 6/19-22/89. Industrial Presentations, Inc., PP. 20-27