The Potential and Prospects for Alleviating Longwall-Mining Concerns Through the Use of Backstowing

Abstract

This study examined the potential for controlling longwall-induced subsidence by pneumatically backstowing the void created by mining with waste rock, and having the process scheduled as a unit operation of the mining activity. After a review of background literature, interviews with representatives of various mining companies, public-interest groups, and State and Federal regulatory agencies, a case-study evaluation of pneumatic stowing in a southwestern Pennsylvania mine site was conducted. The significant result of this investigation indicates that current stowing technology cannot keep pace with the production potential of U. S. longwall systems. At the case-study mine site, concomitant stowing would reduce subsidence by 50% of that incurred during full longwall caving, but the longwall coal production rate would decrease from 4,000 st per shift in the non-stowing case to 1,500 st in the stowing case. A preliminary cost analysis reveals that pneumatic stowing would add $6 to $10 to the operating cost of producing a ton of coal at the case-study site.