The Clean Air Act of 1992 required lower sulfur dioxide emissions, increasing demand for low-sulfur coal. Some of the the low-sulfur coalbeds in the Appalachian Coal Region occur at depths ranging from 500 to 2,000 feet. Historically, coal in this region has been mined without consideration for the influence on other adjacent coalbeds. As a consequence of this practice, environmentally acceptable compliance coal may be more difficult to mine because of ground control problems associated with multiple-seam mining. Developing design technology or models to safely mine coal above or below an existing mine provides an economic and employment opportunity and a domestic source for U.S. energy requirements. Multiple-seam mining requires a comprehensive understanding of the stress transfer that occurs between two coalbeds. Obviously, mine design is crucial for roof, rib, and floor stability. Pillar and entry dimensions, positioning, as well as the timing during mine development, affect overall conditions in the mines.
National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 626 Cochrans Mill Road, Pittsburgh, PA 15236