Rock Mechanics for Industry, 37th U.S. Rock Mechanics Symposium, Vail, Colorado, 6–9 June 1999
Authors: R. R. Goodrich and J. F. T. Agapito (AAI), and C. Pollastro, L. LaFrentz and K. Fleck (Energy West Mining Company)
Energy West Mining Company operates the Deer Creek coal mine located in the Wasatch Plateau about 40 km (25 miles) southwest of Price, Utah, USA. Longwall panels at depths in excess of 610 m (2000 ft) have been successfully retreated. Visual observations and stress measurements indicate that load transfer distances greater than 229 m (750 ft) have been experienced in the west side panels off the 3rd North mains. During retreat of longwall panels, ground conditions deteriorated significantly in the development section for the next longwall in the sequence located approximately 229 m (750 ft) away. Deteriorated ground conditions included a pillar burst, floor heave, rib spalling, and roof falls. Stress measurements suggest 13% excess load near this gateroad over the anticipated vertical stress. The long load transfer distances observed are believed to be primarily due to the massive and strong Castlegate Sandstone in the overburden strata.