ABSTRACT:

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 f0 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 3 ? 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.

INTRODUCTION

The Deer Creek Mine is operated by Energy West Mining Company. It is located in the Wasatch Plateau about 40 km (25 miles) southwest of Price, Utah, USA

Longwall mining has been conducted in the mine for the last 18 years. In recent years, longwall panels at depths in excess of 610 m (2000 ft) have been successfully retreated despite stability challenges, including effects of deep cover, sandstone channels, abutment stresses, faults, and weak roof and floor (Agapito et al. 1997, Goodrich et al. 1998).

During retreat of the 5 t? West longwall panel in the west side panels off the 3 e North mains, loading was noticed in the development section for the next longwall (4th West headgate) at a distance of 299 m (750 ft) away (Fig. 2). This behavior was repeated, and amplified, during retreat of the 4 t? West longwall panel where loading was noticed in the development section of the 3 e West headgate. This load transfer distance was greater than distances previously observed at the Deer Creek Mine. Excess loads manifested themselves as floor heave and pillar rib failures approximately coincident with the face position during retreat of the previous panel. Excess loads were quantified using overcoring stress determinations.

This content is only available via PDF.
You can access this article if you purchase or spend a download.