ABSTRACT:

Canyon Fuel Company operates the SUFCO coal mine located in the southern Wasatch Plateau Coal Field approximately 48 km (30 miles) east of Salina, Utah, USA. The mine produces coal from the Upper Hiawatha Seam of the Mesa Verde Group (Cretaceous) strata. Annual subsidence monitoring, mostly by aerial photogrammetric methods, has been conducted for the last 22 years. In 1998, detailed survey measurements of vertical and horizontal displacements over a longwall panel were conducted in order to better understand the response of the 61-m-thick (200-ft-thick) Castlegate Sandstone and to develop a failure criteria for naturally occurring rock formations. Measurements indicate magnitudes and directions of transient and permanent deformation over the panels and gateroads as a result of longwall panel retreat. Vertical subsidence magnitude ranges up to approximately 1.62 m (5.3 fi). Magnitudes of horizontal movement measured over the panel have been up to 0.19 m (0.62 ft).

INTRODUCTION

The SUFCO Mine, operated by Canyon Fuel Company, is located in the southern Wasatch Plateau Coal Field approximately 48 km (30 miles) east of Salina, Utah, USA (Fig. 1). Subsidence monitoring has been conducted for over 20 years at the SUFCO Mine. Monitoring records include subsidence over room-and-pillar and longwall panels.

Annual subsidence monitoring has been mostly by aerial photogrammetric methods, but monument surveys have been conducted periodically for collection of additional data. In some areas, surface subsidence has resulted in subsidence cracks, failure of escarpments, and in one location, the collapse of a natural bridge. In 1998, detailed survey measurements of vertical and horizontal displacements over longwall panel 12L4E were conducted in order to better understand the response of the strata to longwall mining.

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