Field Investigation of Sandstone Escarpment Stability at East Mountain, Utah, USA

Abstract

During the last three decades, a significant amount of research has been directed to developing predictive tools for assessing the stability of the Castlegate Sandstone escarpment, travel distances for the debris and the need for any control measures in Central Utah. The cliff-forming Castlegate Sandstone is 60 m thick at the study mine in Utah and lies approximately 250 m above multiple-seam coal reserves. To assess escarpment stability, the authors used multiple regression analysis and extensive data on geology, mining, and escarpment stability collected over many years. The volume of failed rocks was used as the response variable. Mine layout options were developed to minimize cliff instability and frequency of mining-induced surface fractures. Geologic and geometric variables were obtained along 3.7 km of escarpment exposure at 180 study locations. A regression analysis of data from 29 study locations showed that surface topography plays a critical role in influencing escarpment stability. With additional data collected over the next longwall block, important variables were identified including canyon slope, thickness of Castlegate Sandstone and mining influence angle. Finally, the model was used for prediction of escarpment stability in area 3. In remote mining areas of Utah, warning signs were posted at the study areas.