ABSTRACT

This paper presents preliminary results of numerical modeling conducted by the Bureau of Mines, Denver Research Center, to illustrate the capabilities of the boundary-element method in predicting, comparing, and assessing the effects of mining beneath massive sandstone escarpments. Mining under escarpments is rapidly becoming a major environmental concern in the Western United States. As an escarpment is undermined, the resulting subsidence induced by the mining has the potential to cause blocks of material to fail along existing joint planes and slide or topple down the talus slope below. This failure has the potential to impact wildlife habitat, raptor nesting sites, vegetation, and other land uses.

A two-dimensional boundary-element analysis was conducted along a vertical cross section through the Cottonwood Mine near Huntington, Utah. The analysis along this section took into account mining of both the 6th and 7th East longwall panels underlying the massive Castlegate Sandstone. Stress and displacement plots show the effect of mining these two longwall panels on the stability of the overlying Castlegate Sandstone escarpment, based on an elastic continuum model. An additional analysis was conducted to show the effects of altering the layout of these two panels on reducing the potential for escarpment instability.