Stabilization of mine waste through the application of soil nailing

The traditional soil nailed structure incorporates grouted or driven nails, and a wire mesh reinforced shotcrete facing to increase the stability of a slope or wall. This thesis describes the construction and monitoring of a full-scale demonstration of nailing to stabilize coal mine spoil (waste from contour surface mining). The purpose of the investigation is to evaluate the performance of nailed slopes in mine spoil using methods proven for the stabilization of soil walls and slopes. The site in eastern Tennessee is a 8 meter high slope of dumped fill, composed of residual soil, weathered shale chips, sandstone, and coal. The slope was formed by "pre-regulatory" contour surface mining operations and served as a work bench during mining. The material varies in particle size from clay to boulders, and has a small amount of cohesion. Portions of the slope have experienced slope instability and erosion which have hampered subsequent reclamation activities.

Three different nail spacings and three different nail lengths were used in the design of the stabilized sections. A fourth unreinforced control section was excavated and later observed to have failed. The study sections were instrumented and monitored for nail stresses and slope deflection. Measurements from the instrumentation revealed slight increases in nail stress during the study period, with little slope movement detected. Following completion of the slope, an analysis of the as-built soil nailed structure was performed and a method was devised to create and analyze an equivalent slope from the as-built nail locations.

The study suggests soil nailing is an applicable stabilization method for slopes composed of mine spoil. The major advantage of soil nailing is the ability to vary the design as differing subsurface conditions are encountered. The proposed method permits variable nail spacings to be easily incorporated in most analysis methods.