SLOPE STABILITY AND SUBSIDENCE INVESTIGATION, RALEIGH COUNTY, WEST VIRGINIA

In May, 2003 two large subsidence cracks were reported on an abandoned surface mine bench atop Kayford Mountain, Raleigh County, West Virginia. These subsidence cracks are expressed as nearly vertical cracks that run several hundred feet long and have displaced a mass of rock from a knob on Kayford Mountain by 2 to 4 feet. Residents of the nearby town of Dorothy, West Virginia, which is in the valley below Kayford Mountain, feared potential slope instabilities including a massive (global) failure of the knob as well as the generation of large rockfalls, in the present condition of the mountain and as mountain top mining operations enter into this permitted area. The cracks were attributed to subsidence in one or more of the 4 coal seams (depths ranging from 430 to 1200 feet below the bench) that were deep mined in the area at various times over the past 65 years. To investigate the cause and potential instability of the knob, two core borings totaling 1838 lineal feet were performed. Observations from the core borings confirmed the location of the subsidence event that caused the cracks and the stability of the hillside was evaluated. Rockfall simulations using the Colorado Rockfall Simulation Program were performed to address the concern of falling blocks affecting the nearby residents. Furthermore, recommendations were made concerning mining operations as they enter the area.