English

Abstract

The disposal of excess spoil created by coal mining operations in the Appalachian Coal Field is usually accomplished by placing this material in valley fills. As a result, hundreds of excess spoil fills have been built in Kentucky, Tennessee, West Virginia, and Virginia. The stability of these structures is regulated by the Federal Office of Surface Mining and state regulatory authorities. A joint Office of Surface Mining and Kentucky Department for Surface Mining fill team inspected an excess spoil fill located just outside Prestonsburg, KY. The fill was finished in 1998. In the design of the fill, the phreatic surface was assumed to be very low, resulting in a factor of safety of 1.5 for slope stability. The factor of safety (FS) for a slope is defined as the ratio of the moment resisting sliding over the moment causing sliding. However, during the field inspection water was observed exiting the structure at about 1/3 the height of the fill, resulting in a factor of safety near 1.27. There is concern that during the late winter and spring wet season, the phreatic surface could increase further. Failure of the fill could result in blockage of a headwater stream with potential increased sediment loads to the nearby Corps of Engineers Dewey Lake, contaminating water in the reservoir, and effect a proposed industrial, residential, and recreational development project nearby. This paper reports the results of a study that installed a comprehensive deformation monitoring system on the fill, investigated water movement, and tested soil samples obtained at the site. The deformation of the fill at a number of surface points has been surveyed over three years. The moisture content changes at selected locations on the surface of the fill were monitored as well. Soil properties for slope stability analysis have been determined in the laboratory. This study is supported by grants from the National Science Foundation and Office of Surface Mining.