HIGH STRENGTH EROSION CONTROL MAT SUPPORTS VEGETATION ON A CUT ROCK SLOPE

During the widening of U.S. Highway 25E from Clinch Mountain to U.S. Highway 11W in Grainger County (USA), the Tennessee Department of Transportation (TNDOT) was faced with the challenge of cutting a 0.5H:1V rock slope and preventing fragile limestone, sandstone and shale deposits from falling near passing motorists. Although hard armor solutions such as retaining structures and shotcrete were considered, concern over the aesthetics of highway expansion and costs associated with 7.5 km of potential hazards forced TNDOT to create an innovative vegetative solution. These 42.5 meter tall rock slopes were hydraulically seeded, anchored with wire mesh and rock bolts and stabilized with a unique three-dimensional woven geotextile erosion control mat. Presented herein is a detailed case history of a unique application of a high strength permanent erosion control mat on a challenging project. This project summary documents the feasibility study, design parameters, specification and contract document preparation, supply and installation of specially-fabricated 3.6 meter wide rolls. Also included are cost comparisons and construction techniques for future users. A series of installation photographs accompanies this paper to create a practical technical reference for all involved in geosynthetics.