REMOTE AND FIELD MONITORING OF HIGHWAY SLOPES IN GRAINGER COUNTY, TN

Landslides on highways are common geologic hazards affecting transportation routes within the steep hillsides and thick soil cover of the Cumberland Plateau, Ridge and Valley, and Appalachian Mountains regions of Tennessee. Landslide events disturb state routes and demand immediate attention, superseding other scheduled projects; the repair cost significantly strains available resources. State Route (SR)-32, which crosses Clinch Mountain in northeast Grainger County, Eastern Tennessee, lies within the Valley and Ridge Physiographic Province. Multiple slide areas along the eight-mile section of SR-32 of Clinch Mountain comprise thickly/medium-bedded, well-sorted Clinch Sandstone with locally gray siltstone and shale. Bedding strata dip toward the southeast into the roadway along the road. At lower elevations and ravine fills, the roadway is on colluvium and weathered shale, prone to slope failure. This study presents remote and field studies on three slopes along SR-32, including repeat LiDAR change detection to assess visible surface changes. The change detection analyses helped to select areas of interest, extract slope profile elevation data, and perform an informed limit equilibrium factor of safety analyses. The results represented areas of existing and new movements, estimated area and volume of erosion and deposition, plus the rate and magnitude of apparent movements. The factor of safety analyses of all three slopes yielded values close to one, considering limited soil cohesion values. With frequent rainfall in the slopes, the added soil pore water pressure significantly reduced the soil shear strength, putting the slopes at a high risk of failure, especially as the margin of safety is minimal.