CREATING A MULTI-STEP FIELD AND MODELING APPROACH TO MONITOR ACTIVE SOIL SLOPES ALONG TENNESSEE HIGHWAYS

Geotechnical asset management (GAM) of landslide risks along highways is essential for safety and hazard mitigation. Slope instability is a concern in Tennessee, where highways often traverse steep terrain with complex geology and soils. Road construction such as road cuts, fill embankments, and drainage can reduce slope stability, compounding environmental factors like extreme rainfall and saturated soils. Tennessee Department of Transportation (TDOT) has identified a need for a statewide GAM inventory of soil slope hazards. The purpose of this project was to (i) create a soil slope rating system for Tennessee roadways based on the federal Unstable Slope Management Program (USMP), (ii) produce a field survey form to allow field workers to populate a GIS web database with ground verified landslide hazards, and (iii) conduct a sample inventory and a detailed review of select high-hazard slopes using field and remote sensing techniques. A field survey form was created with ArcGIS Survey123 based on USMP guidelines and TDOT specifications. The survey uses a smartphone application to automatically calculate category scores and generate an overall risk rating score for each slope based on user 55 user input criteria. For each site an indexed geopoint is created in an online database recording location and survey data, ratings, field notes, images, and overall slope rating score. Our preliminary field trial of the system generated a sample inventory of twenty-two slopes with overall slope risk scores ranging from 369 (Fair) to 1104 (Poor). Five high-risk sites were selected for further study. Analysis was performed via unmanned aerial system (UAS) photogrammetry and 3D modeling, existing remote sensing data to review past movements, and limit equilibrium method of slope stability. UAS analysis showed continuous slope movement and initiation of new scarps. Movements took place along the soil-bedrock boundaries as shown through limit equilibrium method. This research presents a multi-step approach to monitor active soil slopes along Tennessee highways and serves as a template for comprehensive statewide targeted management of unstable slopes.