Predicting Soil Erodibility Using Electrical Resistivity Tomography

Scour is responsible for approximately 60% of all bridge collapses in the United States. A large number of bridges are listed in the National Bridge Inventory as scour critical; however, evaluating scour potential based on soil sampling and laboratory testing can be cost prohibitive, as erosion testing using available apparatuses is time consuming. Various soil characteristics that affect the erosion of soil also influence in situ bulk electrical resistivity (ER) measurements collected using electrical resistivity tomography (ERT). The objective of this study was to predict soil erodibility using ERT. Fourteen bridge sites were used for ERT and erosion testing. The results of this study indicate that an ER over 50m has a 93% probability of classifying the soil as high erodibility. As such, ERT can be used to rapidly prioritize existing bridges where soils near the surface are likely classified as highly erodible. These bridges would then require a more detailed investigation to characterize soil erosion potential. The application of using ERT to predict soil erodibility was validated using an additional experimental site.