Assessment of active landslides using field electrical measurements

Landslide characterization and hazard assessments require multidisciplinary approaches that connect geologic processes with geotechnical parameters. Preexisting landslide activity, geology and geomorphology, soil strength, and hydrologic conditions are complex factors that affect landslide behavior. Often, the connections among these factors are not made for hazard assessments, forecasting, or slope stability modeling. Therefore, geophysical and geotechnical techniques for landslide investigations are typically assessed independently. This study aims to bring together different techniques to develop a methodology that connects electrical measurements and shear strength. A framework has been developed for using electrical resistivity measurements that will support and facilitate the prediction of shear strength within a slope. In-situ volumetric water content, soil water potential (suction), and electrical conductivity were measured from two shallow colluvial landslides in Kentucky. Repeated surface electrical resistivity survey measurements were used to characterize the failure zone and lithology, and to compare with the in-situ hydrologic measurements. The data show that subsurface moisture conditions over time can be reflected in the inversions of repeated ER surveys, thus allowing electrical measurements and geotechnical parameters to be correlated. This study demonstrates that electrical resistivity can be used as a tool for landslide monitoring and to assess shear strength. These parameters are pertinent to investigating the stability of landslides that are often triggered or reactivated by rainfall.