Linking Geoelectrical Monitoring to Shear Strength - A Tool for Improving Understanding of Slope Scale Stability

Landslides pose a risk to both infrastructure and wider society, managing the geohazard requires and understanding of factors driving slope instability, in particular the response to moisture content. Traditional methods of slope investigation involve discrete point geotechnical measurements which are not spatially sensitive. Recent studies have shown the spatial sensitivity of geoelectrical methods to both the internal geometry of unstable hill slopes and moisture dynamics, demonstrating their value in landslide investigation and characterisation. In this study we present the use of a geoelectrical monitoring system on an active landslide in Lias mudrocks, North Yorkshire, UK. Building on previous studies of the field site, subsurface resistivity distributions determined from time-lapse electrical resistivity tomography (ERT) are converted into shear strength estimates through calibration between electrical resistivity and matrix suction. Geotechnical parameters are determined from shallow borehole samples. Shear strength distributions show agreement with field observations of the slope, relatively low shear strength values (<100 kpa) correspond to the parts of the slope which are actively moving. We suggest there is scope for further work identifying regions of potentially instability on hillslopes through coupled hydromechanical and geoelectrical modelling.