Long-term geophysical-geotechnical monitoring of landslide processes

We assess the use of novel geophysical monitoring approaches to spatially characterise geotechnical properties and processes driving slope failure, and consider the contribution of geophysical technologies to the development of slope-scale early warning systems (EWS). In particular, we focus on geoelectrical monitoring approaches to image moisture driven processes, supported by the use of shallow seismic surveys to illuminate elastic property distributions and changes. We describe an approach for using spatial and volumetric geophysical models of slope structures and processes to better inform geotechnical models of slope stability and estimates of factor of safety.

Key components of the approach have included: automated schemes and instrumentation for measuring and processing field-scale time-lapse geophysical and geotechnical data sets; laboratory based assessments of geophysical-geotechnical property relationships (e.g. between resistivity, moisture content and pore suctions) to aid the interpretation of slope-scale geophysical models; and linked geophysical-geomechanical modelling to provide near-real-time estimates of slope stability to aid forecasting of landslide events. Our approach is illustrated with results from a range of field sites located on natural and engineered slopes. We conclude that the spatially rich subsurface information provided by geophysical monitoring can make a substantial contribution to landslide EWS and can provide an improved understanding of the condition of unstable slopes.