Long-term monitoring of sub-surface change in earth embankment dams

Here we describe the development of a novel characterisation and monitoring approach for embankments such as earth dams. The system, called PRIME (Proactive Infrastructure Monitoring and Evaluation), is based on time-lapse electrical resistivity tomography (ERT), which is a geophysical technique used to non-invasively image subsurface resistivity to depths of tens of metres. Resistivity is a useful property because it is sensitive to compositional variations, changes in moisture content, and ground movement. PRIME is a low-cost system designed for remote operation, allowing resistivity images to be captured automatically and streamed via a web interface. It comprises four key elements: (1) low-power field instrumentation; (2) data telemetry and storage; (3) automated data processing; (4) and web dashboard information delivery. These elements form the basis of an asset condition monitoring approach that provides near-real-time spatial information on both subsurface processes and surface responses The use of this approach is illustrated with reference to a series of studies relating to earthwork condition monitoring. These studies demonstrate that PRIME provides a means of spatially tracking complex subsurface moisture driven processes (such as leakage or settlement) that would be very difficult to characterise using other approaches (e.g. surface observations or intrusive sampling).