Geoelectrical Monitoring of Seasonal Moisture Content Changes in an Earth Embankment

Earth structures, such as embankments, require ongoing monitoring and maintenance to identify potential failure zones and to compensate for the effects of settlement. Extreme weather events leading to prolonged periods of desiccation or saturation are becoming more frequent and threaten embankment stability. In this paper we develop electrical resistivity tomography (ERT) as a non-invasive tool for characterising and monitoring earth embankments. A study is described in which ERT was applied alongside conventional intrusive techniques to investigate and monitor a section of Victorian Great Central Railway embankment, near Nottingham, UK. A number of modes of deployment were considered including linear 2D ERT arrays both parallel and perpendicular to the long-axis of the embankment and 3D imaging arrays. The resulting ERT images, when calibrated using intrusive geotechnical testing and core samples, revealed the spatial variability of the embankment soils. Parallel ERT sections were used to identify major discontinuities between material types at locations associated with poor track geometry. Perpendicular ERT sections also revealed significant internal heterogeneity, and were used to monitor seasonal changes in the moisture content within the embankment.