Non-invasive time-lapse imaging of moisture content changes in earthembankments using electrical resistivity tomography (ERT)

摘要

Earth structures, such as embankments, require ongoing monitoring and maintenance to identifypotential failure zones and to compensate for the effects of settlement. Extreme weather events leading toprolonged periods of desiccation or saturation are becoming more frequent and threaten embankment stability.In this paper the development of electrical resistivity tomography (ERT) as a non-invasive tool for characterizingand monitoring earth embankments is described. A study is presented in which ERT was applied alongside conventional intrusive techniques to investigate andmonitor a section of Victorian era embankment on the Great Central Railway. ERT electrodes were permanentlyinstalled as a series of linear 2D arrays, both parallel and perpendicular to the long-axis of the embankment. Theresulting ERT images, when calibrated using intrusive sampling methods, revealed the spatial variability of theembankment soils and were used to identify major discontinuities between material types at locations associatedwith poor track geometry. Subsequently time-lapse ERT images were used to monitor moisture content changesin the embankment; these images revealed both the spatial extent and magnitude of water content variations,and were used to assess the effect of an exceptionally prolonged and heavy period of rainfall during the summerof 2007.