Using the resistivity method for leakage detection in a blind test at the Rossvatn embankment dam test facility in Norway

Internal erosion is a cause of embankment dam failure, thus it is important to develop methods for seepage monitoring and internal erosion detection. In order to evaluate the potential of resistivity monitoring to give an early warning of such leakage/erosion, a test was undertaken on a rockfill embankment dam with a central glacial till core at the Rossvatn test facility in Norway. Three defects, consisting of permeable material, were built into the dam at various depths and locations unknown to the personnel carrying out the measurements and data interpretation. A numerical modelling pre-study was carried out, showing that all the actually constructed defects were too small to be detected by single time investigation. In the final test, repeated measurements were undertaken with different reservoir levels, i.e. a limited monitoring approach. This increased the detection capability, confirming the value of the geophysical approach and that monitoring is superior to single time investigations