Monitoring internal erosion in embankment dams using 3D Electrical Resistivity Tomography: Älvkarleby test embankment dam

One major risk threatening embankment dam integrity is internal erosion of the core. Internal erosion progresses inside the dam but it is difficult to detect with conventional methods. Electrical Resistivity Tomography (ERT) is a potential-based method that can sense the interior of the dam, and this study aims to evaluate the capability of ERT as a complementary monitoring technique for discovering internal erosion. A test embankment dam with some defects incorporated inside the core and fine filter in Älvkareby, Sweden, has been constructed with the purpose of assessing different monitoring techniques including ERT. Buried electrodes and sensors for other monitoring instruments were placed inside the dam. The collected ERT data were inverted using a 3D time-lapse inversion model implemented in pyGIMLI/pyBERT package. The results revealed a layered resistivity structure in the core and several unintentional anomalous zones. Furthermore 2 out of 5 defects in the core were located, namely horizontal and vertical crushed rock zones, with a slight location shift for the horizontal zone. A concrete block defect was indicated, although not as distinctly and with a lateral shift. The two remaining defects, a crushed rock zone at the abutment and a wooden block were not discovered.