Integration of seepage modelling and electrical resistivity monitoring data for the Älvkarleby test embankment dam, Sweden

The Älvkarleby test dam, constructed in Sweden, was designed with several intentionally created defects to serve as a controlled environment for evaluating various monitoring techniques. Among these, a unique three-dimensional (3D) Electrical Resistivity Tomography (ERT) setup was implemented. The ERT survey design, combined with full 3D calculation of the geometric factor and inversion constrained by the dam's internal zonation, enabled high-resolution mapping of spatial resistivity variations within the core and filter zones. Up to 14,000 ERT data points were collected daily, providing a detailed representation of the dam's internal conditions. Additional monitoring included pore pressure piezometers, Thomson weirs and turbidity sensors. In this study, a seepage model of the Älvkarleby test dam was developed to obtain comprehensive insights into its performance. A novel modelling approach was applied in which material properties for the core and fine filter were derived from a combination of laboratory test results and interpretations of the 3D ERT data. Anomalous zones identified through ERT, together with the known intentional defects, were explicitly incorporated into the model geometry. For other dam zones than the core material properties were based solely on laboratory measurements. A trial-and-error calibration process was performed by comparing calculated pore pressures and leakage rates with the corresponding measurements until optimal agreement was achieved. Two additional seepage models were developed for comparison: one without any defects and another incorporating the intentional defects only. Results demonstrated that only the seepage model guided by ERT data achieved better agreement with measured values. • ERT has the potential to use as a monitoring method in embankment dams. • The material properties used in the seepage model can be guided by the ERT model. • Seepage model guided by the ERT model has a better agreement with the measured data. • ERT can detect internal erosion in embankment dams.