Embankment Dam Seepage Evaluation from Resistivity Monitoring Data

Methods for monitoring seepage are important for dam safety of embankment dams. Increased seepage may be associated with internal erosion in the dam, and internal erosion is one of the main reasons for dam failures. Internal erosion progresses inside the dam, and is difficult to detect by conventional methods. Therefore, there is a need for new or improved methods. The resistivity method is a non-destructive method that may accomplish this task. A method for evaluating the seepage from resistivity monitoring data is theoretically described and tested for four selected areas in the foundation of the Sädva dam. Seasonal resistivity variations are apparent in the reservoir as well as inside the dam. The four selected areas represent areas with low, via intermediate to high variations in the seasonal resistivity variation. The areas are compared qualitatively and thereby permeable zones within the dam may be identified. Quantitative assessment of the seepage flow is also carried out as an initial test of the described method. It is concluded that the experiences from the Sädva dam are valuable for the application of the resistivity method on embankment dams. The presented method is a promising first step for quantitative assessment of seepage.