Flow Field Fitting Method and Acoustic Doppler Velocity Measurement: A New Approach for Detecting Leakage Pathways in Concrete‐Face Rockfill Dams

Abstract In this study, we aimed to detect the leakage inlets and determine the leakage pathways through a dam, and ensure that the amounts of leakage upstream and downstream are consistent and that there is no leakage around the concrete‐face rockfill dam. The injection of a pseudo‐random current in the water between two aluminum sheets A and B generates a current field that can be measured in water with sensitive current sensors. When the current is channeled along the leakage pathways, the flow field fitting (FFF) method can be used to detect their inlets. We first review the background equations for the seepage and current fields in the FFF method. Then we use the index‐velocity method to calculate the discharge and ensure consistency between the upstream and downstream leakage based on the Doppler effect. Moreover, to illustrate how the FFF method works, we used a numerical simulation to verify the feasibility of the FFF method. Finally, we proceed with a case study in which the FFF method and measured acoustic Doppler velocity are used to identify and map potential leakage pathways bypassing upstream into the downstream flow‐measurement weir. The proposed methodology successfully detected three leakage areas and obtained the discharge in a case study; our results provide engineering geology information for optimizing the layout of grouting holes.