Application of Comprehensive Investigation Methods in Seepage Diagnosis and Prediction of a Clay Core Rockfill Dam

Abstract

Aiming at the problem of intensified downstream seepage in a clay core gravelly soil dam after impoundment, this study adopted a comprehensive approach that integrated surface observation, high-density electrical resistivity tomography, self-potential method, tracer tests, and itemized seepage calculation. The investigation revealed that the seepage is primarily controlled by defects in the concrete cutoff wall of the dam foundation and the heterogeneous permeability of the clay core. Key permeability parameters were obtained through inversion of observed data, and the seepage discharge at different water levels was calculated item by item using Darcy's law. The results show that under the current water level, the measured total seepage discharge is 103.64 L/s, while the calculated value is 100.54 L/s, yielding an error of only 3.08%. This close agreement verifies the reliability of the derived parameters and the applied methodology. The total seepage discharge is predicted to reach 241.28 L/s at the normal impoundment level. This research provides a direct basis for the danger elimination and reinforcement of the dam. The integrated diagnostic and verification methodology developed in this study can serve as a valuable reference for investigating seepage in similar earth-rock dams.