Numerical model for breach of concrete face sand-gravel dams due to overtopping

Based upon the data of field investigations and back analysis of centrifugal model tests for the beach case of the Gouhou concrete face sand-gravel dam (CFSGD), a numerical model for breach of CFSGD is developed. The major highlights of the model are the adoption of soil erosion equation which can consider the erosion of bed load and suspended load to depict the erosion process of sandy gravels with a wide range of gradation, and the establishment of analogy to simulate the failure process of concrete face slabs under varying loads during the dam breach. The analysis of the case study of the Gouhou dam breach is used to testify the proposed model, and the comparison between the calculated and measured results shows the relative errors of less than ±15% for the output of breach parameters, which contain the peak breach flow, breach top and bottom widths of the rockfill body, numbers of the failed concrete face slabs and their failure lengths, as well as the failure time of dam breach. Owing to the bending of concrete face slabs, the breach hydrograph has a serrated increase. In addition, the sensitivity analysis indicates that the soil erodibility and grain-size distribution significantly affect the prediction of the breach flow of the dam.