Physical modeling into outflow hydrographs and breach characteristics of homogeneous earthfill dams failure due to overtopping

The main objective of the present study is to introduce new empirical equations for the determination of breach geometrical dimensions and peak outflow discharge(Qp). Therefore, a historic failure database of 109 embankments was collected and examined. The most important factors that affect the breach evolution, including grading size, hydraulic, and outflow characteristics are also studied. Some of the parameters used for the determination of Qpand average breach width(Bave) have a significant effect on the erosion process, but they are less reflected in the technical literature. To study the behavior of noncohesive soils during overtopping, 15 physical tests were performed at the laboratory, and the effects of interfering parameters were investigated. The experimental output hydrograph was used to simulate the hydrographs resulting from the failure of real dams, and recent artificial intelligence techniques along with linear and nonlinear regression models were employed. The area-time analysis of the laboratory hydrographs shows that the soil particle size and the characteristics of reservoir-basin significantly affect the rate of breach formation and outflow discharge. New relationships are introduced, based on the breach characteristics, by a combination of historical and experimental data, as well as case studies conducted on the hypothetical failure of 10 operational dams. The mathematical model is also used to simulate the process of breach evaluation. Based on statistical indices, comparison of the results, and sensitivity analysis, the developed equations can better express the susceptibility of materials to erosion and their application can minimize downstream vulnerabilities.