Experimental Investigation into Outflow Hydrographs of Nonhomogeneous Earth Dam Breaching due to Overtopping

In this research, physical modeling of nonhomogeneous earth dams with clay cores was performed. The effects of dam slope, dimensions, and geometrical shape of the core, as well as the materials used for the core and body, on the breaching process and corresponding output hydrographs were studied. The breaching processes of each experiment were recorded using three digital cameras, and both quantitative and qualitative results were extracted. A decrease in the dam slope decreases the peak outflow, and the corresponding output hydrograph has a lower peak discharge and longer occurrence time. In addition, results show that the cohesion of materials is a prominent factor in the breaching of the core, and with a more cohesive core, the peak outflow and occurrence time considerably increase (by approximately 40% and up to 50%, respectively). For core materials with lower cohesion, erosion of the core and body occurs simultaneously, and consequently, the breach formation process is similar to a homogeneous dam. Finally, the hydrographs of dams with various practical core shapes show that the construction of an inclined core will increase the peak outflow up to 55% and weaken the dam behavior during overtopping. In these experiments, the trapezoidal cores presented the best results.