An experimental examination of riprap effects on homogeneous embankment dams overtopping breach

The overtopping phenomenon is the most common cause of embankment dams’ failure, and it includes a complicate process. In present research, a physical model of an earth dam covered by riprap was constructed, and its hydraulic outcomes were compared with a benchmark model by providing a three-scenario framework. The main results indicated that the breach process of physical models follows three stages including: initiation, development, and termination. Furthermore, the use of riprap has no significant effects on the peak flow discharge caused by the breach procedure. In the first scenario, without a filter layer, the breach process had the highest resemblance to the benchmark model. For the second scenario, by employing a composite system, the occurrence of 129% increase in the breach time and the longest duration of the end stage were recorded. For the third scenario, by employing a composite system at the downstream slope, 86% increase in breach time and no change in the terminal stage duration was observed. Besides, the mass of eroded material was calculated according to the achieved sedimentation pattern. In the second scenario, the maximum thickness of sediment was measured; it proved the transport influence of riprap at the downstream of laboratory channel. A relatively symmetrical sedimentation pattern was then observed. Moreover, more than 50% of riprap material was transported to the downstream. This paper comprises the simultaneous measurements of breach geometry, flow hydrograph, and ultimate sedimentation patterns may help researchers in this field of study, indeed.