EXPERIMENTAL STUDY OF BREACH GROWTH PROCESSES IN SAND DAMS OF QUAKE LAKES

This paper describes an experimental study into the angle of repose for uniform sediment particles, which is important in describing the dam-break process. Two types of setups, Hele-Shaw cell and drum, were used in the experiments. Each experiment was conducted in two media, namely air and water. Based on the experimental data, an empirical formula that describes the angle of repose for uniform sediment particles under different mediums was developed. From the dam-break experiments, in general, four stages can be identified in the process of breach erosion. In Stage I, the downstream slope angle of the channel increased from an initial value θ0 to θ1. In Stage II, retrograde erosion of the crest at the breached point occurred at constant angle due to seepage flow, leading to a decrease in the width of the crest of the dam in the breach. This stage ends when the crest vanishes. In Stage III, the breach continues to grow mainly laterally with the erosion propagating to the upstream slope, with the retrogressing downstream slope maintaining a constant slope. In Stage IV, the flow velocities in the breach become so small that the breach erosion stops. The results also show that the dam-breach growth process is developed with the eroding crest retrogressing at critical angle of sediment particles used for building the dam for Stages II and III and the results agree well with previous studies.