Moraine dam breaches occur suddenly and have severe consequences. However, breach-process prediction is challenging. Breach-notch excavation is crucial for risk reduction, but no consensus have been reached regarding the optimal notch shape. This study considers the typical characteristic parameters of the Jialongcuo glacial lake and trapezoidal, triangular, and compound notches. In this study, three flume tests were conducted to study the breach-shape impact on the peak discharge and erosion development of the dam during dam-breaching process, while controlling the excavation volume and depth. The compound- and triangular-breach peak discharge values surpass that of the trapezoidal type by 18.4% and 12.2%, respectively. Additionally, the trapezoidal breach exhibits average erosion rates that are > 50% lower, both laterally and vertically, at its initial erosion section, indicating milder erosion and improved outflow efficiency. The results emphasize that the notch-bottom width is critical, and that a trapezoidal notch with equal depths yields higher initial outflow efficiency owing to its greater bottom width. An analysis based on dam erosion process theory agrees with the experimental results and confirms the conclusions. Based on the erosion rates taken from the experiments, a comparison of sediment transport values is given for the three tests. The results indicate that the trapezoidal notch has a relatively small bed load transport. Our work is expected to provide references for the selection of better notch shape.

冰碛大坝溃坝突然发生，后果严重。然而，破坏过程预测具有挑战性。突破缺口开挖对于降低风险至关重要，但对于最佳缺口形状尚未达成共识。本研究考虑了加隆措冰川湖和梯形、三角形和复合凹口的典型特征参数。本研究通过3次水槽试验，研究溃坝过程中溃口形状对大坝洪峰流量和侵蚀发展的影响，同时控制开挖量和深度。复合型和三角型突破峰值流量值分别超过梯形型18.4%和12.2%。此外，梯形缺口在其初始侵蚀部分的横向和垂直方向上的平均侵蚀率均低 50% 以上，表明侵蚀较温和，流出效率提高。结果强调，凹口底部宽度至关重要，并且具有相同深度的梯形凹口由于其较大的底部宽度而产生更高的初始流出效率。基于大坝侵蚀过程理论的分析与实验结果一致，证实了结论。根据实验中的侵蚀率，对三个测试的泥沙输送值进行了比较。结果表明，梯形缺口具有相对较小的床荷运输。我们的工作有望为更好的缺口形状的选择提供参考。