Abstract An underestimation of local scouring in loose cohesionless landslide deposits may cause rapid and episodic failure of a hazard mitigation structure. A rock avalanche triggered by the 2008 Wenchuan earthquake generated an abundance of erosion-sensitive sediment in Yangjia Gully, resulting in several debris flows. Twelve concrete pile check dams were constructed along the gully to mitigate debris flow hazard in 2017. However, three of the downstream check dams progressive collapsed during the next two years. Field investigations revealed at the downstream of most check dams an accelerating scour, which quickly led to their instability and failure. Energy dissipation structures built at the toe of the dams moderated the local scour but did not prevent it. Repeated field investigations and flume experiments were carried out to better understand the process of bed erosion. The erosion rate is substantially high, and appears to be irreversible without artificial intervention once a hydraulic drop is formed. The presented case in Yangjia Gully shows the consequence of underestimating rapid erosion. Furthermore, several suggestions are proposed for hazard mitigation engineering in erosion-sensitive deposit.

中文翻译：

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无粘性滑坡坝的快速发作性侵蚀：从杨家沟检查坝的流失到冲刷和水槽实验的见解

摘要 对松散无粘性滑坡沉积物中局部冲刷的低估可能导致减灾结构的快速和间歇性失效。2008 年汶川地震引发的一次岩崩，在杨家沟内产生了大量的侵蚀敏感沉积物，导致了多次泥石流。2017 年，沿沟渠修建了 12 座混凝土桩止水坝，以减轻泥石流危害。 然而，下游的 3 座止水坝在接下来的两年中逐渐倒塌。现场调查显示，在大多数检查坝下游，冲刷速度加快，很快导致其不稳定和破坏。建在大坝趾部的能量耗散结构缓和了局部冲刷，但并没有阻止它。为了更好地了解河床侵蚀的过程，进行了反复的实地调查和水槽实验。侵蚀率非常高，并且一旦形成水力下降，在没有人工干预的情况下似乎是不可逆的。杨家沟的案例显示了低估快速侵蚀的后果。此外，对侵蚀敏感矿床的减灾工程提出了若干建议。