Abstract

A concrete-faced sand-gravel dam (CFSGD) is likely to experience a dam breaching accident once there is leakage through the concrete face slab joints or overtopping of the dam. This study aimed to examine the physical process of a CFSGD overtopping breach and considered the influence of the failure of the vertical joint water barrier. The similarity criterion of the model test was deduced and the face slab that met the requirements of the model test was prepared. Through flume model tests, the process of overtopping dam breach was divided into four stages, i.e. Stage I, seepage erosion stage, Stage II, gradual erosion stage, Stage III, violent dam breach stage and Stage IV gradual stabilisation stage. The results showed that under the influence of seepage erosion, the initial breach of the dam occurred at the upper edge of the seepage surface of the downstream slope. The flow process line of the breach was of a ‘lean and high’ type, and there was a clear increase in the average rate of undercutting and horizontal expansion of the breach, highlighting the important influence of the early seepage erosion stage on the later dam breach process.

摘要

混凝土面板砂砾石坝（CFSGD）一旦混凝土面板接缝处发生渗漏或大坝溢出，很可能发生溃坝事故。本研究旨在检查 CFSGD 越过裂缝的物理过程，并考虑垂直接头水屏障失效的影响。推导模型试验的相似性判据，制作出满足模型试验要求的面板。通过水槽模型试验，将溃坝过程分为Ⅰ期、渗流冲刷期、Ⅱ期、渐冲期、Ⅲ期、猛烈溃坝期和Ⅳ期逐渐稳定期四个阶段。结果表明，在渗流侵蚀的影响下，大坝的初始决口发生在下游边坡渗流面的上缘。裂口流线为“瘦高”型，裂口平均底切率和水平扩展率明显增加，突显了早期渗流冲刷阶段对后期大坝的重要影响违约过程。