爬高型堰塞坝漫顶溃决机理研究∗

Study on the Overtopping Breach Mechanism of Climbing type Landslide Dams

摘要:

我国西南地区频发的地质构造活动和极端自然灾害诱发了大量的堰塞坝，属于堰塞坝的高发地，其形成的堰塞坝具有突然性强、危险性大的特点，严重威胁所在流域人民的生命财产安全，深入研究爬高型堰塞坝溃坝过程可为除险减灾提供科学理论支撑。为此，以土颗粒级配、背水面坡度、爬高型堰塞坝坝顶形状为影响堰塞坝漫顶溃决的主要因素，从漫顶溃决过程、溃口流量过程、溃口演变过程、溃后残留坝体及下游淤积情况等方面，分析了爬高型堰塞坝漫顶溃决演化过程。试验结果表明：随着土石料级配变宽，坝体整体稳定性增强溃决历时延长，洪峰流量减小，峰现时间较晚，残留溃口上宽小坝体体积大，距坝趾泥沙输移长度短且距坝趾1 m 处泥沙厚度薄；背水坡面越陡，水流获得的动能越大，加速了整个坝体溃决过程，溃口扩展得到充足发育，洪峰流量增大，峰现时间提前，残留溃口上宽较大坝体体积小，距坝趾泥沙输移长度长且距坝趾1 m 处泥沙厚度较厚；宽深比越大，则溃口相对位置越高，冲蚀阶段所具有的水头差大，加速了坝体冲刷进程，溃口扩展得到充分发育，残留溃口上宽尺度大坝体总量小，距坝趾泥沙输移距离远且距坝趾1 m 处泥沙厚度较厚。

Abstract:

Frequent geological activities and extreme natural disasters in Southwest China have in-duced a large number of landslide dams, making the region a high-risk area for such formations. Thesedams are characterized by their sudden occurrence and high danger, posing serious threats to the livesand property of people in the affected river basins. An in-depth investigation into the breaching processof climbing-type landslide dams can provide essential theoretical support for hazard prevention and mit-igation. This study focuses on the primary factors affecting the overtopping breach of climbing-typelandslide dams, including soil particle gradation, backwater slope gradient, and dam crest shape. Theovertopping breach evolution process of the dam was analyzed in terms of overtopping breach process,breach flow process, breach evolution process, residual dam structure, and downstream sedimenta-tion. Experimental results indicated that as the gradation of soil and rock materials became broader,the overall stability of the dam increased, the breach duration extended, and the flood peak flow de-creased. In addition, the peak occurrence was delayed, and the residual breach top width was smallerwith a larger dam body volume. The sediment transport distance from the dam toe was shorter, andthe sediment thickness at 1 meter from the dam toe was thinner. Conversely, a steeper backwaterslope resulted in greater kinetic energy of the water flow, accelerating the breaching process. This re-sulted in a fully developed breach, an increase in flood peak flow, earlier peak occurrence, and a widerresidual breach top with a smaller dam body volume. The sediment transport distance from the damtoe was longer, and sediment thickness at 1 meter from the dam toe was greater. Additionally, a larg-er width-to-depth ratio led to a higher relative breach position and a greater head difference during theerosion stage, accelerating the erosion process. This resulted in a fully developed breach, larger resid-ual breach top width, smaller total dam body volume, a longer sediment transport distance from thedam toe, and greater sediment thickness at 1 meter from the dam toe.