非均质结构堰塞坝溃决机理模型试验

堰塞坝是由滑坡等失稳地质体快速堆积并阻塞河道而形成的天然坝体，溃决后会对下游人民生命财产安全造成严重威胁。深入开展非均质结构对堰塞坝溃决过程的影响研究，可为堰塞坝灾害的风险评估和应急处置提供重要参考。依托自主研发的水槽试验装置，通过开展不同结构类型堰塞坝的溃决模型试验，分析了均质、竖向非均质和水平非均质结构对坝体溃决的影响。研究发现：1）堰塞坝侵蚀过程受局部区域材料性质影响严重。2）均质坝中，随着中值粒径增大，材料抗侵蚀能力增强，溃决特征先由层状冲刷变为陡坎侵蚀，再变为多级陡坎侵蚀，峰值流量逐渐减小，峰现时间逐渐推迟。3）竖向非均质坝中，坝体上部材料主要影响溃口形成阶段历时和坝前水位；中部材料主要影响溃口发展阶段的溃口下切速率；底部材料主要影响下游坡脚稳定性和残留坝体形态。受溃口加速下切和溃决流量增加彼此间相互叠加影响作用，中部及底部材料分布对峰值流量的影响最为显著。4）水平非均质坝中，坝体内部4个区域对溃口发展的影响不同。过流侧上方材料影响溃决前期的溃口下切速率；过流侧下方、对岸侧上方材料分别影响溃决中后期的溃口下切、展宽速率；对岸侧下方材料对溃口发展影响最小。泄流槽设计时，应考虑非均质结构的影响，基于坝体结构特征采用工程措施限制溃口深切、促进溃口展宽，以降低峰值流量。

Experimental Investigation on the Breaching Mechanisms of Landslide Dams with Heterogeneous Structures

Landslide dams are natural dams formed by river blockages with high speeds caused by landslides, collapses, and so on. Dam failures pose great threats to people and infrastructure upstream and downstream. A deep understanding of the influence of heterogeneous structures on dam breaching can provide an important scientific basis for the risk assessment and emergency treatments of landslide dams. In this study, laboratory physical modeling tests were conducted to investigate the effects of homogeneous, vertical heterogeneous, and horizontal heterogeneous structures on the breaching process. The experimental results showed that: 1) The erosion process of landslide dams was significantly affected by the material properties of the local location. 2) For the homogeneous dams, when the median diameter of materials increased, the breaching characteristics would change from laminar scouring to scarp erosion, then to multistage scarp erosion, the peak discharge would decrease, and the peak arrival time would be delayed. 3) For the vertical heterogeneous dams, the upper material mainly affected the duration and the upstream water level of the breach initiation stage; the middle material mainly affected the vertical erosion rate in the breach development stage; the bottom material mainly affected the stability of the downstream slope and the geometry of residual dam. The material distribution of the middle and bottom layers had the most significant effect on the peak discharge, because of the positive interaction between the breach deepening and the outflow accelerating. 4) For the horizontal heterogeneous dams, the upper material on the overflow side affected the initial vertical erosion rate; the bottom material on the overflow side and the upper material on the opposite side affected the subsequent vertical and lateral erosion rates, respectively; the influence of the bottom material on the opposite side was minimum. When designing the discharge channel, the influence of heterogeneous structures should be considered. Engineering measures should be adopted to restrict the breach deepening and promote the breach widening to minimize the peak discharge.