堰塞体漫顶溃决溃口冲蚀特性试验研究

Experimental investigation on the erosion characteristics of landslide dam failure induced by overtopping

针对堰塞体漫顶溃决室内试验中库容普遍过小的现状,开展了较大库容下堰塞体漫顶溃决试验,观测分析了溃口冲蚀特性和演化规律。研究结果显示堰塞体漫顶溃决的冲蚀过程可分为初始阶段、加速冲蚀阶段和减速冲蚀阶段,各阶段动力特性和冲蚀特性均有显著差异。初始阶段冲蚀特性表现为局部跌坎的溯源冲刷,加速冲蚀阶段为全断面高速下切,减速冲蚀阶段为上游冲刷下游淤积。溃决期间侵蚀速率峰值出现在溃决加速阶段,同时溃口流量峰值总是滞后于侵蚀速率峰值。初始坡比1∶3条件下,在初始阶段与减速冲蚀阶段堰塞体下游坡面坡度持续变缓,在加速冲蚀阶段则先变陡后变缓;坝顶坡度在初始阶段变陡,在加速冲蚀阶段和减速冲蚀阶段不断变缓。冲刷历时方面,上游入库流量变化对初始阶段历时存在较大影响,但对加速冲蚀阶段和减速冲蚀阶段影响较小。初始阶段泄流槽内局部抗冲刷能力较强的材料会阻碍溯源冲刷发展,对该阶段历时产生一定影响。研究结果有助于深入认识堰塞体漫顶溃决机制,并为相关防洪减灾工作提供参考。

This study addresses the limitation of laboratory tests with underestimated storage capacities by conducting experiments on the breach failure of landslide dams with larger storage capacities.The erosion characteristics and evolution patterns of the breach were observed and analyzed.The research identifies three stages in the erosion process:the initial stage,accelerated erosion stage,and decelerated erosion stage,each exhibiting distinct hydraulic and erosion characteristics.Notably,the initial stage displays'local drop'type headwater erosion,the accelerated erosion stage features high-speed downward erosion across the entire section,and the decelerated erosion stage is marked by erosion in the upstream and sedimentation in the downstream.Peak erosion rate occurs during the accelerated erosion stage,and peak discharge follows afterward.The downstream surface slope of the landslide dam varies continuously during the initial and decelerated erosion stages,while it increases and then decreases during the accelerated erosion stage.The dam crest slope increases in the initial stage and decreases in both the accelerated and decelerated erosion stages.Upstream inflow significantly affects the duration of the initial stage,with a smaller impact on the accelerated and decelerated erosion stages.Materials with strong local erosion resistance in the spillway hinder headwater erosion during the initial stage,influencing its duration.These findings provide valuable insights into the breach failure mechanism of landslide dams and contribute to flood control and disaster reduction efforts.