堰塞坝溃决-消亡过程水土物质运移机理分析及动态风险评估

Due to the frequently-occurred tectonic movements and extremely meteorological disasters, landslide dam formed worldwide at an alarming rate in the past few years, incurring serious disasters and influences. The present studies on landslide dam mainly focus on the stability and dam breaching process. The water-soil transportation during dam breaching and vanishing process and the corresponding influences are lack of sufficient concern, which may bring large-area, long-period and high-intensity damages to the downstream areas. The program aims to find out the material distribution law of different landslide dams, reveal the mechanisms of water-soil transportation during dam breaching and vanishing process and obtain the evolution law of the dynamic risks involving the time effect. The studies would build a landslide dam database with water-soil transportation information, develop efficient technology for achieving the dam breaching materials based on UAV hyperspectral remote sensing analysis, present a model for analyzing the water-soil transportation during dam breaching and vanishing process, and provide a method to assess the corresponding dynamic risks. The results obtained from the studies are meaningful in both academic and practical phase to guarantee the safety of human lives and properties, systematically mitigate the risk of landslide dams and guide the scientific planning and sustainable development of urbanization in mountainous areas.

近年来，由于地质构造运动活跃、极端气候灾害频发，堰塞坝的发生频率和数量都呈集中爆发态势，并造成巨大灾害和影响。现有关于堰塞坝的研究主要集中在坝体稳定性和溃坝过程分析，较少关注溃决和消亡过程的物质运移及其由此带来的大范围、长时间、高强度的影响。本项目拟通过现场调查、模型试验、数值模拟、理论分析、风险评估等相结合的方法，分析不同类型堰塞坝物质空间分布规律，揭示由宽级配且非均匀材料组成的堰塞坝溃决及消亡过程水土物质运移机理，并查明其动态风险演化规律。项目拟建立一个堰塞坝水土物质运移案例数据库，开发基于无人机高光谱遥感分析的堰塞坝溃决物质快速获取技术，提出堰塞坝溃决和消亡过程的水土物质运移分析模型和动态风险评估方法体系。研究成果将对保障堰塞坝所在流域生命财产安全，系统管控其动态风险，指导山区城镇科学规划建设和可持续发展有重要的理论和实际意义。

本项目针对堰塞坝溃决消亡、水土物质运移以及由此带来的大范围、长时间、高强度的影响进行了相关研究并得到如下结果：（1）揭示了宽级配材料及非均匀结构对堰塞坝溃决影响机理。通过自主研发的模型试验装置开展了不同形态、材料和结构特征的堰塞坝溃决模型试验，发现坝高、下游坝坡的增加，坝宽和中值粒径的减小会导致峰值流量增加、峰现时间提前；发现了不同材料坝体溃口模式：细粒为主发生层状冲刷破坏，连续级配发生陡坎溯源破坏，缺失级配发生管涌破坏，粗粒为主未发生破坏；中间软弱夹层的的竖向非均匀结构坝体发生最大峰值流量，水平非均匀结构坝体溃决峰值流量与泄流槽所在位置密切相关；滑坡涌浪导致溃坝提前发生，大幅度缩短溃决时间并增大峰值流量。（2）阐明了堰塞坝溃决及消亡过程的水土物质运移规律。提出了基于动态流体网格的坝体材料渗流潜蚀离散元流固耦合分析模型，得到了宽级配材料潜蚀发生条件及对材料力学性质的影响规律；发现了梯级堰塞坝级联溃决洪水放大效应的临界条件，建立了多坝连续溃决及物质运移分析模型；探究了堰塞坝溃决消亡后水土物质的运移规律，通过唐家山堰塞坝溃决案例分析，发现最大含沙率随着与溃口距离的增加而减小。（3）建立了考虑时间效应的堰塞坝溃决和消亡过程的动态风险评估模型。基于自主建立的堰塞坝大型案例数据库，提出了堰塞坝稳定性和寿命快速预测模型。考虑堰塞坝溃坝洪水演进提出了动态风险评估方法，并开展了唐家山梯级堰塞坝的定量风险评估。基于影响图方法建立了堰塞坝溃坝预警决策模型，发现溃坝概率和风险人口的增加将显著改变最佳预警策略。开展对金沙江白格两个同址堰塞坝的风险评估，发现由于叠加作用第二个堰塞坝的溃坝流量和风险显著大于第一个坝，开挖泄流槽可以降低溃坝风险。研究成果应用于唐家山、白格、加拉、冻错曲等多个堰塞坝溃决流量预测和风险评估。