堰塞湖不同演变模式下水沙作用机理研究

The evolution process and its stability mechanism of the blocked lakes are the hot issues in the research fields of mountain hazards and river restoration, of which the mechanisms of water-sediment interaction during the deformation of the blocked dams are the key concerns. Under the circumstance of accelerated generation of the blocked lakes, it is urgent and essential to evaluate and classify the most important factors that impact the blocked lake evolution process and to study the water-sediment characteristics and the erosion mechanism therein. However, current knowledge on such subject is rudimentary, and further study is needed both qualitatively and quantitatively. The objective of the present study is to look thoroughly into the evolution modes and the subsequent process. By means of field survey, data collection, flume experiments and theoretical analysis, the trigger conditions for different evolution modes of the blocked lakes would be investigated. And as well the hydrodynamics of the water-sediment behaviors for certain evolution modes would be discussed. A series of indexes for determining the evolution modes would be carried out and the physical picture of evolution process with neat details would be drawn. The outcome of the present research would provide theoretical and technical support for the emergency settlement of the blocked lakes and the evaluation of their stability. Moreover, the results of the present study would improve and updates the theories, concepts and methodologies in the research field of mountain hazards and river restoration.

堰塞湖演变过程及稳定性机理研究是目前山地灾害研究和山区河流修复研究最为前沿的热点问题之一，其核心内容是堰塞湖演变过程中的水沙相互作用机理。在更多的堰塞湖正加速产生的历史背景下，梳理影响堰塞湖演变过程的关键因素，探究不同演变模式下水流特性、泥沙运动特性以及二者相互作用造成的侵蚀规律，具有重要性和紧迫性。目前对于堰塞湖留存/溃决演变机理的认识仍然是初浅、唯象的。定性、定量探讨堰塞湖演变模式及相应模式下水沙相互作用机理研究亟待深入。本项目拟以堰塞湖演变模式及演变过程为研究对象，利用野外考察、资料收集、概化水槽试验及理论分析方法对堰塞湖不同演变模式的发生条件和典型演变过程中水沙动力特性展开系统研究，建立不同演变模式的判定指标，构建不同演变模式下构建水沙相互作用造成坝体侵蚀的物理图形，为堰塞湖应急措施和稳定性评价提供理论和技术支持，实现堰塞湖次生灾害及河流稳定性研究在理论、概念与方法上的完善和更新。

本项目以堰塞湖演变模式及演变过程为研究对象，主要通过系列原型观测、资料分析以及试验模拟研究提出了堰塞湖6种不同溃决演变模式，基于大量水槽概化试验阐明了影响堰塞湖演变的主要因子为初始流深、坝体材料特征粒径、孔隙率、不均匀系数和曲率系数；在确定坝体材料渗透系数与特征粒径、孔隙率、不均匀系数和曲率系数的关系基础上，建立了堰塞湖演变模式判别的指标参数I，I值作为基于大量试验数据拟合所得不同溃决模式的指示参数能够作为试验设计相似准则（令比尺λI=1，若取λCu和λCc为1，则只需保证λd0/d10=1即可）或原型状态初步研判指标。通过水槽试验探讨了堰塞湖最常见漫顶渐溃模式下水流特性、泥沙运动的行为机理，构建水沙相互作用造成坝体侵蚀5个阶段的物理图形，可为堰塞湖应急措施和稳定性评价提供理论和技术支持，并实现堰塞湖次生灾害及河流稳定性研究在理论、概念与方法上的完善和更新。