漫顶溃决型泥石流形成机理研究

With the global warming and frequently occurred extreme weather and climate events, coupled with seismic effects, the number of outburst debris flow triggered by overtopped natural dam failure has risen. The outburst debris flow which triggered by the unsteady flow erosion is different from every other type of debris flow. The prediction of this type of debris flow is not feasible because the formation mechanism of outburst debris flow is still unrevealed. The research is intended to focus on the quantitive evaluation of volume concentration of outburst flow. For this reason, flume tests with different channel bed slopes and channel compositions will be, firstly, designed based on findings from field investigation and data collection. Secondly, the focused law in this study is to probe the erosion ability of outburst flow and the evolution of volume concentration for outburst flow. Such, the formation mechanism of this type of debris flow can be revealed. And, the forecasting model of this type of debris flow can be developed on the basis of stream power of flow and critical stream power for initiation of sediment. This research can provide a scientific foundation for the forecasting of this type of outburst debris flow and its early warning.

近年来由于极端天气事件频发，加之地震效应，引发大量堰塞坝漫顶溃决，导致漫顶溃决型泥石流灾害数量增多。漫顶溃决型泥石流是由非恒定水流逐渐侵蚀下游河床而形成的，区别于其它类型泥石流的形成过程。因目前对该类泥石流的形成机理认识不足，尚未建立反映真实泥石流形成过程的判识模型。本项目聚焦认清漫顶溃决水流体积浓度演化规律的关键科学问题，拟在资料搜集和野外调查的基础上，通过室内水槽实验分析非恒定溃决水流的水力特征和侵蚀挟沙特性，研究漫顶溃决水流体积浓度演化规律，揭示漫顶溃决型泥石流的形成机理。基于形成机理，从功率角度，分析泥石流形成过程中水流功率、起动功率等物理量间的关系，提出预测该类泥石流形成的判识模型。本研究为漫顶溃决型泥石流灾害的判识提供参考，对泥石流风险评估具有重要的指导意义。

围绕漫顶溃决水流的水力特征与侵蚀挟沙能力，漫顶溃决水流体积浓度演化规律，漫顶溃决型泥石流的判识模型三个研究内容，通过野外考察、数据搜集、室内试验、理论分析、数值模拟等，开展研究，圆满地完成了任务书要求的工作，取得成果如下：（1）通过野外调查和资料搜集，搜集了1000余例堰塞湖漫顶溃决型泥石流，其中包括各参数较全的案例300余例。这些数据为分析漫顶溃决型泥石流的形成规律、演化特征和预警预报研究提供了宝贵的数据支撑。（2）通过室内物理实验，分析了堰塞坝溃决过程中漫顶溃决水流的流速、流量、溃口尺寸、侵蚀率的变化规律，明确了溃决水流的水力特征，提出了预测溃口尺寸变化的模型，给出了溃决流量的计算方法，为泥石流预测提供了水动力条件的分析工具。（3）研究了堰塞坝不同溃决模式的形成条件和溃决特征，分析了溃后河道的演变特征，进一步明确了溃决水流在河道上的侵蚀挟沙能力。（4）通过物理实验再现了漫顶溃决型泥石流的形成，分析了体积浓度演变特征，为分析泥石流形成条件提供了数据支撑。并且，提出了预测漫顶溃决型泥石流浓度变化全过程的数学方程，给出了泥石流的判识模型。研究成果为漫顶溃决型泥石流的预警预测提供了理论支撑。发表论文12篇，其中SCI 8篇，EI 2篇，CSCD论文1篇，会议论文1篇；获授权发明专利2项，软件著作权1项；以本研究为基础，获国家自然科学基金面上项目1项。