粘性泥石流入汇区河床堆积动力过程研究

Deposition of viscous debris flow at the junction into river strongly changed the process of geomorphology evolution of river bed. Hence it is an important issue of geomorphology, dynamics and disaster that how to reasonably describe the process of dynamical accumulation in confluence. Field surveys and experiments have indicated some extraordinary phenomena of debris flow moving into river, such as the acceleration of “water-slide” snout, the deposition of bounce of fluid phase in opposite bank, and the superposition of surge deposit. Designing the physical experiment, based on the dynamic theoretical derivation and case calculation of mixed fluid, the “semi-coupled” dynamical accumulation model of interaction of viscous debris flow and water has been established. The main study including: 1) Based on indoor large-scale experiments, to explore the physical process and influence of control parameters of viscous debris flow in confluence. 2) Based on the theory of mixed fluid, the method of continuous media mass and momentum, to build a “semi -coupled” dynamical accumulation model of interaction of viscous debris flow and water. 3) Selecting more than 10 events of viscous debris in confluence of upper area of Minjiang River in recent years as case, to simulate the dynamical accumulation process of viscous debris flow in confluence of various basin situations, verify and correct the dynamical model, perform the dynamical numerical simulation. This study is of great significance to the delineation of the risk area of viscous debris flow and the evolution of the basin’s geomorphology.

粘性泥石流入汇主河强烈地改变入汇区的河床堆积地貌演化过程，如何合理描述这一过程是流域地貌、河流动力学和灾害学的重要问题。本项目基于岷江上游大量泥石流入汇事件的特征调查，从粘性泥石流入汇的特殊现象——龙头“水滑”加速、异岸“液流反弹”堆积和阵流“元堆积”现象出发，设计物理模型实验，基于混合流体动力学理论推导和案例实算，建立粘性泥石流-水流交互作用的“半耦合”堆积动力学模型。主要研究内容包括：1）基于室内大型实验，探明粘性泥石流入汇的物理过程和控制性参数影响；2）基于混合流体动力学理论、连续介质质量和动量方法，构建粘性泥石流-水流交互作用的“半耦合”堆积动力学模型；3）选择近年岷江上游其余10余起入汇事件作为算例，开展不同流域情景下粘性泥石流入汇区河床堆积动力过程模拟，验证并修正模型，进行粘性泥石流入汇区河床堆积动力演化数值计算。本研究对粘性泥石流风险区范围划定和流域地貌演化具有重大意义。

粘性泥石流入汇主河强烈地改变入汇区的河床堆积地貌演化过程，如何合理描述这一过程是流域地貌、河流动力学和灾害学的重要问题。粘性泥石流入汇主河的动力学实质是非牛顿流体与牛顿流体的交互作用，如何有效描述两者的交互过程和机制，是本项目的难点。本项目主要研究粘性泥石流完整入汇堆积的动力学过程，获得如下成果：1. 基于我国西藏帕隆藏布流域、四川大渡河以及岷江流域大量泥石流入汇事件的调查，认知粘性泥石流入汇主河特殊现象和物理过程，统计分析堆积动力过程的主要控制性参数，建立岷江上游堰塞湖灾害信息查询系统（C/S和B/S）。2. 解决室内实验条件下模拟野外泥石流自然性态的技术问题，发明一种泥石流入汇主河过程实验测量系统及测量方法。选择天摩沟为研究区，开展107组原型缩尺实验，探究泥石流龙头运动速度变化特征、泥石流入汇过程掺混及输移特征，建立表征入汇过程掺混特征及输移情况的表达式，建立泥石流入汇堵河形态计算式。3. 对比验证岷江流域其他沟道泥石流入汇堆积体的分布规律与研究区的基础地理信息数据，揭示泥石流入汇口河床局部演化特征和河道演变的滞后响应规律。本研究对粘性泥石流风险区范围划定和流域地貌演化具有重大意义。