水库支流拦门沙坎冲蚀过程及力学机制研究

The erosion of sandbar-dotted at the tributary confluence of the Reservoir takes an important role to the overall efficiency. Due to the scouring process often accompanied by water falling and scarp slump, the mechanical mechanism is complex that involves the hydraulics, the sediment movement mechanics, and the soil mechanics. The filed measured data is absent, and the experimental study is difficult because of soil force similarity criterion. Until today there are also unable to know well about the erosion process and sediment movement law. Seting Xiaolangdi reservoir located in the Yellow River as an object, and taking Xiaolangdi reservoir physical model and the related model design theory as the foundation, Firstly, the study researches the process and mechanism of the similarity criterion of the hydraulics, the sediment movement, and the soil sapping instability mechanics; and then, the relation and mechanical mechanism of headward erosion taken by the flow condition and soil characteristic has been studied. and then analyses the response influence between the key factors and the headcut，geometric features and the backward law, as also quantitative expression relationship; Finally a predication mode for erosion and the sediment transport are extracted. The theoretical value and application prospect of research results is important.

水库支流拦门沙坎的冲刷与消控对水库综合效益的充分发挥具有重要作用。由于该冲刷过程常伴有局部跌水和陡坎滑塌，力学机理复杂，涉及水力学、泥沙运动力学和土力学等多门学科；缺少原型系统实测资料，试验研究因涉及到土力相似准则难度较大，时至今日也尚未能对其冲刷过程和水沙运动规律准确把握。本研究以黄河小浪底水库为背景，以已有黄科院小浪底水库物理模型及其相关物理建模理论为基础，研究支流拦门沙坎冲刷试验中的涉及到的水流运动、泥沙输运、河床冲淤及局部滑塌等方面的相似准则协调性与统一性；进一步完善针对陡坎滑塌蚀退的模型试验，开展水库支流拦门沙坎冲刷和输沙的研究；复演拦门沙坎的冲刷与溯源蚀退过程，探明拦门沙坎溢流冲刷、沟槽发育及陡坎蚀退机理，建立相应计算与预测模式，为控制水库拦沙期泥沙淤积特征、充分利用支流库容、延长水库拦沙期寿命提供支撑，具有科学意义和实用价值。

本项目研究水库降水运用时，拦门沙坎的冲刷与溯源蚀退过程，探明拦门沙坎溢流冲刷、沟槽发育及陡坎蚀退机理，建立相应计算与预测模式，为控制水库拦沙期泥沙淤积特征、充分利用支流库容、延长水库拦沙期寿命提供技术支撑。以黄河小浪底水库为背景，基于原型资料和理论分析，以黄河水利科学研究院现有小浪底水库物理模型为基础，研究支流拦门沙坎冲刷试验中的涉及到的水流运动、泥沙输运、河床冲淤及局部滑塌等方面的相似准则协调性与统一性；进一步完善针对陡坎滑塌蚀退的模型试验，开展水库支流拦门沙坎冲刷和输沙的研究。.本项目取得实质性进展和成果有三。一是水库支流拦门沙坎溯源冲刷机理及关键因子影响机制研究。完善水槽概化试验方法及关键水力因子、河床形态测量方法。针对水库降水冲刷过程中粘性淤积物的滑塌过程、土力学特性和力学机理，采取局部水槽概化试验和力学推导，观测了拦门沙坎上下游水力因子，明晰该冲刷过程发生的力学机理；研究了干支流交汇不同情境、水流条件、初始地形和水库运用条件对冲刷过程、冲刷量、冲刷形态及河势调整的影响特征。二是水库支流拦门沙坎滑塌力学特性分析及输沙模式研究。基于严格水动力学推导了冲刷过程与输沙数学表达，建立滑塌的临界水力-土力条件条件、堆积形态及输沙过程的数学描述。项目执行中，为精细研究沙坎的冲刷过程，将沙坎冲刷分为三个区域进行分别研究，分为沙坎上游Ⅰ区、沙坎立面Ⅱ区和沙坎下游Ⅲ区。对各分区，按照受力及冲刷特征，进行分类研究。三是水库支流拦门沙坎溯源冲刷模式检验及初步应用。将建立的计算方法嵌入已有水库数学模型，以小浪底水库为背景，结合小浪底水库支流溯源冲刷完整模型试验数据，进行系统检验与率定，结果良好。并对小浪底支流拦门沙冲淤演变过程进行了预测。