山区河流河床粗化层失稳机理及再造过程研究

Characteristics of the flow and sediment supply is notoriously episodic and can occur by earthquakes,flash floods and other natural disasters.Dams interrupt the continuity of sediment transfer that causes sharply decreases of sediment supply in the downstream reach. The change of water and sediment conditions in the watershed has put forward new requirements for the study of the river water and sediment movement and river channel process, especially the research on the breakup and reestablishment of the armour layer in mountain river is one of the key scientific problems. Based on the theory of fluid dynamics, sediment dynamics and river channel process,here we studied the structural characteristics and impact characteristics of the roughened layer in mountainous areas, discussed the mutual restraint model of river bed erosion and coarsening under different sediment supply conditions,and revealed the river bed response mechanism of breakup and reestablishment of the armour layer. Throughing the method that combination of theoretical analysis, field investigation and laboratory experiments, the method of calculating the resistance of the coarsened protective layer, the method of resistance decomposition and the comprehensive resistance are established, simultaneously, the critical condition of the coarsening layer in breakup process and the method of calculating flow conditions, sediment transport and river channel process in the reconstruction process are put forward, which achieve the improvement and update of the study in theory, concepts and methods. The research results will enrich the research contents of river dynamics, and provide theoretical and technical support for the river engineering planning and design, flood control and disaster mitigation, river regulation, water intake and sediment control and so on.

地震、山洪等自然灾害引发河流来水来沙特性改变，而大坝阻隔致使下游河道沙量骤降。流域水沙条件的改变对山区河流水沙运动及河床演变研究提出了新要求，其中山区河流河床粗化层失稳机理及再造过程研究是关键科学问题之一。本课题组以流体力学、泥沙运动力学与河床演变学为基础，研究山区河流粗化层结构特性与抗冲特性，探讨不同泥沙补给条件下河床冲刷与粗化的相互制约模式，揭示河床粗化层失稳机理及其再造过程中的河床响应机制。通过理论分析、野外调研与室内水槽试验相结合的方法，建立粗化保护层的阻力构成模式、阻力分解及综合阻力的计算方法，提出粗化层失稳的临界条件及失稳与再造过程中的水流条件、泥沙输移与河床演变的计算方法，实现本研究在理论、概念及方法上的完善与更新。研究成果将丰富河流动力学的研究内容，为该类河道的工程规划与设计、防洪减灾、河道整治、取水防沙等提供理论与技术支撑。

流域自然条件以及人类活动影响导致山区河流河床粗化层长期处于形成-破坏-再形成的动态循环过程。项目围绕“山区河流河床粗化层失稳机理及再造过程的动力学机制”这一科学问题，采取野外观测、室内实验与理论分析相结合的方法，重点研究了山区河流河床冲刷与粗化的相互制约模式、粗化层失稳机理及其临界条件、粗化层失稳与再造过程中的河床响应机制，取得了如下创新成果：发现了“床面切应力大于1.2倍原粗化床面切应力”的卵砾石河流静态粗化层失稳临界条件，揭示了卵砾石河流河床粗化层失稳的物理机制；建立了通过“河床高程二阶结构函数顺水流方向差异”表征卵砾石河流粗化层形成与失稳过程中河床结构特性的量化方法；揭示了卵砾石河流粗化层失稳过程推移质运动规律，建立了卵砾石河流粗化层失稳后推移质输沙率峰值、推移质输沙率到达峰值后的衰减过程以及卵砾石河流粗化层失稳与再造过程河床表层级配的计算方法。上述成果丰富和完善了河流动力学的研究内容，可为山区河流水沙灾害防治、河道整治等提供理论与技术支撑。项目发表学术论文6篇，其中SCI/EI收录5篇；获授权/申请国家发明专利2项；在国内外学术会议做学术报告6次，其中大会特邀报告3次，分会场报告3次；培养博士1名、硕士4名。