二元结构河岸侵蚀失稳与不平衡输沙交互作用机理研究

Bank failure is an emergency in the process of near bank riverbed erosion in alluvial river. And the failure block, as an extra sediment source, results in extremely non-equilibrium sediment transport locally and changes of shoreline and river regime, which influence the river development and utilization. Taking the typical dualistic structure bank in the mid-Yangtze River as background, the project studies the bank erosion and non-equilibrium transport of failure block. Based on field data analysis, theoretical research and experiment are integrated to study dualistic structure bank failure and failure block action in non-equilibrium sediment transport. In this project, a mechanical model is established to simulate the erosion and failure process of dualistic structure bank. The scope of failure block storing at bank foot is expected to be defined. Then, the hydraulic decomposition and transport mode of failure block will be explored ,which refer to exchange with the riverbed through non-equilibrium suspended-load or bed-load. Finally,the above mechanical model of bank failure and the river mathematical model are coupled to reveal the interaction between bank failure and bed deformation. The photogrammetric technology is applied in experiment measurements,with non-contact,no interference and superiority to traditional measurement technology. The research may promote intersection among river dynamics, soil mechanics and close-range photogrammetry. The results are of scientific and practical importance for predicting and controlling river regime and planning water environment function.

冲积河流河岸失稳坍塌是近岸河床侵蚀积累的突变形式，失稳体引起泥沙源陡增导致局部水沙强不平衡输移，引发岸线与河势变化，影响河流开发利用。本项目以长江中游具有二元结构河岸的典型河段为背景，针对河岸侵蚀失稳及失稳体在河床上不平衡输移这一复杂水土耦合作用问题展开研究。采用理论分析及概化物理模型试验等手段，建立模拟二元结构河岸侵蚀失稳过程力学模型，界定失稳体在河岸坡脚的堆积型式；探索失稳体在河床上被水力分解、以悬移质或推移质形式与河床进行不平衡交换规律及影响因素。耦合河岸侵蚀失稳力学模型与河流水沙数学模型，预测典型河段演变及河势参数变化，揭示河岸侵蚀失稳与河床冲淤演变交互作用过程及反馈机理，系统构建其耦合作用模式。试验中引入无接触实时近景摄影测量技术，弥补传统监测手段不足。项目可促进河流动力学、土力学及摄影测量学等学科交叉，研究成果对适时预测并控导河势、指导水体环境功能规划有着重要的科学及实用价值。

冲积河流河岸失稳坍塌是近岸河床侵蚀积累的突变形式，失稳体引起泥沙源陡增导致局部水沙强不平衡输移，引发岸线与河势变化，影响河流开发利用。本项目以长江中游具有二元结构河岸的典型河段为背景，采用理论分析及概化物理模型试验等手段，针对河岸侵蚀失稳及失稳体在河床上不平衡输移这一复杂水土耦合作用问题展开研究。研究表明，水流冲刷过程中岸坡破坏是水流淘刷岸坡坡脚、岸坡崩塌及崩塌体淤积坡脚并在河床上分解、输移并掺混的交互作用反复循环过程；研究提出湍动能法、Preston管经验公式法以及k-ε数值模拟法等弯道壁面切应力计算方法；发现近岸河床的可冲刷性越强，岸坡崩塌的发生及崩塌体的分解输移程度越强；发现若岸坡与河床组成相同，同水力条件下岸坡崩塌总量大于河床冲刷总量；河床相对冲刷率随岸坡冲刷坍塌量的增大而减小，其值范围为0.40～0.92；发现弯道凹岸边壁切应力最大点发生在距河床0.15–0.75水深处；建立了考虑岸坡切应力分布的BSM模型，其预测精度明显高于BSTEM 模型。项目可促进河流动力学、土力学及摄影测量学等学科交叉，研究成果对适时预测并控导河势、指导水体环境功能规划有着重要的科学及实用价值。