涌潮水流及其引发的河床渗流对圆柱桥墩局部河床冲刷影响机理研究

In strong tidal estuary, tidal bore is a kind of intense and common flow motion.Tidal bore shocks the bridge piers severely and induces strong local scour around bridge piers, which forms a potential threat to the safety of bridges. However, at present, there is short of full understanding on the flow characteristics around bridge pers and failure mode under tidal bore.This project aims at the basical problems for the safety of bridge piers in strong tidal estuary. A method of combining the field inspection, physical experiments, theoritical analysis and numerical simulation will be used to significantly study the sediment motion under tidal bore, flow structure around cylinder bridge piers, seepage flow characteristics and local scour characteristics deeply. Besides, based on OpenFOAM,a multiphysics fields solving library, the coupled solution of flow field ,seepage field and scouring process will be realized, and the relationships between flow field,seepage field and scour characteristics will be sorted out.This project will imply the flow and scour characteristics around bridge piers under tidal bore,which updates the theory of bridge hydrodynamics and supplies technical support for accurately evaluting the safety of bridge.

在强涌潮河口区域，涌潮是一种比较剧烈且常见的水流运动。强烈的涌潮会对桥墩基础造成剧烈的冲刷和强烈的冲击作用，从而对桥墩基础安全构成潜在威胁。而目前，对于涌潮作用下桥墩局部水流结构及基础破坏模式尚无清晰的认识。本研究围绕强涌潮河口桥墩基础安全基本科学问题，通过野外观测、物理试验、理论分析和数值模拟等手段，对涌潮作用下泥沙运动规律、圆柱桥墩局部水流结构、河床渗流特性及局部冲刷特性进行深入研究，同时，基于OpenFOAM开源多物理场计算库，实现涌潮水动力场、河床渗流场与河床冲刷变形的耦合模拟，理清桥墩局部流场、土体渗流与河床冲刷之间的内在联系。揭示涌潮作用下桥墩局部冲刷机理。研究成果将丰富桥墩局部水动力及冲刷相关知识，也能为涌潮影响河口区域的桥梁工程的安全评估与建设提供技术支持。

在强涌潮河口区域，涌潮是一种比较剧烈且常见的水流运动。强烈的涌潮会对桥墩基础造成剧烈的冲刷和强烈的冲击作用，从而对桥墩基础安全构成潜在威胁。本项目采用涌潮水槽模型试验、数学模拟和理论分析方法，系统研究了涌潮作用下泥沙运动特性、桥墩局部水动力特性、海床渗流特性及局部冲刷特性。本项目取得的主要成果总结如下：（1）揭示了涌潮作用下泥沙悬浮规律并建立了相关的涌潮含沙量垂线分布经验公式。（2）探究了波状涌潮及旋滚涌潮条件下孔隙水压力垂向分布规律及渗流水力梯度变化规律，波状涌潮情况下海床表面土体受到向上渗流力作用，易于泥沙起动，而旋滚涌潮情况下海床表面土体则受到向下的渗流力作用，对泥沙起动有一定的抑制作用。（3）基于边界生成法，建立了涌潮精细化三维水动力数值模型，结合物理实验揭示了涌潮压强及受力时空分布规律。（4）通过开展桥墩局部冲刷试验，揭示了涌潮作用下桥墩局部冲刷特性，建立了涌潮作用下桥墩冲刷深度经验公式。（5）假定海床为刚性多孔介质，建立了考虑了渗流的涌潮作用下圆柱桥墩局部冲刷模型，初步探讨了涌潮渗流对桥墩冲刷影响的贡献度。