Abstract: The main disease of pile foundation bridges is the decrease in the height of pile-soil interaction caused by foundation scour, which reduces the bearing capacity of the pile foundation. In traditional scour numerical model, it is assumed that the sediment in the upstream riverbed is not initiated and the water flow remains clear without sediment, ignoring the influence of suspended mass on scour depth in actual turbid water environments. In order to predict the scour evolution of the bridge submerged foundation in turbid water environments, the series model extension method was employed on the basis of the computational fluid dynamics method, a numerical calculation model for multi-phase live-bed scour was established with the combination of the theory of sediment initiation and transport. Compared with Melville classical scour test, the accuracy of the numerical model was verified. Taking a typical pile foundation bridge as the research object, the changes in local scour depth and the final equilibrium scour depth of the bridge foundation were predicted and compared with empirical formulas and field scanning results. The research results show that the empirical formula used in the specification is conservative in calculating the scour depth. The proposed multi-phase simulation method of the live-bed scour evolution can provide a more accurate prediction of the scour depth, which is closer to the field scanning results.

Key words: bridge engineering; foundation damage; live-bed scour; riverbed evolution; numerical simulation; field scanning

摘要： 桩基础桥梁的主要病害为因基础冲刷导致桩土作用高度减小，使桩基承载能力降低。传统冲刷数值模型中，假定上游河床泥沙未启动，水流保持清澈无泥沙，忽略了实际浑水环境下悬移质对冲刷深度的影响。为预测浑水环境下桥梁水下基础冲刷演变，基于流体力学方法，采用系列模型延伸法，结合泥沙起动、输运理论构建立多相流动床冲刷数值计算模型，与Melville经典冲刷试验对比，验证了数值模型的准确性。以某座典型的桩基础桥梁作为研究对象，预测桥梁基础局部冲刷深度变化及最终平衡冲刷深度，并与经验公式和实地扫测结果进行对比。研究结果表明：规范采用经验公式对冲刷深度计算较为保守，笔者提出的多相流基础动床冲刷演变模拟方法可以提供更准确的冲深预测，与实地扫测结果更为接近。

关键词: 桥梁工程；基础损伤；动床冲刷；河床演变；数值模拟；实地扫测