基于长期监测的桥梁基础冲刷深度预测模型及平面形态演化研究

To avoid the scour-induced failure of bridge infrastructures, a theoretical study of the bridge scour developments/trends in both depth and plane are significantly desirable, which can also be the theoretical principle during conducting bridge scour monitoring and establishing relative codes. However, the current study is manly based on the experimental data in the laboratory environments which is obviously different from the field environments of the most bridge infrastructures. The lack of complicated field information around the bridge scour makes the study object excessively ideal and simple, which would result in impractical (sometimes incorrect) results. In this proposal, the bridge scour in the real complicated field environments is theoretically studied based on existing long-term real-time scour data in bridges through the proposal applicant's own monitoring. Firstly, two databases, monitored scour database and predicted scour database, were established for a comparative study. Then using the parameter modification techniques, the existing formulas of bridge scour depth based on the experimental data can be improved or re-built for satisfying the field applications (complicated environments) on the most bridge infrastructures, which turns out a new prediction model of bridge scour depth. Parametric and sensitive analyses were also conducted combining the monitored data and finite element model to investigate the mechanism of bridge scour development in plane. A mathematical in-plane development model of the deepest bridge scour was finally obtained in terms of the field environmental parameters. The research findings form a good theoretical basis for forecasting the scour-induced disaster of existing bridges, designing bridge scour monitoring, and establishing relative codes, which is very desirable in solving the hydraulic problems of bridge structures.

桥梁基础冲刷深度准确预测并掌握其平面形态演化机理是避免桥梁基础冲刷灾害、制定合理冲刷监测方法及相应规范的重要理论基础。目前该方面研究主要基于模型实验数据，但实验室环境与桥梁基础所处真实环境差距较大，缺失实际桥址复杂(环境)信息导致研究对象过于理想化、单一化，研究成果难以实际应用。本项目基于申请人已有的桥梁基础冲刷长期监测数据，针对实际复杂环境中桥梁基础结构，分别建立冲刷深度监测、预测数据库，避免直接基于监测数据推导模型，而是对基于实验室数据的现有冲刷深度计算公式进行修正及补充，从而提出适用于实际复杂环境下的桥梁基础冲刷深度预测模型；同时采用监测数据与仿真模型进行参数及敏感性分析，探明冲刷最深位置平面形态演化机理，提出基于环境参数的桥梁基础冲刷最深位置平面形态演化模型。研究成果可用于实际桥梁基础冲刷灾难预报、监测方案设计及相应规范标准制定，对克服我国桥梁基础水利病害难题具有较高研究价值。

桥梁基础冲刷深度准确预测并掌握其平面形态演化机理是避免桥梁基础冲刷灾害、制定合理冲刷监测方法及相应规范的重要理论基础。目前该方面研究主要基于简单理论模型或理想实验数据，与桥墩所处真实环境差距较大，缺失实际桥址复杂信息导致研究对象过于理想、单一化，研究成果难以实际应用。本项目针对既有存在问题，分别提出三种桥梁基础结构三维冲刷的精细化分析方法：(1)针对河床提出基于动网格自更新技术的河床变形模拟方法；(2)针对水流-泥沙混合流提出基于欧拉多相流的桥墩周边流场数值模拟方法；(3)针对洪水季节常发的动床冲刷提出考虑悬移质的桥墩动床冲刷数值模拟方法。利用B.W.Melville经典试验，分别从冲刷坑形状、桥墩周边流场及冲刷坑深度等方面对本项目提出的精细化分析方法进行精度验证；从悬移质分布的角度定性验证所提出动床冲刷计算方法的合理性与准确性；利用精细化参数分析，确定不同冲刷环境参数对桥墩冲刷空间形态的影响。另外，本项目针对复杂环境下桥墩冲刷深度还提出两种实时监测方法：(1)基于布拉格光栅传感器的桥墩冲刷动态监测方法，该方法可准确监测包括冲刷后河床回填的全过程；(2)基于结构动力特征的桥墩冲刷状态识别方法，该方法可借助常规桥检项目对桥墩冲刷状态进行较为便利的定性、定量分析。本项目研究成果可用于实际桥梁基础冲刷理论分析、灾难预报、监测方案设计及相应规范标准制定，对克服我国桥梁基础水利病害难题具有较高的研究价值。