山区公路纵向桥段水流形态及桥墩局部冲刷特征研究

A longitudinal bridge has great influence on the river flow form in mountain area, which can easily cause local scour of the piers. This is related to the bridge safety. This application is to explore the characteristics of the flow form and the local scour of the piers of longitudinal bridge sections of highway in mountain area. To reveal the influence of the piers on the flow form and the local scour characteristics of the piers is other intention. The research method is to combine theoretical and model experiments. Based on the field investigation, main factors that impact the erosion and deformation of the riverbed will be analyzed. According to the orthogonal fixed-bed model experimentation, influence of the longitudinal piers on the flow characteristics will be explored. Through orthogonal live-bed model experimentations, the types and characteristics of the whirlpool system around the bridge piers will be revealed. The mechanism, depth and range of the local scour of pier will be analyzed. The local scour characteristics of the pier in the longitudinal bridge will be revealed. On the basis of those investigation and experimentations, method of determining the local scour depth and the relevant characteristic parameters of the longitudinal piers will be proposed with a view to filling the gaps in theoretical research in this field. The results can lay the theoretical foundations for predicting river bed deformation and protecting local scour of the piers in the longitudinal bridge sections of highway in mountain areas.

纵向桥方案对山区河流水流形态影响极大，极易造成桥墩局部冲刷，关系到纵向桥结构的安全。本项申请拟以山区公路纵向桥工程为背景，探索山区公路纵向桥段水流形态特征及桥墩局部冲刷特征，揭示纵向桥段桥墩布设方案对水流形态特征及桥墩局部冲刷特征的影响规律。研究方法拟以理论与模型试验并重。通过实地调查，分析确定纵向桥段河床冲刷变形的主要影响因素；通过多因素多水平定床正交模型试验，探索纵向桥段桥墩布设方案对水流形态特征的影响规律；通过多因素多水平动床正交模型试验，揭示纵向桥墩绕流漩涡体系类型及特点，探索纵向桥墩局部冲刷机理、冲刷深度及范围的特征，揭示纵向桥段桥墩布设方案对桥墩局部冲刷特征的影响规律，提出纵向桥墩局部冲刷深度的计算方法和相关特征参数的确定方法，以期填补在这一领域理论研究的空白。研究成果可为山区公路纵向桥段河床变形预测及桥墩局部冲刷防护奠定理论基础。

本研究针对山区公路工程纵向桥段河道水流形态及桥墩局部冲刷问题，通过文献分析、实地调查等手段，运用主成分分析法提出了影响纵向桥段水流形态及桥墩局部冲刷特征的主要因素；运用多因素多水平室内定床模型实验及基于计算流体力学的数值模拟方法，研究了纵向桥跨径、桥墩布设形式、桥梁轴向与水流流向的夹角、桥墩直径等因素对顺直和单弯河道的流速、河床表面附近过剩切应力、河道水位等参数的影响规律；基于室内动床模型实验，研究了纵向桥跨径、桥墩布设形式、桥梁轴向与水流流向的夹角等因素对纵向桥墩局部冲刷深度、冲刷范围等特征的影响规律。研究成果可为山区公路纵向桥段河床变形预测及桥墩局部冲刷防护提供可靠的理论依据，尤其是对纵向桥墩局部冲刷深度的确定及防护设计，具有重要的理论意义和工程应用价值。

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