消减波浪荷载的桥梁沉箱基础外形设计研究

Research on Shape Design of Bridge Caisson Foundation to Reduce Wave Load

基于波浪场中动水压强的空间分布特征,提出了消减跨海桥梁沉箱基础波浪荷载的方法:一是优化基础横截面外形,调节基础横截面外轮廓不同位置波浪压力的相位差,减小基础所受到波浪力和力矩;二是优化基础竖截面外形,减小水面附近波浪能量集中区域的截面尺寸,增大靠近海床面区域的截面尺寸,将基础下部的迎浪面设置为外伸斜面,利用斜面上波浪压力竖向分力产生的力矩抵消部分水平分力产生的力矩,从而消减桥梁基础上的总波浪力矩。对于大尺度矩形和圆端矩形截面的桥梁深水沉箱基础,基于势流绕射理论和边界积分方法进行分析,结果表明,相比于矩形截面,采用圆端矩形截面可有效减小基础的波浪力和力矩;相比于上下等截面的基础,采用下部迎浪面设置外伸斜面的基础可以大幅减小基础的波浪力矩。研究成果可为跨海桥梁深水基础设计提供参考。

Based on the spatial distribution characteristics of hydrodynamic pressure in the wave field,methods of reducing the wave load on caisson foundation of sea-crossing bridge are proposed.The first is to optimize the shape of foundation cross section,adjust the phase difference of wave pressure at different positions of the external profile of the foundation cross section,which can reduce the wave force and moment on the foundation.The second is to optimize the shape of foundation vertical cross section,reduce the section size near the water surface while increase the section size near the seabed,and set the surface facing the waves at the lower part of the foundation as an overhanging inclined plane,which can make use of the moment generated by the vertical component of the wave pressure on the inclined plane to offset the moment generated by part of the horizontal component,and thus the total wave moment on the bridge foundation is reduced.Based on potential flow diffraction theory and boundary integral method,the analysis of large scale rectangular and circular end rectangular bridge deep caisson foundation is carried out.The results show that compared with the rectangular section,the circular end rectangular section can effectively reduce the wave force and moment on the foundation.Compared with the foundation with the same cross section above and below,the wave moment of the foundation can be greatly reduced by setting the surface facing the waves at the lower part of the foundation as an overhanging inclined plane.The research results can provide reference for the design of deep water foundation of sea-crossing bridge.