Key Technologies for Deep-water Trestle Bridge Construction in Complex Sea Areas
The main bridge of the Xihoumen rail-cum-road bridge on Ningbo-Zhoushan railway is(70+112+406+1 488+406+112+70)m cable-stayed suspension cooperative system bridge,which is currently the world's largest rail-cum-road bridge.the water depth of 5#and 6#piers is nearly 60 m,the maximum flow velocity with a 20-year return period is 3.18 m/s,the design basic wind speed with a 20-year return period is 39.5 m/s,the average wave height with a 20-year return period pier is 3.48 m,and there is no overburden near 5#pier.In view of the characteristics of complex sea areas such as water depth,rapids,strong winds,wave height,and bare rocks,the deep-water trestle bridge composed of the jacket foundation+the superstructure of No.I beam of the bridge was adopted,which solved the problems of difficult construction of the ordinary"fishing method",low overall stiffness,and inability to resist the action of large water flow and wave force.Taking the 5#—6#pier trestle bridge as an example,the key technologies such as jacket production,transportation,installation and superstructure construction in the construction process of jacket method was elaborated in detail in this paper.The results show that the deep-water trestle bridge of the jacket foundation+the superstructure of the No.I beam of the bridge has large overall stiffness,good stability,and significant effect on resisting wave force.And the installation time is short,the positioning accuracy is high,which can reduce offshore operations,improve work efficiency,and reduce safety risks.
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