公铁合建跨海桥梁裸岩区深水基础设计

一公铁合建跨海大桥跨越8万t级航道,采用(1 050+980)m双悬索桥结构。桥址区建设条件复杂,水深45 m,最大潮差6.29 m,最大设计流速3.27 m/s。主通航孔小里程侧主塔墩基础位于裸岩区,是该桥设计的关键。通过对比圆端形设置沉井、圆环形设置沉井、钻孔桩基础3种基础形式,推荐主塔墩基础采用圆端形设置沉井基础。在确定了持力层、海床防冲刷措施、基坑开挖方案的基础上进行圆端形设置沉井基础的结构设计及检算,并细化钢沉井浮运及施工组织方案。结果表明:圆端形设置沉井基础在施工难易程度、受力合理性、造价等方面均存在较大优势,适用于该桥裸岩桥址区域。

Design of Deep Water Foundation in Bare Rock Area for Sea Crossing Bridge Jointly Constructed by Highway and Railway

A sea crossing bridge jointly constructed by highway and railway spans 80000 DWT waterway,and adopts structure scheme of(1050+980)m double suspension bridge.The construction conditions of the bridge site are complex,the water depth is 45 m,the maximum tidal range is 6.29 m,the maximum design velocity is 3.27 m/s.The main tower pier foundation at the small mileage side of the main navigation hole is located in the bare rock area,which is the key to the bridge design.By comparing the foundation forms among open caisson with circular end,open caisson with ring and bored pile foundation,it is recommended that the open caisson foundation with circular end should be adopted for the main tower pier foundation.Based on the selection of bearing stratum,anti-scour measures of seabed and excavation scheme of foundation pit,the structural design of open caisson with circular end was carried out,and the structural checking calculation was implemented.The floating transportation and construction organization scheme of steel open caisson were refined.The results show that the open caisson foundation with circular end has great advantages in construction difficulty,stress rationality and cost,which is suitable for the bare rock bridge site area of this bridge.