围堰明挖法多层越江通道工程深基坑方案选型的技术经济分析

Technical and Financial Analysis on Deep Pit Excavation of a Multi-storey Cross-river Passenger Project using Cofferdam Construction

围堰明挖法是通过开挖不同规模的基坑,实现结构布置复杂的水下隧道的有效手段。海口文明东越江通道采用围堰明挖法施工,利用多层隧道结构实现地下互通式立体交叉,基坑开挖最大深度达22.6 m,在匝道节点处的基坑存在“高低坑”的情况。针对此基坑结构布置特点,在基坑工程技术经济性分析原则的基础上,对坑中坑开挖和全断面开挖方案进行比选研究。结果表明:坑中坑开挖方案可在确保工程质量的前提下,降低基坑总造价,取得很好的社会及经济效益。相关经验可供类似工程参考。

The cofferdam method is an effective way of constructing underwater tunnels with complex structural arrangements by excavating different scales of foundation pits.The Wenming East Cross-river Passage project in Haikou,China,adopted the cofferdam method to build a local multi-story tunnel involving underground grade separation,where the maximum depth of the foundation pit is 22.6 m and pits with varying depth sit at various ramps.According to structural layout characteristics of this foundation pit,based on the technical and economic analysis principle of foundation pit engineering,comparison and selection of pit in pit excavation and full section excavation schemes are studied.The results show that the pit with an internal pit excavation scheme can effectively reduce the total cost of the foundation pit and achieve significant social and economic benefits while ensuring quality and security of the project.Relevant experience can be used as a reference for similar projects.