Submerged floating tunnel (SFT or SFTB, submerged floating tube bridge) is a floating tube bridge, submerged at a defined position under the water level. In this study, four types of SFTs, such as shoreanchored, piersupported, pontoonstabilized, and mooring stabilized, are discussed. The main tubular structure of the SFTs can have several crosssection shapes and types, including dividing the carriageways into multipletubesystem, connected by transversal elements, to provide additional safety in case of fires and operability in case of accidents. Related guidelines for STFs are introduced. The International Federation of Structural Concrete has published, in 2020, a 〖WT５《TNR#I》〗Design Guideline for SFTBs〖WT５《TNR》〗 (〖WT５《TNR#I》〗fib〖WT５《TNR》〗 Bulletin No.96) to help the technical community with the design of solutions for SFTBs. The International Tunneling and Underground Space Association has published, in 2023, an 〖WT５《TNR#I》〗Owner's Guide to STFs〖WT５《TNR》〗 (〖WT５《TNR#I》〗Owner Guide〖WT５《TNR》〗) to help the infrastructure′s owners to understand when the SFT could be a competitive solution, especially comparing it to traditional tunnel solutions. Currently, the Norwegian national standards have been the first to include this structure in the bridge national handbook (2020). Furthermore, 21 cases/studies/designs/proposals of STFs are listed and the hot topics, including fluid structure interaction and impacts, are briefly introduced. The SFTs can reduce the main sea loads on the structure, the slopes of the tunnel and the connected structures, the length of the crossings, the disturbance to the undersea landscape, and the acoustic impact in the surrounding area. It is concluded that the growing attention on the topic of environment and the possibilities given by recent materials and technologies in reducing the climate impact will hopefully represent a new era of possibilities for the diffusion of this clever structure.

阐述了水下悬浮隧道（又称水下悬浮管桥）的概念； 探讨了悬浮隧道结构的4种支撑形式，即岸锚式、桥墩支撑式、浮筒固定式和锚索固定式，并对4种支撑形式的适用性进行了对比；对悬浮隧道的跨海形式及主隧道结构断面形式进行了讨论，分析了多管系统+横通道连通形式在火灾及事故发生时的安全性。介绍了国际上悬浮隧道的相关标准： 国际结构混凝土联合会（fib）在2020年发布了《水下悬浮管桥（SFTB）设计指南》（fib公告第96号），旨在为技术界提供水下悬浮管桥方案设计指南；国际隧道和地下空间协会（ITA）在2023年发布了《水下悬浮隧道（SFT）业主指南》，旨在向基础设施业主说明，水下悬浮隧道相比传统隧道的适用性；另外，挪威国家标准已率先将悬浮隧道结构纳入国家桥梁手册（2020）。梳理了悬浮隧道已有的理论研究，介绍了目前水下悬浮隧道比较热门的研究课题，比如流体-结构相互作用和冲击等。分析了水下悬浮隧道的优势，不仅能够减小主要的海洋荷载对结构的影响，而且可以降低隧道和相连结构的坡度，缩短穿越距离，保护海底地形以及减少对周围区域的噪声影响。随着人们对环境问题的日益重视，以及新材料和新技术为减少气候影响带来的机遇，悬浮隧道有望获得进一步的推广。