In this study, time-domain dynamic analysis of a submerged floating tunnel (SFT) is carried out under wave and seismic excitations to evaluate the safety of a train passing through a tunnel. The in-house program is modified to simulate dynamics of the SFT and the train. The equation of motion for the SFT is based on the rod theory, and the vehicle is modeled by the rigid-body dynamic method. Their interaction is based on the corresponding assumption and the simplified Kalker linear creep theory. To validate the developed program, the vertical response of the tunnel and the mooring tension under the moving vehicle load are compared with a commercial program, OrcaFlex, in the calm water condition. The designed SFT satisfies the safety criteria under given environmental loads.


A submerged floating tunnel (SFT), which is applicable to the deep-sea crossing, can be an innovative alternative to bridges and immersed tunnels. Many proposals and cases studies have been conducted in the world after Norway's first patent in 1923. Høgsfjord/Bjørnafjord in Norway (Engebretsen et al., 2θ17; Remseth et al., 1999; Skorpa, 1989), Funka Bay in Japan (Fujii, 1996; Lu et al., 2011), the Strait of Messina in Italy (Faggiano et al., 2001), Qiandao Lake in China (Martinelli et al., 2011; Mazzolani et al., 2008), Qiongzhou Strait in China (Jiang et al., 2018), and the Mokpo-Jeju SFT in Korea (Han et al., 2016) are the primary places where SFT constructions are or were considered. Unfortunately, there is no existing SFT structure in the world (Lee et al., 2017). However, similar deep-water and long-distance crossing designs, such as the 35.6-km-long Hong Kong-Zhuhai-Macao Bridge (Hu et al., 2015; Wang et al., 2018) and the 18-km-long Fehmarnbelt fixed link (Pedersen and Brandum, 2018), support feasibility of the SFT concept. Specifically, the Hong Kong-Zhuhai-Macao Bridge was constructed in 2018, and there are a lot of practical technologies, e.g., the waterproofness of the segmented joint (Lin et al., 2018d), outdocking, towing, and mooring of immersion (Lin et al., 2018b), including the experimental study of the towing technique (Lin et al., 2018c). These well-developed technologies can also be applied to the installation of the SFT.

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