Experimental study on the hydrodynamic behavior for a novel compound anti-vibration submerged floating tunnel system

Anchor cable-type submerged floating tunnel (SFT) is susceptible to large amplitude vibration responses under wave-current excitations. This becomes a critical issue to the safety, stationarity, and driving comfort of SFT. In this study, a novel compound anti-vibration SFT system is proposed, featuring a three-tube SFT reinforced with a rigid truss and an external floating energy dissipation device with polyvinyl chloride (PVC) porous media. The hydrodynamic behavior of the proposed compound SFT system is experimentally explored and compared with that of conventional SFTs utilizing a large wave-current flume. Sensitivity analysis for the key parameters of SFT is conducted using hydrodynamic parameters (such as wave height and wave period), structural type, and structural parameters (draft depths). The results show that the proposed SFT system has excellent anti-vibration performance when compared to conventional SFTs, reducing over 10 and 60 times in translational and rotational motion, respectively. The proposed SFT system with the floating tank at half draft depth shows the best anti-vibration performance under different wave-current excitations. The proposed SFT system achieves excellent anti-vibration performance without increasing the burden on cable tension, solving a common issue in conventional anti-vibration methods. The findings offer valuable insights into the anti-vibration design and application of SFT.