Design of submerged floating tunnel subjected to solitary wave impact using SPH method

The submerged floating tunnel (SFT) is a promising underwater transportation solution for deep-water crossings. Existing designs primarily address ordinary wave actions, while tsunami impacts on SFTs remain understudied despite the threat posed by tsunamis to nearshore infrastructure. This study employs a smoothed particle hydrodynamics (SPH) model to investigate the hydrodynamic characteristics of SFTs under a tsunami-like solitary wave impact. The SPH model is first validated against published experimental data. Parametric studies then examine the effects of cross-sectional shape (CSS), buoyancy-weight ratio (BWR), and mooring cable angle (MCA) on kinematic motions and mooring forces. Results show that the SFT exhibits coupled sway, heave, and roll motions. Compared with an elliptical CSS of equal area, a circular CSS reduces the maximum motion amplitudes by between 4.2% and 53.2% and the maximum mooring forces by 41.7% and 46.8%. Increasing the BWR from 1.2 to 1.4 reduces the maximum motion amplitudes by between 12.9% and 53.8% and the maximum mooring forces by 6.9% and 45.4%. Lowering the MCA from 60° to 45° reduces the maximum motion amplitudes by between 19.0% and 48.1% and the maximum mooring forces by 11.3% and 33.3%. These findings provide guidance for the design of SFTs subjected to tsunami impacts.