Experimental study on the hydrodynamic behavior of a multi-segment submerged floating tunnel under wave action

This paper presents a hydroelastic model test of a multi-segment submerged floating tunnel (SFT) at a geometric scale ratio of 1:50, in which the displacement response and tether tension characteristics of the structure under regular wave action are systematically investigated and compared with numerical simulations. The results show that parametric resonance is excited when the incident wave frequency approaches twice the SFT's sway and roll natural frequency. Under this resonance condition, both the sway and roll motions are dominated by the half-wave-frequency component, while the heave response has its primary frequency near the wave frequency together with a pronounced 1.5 times wave-frequency component. Moreover, parametric resonance leads to a notable increase in the amplitude of dynamic pressure at the measurement point on the wave-facing side of the tunnel tube. During resonance, the tether tension is governed mainly by the direct wave excitation and the sway-wave coupling, rather than by the large sway displacements themselves. The longitudinal deformation pattern of the free-boundary truncated model under wave action differs markedly between the horizontal and vertical directions, and the boundary condition directly governs the location at which the maximum structural deformation occurs.