Experimental study on evaluating hydrodynamic performance of a novel submerged floating tunnel

A submerged floating tunnel (SFT) is susceptible to significant vibrational responses when subjected to intricate and challenging conditions of the deep-water ocean environment. This is primarily due to the inherent attributes of large flexibility and lower damping exhibited by flexible components of an SFT. To the best of the authors' knowledge, a majority of the current SFT concepts do not completely satisfy the motion-limit values mandated by the relevant standards. In this study, a novel SFT concept is introduced to bolster its vibration suppression capacity through the optimization of the superstructure and substructure by using a three-tube structure and a rigid truss structure, respectively. To evaluate the efficacy of the novel SFT, a comprehensive series of experiments are conducted in a wave-current flume to scrutinize the vibration suppression performance of this novel SFT configuration, juxtaposed against conventional design concepts. The insights are revealed based on a comparative analysis in both the time and frequency domains, encompassing a range of key parameters, and by performing a sensitivity analysis specific to the present model. The results show that the superposition effect of wave and current coupling has a lower impact on the motion response of the proposed SFT with higher mooring stiffness. Despite the increase in cable tension (1–2 times) for the proposed SFT design, the corresponding vibration suppression performance is found to improve by 3–9 times. This experimental investigation holds profound theoretical and engineering significance, as it contributes pivotal knowledge to the field of vibration suppression for the SFT.