Comparison Study and Forensic Analysis between Experiment and Coupled Dynamics Simulation for Submerged Floating Tunnel Segment with Free Ends under Wave Excitations

This paper presents dynamic-behavior comparisons and related forensic analyses of a submerged floating tunnel (SFT) between numerical simulation and physical experiment under regular and irregular waves. The experiments are conducted in the 3D wave tank with 1:33.3 scale, and the corresponding coupled time-domain simulation tool is devised for comparison. The entire SFT system consists of a long concrete tunnel and 12 tubular aluminum mooring lines. Two numerical simulation models, the Cummins equation with 3D potential theory including second-order wave-body interaction effects and the much simpler Morison-equation-based formula with the lumped-mass-based line model, are designed and compared. Forensic analyses for mooring-line adjustments in the simulation are carried out in view of the best representation of the physical system. After that, the measured pre-tension distribution and system stiffness of twelve mooring lines are well reproduced in the numerical model. Subsequently, the dynamic responses and mooring tensions of the SFT are compared under regular and irregular waves. The measured and simulated results coincide reasonably well for both regular- and irregular-wave conditions.