A comprehensive two-dimensional (2D) time-domain numerical model is established to investigate the interaction of irregular waves and submerged structures with different sections. The model specifically focuses on the dual-lane submerged floating tunnel (SFT) designs, encompassing elliptical, twin-circular, and round rectangular sections. For the hydrodynamic analysis, we adopt the second-order potential flow theory, while for the mooring line simulations, we employ the slender rod theory, taking into account the entire hydrodynamic load acting on it. In the coupled dynamic analysis, the fourth-order Adams–Bashforth–Moulton method, Newmark-β method, and Newton–Raphson iteration scheme are utilized for the coupled motion equation of the floating body and the dynamic equation of the mooring riser system. Experimental free decay tests are conducted to determine the damping coefficients of various section shapes in different directions. Our analysis delves into the detailed motion responses and mooring tensions of the SFTs with different section forms under irregular waves. We compare and contrast these responses in both time and frequency domains, particularly focusing on movement trends. The elliptical section structure emerges as the most stable design based on our comparisons. These findings provide valuable insights for the selection of optimal section shapes for dual-lane SFTs.

Existing bollard force measurement methods have not yet been able to realise simple, accurate, and efficient measurements of the bollard force of a single ship’s cable. In this paper, an experimental study on the measurement of ship bollard force is carried out with reference to the calculation method of measuring the cable force of a diagonal cable. Based on the fundamental frequency method and the frequency difference method, a new comprehensive method is proposed to detect the fundamental frequency of cable vibration. A study on the identification of the cable condition based on the measured vibration data is also carried out. Experimental studies on the error rate of different data acquisition positions, excitation methods, excitation positions, wetted cables, different temperatures, and other influencing factors were conducted, and a new excitation method based on environmental excitation and artificial excitation was proposed. By analysing the calculated values of the vibration frequency method and the tensile values of the prototype test platform, it is concluded that the data acquisition position, excitation position, and excitation method have a small influence on the measured value of the ship’s bollard force, and the range of the error rate increases by about 1.5% under the wetting of the cable and ±2% under the low temperature (2 °C), with the integrated error range of −5% to 4%, and the error rate can satisfy the normal distribution well, and the measurement accuracy is corrected by correcting the length of the cable. The measurement accuracy is corrected by correcting the cable length. It is proved that the method has strong feasibility and applicability, and can effectively realise simple, accurate, and efficient measurement of ship bollard force.