A tension leg mooring system based on the three-dimensional potential flow and dynamic mooring theories is proposed to improve the hydrodynamic performance of a submerged platform. Frequency-domain and time-domain analyses are conducted using ANSYS AQWA while considering the shallow water effect, the draft of the submerged platform, and the mooring line and construction-related parameters. The response amplitude operators (RAOs) of the submerged platform are obtained. As the platform is submerged into the water, the heave and roll responses and their natural motion periods decrease, improving the wave stability and adaptability of the platform. The dynamic responses of the submerged platform during the working condition are analyzed, focusing on the motion of the platform at different locations. Time-domain simulations of the tension leg mooring system are conducted, considering the coupling effect of the heave and roll. The maximum heave values are obtained for different wind, wave, and current conditions to reduce the heave and roll motion of the platform. When the leveling machine is located at the corner of the platform, the limit conditions of the environmental parameters must be considered to meet the leveling accuracy requirements. Parameter optimization is conducted for the draft of the platform and the pretension force of the tension leg under different conditions to improve the leveling accuracy. The optimized mooring has a leveling accuracy of ± 40 mm. This study provides an approach to determine the parameters of the tension leg mooring system for the design of shallow water construction platforms for water transportation engineering.
Immersed tunnel engineering is used in road construction to cross rivers and straits. It has been used since the beginning of the last century and is widely applied (Lunniss and Baber 2013). Due to the advantages of a shallow buried depth, low foundation requirements, and a short construction period, immersed tunnel design has been used by many developed countries globally. This technology has high design and construction requirements. The foundation is a crucial aspect of immersed tunnel construction because it affects the deformation stability during construction and operation. An increasing number of tunnels have been constructed using the pre-bedding method (Hu, Xie et al. 2015). This method was used in combination with a specially designed ship to install the foundations of the Busan-Geoje Link (Janssen, de Haas et al. 2006) and Hong Kong-Zhuhai-Macao Link (Hussain, Wong et al. 2011). Leveling ships are designed to reduce the impact of the wind, waves, and current on the leveling accuracy of the foundation and are used for three reasons: installing the pile legs, lifting the leveling structure above the water surface during construction, and reducing the impact of waves (Hu, Xie et al. 2015). The feeding structure and leveling structure are separated, and leveling is achieved by the underwater leveling equipment to reduce the influence of waves and improve the leveling accuracy. Leveling platforms with a semi-submersible hull are required to reduce the influence of waves.
