Influence of a Seabed Trench on a Taut Mooring Line

Taut mooring systems have become a prospective solution for the station keeping of offshore floating facilities in deep water. In such scenario, the associated anchor foundations may withstand substantial uplift loads. To maximize the holding capacity, it is common to attach the anchor chain to the suction caisson at 60 to 70 % of the embedded depth. However, new phenomenon has been observed, which may be a challenge to the integrity of mooring systems, such as the trenching of the seabed near the suction caissons of floating systems. It is unclear whether trenching will induce significant effect on the integrity of mooring systems. To evaluate the influence of the seabed trenching, where existing commercial codes have not covered, a numerical model has been developed in this study. Based on this developed model, numerical simulations have been conducted with and without considering the trenching effect at the seabed. It is found that the seabed trench has a limited influence on the tension at fairlead but has a significant influence on both the tension and the inclination angle at padeye.