Numerical investigations on the installation of dynamically installed anchors with attached mooring line

Dynamically installed anchors (DIAs) are considered to be one of the most efficient mooring solutions for taut mooring systems. During their installation, DIAs are released from a certain height above the seabed and reach high velocities (up to 35 m/s) before impacting the seabed. However, a potential issue with DIA installation is that the anchor may not remain completely vertical during descent, resulting in the anchor impacting the seabed at an oblique angle and a significant reduction in holding capacity. To address this issue, this paper proposes a new numerical model for DIAs with attached mooring lines, which can consider the forces acting on anchors and mooring lines. A total of 176 numerical simulations were conducted under different initial configurations of mooring lines, and 128 simulations were performed, taking into account the influence of the horizontal motion of Anchor Handling Vessels (AHV). By comparing the velocity, embedment depth and tilting angle, possible combinations of the mooring line configurations in situ were back-analyzed. The simulations results show that the presence of the mooring line significantly reduces the final penetration depth of the anchor, and that the proposed installation model accurately simulates the change process of velocity and displacement during installation. Additionally, when DIAs impact the seabed at an inclined state, the tilting angle will increase due to soil resistance on the anchor tip. Finally, the initial state of the DIA at release is influenced by the horizontal motion of the AHV, which can influence the tilting mechanism of the DIA.

Automated summary

This paper proposes a new numerical model for dynamically installed anchors (DIAs) with attached mooring lines, which can consider the forces acting on anchors and mooring lines. A total of 176 numerical simulations were conducted to analyze the anchor installation under different mooring line configurations, and the results showed that the presence of mooring lines significantly reduces the penetration depth of the anchor. The research findings provide guidance for a better understanding of the working principle of dynamically installed anchors.