Installation and bearing capacity of ring anchor for floating offshore wind turbine
Offshore wind farms are expanding into deeper waters, with floating wind capacity projected to reach nearly 270 GW by 2050 (DNV, 2023). Unlike fixed-bottom turbines, floating turbines rely on seabed anchors for station-keeping.
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Depending on the type of floaters and whether the mooring system is shared, the configuration of mooring lines can vary greatly, which will, in turn, affect the loads on the seabed anchors. Additionally, anchor selection for floating wind projects must consider the large scale of deployment, often involving thousands of anchors in a typical floating wind farm. Despite the development of various anchor solutions to date, there is still a need for more sustainable, efficient, cost-effective, and easier-to-install anchor solutions.
Deeply embedded ring anchor (DERA)
Inspired by suction anchors and suction embedded plate anchors (SEPLAs), an innovative deeply embedded ring anchor (DERA) has been developed for station-keeping of floating wind turbines. The DERA, a cylindrical anchor with open ends, is installed deeply using either suction or vibration. Its circular design enhances stability during installation and mitigates structural issues typically associated with SEPLAs. Once installed, the mooring line attached to the DERA is tensioned, causing the anchor to rotate or "key" into a position nearly perpendicular to the pullout direction. This keying process, similar to SEPLAs, results in higher soil resistance at greater depths due to the deep flow mechanism, thereby improving loading efficiency.
Objectives
The main objectives of this project are to understand the anchor behaviour during installation and operation phases, including:
- The force and trajectory of DERA during keying process
- The whole-lief in-place bearing behaviour
Methodology
A holistic approach, using both centrifuge and numerical modeling, will be employed to investigate DERA's response. Different dimensions and embedment depths will be tested during both keying process and under monotonic and cyclic operation loads. Numerical model, validated by experimental data, will be developed and used for parametric studies. In the end, a simple calculation model will be developed for predicting DERA response, which can be used in the integrated analysis of offshore floating wind turbines.
