Concept of Expandable Plate Anchor (ExPLA) for floating offshore wind and its evaluation through 1 g model tests

This paper introduces an expandable plate anchor (ExPLA). It is a novel anchoring system for floating wind turbines. The ExPLA is a plate anchor consisting of two plates connected by a hinge. It is installed on the seafloor in a folded state to minimize penetration resistance. When the hinge is pulled up, the folded plates expand horizontally and exhibit a high anchoring capacity. To evaluate the feasibility of this concept, 1 g tests were conducted using 1/100 scale models. The folded anchor model was embedded at three depths in its folded state and then pulled upward to verify whether it expands. The expansion process was observed directly using a visualization technique based on transparent quartz and refractive index matching. The test results demonstrate that anchors with specific geometries can expand as these are pulled out. The key observations identified the geometrical parameters: a back slope angle of at least 20° ensures successful expansion, whereas a dip angle over 20° reduces the pullout distance required for deployment. The theoretical considerations based on the moment equilibrium around the hinge are consistent with the experimental results and reveal the relationships among the earth pressure coefficients, frictional angles, and anchor geometry. Finally, the potential and limitations of the ExPLA as an anchoring system for floating wind turbines are presented.