Seafloor anchoring for platforms in the Messina Strait

Abstract

The importance of properly designing and selecting an anchor is key to reliable techniques for floating offshore platforms including power generation from marine currents. Numerous studies have demonstrated how the uplift capacity of embedment anchors is highly dependent on the soil properties and the anchor geometry. This work focuses in detail on the behavior of vertically loaded circular anchors to keep a floating structure stationary in the offshore environment. The main goal of this research was to find and evaluate an alternative to the foundations employed in the M. Eng. 2009/10 offshore project. The initial option consisted of drag embedment anchors and suction anchors as the foundations for the floating structure located in the Messina Strait that carries a horizontal-axis marine current turbine. Examining past theories and tests, and using dimensional analysis, we determined that circular plate anchors of 4.22 m and 2.72 m in diameter represent a good alternative design for the foundations of the front and back floating platforms. These anchors have an embedment depth-to-diameter ratio of 3 and a plate thickness-to-diameter ratio of 3%. Therefore, in comparison to the initial foundation options developed in the M. Eng. project, the solution with circular anchors has the advantage to reduce the overall dimensions of the anchors, reduce the material necessary for their manufacture, minimize the duration and cost of installation, and provide an efficient anchoring system independent of the local current direction.