Horizontal Load Capacity of Multiline Ring Anchor in Soft Clay-Paper

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The study evaluates the horizontal undrained load capacity of a multiline ring anchor (MRA), a deeply embedded anchor proposed for floating offshore wind turbines. Three-dimensional finite element analyses were used to investigate how anchor aspect ratio, mooring-line attachment depth, and wing-plate configuration affect capacity in soft clay.<br /><br />Results show that wing plates can substantially increase the MRA’s ultimate horizontal capacity. For the configurations studied at the same projected area and load orientation, adding two wings increased maximum capacity by 83%; four wings provided a further 1% increase, and six wings a further 12%. Wing plates had little effect on the optimal load-attachment depth or on the anchor’s force–moment interaction characteristics. However, capacity varies with load direction: two-wing anchors are more sensitive to changing load angles than six-wing anchors.<br /><br />The MRA’s short length makes resistance at its top and tip more important than for conventional suction caissons, and capacity is particularly sensitive to where the load is applied. For the modeled uniform soil, optimal attachment is approximately at the anchor’s midpoint. The anchor’s deep embedment reduces the influence of the seabed surface, but numerical estimates of end resistance for short anchors remain uncertain and warrant further research.<br /><br />Overall, the analyses indicate that wing plates are an effective way to improve the load capacity of a compact MRA in soft clay, while further work is needed to establish reliable estimates of end effects.

Keywords

multiline ring anchor

horizontal load capacity

deeply embedded anchor

floating offshore wind turbines

finite element analysis

soft clay

wing plates

mooring-line attachment depth

anchor aspect ratio

end resistance