Abstract

Footprints were left on the seabed due to previous operations, and the problem of the spudcan-footprint interactions gradually becomes one of the major concerns of jack-up unit installation. The spudcan is subjected to eccentric loading conditions, which can lead to structural failure and the overturn of the jack-up unit. This paper reports the global behavior of the three-legged jack-up unit with a novel rectangular-shaped spudcan when it needs to reinstall near an existing footprint. The coupled Eulerian-Lagrangian (CEL) approach was used. A simplified three-legged jack-up unit model was developed and the flexible stiffness between the hull and legs was considered. The free-rotation heading and force-controlled loading conditions were also adopted. The bending moment distribution along the legs, horizontal force and the overturn of the jack-up unit are discussed to assess the potential of the jack-up unit sliding toward the footprint center. The critical offset distance was found at 0.3D and an offset distance of at least 1 times of the spudcan diameter is able to diminish influence of the footprint. The ability of the novel rectangular large spudcan with a flat base is shown to be effective at easing spudcan-footprint interactions, compared with generic circular spudcan.

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