Numerical investigation on reinstallation of jack-up unit with rectangular spudcan close to footprint

Abstract

This paper presents the jack-up unit reinstallation loads in clay when it has to be reinstalled near an existing footprint due to a previous installation and removal. Large-deformation finite element analyses are performed by using the coupled Eulerian-Lagrangian (CEL) method. A three-leg jack-up unit model is used for the global investigation of the spudcan-footprint interactions. The novel rectangular-shaped flat-based spudcan is considered. A detailed parametric study is carried out with varying influential factors including spudcan shape, offset distance and footprint shape. The effects of these factors are evaluated based on the magnitudes of induced bending moment, horizontal force, lateral displacement and rotation. Compared to the generic conical spudcan, the novel spudcan reduces the peak horizontal force, lateral displacement and rotation by 40%. But it has a larger bending moment at the spudcan level, due to the corner effect. It is found that the bending moment at the hull level position is 800% larger than that at the spudcan level. The flat-based spudcan is effective at decreasing footprint-spudcan interactions, reducing the loads on the leg by about 30%. The critical offset distance is found to be that the spudcan center is at the edge of the footprint.