Study on spudcan reinstallation next to a footprint using large deformation finite element method

Abstract

Safety problems may occur to the jack-up rig when it is installed near the old footprint. In this study, three-dimensional large deformation finite element simulations using the Coupled Eulerian–Lagrangian (CEL) method have been carried out on the spudcan–footprint interaction problem. The correctness of the CEL method is verified through comparison with existing centrifuge tests. Uniform and non-uniform clays with different shear strength profiles encompassing the typical strength range of practical interest are considered as the subsea soil. The principle of thermo-mechanical coupled analysis is provided, after which this method is used to realize the updating of clay strength profiles in non-uniform clays. The influences of initial penetration depth, offset distance and shear strength profile on horizontal and moment loads are investigated. Distributions of soil load on the spudcan are presented, and their effect on the resulted inclined loads during spudcan reinstallation is analyzed. In both uniform and non-uniform clays, two peak values are obtained on the horizontal and moment load profiles during the reinstallation near the footprint. The relationship between the normalized maximum value of the horizontal load and initial penetration depth is described as a combination of linear and quadratic equations. While for the peak moment load, the offset distance is the main influencing factor. Finally, failure mechanisms of the surrounding soil during the penetration influenced by the footprint are discussed by defining four failure mechanism stages.