Spudcan penetration behaviour on a sloping seabed by numerical analysis and centrifuge modeling

Installation of a jack-up platform is challenging on a hard sloping seabed. The installation and pre-loading can generate large bending moments on the spudcan and hence in the legs. Consequently, it may reduce the safety of the whole jack up system. The ISO jack-up standard (ISO 19905-1, 2012) states that issues associated with positioning of spudcan on a hard sloping stratum shall be carefully considered. However, only few studies have been done on spudcan penetration resistance on a sloping seabed. This study aims to evaluate the spudcan penetration resistance on a sloping seabed by using numerical method. Three dimensional large deformation finite element (LDFE) analyses are performed to investigate the spudcan penetration behaviour on a sloping seabed. The foundation responses including failure mechanism, displacements, vertical and horizontal resistance calculated from the LDFE analyses are compared to a centrifuge modeling tests. It is observed that the spudcan penetration into the sloping seabed generates asymmetric stress distribution, which induces horizontal resistance and moment on the spudcan leg. The increase and decrease of the horizontal resistance is depending on the initial stress distribution under the seabed. Overall, the vertical and lateral penetration resistances from the centrifuge model testing and the numerical analysis present consistent trends. In addition, the failure mechanism are presented at the different stages during the spudcan penetration.