Centrifuge model study on spudcan-footprint interaction

Abstract

Owing to its mobile nature, a jack-up unit may be installed at a site with existence of footprints left by the previous rig for workover. If a jack-up is installed in the vicinity of footprints, the spudcans have a tendency of sliding towards the footprints. To date, relatively few studies have been conducted to investigate this problem and no guidelines are available to ensure a safe installation. This has highlighted the need for a more systematic study. An extensive centrifuge model study was conducted to investigate spudcan-footprint interaction. Herein, a footprint is referred to a seabed condition with changes in physical profile (depression) and soil properties underneath it. In firmer clays, the interaction is dominated by the physical profile of the depression. In softer clays, spudcan-footprint interaction is found to be dominated by the shear strength variation of the soil beneath the depression. Furthermore, the degree of soil strength variation is found to change with time as excess pore pressures generated by the previous spudcan installation dissipate. Dimensional analyses are performed to generalize this complex problem.