On Cubic Spudcan Deep Penetration in Dense Sand Overlying Non-Uniform Clay

Abstract

Installing spudcans for jack-up rigs in a layered seabed with an interbedded strong-over-soft layer is challenging in the offshore industry due to possible punch-through failure. The methods currently used to predict punch-through failure mainly focus on generic spudcans, usually ignoring the geometric features of the spudcan. The aim of this study is to determine whether the punch-through potential of a generic spudcan is applicable to a cubic spudcan of a BH12# jack-up rig installed in dense sand overlying non-uniform clay. We conducted a series of large deformation finite element (LDFE) analyses on dense sand overlying non-uniform clay using a generic spudcan and a cubic spudcan. The thickness of the sand layer was also varied to cover a range of practical interest. The special cubic spudcan was found to be less likely to induce punch-through failure on sand-over-clay sediments compared with the corresponding generic spudcan. Herein, we propose a method to predict the degree of post-peak bearing reduction, which is a key measure of the severity of punch-through failure.

Keywords

• jack-up rig
• cubic spudcan
• punch-through failure
• dense sand overlying non-uniform clay
• coupled Eulerian–Lagrangian