ABSTRACT

The use of mobile jack-up rigs has significantly increased recently. A mobile jackup rig is typically supported by three to four independent legs where each leg is equipped with a footing known as “spudcan”. The spudcan is generally circular or polygonal in plan, with a shallow conical underside and a sharp or truncated conical tip. These days, the spudcan diameter can be in excess of 20 m. This type of foundation is not custom-designed for a specific site condition (Poulos 1988). As a result, the spudcans may experience very deep penetration during installation, particularly in soft seabeds. Under static preload, penetrations of 2 times spudcan diameter are commonly encountered in the field (Craig & Chua 1991). The deep penetration of spudcan in impermeable sediments often results in great difficulties in extracting the legs during its removal. The extraction can be time consuming which has economic consequence to the offshore industry.