ABSTRACT
Previous studies have shown that the upward sleeve helps to enhance the spudcan bearing capacity in clay deposits. However, it is also concerned that this novel leg design may cause other problems such as extraction difficulty, the extraction resistance is demonstrated to increase with the increase of spudcan operation period. To address this problem, centrifuge model tests are performed herein to identify the upward sleeve effect on the post-consolidation extraction resistances of spudcan foundation in lightly over-consolidated clay. The centrifuge results show that compared with spudcan without sleeve, spudcan with square sleeve tends to yield a larger penetration resistance but lower maximum extraction resistance. This may be partially attributed to that the backfill soil during spudcan penetration is restricted outside the sleeve and the extraction resistance arising from the soil weight above the spudcan footing is hence reduced. This finding may demonstrate that including a sleeve at the lower part of the jack-up lattice leg with the same leg cross section area is feasible for offshore jack-up rigs, which will help to reduce the leg penetration without causing further extraction difficulty.
