Effect of sleeves and skirts on mitigating spudcan punch-through in sand overlying normally consolidated clay

摘要

Punch-through failure of mobile jack-up rigs is still a main concern for spudcan foundations. Using centrifuge model tests and numerical modelling, this paper examines the mitigating effect of top-mounted sleeves and a downward skirt on spudcan punch-through in medium dense sand overlying clay. The findings show that the top-mounted sleeves and downward skirt are both useful separately for reducing punch-through distance. The top-mounted sleeve functions by interfering with soil backfilling above the spudcan and maintaining confinement to the sides. This results in an earlier recovery in penetration resistance and reduces the peak-to-trough drop in resistance. The downward skirt appears to mobilise the soil further ahead of the spudcan, which reduces the peak penetration resistance and increases the rate of post-trough recovery in penetration resistance. A combination of a top-mounted sleeve with a downward skirt appears to confer a smaller peak-to-trough drop in resistance and higher rate of post-peak recovery, and thereby a much smaller punch-through distance. The results would suggest that, compared with the downward skirt, the top-mounted square sleeve with a similar area ratio to the existing lattice leg is supposed to be a more effective option in mitigating spudcan punch-through failure.