Behaviour of vertically loaded spudcan foundations under sustained uplift

Abstract

Extracting a spudcan foundation in clay is frequently challenging and time-consuming due to the substantial pull-out force needed to overcome the soil breakout resistance. The actual mode of spudcan extraction in the field is that the spudcan is extracted under a constant force provided by the buoyancy of the hull rather than the undrained displacement uplift. This paper investigates the behaviour of the vertically loaded spudcan foundations under sustained uplift through centrifuge experiments and coupled pore fluid-effective stress large deformation finite element simulations. The finding indicates that the threshold sustained load of spudcan failure is approximately 60% of the undrained breakout resistance. When the sustained load is higher than this threshold, the uplift displacement of the spudcan is similar to the soil creep curve, characterised as accelerating at the beginning, then entering a stable stage, and finally tending to accelerate uplift until the spudcan pull-out failure. The failure mechanisms under different uplift modes are also revealed. Under sustained loading, the soil disturbance area increases with the sustained load, gradually manifesting local circulation around the spudcan. Total stress and pore pressure responses lie in the sustained consolidation status under various levels of sustained force.