Case study of spudcan punch-through in layered soil with interbedded thin stiff clay

Punch-through failure may occur when the spudcan is installed in layered soil, which can result in a detrimental effect to the jack-up unit and jeopardize personnel. This paper introduced a practical case of spudcan punch-through which occurred in a kind of multi-layer soil which has a thin stiff layer and a transition layer locating between soft layers. The existence of the transition layer blurs the difference of soil strength. To explore the failure mechanism set behind the field case, LDFE analyses were conducted with the Coupled Eulerian-Lagrangian (CEL) method. The results indicated that the failure of soil changes between three failure mechanisms of general shear, punch-through and squeezing with the penetration of spudcan. The transition point of failure mechanism can be identified through the depth of failure surface based on the LDFE results. According to the failure mechanism, a modified approach was set out in estimating the spudcan penetration resistance in the multi-layer soil, which matches the field data well on the basis of the soil strength obtained by laboratory element tests.