Numerical modelling of sand plug formation during punch-through of a spudcan footing

Abstract

Jack-up vessels are widely used within the offshore industry both to service oil and gas platforms, and more recently also for installation of wind turbine generators and their foundations. When a jack-up vessel jacks next to an existing structure, the soil displacements induced by penetration of the spudcan footings of the jack-up may lead to loading and deformation of the structure. In order to assess this loading, an accurate understanding of the flow of soil around the penetrating spudcan is required. Spudcan penetration in layered soils provides additional complexity compared to uniform ground conditions. This paper focuses on the case of sand overlaying clay, where a sand plug can form under the spudcan base during punch-through. The bearing pressure of the spudcan and deformation patterns in the soil adjacent to the spudcan are modelled in a finite element model using Plaxis 2D with updated mesh formulation to allow for the modelling of large soil deformations. The results are found to provide a reasonable match with displacement measurements from centrifuge tests, albeit with larger difference for derived bearing pressure. Hence, the developed model can be used to model soil displacements induced by spudcan loading in an accurate and computationally efficient manner.