In this paper the installation process of spudcan foundations into sand overlying clay is simulated using the Coupled Eulerian-Lagrangian method (CEL). Extended hypoplastic models are used to simulate the soils: the sand is simulated using the hypoplastic model, whereas the underlying clay is simulated using the visco-hypoplastic model. The hypoplastic model is well suitable to describe the nonlinear and inelastic behavior of granular soils. Typical sand characteristics like dilatancy, contractancy and different stiffnesses for loading and unloading can be modeled. The visco-hypoplastic model describes the mechanical behavior of the cohesive soils allowing for viscous effects, i.e. creep, relaxation and rate-dependence. The numerical model is validated against the experimental results of a centrifuge model test. The bearing capacity curve as well as the velocity field from the numerical simulation is compared with the centrifuge model test results. The failure mechanisms of the spudcans on dense sand overlying clay are revealed by illustration of the development of the shear band. With use of the validated numerical models, the influences of the consistency stated of sand on the bearing capacity as well as the failure mechanisms are investigated.
Offshore jack-up rigs are often used in deep water for oil drilling and gas well operations. The understanding of the failure mechanisms of oil underneath spudcan foundations is not sufficient, when a spudcan is penetrating into the layered seabed. In recent years, the use of numerical methods may be a helpful tool to predict the bearing capacity of foundations. In order to overcome the mesh distortion problems some numerical methods, e.g. Arbitrary Lagrangian-Eulerian method (ALE), Coupled Eulerian-Lagrangian method (CEL), have been developed. An ALE approach has been implemented by Hu and Randolph (1998a, b) in the finite element code AFENA and called Remeshing and Interpolation Technique with Small Strain (RITSS).
