A plasticity model for predicting the load displacement behaviour of a typical spudcan foundation for offshore jack-up platforms under combined vertical, horizontal, and moment loading in soft clay is presented. Results from geotechnical centrifuge experiments of a spudcan embedded vertically to 0.7, 1.0, and 1.45 footing diameters are described. Augmented with finite element results, these centrifuge experiments are used to evaluate the plasticity model components. As a result of soil backflow on top of the spudcan, enhanced combined bearing capacity was measured and this is reflected in increased yield surface size. A tensile vertical load capacity is also incorporated. The excellent predictive capabilities of the model are demonstrated by retrospectively simulating a selection of centrifuge tests.