Effect of spudcan penetration on laterally loaded pile groups

Abstract

Engineering cases, where jack-up rigs with large-diameter spudcan foundations operate near a jacket platform supported by pile groups, are increasing. Therefore, the group interaction of lateral-loaded pile groups should be re-evaluated. A pile group analysis method that is able to evaluate the effect of spudcan penetration on the pile group interaction is proposed in this study. This method is based on the modified Poulos method and is universally used in current ocean engineering practices. The pile group interaction-induced additional pile head deflection of a pile group, when subjected to both spudcan penetration and the influence of another pile group, is initially determined by elastic analysis. Next, the nonlinear foundation beam (NFB) method is adopted to calculate the head deflection of an isolated pile, which we utilise to calculate the head deflection of the pile group after considering the effects of spudcan penetration. Finally, the Y multiplier is obtained by several pilot modifications of p-y curves of the isolated pile in the NFB model, whose variation during spudcan penetration indicates the effect that such penetration has on the pile group interaction. Predicted results were compared with those of the centrifuge model test, and further with numerical simulation results, in order to prove the validity of the method in analysing a free-head and a fixed-head pile group.