Analysis of pile groups subjected to torsional loading

An analytical method is developed to analyse the torsional response of free-standing pile groups with rigid pile caps. The proposed approach captures the coupling nature of the torsional and lateral resistances in the problem. The general interaction between two identical piles subjected to lateral loads of equal magnitude but in arbitrary directions is first analysed by the use of Mindlin's point load solution. Then, the interaction effects on the horizontal displacement or rotation of one pile caused by the torsional or horizontal loading on an adjacent pile, i.e., torsional-horizontal interactions, are considered. Subsequently, the interactions among the individual piles are combined to obtain the overall torsional stiffness of the pile group as well as the load distribution within the group. The proposed approach is used to predict the behaviour of pile groups considering a range of group sizes, pile spacings, pile stiffnesses and pile slenderness ratios. Finally, the results of centrifuge model tests on 2 × 2 and 3 × 3 pile groups embedded in a loose sand bed are used to validate the proposed analysis method. The predicted pile group response and load transfer agree reasonably well with the test results.