Pile groups under axial loading: an appraisal of simplified non-linear prediction models

The settlement behaviour of vertically loaded pile groups has been the subject of an extensive body of research over the past two decades. In particular, this work has identified the over-conservatism associated with predictions of pile interaction derived from elastic theory and the corresponding amplification of group settlement relative to single pile values. Researchers have since redoubled efforts to refine settlement predictions for pile groups towards more economical design, largely through more rigorous treatment of soil stiffness non-linearity. Although foundation design engineers are increasingly employing three-dimensional continuum analyses to quantify pile interaction on a site-specific basis, simplified design approaches remain an integral part of preliminary foundation design. The purpose of this paper is to undertake a critical examination of these methods with a view to increasing their potential for take-up by foundation engineering practitioners. A database of simplified models has been collated for the prediction of non-linear pile interaction that exists within vertically loaded pile groups. These models are categorised as either analytical or empirical. The development, limitations and range of applicability of these models are explored in detail in the context of some published case histories.peer-reviewe