Finite element analysis of mechanisms of pile group behaviour

Solutions are presented for the non‐linear load‐settlement behaviour of square‐configuration pile groups. The groups are represented by an equivalent axially symmetric model, and a non‐linear finite element is used to examine the mechanisms of group behaviour and their variation with pile spacing. It is shown that, at close spacings, the block failure mechanism occurs, with significant plastic zones being developed below the group and full pile‐soil slip only being developed along the outer piles. As the pile spacing increases, the failure mechanism gradually changes to the ‘single‐pile’ mode, whereby full pile‐soil slip occurs along all piles. Within the limitations of accuracy of the finite element solution, the values of group settlement ratio and efficiency are in reasonable agreement with values derived from existing theories.