Lateral limiting pressure on square pile groups in undrained soil

In this paper, the lateral limiting pressure on square pile groups in undrained soil is explored using two-dimensional finite-element modelling. A parametric study is conducted to assess the role of pile–soil adhesion, group size and pile spacing on group capacity and corresponding failure mechanisms. Results from the finite-element output show that large groups of closely spaced piles exhibit significant reductions in lateral capacity compared to equivalent single pile values. Significant variations in the load sharing across the group are also observed, with the corner piles experiencing loads up to 162% above the group average for a 25-pile group. A simplified closed-form design approach is developed using a modified Ramberg–Osgood formulation to predict the lateral group capacity. The proposed approach is shown to provide excellent agreement with the numerical results and a rigorous upper-bound prediction of a selection of field data and predictions determined using existing design guidelines