Lateral bearing characteristic of pile groups in coral sand under combined loading

To investigate the influence of vertical load on the lateral pile-soil-pile interaction of pile groups in coral sand, a series of model tests on 2 × 2 pile groups were conducted in this study. The experimental program involved detailed measurements and analyses of load-displacement responses, bending moments, tilting angles of pile cap, lateral displacements, variations in horizontal earth pressure, and mobilized lateral soil resistance. Special emphasis was placed on the degradation of soil stiffness due to shadowing effects, edge effects, and vertical stress redistribution. Results demonstrate that vertical loads significantly enhanced the lateral bearing capacity and reduced the rotation angles of pile cap, improving the overall stability of the pile group. Vertical loading can improve the lateral response of pile groups, particularly benefiting the leading pile, which exhibited greater p-y responses and mobilized higher soil resistance in shallow layer. Additionally, derived p-y curves and p-multipliers confirmed increased soil resistance for the leading pile, with the p-multiplier exceeding 1 under higher vertical loads. These findings underscore the necessity of accounting for both vertical loading effects and the unique properties of coral sand in the design of offshore pile group foundations.