Centrifuge tests on horizontal bearing characteristics of pile groups in coral sand

Coral sand is characterized by the unique properties different from conventional sediments. To investigate the horizontal bearing characteristics of 2 × 2 pile groups in coral sand foundation, a series of centrifuge model tests were conducted, focusing on the effects of pile spacing and vertical dead loads. In this study, the load–displacement responses, bending moments, lateral deflections, and axial force variations were measured. Additionally, soil resistance, p−y curves, and p-multipliers were calculated and analyzed. Results show that increasing pile spacing from 3 to 5D and 7D enhanced the bearing capacity of the pile group by 24.7% and 77.0%, respectively. Compared to the leading pile, the rear pile exhibited reduced bending moments, increased lateral displacements, and lower soil resistance and p-multipliers due to pile–soil–pile interaction and the shadowing effect. Furthermore, the applied vertical dead load amplified the lateral displacement and bending moments of pile due to the P−Δ effect while enhancing soil resistance and increasing p-multipliers through vertical compression. These findings provide valuable insights for future experimental and theoretical research on pile groups in coral sand foundations.