Lateral bearing characteristics and p-y model of single pile in coral sand considering effect of vertical load

In offshore engineering, the combined vertical and lateral loading is the most critical load-type of pile while in service. Given the unique mechanical behavior of coral sand, a series of model tests was conducted in this study to investigate the influence of vertical load on the lateral bearing behavior of single piles embedded in coral sand. The load-displacement relationships, bending moments, inclination angle of pile shaft, changes in horizontal soil pressure, and pile end resistance were measured and analyzed. Test results show that the presence of vertical load significantly improves the lateral bearing capacity of piles in coral sand; however, the improvement effect exhibits a clear trend of initial enhancement and then reduction with the increase in vertical load. Under vertical-lateral combined loading, measured bending moments, inclination angles, and lateral soil pressure change were consistently lower than those under pure lateral loading due to the vertical compression effect, and the lateral soil resistances ( p ) under combined loading were significantly higher than those under pure lateral loading. Furthermore, the applicability of these existing p-y models was systematically evaluated, and a modified p-y model was proposed by incorporating the influence of particle size and load type. These findings provide valuable insights into the design and construction of piles subjected to complex loading conditions in coral sand environments. • Lateral response of single pile under combined loading in coral sand was investigated. • Vertical load can enhance lateral bearing capacity, but beneficial effect first increases then decreases with load level. • Combined loading reduces pile bending, rotation, and soil pressure variations via vertical compression effect. • A modified p-y model with vertical load and particle size effects was proposed and validated.