This paper addresses the critical challenge of selecting suitable pile foundations in port engineering by systematically investigating the axial bearing behavior of large-diameter steel pipe piles and prestressed high-strength concrete (PHC) piles. The study integrates both numerical simulations and field tests within the context of the Yancheng Dafeng Port Security Facilities Project. A self-balanced static load numerical model for PHC piles was developed using Plaxis 3D, enabling the simulation of load-displacement responses, axial force transfer, and side resistance distribution. The accuracy of the model was verified through a comparison with field static load test data. With the verified model parameters, the internal force distribution of steel pipe piles was analysed by modifying material properties and adjusting boundary conditions. A comparative analysis of the two pile types was conducted under identical working conditions. The results reveal that the ultimate bearing capacities of the 1# steel pipe pile and the 2# PHC pile are 6734 kN and 6788 kN, respectively. Despite the PHC pile having a 20% larger diameter, its ultimate bearing capacity is comparable to that of the steel pipe pile, suggesting a more efficient utilisation of material strength in the latter. Further numerical simulations indicate that, under the same working conditions, the ultimate bearing capacity of the steel pipe pile exceeds that of the PHC pile by 18.43%. Additionally, the axial force distribution along the steel pipe pile shaft is more uniform, and side resistance is mobilised more effectively. The reduction in side resistance caused by construction disturbances, combined with the slenderness ratio (L/D = 41.7) of the PHC pile, results in 33.87% of the pile’s total bearing capacity being attributed to tip resistance. The findings of this study provide crucial insights into the selection of optimal pile types for terminal foundations, considering factors such as bearing capacity, environmental conditions, and economic viability.

Post-grouting techniques in pile foundations effectively improve the pile–soil interface conditions. Because of the complex mechanics of the pile–soil interface after grouting, the influence of grouting pressure and grouting amount on the shear performance under different depths of confinement are not yet fully understood. This paper employs a self-developed shear apparatus to conduct large-scale direct shear tests on the pile–soil interface, simulating the characteristics of distributed post-grouting with small spacing and multiple grout injections and systematically investigating the shear mechanisms of the pile–soil interface under various grouting amounts, grouting pressures, and normal pressure conditions. The results indicate that normal stress and grouting amount have a greater impact on the ultimate shear stress of the interface than grouting pressure. Under constant normal stress and grouting pressure, increasing grouting amount significantly enhances the shear strength and initial shear modulus of the interface. However, the improvement in mechanical properties with increased grouting amount diminishes as normal stress increases. Under different grouting and loading conditions, the cohesion and friction angle of the grouted pile–soil interface are significantly enhanced to varying degrees. The grout improves the mechanical properties of the interface by enhancing the effective cohesion, with the coefficient of shear strength enhancement ranging from 1.72 to 1.92. Furthermore, distributed post-grouted piles exhibit superior load-bearing deformation capabilities compared with traditional grouting methods, validated effectively in field experiments. The softening model and hyperbolic function model conform to the side resistance-displacement curves before grouting, whereas the hyperbolic function model better fits the side resistance-displacement curves after grouting. The research findings reveal the shear mechanisms of distributed post-grouted pile–soil interfaces, providing important references for theoretical studies on the bearing capacity of post-grouted piles.