Simplified Analytical Method to Evaluate the Ultimate Uplift Capacity of Squeezed Branch Piles Validated by In Situ Full-Scale Tests

The deep soft clay layers typically exhibit low uplift skin friction in coastal reclamation areas. Squeezed branch piles (SBPs) demonstrate a superior interlocking behavior with the surrounding soil and enhance the uplift bearing capacity (UBC). However, determining the ultimate UBC of SBPs remains difficult due to the complex soil–pile interaction mechanism. In this study, a shear failure theory for the soil on the plates is established considering the dimensions and embedment depths of the branches and plates and the physical and mechanical properties of the soil layers in the coastal reclamation areas. A simplified analytical method for evaluating the UBC of branches and plates is proposed based on the shear failure theory and validated by the in situ full-scale tests of SBPs. The results indicate that the axial force along the pile shaft is transmitted from top to bottom and gradually attenuates, with abrupt changes occurring at the locations of branches and plates. Moreover, the uplift bearing capacity of the plates is at least 24% higher than that of the branches. The soil failure surface initiates at the plate and gradually develops upward, eventually forming a downward-opening parabolic shape when the plate is subjected to upward loading. The UBC of the branches and plates obtained using the simplified analytical method deviates by less than 10% from the measured values. The branches and plates exhibit a significant densification effect on the surrounding soil, enhancing the bearing capacity by approximately 93% compared to the investigation-based values in the clayey sandy gravel layer. This effect diminishes progressively with increasing depth. The simplified analytical method enables a rapid evaluation of the UBC of branches and plates, effectively reducing the material and time costs associated with in situ full-scale tests. Owing to its simplicity and strong applicability, the method demonstrates good potential for broader implementation and provides a valuable reference for future engineering practice involving SBPs.