Vertical Bearing Characteristic of Precast Hybrid Reinforcement Concrete Pipe Pile Considering Different End Forms in Stiff Silty Clays

Abstract

Precast prestressed reinforced concrete (PRC) pipe piles are increasingly adopted where static pressing is impractical; however, design-oriented evidence for their vertical bearing behavior in stiff silty clays remains limited. This study combines site static cone penetration tests with full-scale static load tests on hammer-driven PRC pipe piles with open-ended and closed-ended tips to clarify the governing load transfer mechanism and to improve capacity prediction for engineering design. The results show that pile tip configuration was a key factor influencing the bearing behavior of PRC pipe piles. Open-ended piles experience stronger driving-induced disturbance in the tested stiff clay layers, leading to lower mobilized shaft resistance than closed-ended piles. The responses of both pile types can be well described by a bilinear strain hardening load transfer relationship. Building on these observations, a three-stage load transfer function based on Rusch elastoplastic theory was developed and calibrated using test data, achieving improved ultimate bearing capacity prediction compared with conventional design parameter selection. For designs in stiff silty clay, median values of shaft resistance are recommended for open-ended piles; however, the upper-bound values of shaft and base resistances can be adopted for closed-ended piles. These recommendations should be applied cautiously beyond the tested pile configurations, soil properties, and installation method.