Centrifuge modeling of penetration behavior and bearing characteristics of open-ended and closed-ended piles in saturated sand

Centrifuge model tests were conducted on two model piles with identical dimensions to investigate the penetration behavior and bearing characteristics of open-ended and closed-ended pipe piles in saturated sand. The experiments sequentially simulated the installation process followed by static compressive and uplift static loading tests. A monitoring system capable of measuring the soil plug height inside open-ended piles under elevated gravity conditions was developed and validated. The formation mechanism of soil plugs during installation was examined, revealing that the soil plug height initially increased proportionally with penetration depth but its growth rate rapidly decreased beyond a critical depth until full plugging occurred. Using strain gauges uniformly distributed along the pile shaft, together with LVDT displacement sensors and an axial load cell at the pile head, the penetration resistance, axial force distribution, unit shaft friction, and ultimate compressive and uplift capacities were analyzed. The results show that during installation, all resistance components increased with depth: shaft friction contributed a smaller but accelerating proportion, while base resistance dominated with a steadier growth rate. The penetration resistance of the closed-ended pile was greater than that of the open-ended pile. During static loading, both piles exhibited similar bearing characteristics, although the open-ended pile showed a slightly higher compressive capacity. Under uplift loading, both pile types demonstrated degradation in unit shaft friction at the pile tip.