饱和砂土中开闭口桩静压贯入过程及承载特性离心模型试验研究

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

    • 摘要: 为了探究开口和闭口桩在饱和砂土中的静压贯入特性与承载性状差异,对两根尺寸相同的开、闭口模型桩依次进行了安装过程和抗压抗拔静载测试的离心模型试验。设计并验证了能够在超重力环境下实现开口管桩内部土塞高度监测的装置,研究了开口管桩安装过程中的土塞形成规律,发现在贯入初期土塞高度与贯入深度基本一致,在贯入一定深度后土塞增长速率迅速减小,直至完全堵塞。采用桩身均匀布置的应变片,结合桩顶LVDT位移传感器和轴向压力传感器,研究了开、闭口桩不同阶段的贯入阻力、桩身轴力、单位侧摩阻力与极限抗压抗拔承载力,结果表明:安装过程各部分阻力都随着深度增加而增加,侧摩阻力的占比较小但增速加快,桩端阻力的占比较大但增速稳定,闭口桩的贯入阻力大于开口桩。静载试验表明两根桩的承载特性相似,开口桩的抗压承载力稍大于闭口桩,两根桩的抗拔单位侧摩阻力在桩端处都呈现退化现象。

       

      Abstract: 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.

       

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