The pile foundation under a high-speed railway (HSR) not only bears the self-weight of the superstructure, but also bears a long-term vertical periodic load during its service. In this study, a large-scale vertical dynamic load test and particle flow numerical simulation method were adopted to investigate the axial cyclic performances of open piles in sand. The results from the dynamic test show that under a dynamic load with cyclic load ratios of 0.1 and 0.2, the surface displacement of the pile decays rapidly as the pile distance increases. Moreover, the higher the vibration amplitude and frequency, the larger the surface displacement. The influence range of the soil around the pile is approximately six times of the pile diameter. It is also found that the external frictional resistance of the upper part of the pile decreases, whereas that of the middle part increases. In addition, the internal friction resistance of the lower part of the pile decreases and gradually stabilizes after approximately 200 cycles. The simulation results show that the influence range of the pile on the surrounding soil is approximately 5–8 times the diameter of the pile under the action of dynamic loading; the vertical displacement of the pile mainly occurs at the beginning of the cycles. The total settlement of the pile foundation increases with an increase in the cyclic load ratio. With an increase in the cycle period, the friction resistance values on the outside of the pile and middle part significantly decrease and increase, respectively. After 10 cycles, the resistance gradually stabilizes, and no evident changes in the internal friction resistance of the pile are observed.

中文翻译：

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高铁荷载作用下开口和闭端管桩承载特性研究

高铁(HSR)下的桩基不仅要承受上部结构的自重，而且在其服役期间还要承受长期的竖向周期性荷载。本研究采用大尺度竖向动载荷试验和粒子流数值模拟方法研究沙地开桩的轴向循环性能。动力试验结果表明，在循环荷载比为0.1和0.2的动荷载作用下，桩的表面位移随着桩距的增加而迅速衰减。而且，振动幅度和频率越高，表面位移越大。桩周围土壤的影响范围约为桩径的六倍。还发现桩上部的外摩擦阻力减小，而中间部分增加。此外，桩下部的内摩擦阻力在大约 200 次循环后逐渐减小并趋于稳定。模拟结果表明，在动力荷载作用下，桩对周围土体的影响范围约为桩径的5～8倍；桩的垂直位移主要发生在循环的开始。桩基的总沉降随着循环荷载比的增加而增加。随着循环周期的增加，桩外侧和中间部位的摩擦阻力值分别显着减小和增大。10个循环后，阻力逐渐稳定，桩的内摩擦阻力没有明显变化。