Abstract The bearing capacity of a pile under vertical cyclic loading is one of key factor in the design of pile foundation. In this study, an innovative large-scale model test of double-wall open-ended pipe pile was conducted to investigate the cyclic bearing characteristics of open-ended pipe pile under various soil conditions and load frequencies. The experimental results show that the ultimate bearing capacity of piles in sand is much larger than that in clay. Under cyclic loading, the cumulative settlement in clay was found to be larger than that in sand, which was clearly indicated by clear increasing and stabilizing trends. Furthermore, the external friction of pipe pile in sand changes in an oblique “V” shape with depth, whereas that of the pipe pile in clay is inclined “W”. With increase in number of cycles, the external friction of upper part of the pipe pile and the internal friction of lower part of the pipe pile in sand decrease first and then tend to be stabilize. On the other hand, the external friction of upper and middle parts of pipe pile and internal friction of lower part of pipe pile in clay observed to have the same trend. Contrarily, the external friction in the middle of pipe pile in sand is an opposite trend. Moreover, the load frequency of dynamic cycle loading tends to have a great influence on the friction resistance, and this influence is more significant in clay than that in sand.

中文翻译：

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砂土中竖向循环荷载作用下明管桩动力响应

摘要 桩身在竖向循环荷载作用下的承载力是桩基设计的关键因素之一。本研究创新性地进行了双壁开口管桩大型模型试验，研究了开口管桩在不同土壤条件和荷载频率下的循环承载特性。试验结果表明，砂土中桩的极限承载力远大于粘土中。在循环荷载作用下，发现粘土中的累积沉降大于沙子中的累积沉降，这清楚地表明了明显的增加和稳定趋势。此外，沙土中管桩的外摩擦力随深度呈斜“V”形变化，而粘土中管桩的外摩擦则呈“W”形倾斜。随着循环次数的增加，管桩上部外摩擦和管桩下部在砂土中的内摩擦先减小后趋于稳定。另一方面，在粘土中观察到的管桩上部和中部的外摩擦和管桩下部的内摩擦具有相同的趋势。反之，沙土中管桩中间的外摩擦则相反。此外，动态循环加载的加载频率往往对摩擦阻力有很大影响，这种影响在粘土中比在沙子中更显着。观察到粘土中管桩上部和中部的外摩擦和管桩下部的内摩擦具有相同的趋势。反之，沙土中管桩中间的外摩擦则相反。此外，动态循环加载的加载频率往往对摩擦阻力有很大的影响，这种影响在粘土中比在沙子中更显着。观察到粘土中管桩上部和中部的外摩擦和管桩下部的内摩擦具有相同的趋势。反之，沙土中管桩中间的外摩擦则相反。此外，动态循环加载的加载频率往往对摩擦阻力有很大的影响，这种影响在粘土中比在沙子中更显着。