Prediction method for time-dependent load-settlement relationship of a jacked pile
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摘要: 考虑天然饱和黏土地层的原位力学特性,采用圆孔扩张模型考虑沉桩效应,结合太沙基一维径向固结理论推导了桩周土再固结过程中土体强度和剪切模量的解析解。在此基础上,根据桩基加载过程中桩侧土体的剪切变形特性,采用指数函数型荷载传递曲线分别建立了静压桩的桩侧和桩端荷载传递模型,提出了考虑时效性的静压桩荷载-沉降关系理论预测方法。通过现场试验对本文解答进行验证,研究了沉桩结束后静压桩荷载-沉降特性随时间的变化规律,分析了静压桩沉桩后不同历时的荷载传递特性。研究结果表明,沉桩结束后静压桩承载特性的变化主要是由于桩侧承载特性的提高;特定休止期后的静载试验结果与静压桩真实承载特性存在一定差异。因此,实际工程中应根据桩周土体力学特性的改变结合静载试验合理确定静压桩的承载特性。Abstract: Considering the in-situ properties of the natural saturated clay strata, the pile installation effects are studied by the cavity expansion model. Based on Terzaghi’s one dimensional radial consolidation theory, the analytical solutions are derived for the time-dependent strength and shear modulus of the soil adjacent to a jacked pile. Then, based on the shear deformation performance of the surrounding soil during pile loading, the time-dependent load transfer models for pile shaft and pile base are established through the exponential function type load transfer curve, respectively, and a theoretical method is proposed for predicting the time-dependent load-settlement curve of a jacked pile in saturated clay strata. The proposed theoretical method is verified by the field tests. The time-dependent load-settlement performance and load transfer properties of the jacked pile after pile installation are studied. The results show that the evolution of the bearing performance of the jacked pile after pile installation is primarily because of the increase in the bearing performance of pile shaft. There are some discrepancies between the actual load-settlement performance of the jacked pile and the static loading test results after specific rest time. Thus, in actual engineering, the time-dependent bearing performance of jacked piles should be evaluated through the static loading tests with the aid of considering the evolution of the mechanical properties of the surrounding soil of piles.
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