Abstract This paper presents a new method for analyzing the nonlinear response of a single, vertical pile with the circular cross-section under torque in layered soils. The nonlinear stress-strain relationships of both soil-pile interface and soil are approximated by the hyperbolic model, whereas the pile material is elastic. The torsional spring stiffness of the soil-pile interface and the soil are determined by traditionally available methods. A four-node finite element model for the soil-pile interface is proposed to represent nonlinear behaviors of the soil-pile interface and the soil, separately. A new iterative scheme for nonlinear analysis of a single pile under torque is also developed that avoids having to solve a large number of simultaneous equations found in traditional solution schemes. The new solution method is based on the tangential stiffness of the soil-pile interface and soil springs, which are determined at each load step. From this solution scheme, an equivalent stiffness of the soil-pile-interface system of each pile element is calculated from the bottom element to the top element while torque and angle of twist are calculated from the top to the bottom elements. The solution gives the distribution of the angle of twist and torque along the pile, and the equivalent stiffness of the soil-pile system and torque-angle of twist curves at any depth. The solution method can be easily applied to the practice field in nonlinear analysis and in designing a single pile under torque in layered soils. The analysis results using the new solution scheme compared well with the results from other analytical methods studied by previous researchers. The proposed method is also used to predict the behavior of two full-scale piles under torques. The predictions are in good to excellent agreement with measurements.

中文翻译：

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非线性土和土-桩界面中的桩在扭矩作用下

摘要 本文提出了一种分析单根圆形横截面竖桩在扭矩作用下在层状土壤中的非线性响应的新方法。土-桩界面和土壤的非线性应力-应变关系由双曲线模型近似，而桩材料是弹性的。土桩界面和土壤的扭转弹簧刚度由传统可用的方法确定。提出了土-桩界面的四节点有限元模型来分别表示土-桩界面和土壤的非线性行为。还开发了一种新的用于扭矩作用下单桩非线性分析的迭代方案，避免了在传统求解方案中求解大量联立方程。新的求解方法基于土桩界面和土弹簧的切向刚度，它们是在每个载荷步确定的。根据该解决方案，从底部单元到顶部单元计算每个桩单元的土-桩-界面系统的等效刚度，而从顶部单元到底部单元计算扭矩和扭转角。该解给出了扭转角和扭矩沿桩的分布，以及土桩系统的等效刚度和任意深度扭转曲线的扭矩角。该求解方法可以很容易地应用于非线性分析和分层土壤中单桩单桩设计的实践领域。使用新解决方案的分析结果与以前研究人员研究的其他分析方法的结果相比很好。所提出的方法还用于预测扭矩作用下两个全尺寸桩的行为。预测与测量结果非常吻合。