基于桩侧广义剪切模型的大直径超长灌注桩承载变形计算方法

大直径超长灌注桩桩身变形较大,桩侧与土体易出现明显的界面滑移,传统剪切位移法难以适合其承载变形计算。基于大直径超长灌注桩桩–土剪切作用性状及桩侧摩阻力发挥特点,采用剪切位移和剪切滑移两阶段法描述其桩侧摩阻力发挥过程,形成桩侧广义剪切模型;在此基础上,采用传递矩阵增量方式建立大直径超长灌注桩承载变形计算方法,并给出计算参数的取值。该方法考虑了桩侧摩阻力发挥的非线性、桩端承载的非线性及桩身材料的非线性,并考虑了桩–土滑移后桩侧摩阻力软化特性及桩端后注浆对桩端承载性状的影响。工程实例计算结果与现场试桩实测值较为吻合,表明基于桩侧广义剪切模型建立的大直径超长灌注桩承载变形计算方法具有合理性与可行性。

Bearing deformation of large-diameter and super-long bored piles based on pile shaft generalized shear model

Because of large deformation of large-diameter and super long bored piles, pile soil slip is easy to appear in the pile shaft. Therefore, the traditional shear displacement method is not suitable for load deformation calculation of the piles. According to the shear characters of pile shaft and soils of the large-diameter and super long bored piles, the two-phase approach, shear displacement phase and shear slip phase, is adopted to describe the action process of pile shaft friction. On this account, a pile shaft generalized shear model is established. Then, the method of incremental transfer matrix is used for nonlinear iterative calculation of the pile load deformation. Moreover, values of the same calculating parameters are also given. For this pile load deformation method, nonlinear behaviors of pile shaft friction, pile tip resistance and pile shaft materials are considered. Besides, pile shaft friction softening property and pile tip post-grouted effect mechanism are also considered. Two engineering cases are calculated by the method. The calculated and measured results are very similar. It is shown that the proposed pile shaft generalized shear model and load deformation method for the large-diameter and super long bored piles are reasonable and feasible.