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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。
The deformation of large diameter overlength cast-in-place piles is large, and obvious interface slip easily occurs between pile sides and soil. The traditional shear displacement method is not suitable for calculation of bearing deformation. Based on the characteristics of pile-soil shearing action and pile-side frictional resistance of large-diameter overlength cast-in-place bored pile, the two-stage method of shear displacement and shearing slip is used to describe the process of lateral frictional resistance of pile and to form the generalized shearing model On this basis, the calculation method of bearing deformation of large diameter overlength bored piles was established by using transfer matrix increment method, and the values of calculation parameters were given. The method takes into account the non-linearity of pile-side friction resistance, the non-linearity of pile-end bearing and the nonlinearity of pile material, and takes into account the softening property of pile-side frictional resistance after pile-soil slip and the pile- End bearing traits. The calculation results of the engineering example are in good agreement with the measured values of the test pile, which shows that the calculation method of the bearing deformation of the large-diameter extra-long cast-in-place pile based on the generalized shear model of the pile side is reasonable and feasible.