【摘要】 【目标】为了研究支盘承载对桩身侧阻特性的影响，本文结合桩周土力学参数，提出支盘桩竖向承载力的计算方法。【方法】首先，由于受荷支盘沉降可分别导致盘上桩侧土卸载、盘下桩周土挤压，以及可导致其相邻各段桩身与桩侧土相对沉降产生变化，将支盘上下桩身划分为侧摩阻力正常段、减小段、不发挥段和增大段，分析支盘单元各段桩身侧摩阻力的特性差异。其次，结合间距较小的支盘间土体会产生共同剪切破坏的特征，构造多支盘支盘桩承载破坏模式。然后，根据支盘单元桩身各段受力与变形特点，分别引入土拱与球孔扩张理论，建立支盘、桩端的端承力、各分段侧摩阻力的计算方法。将各支盘单元的各项侧阻和端阻叠加，得到支盘桩极限承载力计算公式。最后，引入表征土体非线性力学关系的Kondner双曲线模型，进一步构建按桩身沉降确定支盘桩承载力的计算公式，并由既有研究的试验数据验证本文计算方法的合理性。【结果】通过分析支盘沉降引发的桩侧土受力变形效应，确定了桩身分段受力特点，对支盘桩承载机理的揭示更全面；对不同分段分别引入适用的理论进行桩-土相互作用定量计算，可建立基于桩周土力学参数来计算支盘桩承载力的方法。【结论】相比现有研究还需依靠试验和经验来确定支盘桩端阻力和侧阻力的方式，本文方法理论依据更强。研究结果可为支盘桩承载力计算、支盘桩试桩试验数据整理提供理论指导。更多还原

【Abstract】 [Objective]This study investigated the influence of reamed plate bearing on pile shaft resistance. It proposed the calculation method for vertical bearing capacity of squeezed branch pile, based on the mechanical parameters of soil around pile. [Method]First, the pile shaft above and below a bearing plate was divided into four segments due to lateral friction resistance, i.e., normal segment, reduced segment, nonfunctional segment and enhanced segment. Because the settlement of loaded bearing plates could respectively lead to unloading of soil on pile side above the plate and squeezing of soil around pile under the plate; as well as lead to the variation of pile-soil relative settlement to adjacent segmental piles and soil around piles. The characteristic differences of lateral friction resistance of each pile segment were investigated. Second, the bearing failure mode of squeezed branch pile with multi-plates was constructed, combining with the characteristics of common shear failure of soil between small-spacing bearing plates. Third, the soil arching theory and spherical cavity expansion theory were introduced respectively according to the stress and deformation characteristics of each pile segment. The calculation methods were established for the end bearing capacity of bearing plate and pile tip, as well as the lateral friction resistance of each segment. The calculation formula for ultimate bearing capacity of piles was obtained by superposing the resistance of each unit segment. Finally, Kondner hyperbolic constitutive model was introduced to construct the formula for bearing capacity of piles according to the pile settlement. The rationality of the proposed method was verified through existing test data. [Result]The segmental stress characteristics of pile were determined by analyzing the stress and deformation effects of soil around pile induced by the settlement of bearing plates. It leads to a more comprehensive investigation on load-bearing mechanism of squeezed branch pile.The calculation method for bearing capacity of squeezed branch pile can be established based on the mechanical parameters of surrounding soil by introducing applicable theories for different segments to perform quantitative calculations of pile-soil interaction. [Conclusion]The proposed method has a scientific theoretical basis, compared with existing studies that still rely on tests and experience to determine the end resistance and lateral resistance of piles. The findings could provide theoretical guidance for the bearing capacity calculation of squeezed branch piles and the collation of data for test piles.更多还原