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通过对单桩、两桩以及四桩的逆作法复合桩基室内模型试验,研究在极限荷载作用下逆作法复合桩基的荷载与沉降关系及桩、土荷载分担特性。试验结果表明:逆作法复合桩基的荷载-沉降曲线具有两个拐点,分别对应封桩结束并加下一级荷载时刻和基础破坏时刻;逆作法复合桩基封桩前的沉降量介于浅基础与复合地基的沉降量之间,桩不直接参与分担上部荷载,只起到改善土体刚度的作用;合理选择封桩时机可以控制桩、土的荷载分担比;封桩后基础总体刚度大幅度提高,基桩不但参与基础受力而且控制基础沉降;在基桩达到极限承载力之前,基桩分担了大部分复合桩基阶段的荷载,基础的沉降也得到了明显的控制;在基桩达到极限承载力之后,上部荷载又大部分由地基土承担。
Through the in-house model test of single-pile, two-pile and four-pile inverted composite pile foundation, the relationship between load and settlement and the load-sharing characteristics of pile and soil under the action of ultimate load are studied. The experimental results show that the load-settlement curve of the composite pile foundation with the reversed working method has two inflection points, which correspond to the end of the sealing pile and the load moment of the first grade and the moment of foundation failure, respectively. The settlement of foundation and composite foundation, the pile is not directly involved in sharing the upper part of the load, only to improve the stiffness of the soil; reasonably choose the timing of sealing the pile can control the load sharing ratio of soil; The pile foundation not only participates in the foundation but also controls the foundation settlement. Before the foundation pile reaches the ultimate bearing capacity, the foundation pile shares the load of most of the composite pile foundation stages, and the foundation settlement has also been obviously controlled. After reaching the ultimate bearing capacity, the upper part of the load is mostly borne by the foundation soil.