DX桩抗拔承载机理及设计计算方法研究

DX桩（挤扩灌注桩）具有良好的抗拔特性和广阔的工程应用前景。对DX桩与普通桩的抗拔承载特性进行了对比分析，探讨了DX桩的抗拔破坏模式，分析了DX桩的抗拔荷载传递机理及其主桩桩侧与支盘抗拔阻力沿深度的发挥特征。在此基础上，根据DX桩的构造特征，充分考虑主桩桩侧摩阻力和DX桩支盘或3n型分支周围土体摩阻力的影响，建立了极限状态下DX桩抗拔平衡方程，从而导得DX桩抗拔承载力计算公式；对公式中各计算参数的合理选取及相应的试验手段等进行了分析和讨论，给出了DX桩的抗拔设计计算方法与步骤。最后，对影响DX桩抗拔承载力的桩侧土体强度、支盘受荷面与水平面的夹角、支盘数量与间距以及成桩工艺等主要因素进行了定性的分析。

Study on uplift mechanism and calculation of DX pile

DX pile has a remarkable potential in uplift application. Comparing with the ordinary piles, the uplift failure mechanism of DX pile is discussed. Then the mechanism of loading transfer during uplift and the development of uplift friction on the main pile sides and on the branches of DX pile with depth are analyzed in detail. According to the structures of DX piles and the effects of the main-pile-side-friction and the soil-friction around the branches of DX piles, the equilibrium equation of DX piles’ uplift capacity in limiting conditions are deduced. After that, the calculation formula for uplift-bearing capacity of DX pile is drawn. Before presenting the design method and design procedure of DX piles, the related theoretical and experimental methods to decide the formula’s parameters are discussed. Finally, qualitative analysis of the major factors, such as the soil strength, the number of branches, the distances between adjacent braches and the angle between the surface of branches and the horizontal level, which will affect the uplift-bearing capacity of DX piles, are carried out.