桩端后注浆超长灌注桩桩侧极限摩阻力计算方法

目前超长灌注桩普遍应用于大型桥梁、超高层建筑工程中，且常采用桩端后注浆技术，但其桩侧极限摩阻力的确定尚未有切合其实际特点的方法。大量现场实测数据反分析表明，采用 法计算时，存在桩侧土压力大于土层静止土压力的现象。在探讨桩侧土压力增大机制的基础上，对 法进行改进，建立了桩侧土压力确定方法，并给出了桩侧土压力系数的取值公式。工程实例计算结果与试桩实测结果比较分析表明，所建立的桩端后注浆超长灌注桩桩侧极限摩阻力计算方法具有合理性与可行性。

A calculation method of pile shaft ultimate friction of tip post grouted super-long bored pile

Tip post grouted super-long bored piles are generally used in large-scale bridge and super high-rise building projects. However, the reasonable method for calculating the pile shaft ultimate friction is still limited. According to back analysis of some measured data, the lateral soil pressures of the pile shaft are larger than the earth pressures at rest when the method is adopted. The influence factors of the lateral soil pressures of pile shaft are discussed. Then, the traditional method is improved. A method for determining the lateral soil pressures of pile shaft is established. Moreover, a formula for calculating the lateral earth pressure coefficients of the pile shaft is also given. At last, field test piles of two project cases, Shanghai World Expo Underground Substation project and Shanghai Center Tower project, are calculated by the improved method. Through comparing with the measured results, the recommended values of the site investigation and the specification values, the calculation results are more consistent with the measured results. This shows that the calculation method of pile shaft ultimate friction of the tip post grouted super-long bored pile is feasible and rational.