Abstract: 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.

Key words: super-long bored pile, pile tip post grouting, pile shaft friction, pile shaft soil pressure