A practical method of calculation of bearing capacity and settlement of large-diameter post-grouting piles

Based on the static load test data of 716 test piles collected from 139 projects, the practical calculation method of bearing capacity and settlement of large-diameter post-grouted piles was studied. The improvement coefficients of the side friction and base resistance of soil layer were given primarily based on statistics analysis, and the practical calculation approach for the bearing capacity of large-diameter post-grouted piles applicable to different grouting types was presented. The reliability of the proposed approach was verified by a large number of measured data. Moreover, the influence coefficient of post-grouting settlement was introduced based on the settlement calculation method of large-diameter pile foundation without grouting. Based on the statistical analysis, the recommended range of influence coefficient of post-grouting settlement was given, and an empirical estimation method for calculating settlement of large-diameter post-grouted piles suitable for different soil layers was proposed. Finally, the applicability of the proposed method was verified using engineering examples. The research results have been incorporated into the industry standard of the People's Republic of China Code for design of ground base and foundation of highway bridges and culverts (JTJ 3363 - 2019) and the industry standard of national project construction Technical specification for post-grouting of cast-in-place pile of highway bridges (T/CECS G: D67-01-2018), which can promote the wide application of post-grouting technique.