Enhanced mechanism and load-settlement relationship of post-grouting piles

Based on the results of ten in-situ pile load tests of Taizhou Bay Bridge and its connecting projects in six different sites, the load transfer characteristics of grouted piles are analyzed. The hyperbolic load transfer function is used to calculate the load-settlement relationship of the grouted piles on the basis of the mechanism of strengthening effect. The improvement coefficients for side friction and tip resistance in different soil deposits are determined to account for the effect of grouting. Finally, case history is cited to demonstrate the validity of the method. The results indicate that the tip resistance of the grouted piles is mobilized before application of vertical load because of the preloading effect of soil beneath pile tip arising from tip grouting. Thus, the strain incompatibility between the tip resistance and the side friction of pile is improved. Moreover, the tip resistance and side friction of grouted piles will be significantly enhanced under the combined action of ground improvement of the soil beneath pile tip, preloading effect, enlarged tip area and the upward grout penetration along the pile side due to tip pressure grouting. However, ignoring the influence of grout bulb radius or grout climbing height may lead to an undesirable bearing capacity of the grouted piles.