Investigation into the Bearing Performance Enhancement of Pile Tip Post-Grouted Pile Foundations for Super High-Rise Buildings

Traditional bored cast-in-place piles frequently encounter issues such as insufficient bearing capacity and excessive settlement when applied to super high-rise building foundations. These problems primarily arise from construction-induced defects, including pile toe debris and pile side mud cake, which prevent the piles from meeting the stringent performance requirements of super high-rise structures. Although existing studies have confirmed the efficacy of the pile tip post-grouting technique, targeted comparative tests for super high-rise projects in specific geological strata remain relatively limited. In this study, taking a super high-rise tower project as a case study, comparative static load tests were conducted on six large-diameter bored piles: three conventional ungrouted piles and three pile tip post-grouted piles. Synchronous measurements were carried out to characterize the distribution of pile shaft axial force, pile side resistance, and pile end resistance. The test results reveal that pile tip post-grouting increased the average ultimate single pile bearing capacity from 25900 kN to 34250 kN, representing a significant enhancement of 32.2%. Meanwhile, this technique effectively improved both the pile side resistance and end resistance across various soil layers, with the most remarkable improvement observed in the side resistance of deep soil layers adjacent to the pile tip. Furthermore, the settlement deformation performance of the pile foundation was substantially optimized: the load-settlement curve of the post-grouted piles exhibited a much gentler trend, and the stability of pile formation quality was also significantly enhanced. These findings can provide a reliable experimental reference for the design of pile foundations for super high-rise buildings under similar geological conditions.