ENSURING PERFORMANCE OF TIP POST-GROUTED BORED PILES (DRILLED SHAFTS) THROUGH A COMPREHENSIVE QUALITY ASSURANCE PROGRAM

摘要

Tip post-grouting of bored pile (drilled shaft) foundations refers to a method wherecementitious grout is injected beneath the tip of a shaft to improve the overall performance of theconstructed foundation. This technique, when performed satisfactorily and in the appropriate groundconditions, enhances axial load-displacement performance by improving the mobilization of pile’sresistance. Potential benefits associated with tip post-grouting include reduced settlement under loading,better alignment of load transfer curves, and improved ground beneath the base of the bored pile.However, to be able to realize the benefits attributed to this method, the design, construction, of both thebored pile and the post-grouting system must meet a minimum level for quality assurance. The variousfactors affecting the successful installation and performance of a bored pile (e.g., workmanship, basecleanliness, borehole integrity, and concrete placement) have been discussed by numerous practitionersand researchers in the available technical literature. For a conventional (i.e., ungrouted) bored pile,acceptance is based on a combination of visual inspection, material testing, and the results of integrityand/or performance testing of the constructed pile. A properly executed tip post-grouting program can bea relatively comprehensive and complex process, which is typically evaluated throughout the constructionprocess based on the results of prior projects and/or on test pile(s) at the particular site. For tip postgroutingprograms, verification procedures and acceptance criteria should be established during andincorporated into the design process to ensure design intent and objectives are achieved. Projectspecifications should be produced to ensure performance requirements are achieved. This paper willpresent and discuss factors affecting the successful execution of tip post-grouting, including groutingcriteria, instrumentation, reliability and uncertainty with the method and outcome, and verification andacceptance.