Impact of Routine Quality Assurance on Reliability of Bored Piles

Quality assurance (QA) tests, such as integrity tests, are routinely conducted to ensure the safety of pile foundations. QA tests provide additional information and result in changes in estimated reliability of pile foundations. This paper aims to formalize a procedure to quantitatively evaluate the impact of routine QA tests on the reliability of pile foundations. Three cases of reliability analyses based on interface coring of large-diameter bored piles are studied; namely, no toe debris detected, toe debris detected without repair, and toe debris detected and repaired. The prior information of the occurrence probability and thickness of toe debris is established based on a practice survey and accumulated QA data. The Bayesian approach is then applied to update the occurrence probability and the mean toe debris thickness based on outcomes of on-site QA tests and remedial actions taken after these QA tests. Subsequently, the reliability of the piles can be updated. The updated reliability can be significantly higher than that before the QA tests. The degree of reliability improvement depends on the pile specifics, the outcomes from the QA tests, and the remedial actions taken after the QA tests.