Updating occurrence probability and size of defect for bored piles

To ensure performance of large-diameter bored piles, integrity tests are often conducted after pile construction. It is often impractical to inspect 100% of piles due to high costs and possible delays. Accordingly, the presence of defects may not be fully detected as only a limited number of piles can be inspected. The defect sizes may also be insufficiently predicted based on limited tests. This paper proposes a procedure to predict the occurrence probability of defect and the defect size for piles at a site based on coring examinations supplemented with engineers' experiences. This procedure is formalized in the Bayesian framework. To update and estimate the occurrence probability and size of pile defects, the concepts of occurrence probability of defect and encounter probability are presented. Then, a method to evaluate the encounter probability is formulated. The occurrence probability of defect is updated based on results from on-site coring. After measurements on encountered defects are taken, the defect size distribution is updated using the proposed procedure. Results from numerical examples indicate that the occurrence probability of defect can be estimated using the proposed procedure in a more rational way. The inspection results from on-site coring have a significant influence on the estimated occurrence probability of defect. The uncertainty in defect size is substantially reduced after being updated with the information on defect sizes from on-site coring. Analysis results can assist the specification of pile inspection program to assure given level of quality assurance. (C) 2006 Elsevier Ltd. All rights reserved.