Abstract
At certain depths during driving of large diameter displacement piles, rebound greater than 0.25 inches (6.35 mm) occurs followed by a small permanent-set after each hammer blow. High pile rebound (HPR) soils may stop the pile driving and result in a limited pile cap acity. The overburden depth at which HPR occurred is typically greater than 50 ft (15.3m). In some cases, rebound leads to pile damage, delaying of the construction project, and the requir ing foundations redesign. A simple models for evaluating probability of HPR using Cone Pene tration Test (CPT) and Standard Penetration Test (SPT) data are developed based on logistic regression analyses of 18 case histories. The proposed model uses the pore water pressure and sleeve friction and/or SPT blow count with fines content (pass #200 sieve) as input parameters. Comparisons of the proposed probability model with actual pile-driving analyzer (PDA) rebound data are performed to demonstrate the improvements. As a result, the models showed that the probabilities of HPR (percentage) increased as either the pore water pressure or sleeve friction or SPT N-values with fines content. The statistical logistic regression modeling and developed equations showed promise in predicting rebound. This methodology may lead to a simpler evaluation process which allows for the prediction of HPR during the design phase.