Bearing capacity of driven piles in sands from SPT–applied to 60 case histories

In recent years determining bearing capacity of piles from in-situ testing data as a complement of static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating the bearing capacity of piles from SPT data have been explained and compared. A new method based on the N-value from SPT is presented and calibrated. Data averaging, failure zone extension, and plunging failure of piles has been noticed in the proposed approach. A data base has been compiled including 43 full scale static pile load tests and 17 dynamic testings which were analyzed with the signal matching technique by CAPWAP. The SPT data were performed close to pile locations are also included in the data base. A comparison of current methods by error investigation with cumulative probability and Log-Normal approaches demonstrates that the proposed method predicts pile capacity with more accuracy and less scatter than other methods. Results of prediction with good agreement to measured capacities indicate that the proposed method can be used as an alternative for determining the bearing capacity of piles in geotechnical practice.