Evaluation of pile set-up from penetration per blow

摘要

Case histories, published in recent years, show that the long-term increase in bearing capacity of driven friction piles in non-cohesive soil is often large. The present paper describes two cost-effective methods, in which the penetration (set) per blow is used to evaluate the relative set-up. The reliability of the methods was assessed in a comprehensive field-test involving both concrete piles and steel rods, driven in glacial sand. Dynamic loading tests were performed at different points in time, between 0-216 days after end of driving. Both an increase in bearing capacity and a decrease in set per blow were observed over time. The set-up was roughly 40% per log cycle of time for both the piles and the rods. Both methods showed that it was possible to determine the relative increase in bearing capacity with very good accuracy from the set per blow.