Ground engineers are being urged to make more use of pile load testing to improve design and reduce conservatism.
uk project from 3 m to 15 m spire canary wharf
Speaking at the opening day of the Chalk 2018 conference yesterday, Fugro foundation testing service line manager Melvin England said that there was a huge opportunity to add value to pile design.
England used a number of O-Cell bi-directional testing case studies of piles in Chalk to demonstrate the underestimation of the pile capacity.
“O-Cell test results reveal more than traditional top down pile load testing,” he said. “The results provide a real opportunity for optimisation.
“Often the assumed level of mobilised friction in Chalk is 300kN/m2 but tests results show that is considerably out with mobilised friction in the region of 500kN/m2 to 600kN/m2 common.”
Bachy Soletanche chief engineer David Hard later presented a case study of pile testing for the Spire, which broke UK records last year with peak loads of 80MN. Pile test results for the site were also discussed by England and supported the theory of pile capacities being underestimated.
However, Hard said that clients always want their piles designed within current design codes which makes it difficult to base pile designs on this improved understanding without testing conventional designs first.