Frederick Levy, University of Southampton and National Grid UK. This paper was first published in GE’s October 2013 issue.
The National Grid high voltage network requires urgent refurbishment to accommodate the demands of the 21st century. However, there is significant uncertainty surrounding the in-service uplift performance of transmission pylon shallow foundations under dynamic (wind) loading. This uncertainty has been driven by the apparent understrength of foundations when tested using current industry testing practice.
A suite of full-scale tests on transmission pylon foundations was commissioned at a London clay site in Kent. The tests aimed to mimic in-service dynamic loading to reveal the mechanisms associated with rapid foundation uplift. It was shown that foundations founded on London clay mobilised significantly greater uplift capacities at smaller displacements compared with current industry practice.