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April 1, 2020 ITS Money: John Niedzielski, P.E.

John C. Niedzielski, P.E. | Gannett Fleming, USA

Drilled Shaft Load Testing Program for Design of Foundations for an Automated People Mover

The PHX Sky Train is an automated people mover system located at Phoenix Sky Harbor International Airport in Phoenix, AZ. This presentation presents the results of a drilled shaft load test program implemented to provide site-specific measurement of the axial and lateral performance of the project drilled shafts. The load testing program was important for verifying the performance of the drilled shaft foundations on the project and was used to reduce the size of the drilled shafts.


  • The load test provided a direct performance measure using the actual construction means and methods planned for the project in the site-specific soil conditions.
  • AASHTO and FHWA design methods appear to be conservative for axial design of drilled shafts in the site sand-gravel-cobble soils.
  • Without load tests the drilled shafts would be longer, meaning additional time, potentially more issues with caving soil conditions, longer temporary casings and handling longer, heavier cages.