Thinking Bigger – 32-Storey Building on Helical Piles

Helical piles have often been characterized as handy little tools in the toolbox of solutions for structural support of foundations. They have provided options to construct foundations and anchorage in very challenging locations where more common methods were impractical. The stigma of being efficient for lightly loaded foundations has limited their use as highly loaded deep foundations. This paper will dispel the notion that helical piles are not a deep foundation option for large structures by presenting the case study of a 32-storey building in London, Ontario supported on helical piles. The building was constructed in a downtown location where all the problems associated with deep foundations were present – high water table, vibrations, compressible soil layers, limited access, logistics of soil removal, seismic considerations. These issues all had costs associated with them that helical piles and their installation process would limit or eliminate. This paper will present the detailed solution that helical piles offered the constructor of the new building. The solution included pre-design load testing and analysis of the results. The advantages of using helical piles in this case will also be presented from technical and constructability viewpoints to demonstrate why they should be considered for large structures.