Abstract:
Helical piles have often been characterized as handy little tools in the toolbox of solutions for structural support of foundations. They have provided opportunities to rehabilitate, expand and retrofit structures of various sizes. They have also 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, however, has limited their use as high-load deep foundations.
This presentation aims to 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, Canada supported on helical piles. The building was to be located in a downtown location surrounded by existing buildings of various ages. All the usual problems for structural deep foundations were present – high water table, vibration concerns, 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 could limit or eliminate. Still, helical piles were not among the initial recommendations for the foundation of the proposed building.
This presentation will present the detailed solution that helical piles offered the constructor of the new building at 515 Richmond Street in London, Ontario, Canada. 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 should be considered for large structures.