Behaviour of tapered screw pile foundations in unfrozen soils

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Conventional foundations for infrastructure in Canada's permafrost regions are straight-shaft piles, which are not an optimized design as shown by researchers and practitioners. Quick economic growth in Northern Canada has increased the need for new construction and maintenance of infrastructure systems, which require more safe yet economic foundations. The proposed research introduces an innovative foundation type, tapered screw piles (also known as ground screws), as an alternative to the conventional pile foundation. As a result of the specially designed shaft, ground screws have **shown superior behaviour such as large axial capacities, ease of installation, and reusability. However, the performance of ground screws in permafrost or unfrozen soils are still not well engineered and design guidelines for ground screws in permafrost are nonexistent. The proposed research will bridge this research gap. By partnering with Thugga Ltd., the research team will systematically investigate the axial and lateral behaviour of ground screws embedded in unfrozen and frozen soils; identify the load-transfer and failure mechanisms; investigate the short-term and long-term performance of the **ground screws in permafrost; and optimize the installation technique. To fulfill the objectives, the team will conduct in-situ tests of ground screws installed in typical unfrozen soils in Western Canada and typical frozen soils in Northern Canada. The team will conduct laboratory testing of screw segments subject to axial loading, develop numerical models for simulating soil-screw interactions, and propose a design guideline. The outcome of the proposed research will help industrial partner expand the applications of ground screws in existing and emerging industries across Canada. The research will advance our understanding of the performance of the ground screws and soil-screw interactions in unfrozen and frozen environments. The research will benefit Canada's infrastructure systems by providing a capable and economic foundation type.**