Design, installation and verification of CFA piles and common challenges in the Melbourne region

Continuous Flight Auger (CFA) piling is a common foundation type for building and infrastructure projects in and around Melbourne, as well as nationally. The Australian piling market has significant expertise and capability in their design and construction, which has been developed over the past two decades or more, primarily in the building industry. Most of this expertise and experience is held by specialist piling subcontractors. In the building industry, CFA piling projects have been delivered primarily using a design and construct contracting model, where the specialist piling contractor has responsibility for designing, installing and certifying the foundation system. More recently, CFA piling has become popular on infrastructure projects, where responsibility for design, construction and verification involves a broader range of parties, including geotechnical and structural consultants, main contractors and specialist piling contractors. Successful project delivery in this environment requires good understanding and alignment between all parties, and sound design, construction and verification processes. Deficiencies in these processes can lead to conflicts and practical difficulties during the piling works. Further, they can expose designers, contractors and project owners to risks with respect to cost, quality and program outcomes. The geology of Melbourne also presents some challenges in relation to CFA pile design and installation, including a predominance of low strength soils in the Yarra Delta area, deep siltstone bedrock and variable and unpredictable basalt flows. This paper discusses important aspects of CFA piling projects in the building and infrastructure sectors, as well as some commonly encountered challenges in and around central Melbourne. The author endeavours to provide an overview of important aspects of this pile type to assist in broadening the understanding of industry practitioners who are involved in planning and executing CFA piling projects.