Design, Construction and Verification of CFA Piles for Infrastructure and Building Projects

Dr Ben Collingwood

Continuous Flight Auger (CFA) piling has become a common foundation type across both the infrastructure and building sectors in Victoria and nationally. Industry capability and practice in design and construction of this pile type has developed significantly over the past 20 years. While many specialist practitioners are highly skilled and experienced in CFA piling practice, this expertise is often not readily accessible to the broader profession.

In Australia, the use of CFA piling methodology developed initially in the commercial building sector, where it is typically used under a ‘design and construct’ contracting arrangement, where the contractor is responsible for the installation and certification of the foundation system. Design, construction monitoring, inspection, testing and verification processes have evolved in the building sector to suit this contracting environment.

More recently, CFA piling has become prevalent on infrastructure projects. In contrast to the building sector, for infrastructure projects the design is generally carried out by the engineering consultant and the piles are often installed under a ‘construct only’ contract. As construction equipment, methodology and practices significantly influence CFA pile performance, it is critical that appropriate construction monitoring, inspection, testing and verification processes are included in the project documentation and properly implemented. Deficiencies in such processes can lead to conflicts and practical difficulties during the piling works. Further, they can expose designers, contractors and project owners to significant risks with respect to cost, quality assurance and program outcomes.

The presenter’s experience suggests that important issues associated with the use of CFA piles are not broadly understood by many practitioners. Further, the available standards and specifications do not provide consistent guidance and are not always applied.

Dr Collingwood will discuss his view of best practice for the use of CFA piles in both the building and infrastructure sectors, highlighting some important technical, practical and commercial considerations.
A significant case study from a major road infrastructure project will be presented as an example of best practice for site investigation, design, construction and verification of CFA piles in the infrastructure space, along with some recent experience from major building projects in Melbourne.

About the speaker

Dr Ben Collingwood Senior Principal Engineer and Managing Director, FSG Geotechnics & Foundations

Dr Ben Collingwood is a Senior Principal Engineer and Managing Director of FSG Geotechnics & Foundations, where he leads a growing team of professionals practicing in a broad range of geotechnical fields.

After completing his undergraduate degree at Monash University, Ben commenced his industry career in 1995 with a leading tunnelling contractor of the time, Transfield Tunnelling, and geotechnical consultant, Golder Associates, before returning to Monash University to complete a Ph.D. in Geomechanics under the supervision of Dr Julian Seidel and Dr Chris Haberfield.

Upon completion of his Ph.D. project on the effect of construction practices on the performance of rock socketed bored piles, Ben spent 11 years with national piling contractor, Wagstaff Piling. During this time, he was responsible for tendering, design, project engineering and project and construction management for a large number of commercial foundation and retention construction contracts, in both the building and infrastructure sectors. In his roles he developed a detailed understanding of a broad range of deep foundation and retention systems including bored piling, CFA piling, driven precast, steel and timber piling, sheet piling, piled retention systems, diaphragm walls, cut-off walls and ground improvement.
Ben considers himself fortunate to have obtained a blend of technical knowledge, construction management experience and commercial understanding of foundation engineering practice, which provides a broad base for his project and industry involvement.

Since establishing FSG with colleague Dr Julian Seidel in 2010, Ben has led the company in its growth from three initial staff specialising in foundation engineering to a broadly skilled geotechnical consultant employing over 50 staff with offices in Melbourne and Brisbane. Through FSG, Ben has been involved in a broad range of projects within the building, resources, energy and infrastructure sectors, both nationally and overseas.
Ben is the Engineers Australia representative on subcommittee BD-090-03 for AS 5100.3:2017 – Bridge Design – Foundations and Soil Supporting Structures.

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