Current Practice of CFA Piling in Australia and New Zealand-Paper

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The paper reviews current practice in continuous flight auger (CFA) piling in Australia and New Zealand, highlighting differences in equipment, applications and design requirements.<br /><br />CFA piles offer rapid, vibration-free installation and can be economical, including in saturated or unstable soils, provided installation parameters are carefully monitored. Because concrete is placed as the auger is withdrawn, construction is a “blind process”; reliable instrumentation, quality assurance and pile load testing are therefore important. Pile size and depth are limited compared with rotary bored piles.<br /><br />Australia has developed a large, advanced CFA market, particularly in Melbourne, where ground conditions favor deep piles. Large rigs have installed piles over 40 m deep and up to 1.5 m in diameter. CFA is used for foundations and retaining systems such as secant pile walls. Contractor-led design and construction, together with dynamic load testing, support competitive solutions and risk management.<br /><br />New Zealand’s market is smaller, with typical CFA capacity around 1.2 m diameter and 24–25 m depth. Rock penetration and stringent seismic design requirements constrain use; full-length reinforcement cages are often needed, while larger structures commonly rely on bored piles. CFA is nevertheless used for retaining works, moderately loaded foundations and ground improvement. In particular, overlapping-pile lattice structures can mitigate earthquake-induced liquefaction in silty soils.<br /><br />The paper also emphasizes the importance of workable, stable concrete mixes for cage installation and pumping, and of designing and maintaining certified working platforms. Rig loads vary with operational forces, so platform design must account for realistic extraction and pull-down forces to prevent failure. Overall, Australia’s CFA practice is more mature and extensive, while New Zealand’s strongest opportunities lie in suitable medium-scale projects and liquefaction mitigation.

Keywords

continuous flight auger

CFA piling

Australia

New Zealand

pile foundations

secant pile walls

vibration-free installation

quality assurance

seismic design

liquefaction mitigation