Proceeding of the 2018 DFI-EFFC International Conference on Deep Foundations and Ground Improvement, Rome, Italy, (DFI, EFFC)
Current Practice of CFA Piling in Australia and New Zealand
Martin D. Larisch, PhD
Despite the introduction of Continuous Flight Auger (CFA) piles in Australia about 30 years ago, the pile type has not yet been fully accepted in the geographically ‘neighbor’ country of New Zealand. One of the main advantages of CFA piles is the high production rate which can be achieved with the system. This can make CFA piles very economical. Their installation is vibration free and lateral stress relief associated with bored piles can be reduced notably if construction is carried out correctly. Pile diameters and pile lengths are limited compared to rotary piling applications. The construction of CFA piles in water saturated or unstable soils is possible without any additional measures like casings or drilling fluid to keep the excavation stable, as long as installation parameters are monitored and controlled correctly. Compared with conventional bored piles the visual verification of the pile excavation is not possible as concrete is poured whilst the auger is extracted. CFA piling is a "blind process" and advanced quality assurance is critical to construct a conforming pile. Modern piling rigs are fitted with electronic and mechanical sensors and measurement devices to monitor construction parameters during pile construction. Pile lengths in access of 40m have been achieved in Australia with 900mm diameter CFA piles and maximum pile diameters of 1,500mm for pile depth close to 30m were achieved in Australia. In New Zealand, 1,200mm piles with depth around 24m are the current state of practice. The main challenge in New Zealand is around the strong seismic requirements which makes full depth cages necessary. The paper discusses the current state of practice in Australia and New Zealand with a particular focus on seismic design requirements and typical applications for ground improvement, working platforms and basic design principles for foundation piles constructed with the CFA methodology.
|article #2997; publication #1040 (ROME-2018)|