Design and Construction of the Deepest CFA Pile in Australia-Paper

Paper

Pdf Summary

The paper describes the design and construction of approximately 200 continuous flight auger (CFA) piles for a high-rise development in Docklands, Victoria. The site has complex soils extending to around 50 m, underlain by siltstone. High structural loads, including column compression loads up to 35 MN and substantial core tension and shear loads, required robust foundations.<br /><br />Driven precast piles were considered less suitable because of the risk of premature refusal, settlement from weaker soil layers, and the large number of piles and pile caps required. Bored piles were judged too costly and time-consuming. CFA piling offered a more efficient solution, provided the contractor could demonstrate the equipment, expertise, quality controls, and testing needed for exceptional depths.<br /><br />The project used a high-capacity Fundex F3500 rig to install 600 mm and 750 mm diameter piles, generally 30–50 m deep. Three piles were socketed into siltstone to a maximum depth of 53.8 m, which the author identified as an Australian record. Design accounted for the rig’s torque and extraction limits, and some piles founded in soil were designed to rely mainly on shaft resistance.<br /><br />Construction quality was managed through real-time monitoring of drilling depth, penetration rate, torque, extraction rate, concrete pressure, and concrete volume. Procedures addressed base formation, steady auger extraction, concrete supply calibration, auger extensions, and blockages. Engineers reviewed installation records promptly and checked excavated materials against geotechnical information.<br /><br />Verification included dynamic load tests on at least 5% of piles and low-strain integrity tests on an additional 5%. Early dynamic tests were completed within two weeks of piling commencing, allowing the construction approach to be confirmed. The project demonstrates that very deep CFA piling can be successfully delivered when design, specialist equipment, construction procedures, monitoring, and testing are carefully coordinated.

Keywords

continuous flight auger piles

CFA piling

high-rise foundations

Docklands Victoria

deep piles

siltstone socketing

high structural loads

Fundex F3500 rig

pile quality control

dynamic load testing