CFA Continuous Flight Auger
Continuous Flight Auger (CFA) Piling is the quietest form of piling and is a fast and very economical technique. It is a cast in-situ process, very suited to soft ground where deep casings or use of drilling support fluids might otherwise be needed. CFA piling is a non displacement piling system; hence the soil excavated from the pile is brought to the surface. CFA piles can be an attractive alternative to conventional bored piles (faster installation) and to driven piles (much less noise and vibration).
CFA piles can be used for load transfer beneath structural elements and also for contiguous and secant (interlocking) piled retaining walls.
The construction sequence can be seen in the animation accessed from the image at the foot of this page, and consists of;
(1) drilling a full length auger with a hollow stem (temporarily plugged) into the soil using a constant penetration rate.
(2) after reaching the design toe level, concrete is pumped through the hollow stem of the auger while the auger is extracted. It is important that the auger always remains embedded into the concrete
(3) and that a positive concrete pressure is maintained throughout the placement of concrete. CFA piles have to be poured to platform level to facilitate reinforcement installation and avoid pile necking.
(4) After completion of the concrete placement process the reinforcement cage is plunged into the fluid concrete
Piling Contractors CFA range offers the following advantages
- Diameters from 450 to 1200mm
- Depths up to 32m
- Able to carry high load/ shear/ moment capacity
- Low noise and vibration
- Speed of installation
- Can overcome Interbedded clays and sands
- Can deal with water bearing sands and gravels and penetrate weak rocks
Please click to see a timelapse of CFA piling.
It is important to select an experienced company for your CFA piling application as the effect of the construction technique on different ground conditions has to be fully understood. Concrete mix requirements have to be carefully designed to maintain workability yet avoid segregation and bleeding during placement. Underpowered piling rigs can lead to uncontrolled soil transport, causing settlement to adjacent structures.
CFA piles are suitable a foundation piles, for secant pile walls, contiguous pile walls and soldier pile walls.
Piling Contractors undertakes both design and construct or construct only projects using CFA piles.