CFA or Continuous Flight Auger is one of the most frequently used piling techniques. The piling system uses a varying range of rigs large or small which screw a hollow stemmed auger into the ground. When the auger has reached its predefined depth, concrete is pumped through the auger and into now formed cavity. The pump pressure and flow rate are closely monitored at all times.
As the concrete fills the hole the auger is withdrawn, rotating as it moves upwards in order to extract the the previously drilled material. Once the CFA Pile is complete, any excess material is removed and the steel reinforcement can then be added via a number of methods, using a piling rig, an excavator, or by hand. Piles of varying diameters and lengths can be achieved by CFA piling and as such makes this technique extremely versatile.
The beauty of CFA piling is that it can be used within most ground types and conditions, even ground that is prone to movement, or saturated soil. This is possible because the pressure applied by the concrete always supports the side of the excavation, meaning it’s unlikely that the hole will collapse.
In addition to its ability to be used within any ground surface, CFA piling is an efficient piling method which is also extremely quiet, and causes minimal vibrations. The method was first used in this country in 1966 and now it is probably the most common piling technique.