CONTINUOUS FLIGHT AUGER

Foundations of a structure provide support for the building on top of those foundations, transferring the load to the layers of soil or rock that then must have sufficient bearing capacity and suitable settlement characteristics. Put very broadly, foundations can be categorised as shallow foundations or deep foundations.

Pile foundations are classed as deep foundations. They are formed by long, slender elements typically made from steel and reinforced concrete or sometimes timber. A foundation is described as piled when its depth is more than three times its breadth.

Continuous flight auger is a cast in-situ method of piling that was first used in the UK in the 1960s and is now one of the most common techniques. Due to the very low level of vibration, the CFA process is particularly best suited to sites which are environmentally sensitive, have noise and disruption restrictions and have soft or water-bearing ground where deep casings would otherwise be necessary. They can be constructed as single piles or installed as part of a group similar to driven pile foundations, typically for bridge construction or large foundations.

Continuous flight auger begins with a hollow stemmed auger being driven into the ground by the piling rig. Minimal noise and vibration come from this type of rig. Once the depth is reached, concrete is poured into the stem whilst it is slowly extracted. This is then extracted in a controlled manner to create the pile. Sophisticated continuous flight ager piling rigs will have a computer monitor on board that displays the boring and concreting parameters, the speed of rotation and penetration rate during the drilling phase. This information can later be read and used as a further check on the pile.