Continuous Flight Auger Piling

Continuous Flight Auger or CFA as it is usually known is a system of piling where a hollow stemmed auger is screwed into the ground by the piling rig with minimal vibration. When the correct depth is reached as indicated by the site investigation and pile design, concrete is pumped through the hollow stem auger. The concrete pressure and rate of flow is all measured by instrumentation on the piling rig.

The auger is slowly withdrawn whilst being rotated to remove the ground and concrete is simultaneously pumped to the toe of the auger while the pressure and volume is controlled to maintain a positive pressure in the concrete in the ground. When the excavation is complete the surplus material is removed by excavator and the hole is left full of concrete Reinforcement can then be placed using an excavator, piling rig or by hand. Because the side of the excavation is always supported by the pressure in the concrete there is no tendency for the hole to collapse and consequently CFA piles can be constructed in most ground conditions.

The main advantage of CFA

The main advantage of CFA is that it is a relatively quiet and vibration free method and with the right choice of rig can be very quick. Depending on the rig, piles up to 30m long and 1200mm diameter can be constructed using CFA techniques.

The method was first used in this country in 1966 and now it is probably the most common piling technique.

At Tritech Continuous Flight Auger piling is our most common technique. We have constructed numerous schemes using CFA techniques for bearing piles and secant and contiguous pile walls using overall Soilmec CM 48/SP50 and Casagrande B125 rigs for the larger piles and our Klemm 709s for the shorter and more inaccessible piles.

Tritech has a number of CFA Case Studies

CFA in Greenwich

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