There is no one size fits all answer to piling. Different jobs require different methods in order to extract earth and to drive the piles, whether it be because of location, budget restraints or from other restraints that may affect which method can be used effectively and safely.
Continuous Flight Auger (CFA)
CFA forms a pile by using a helical auger that works on the same principle as a household screw. The helical nature of the auger extracts the soil as it is driven into the ground through a circular motion. Once the ground is extracted, concrete is installed by injection under high pressure through a hollow central stem which is fed through slowly as the auger is removed. Into the wet concrete, pile reinforcements, usually in the form of steel cages, are lowered by crane.
Advantages
CFA provides minimal levels of vibration, lower noise levels from the piling rig itself and is more suitable for tension loads at stability elements depending on the ability to install the cage prior to the drying of the concrete.
Disadvantages
If the piles are being driven into sand below the water table then they require driven steel casings to be installed, otherwise the pile bore can collapse. They also require longer piles than driven which ultimately results in longer continuous noise exposure to the driven piles.
Issues with the removal and disposal of potentially contaminated soil do arise in certain locations. In these cases, plans need to be placed before work commences so that soil is dealt with in a safe and timely manner.
Installation programmes for CFA commonly run for 8 weeks which is one of the longest programmes and potentially one of the most expensive.
The process also involves more construction traffic to accommodate the delivery of steel and concrete and to remove any arisings. Cranage is also required to install pile reinforcements.
A major concern with CFA is the risk of in situ concrete drying out due to the leakage of sand which can cause problems with the installation of the steel cages.
Contact the team at Rhino Piling for more information on piling in Manchester.
