The CFA piles combine the advantages of the driven piles with no removal of soil with the versatility of the bored piles. The drilling method allows to excavate in a wide variety of soils, dry or water-logged, loose or cohesive, and also to penetrate through low capacity, soft rock formations 4 tuff, loamy clays, limestones and sandstone, etc.
No shocks or vibrations are induced when the system is performed; this plus the fact that the equipments is fully sound — proofed, as per law requirements, makes CFA the most convenient piling method for construction in town centres.
The execution of the pile without decompression of the soil permits to work close to the existing structures.
Besides, no bentonite mud is needed for the excavation, which means that provision and space for the side plant are reduced, there is no danger of bentonite contamination and, consequently, all problems connected to the disposal of the excavated materials are simplified.
The reduced volume of soil brought up to the surface by the flight auger means less amount of excavated material that has to be transported to the disposal point.
The range of diameters from 40 to 140 cm and depths from 25 to 33 m, allows to overcome problems connected to the project and execution of the pilings.
SOILMEC experience gained in approximately 30 years in the execution of CFA pile, enables to operate the system even in difficult grounds, thanks mainly to the use of different teeth and augers.
Drilling is performed by a helicoidal steel plate welded to a central hollow stem, which is provided at the lower part with teeth to help penetration through the ground.
A disposable shoe, fitted as plug at the end of the stem, prevents the entering of the soil when the auger string is driven down.
The ground is partially pressed sideways by the auger penetration, which results in a thickening and compaction of the soil all around the shaft.
The equipment generally consists of a flanged or tubular type leader — in length depending on pile depth — and of a crawler crane on which the leader is mounted.
Alternatively, the auger system is operated by self-erecting fully hydraulic rigs type R-Series and CM-Series that SOILMEC has especially designed for the CFA pile.