Drilled piles are particularly suitable for foundations of heavy structures when soil has a low load-bearing capacity. They are made of reinforced concrete, with dimensions ranging from 600 to 2000 mm, and they can reach lengths of over 50 metres and withstand loads of hundreds of tons. The excavation is usually made using rotating equipment (buckets or drills). Bentonite slurries are commonly used to support the excavation, but when the geological conditions do not allow their use, sheet piles are used as an alternative.
CFA (Continuous Flight Auger) PILES
The CFA method is largely used when the characteristics of soil or works to be executed allow drilling without using bentonite slurries, reinforcement cages and casing oscillator, or when short execution times are required.
The equipment consists of hollow stem augers with a diameter ranging from 600 to 1500 mm. The use of CFA piles is preferred in soft or incoherent soils, either cohesive and non cohesive, even in the presence of ground water.
FDP (Full Displacement Piles)
FDP are installed by turning and pushing into the ground a special tool that causes the progressive lateral displacement of soft cohesive soils, instead of the excavation and removal of soils.
This method has multiple advantages:
- installation without vibration in the soil or in the surrounding buildings and areas;
- production of little or no waste to be removed. This is particularly beneficial when the soil is polluted or when landfills are distant from the construction site;
- no need of bentonite or reinforcing cages to support the excavation, thanks to the use of dry drilling;
- compaction of soil around the pile, which improves geotechnical characteristics, giving the piles a greater bearing capacity and allowing the reduction of their length, as well as a regular geometry;
- penetration and extraction of the tool into and from the soil occur in a single operation. The insertion and pile casting are automatically handled by an on-board computer. This results in high productivity, low installation costs, and real time control of the quality of piles.