Continuous Flight Auger - The CFA Piling Method
Continuous flight auger is the quietest form of piling and is a rapid and economical construction technique.
CFA piles are formed by drilling a continuous flight auger into the ground, when the bore reaches the required depth the temporary plug that is inserted in the lead auger (This prevents soil from entering the auger hollow stem) is then ejected.
Grout or concrete is pumped down the auger’s hollow stem. Soil decompression is almost unavoidable during this phase of the operation, and the rotating auger is re-inserted while the concrete is injected.
When the grout head has been established, the auger is extracted at a speed consistent with grout supply. It is essential that the grout entirely fills the pile’s cross section, and it is a balance: although the pressure of the grout must be sufficiently high, the auger cannot be removed too quickly or soil may contaminate the pile shaft.
We install 300 mm diameter CFA piles. The process, which is virtually vibration free, is suitable in water-bearing strata; there is no need for casing or bentonite. CFA is suitable for most strata: gravel, sand, clay, soft rock or a combination of these.
Steel Case Driven Piles
Steel cased piles are driven from the bottom of the foundation as opposed to the top, meaning they do not require heavy machinery and can carry loads between 5 and 85 tonnes.
Our driven, cast-in-situ piles are closed-ended, thin-walled steel lining tubes. They are driven into the ground using a cylindrical drop hammer, where they strike a dry-mix concrete plug. The steel tubes, usually two or three metres long, are joined together with full-fillet welding during installation.
The bottom-driven piles have single bar or cage reinforcement and their casings are filled with high-strength concrete or grout. At Dart & Co Foundations, we can install bottom-driven piles with diameters of 75 mm,100 mm,150 mm,220 mm and 273 mm.
Why choose Dart & Co?
We have an extensive range of clients and work closely with developers, surveyors, engineering consultants, local district and county councils and private homeowners.
Our highly skilled chartered-engineering design team is committed to delivering high-quality solutions to mini-piling, underpinning and all types of foundations. Our engineers supply all designs for ground beams, piles and supporting designs and calculations to local authorities for consent.
The piling process at Dart & Co is bespoke, efficient and focused on quality control. As a specialist building firm, we are proficient in installation, design, building and general ground works. To discuss your piling requirements with a member of our team, please contact us for a quotation.