Continuous Flight Auger (CFA) Piling
Foundation Piling has a fleet of CFA piling rigs suited to every application, from restricted access sites or low headroom areas to deep, large diameter CFA piles. These rigs are capable of constructing piles in a variety of ground conditions.
CFA piling is particularly suited to piling through interbedded sequences of clays and water bearing non-cohesive strata. A CFA pile is formed using a long string of augers, with soil displaced via the auger flights. Piles can be drilled to depths of up to 34m with the concrete pumped through the hollow stem of the augers as they are withdrawn from the design depth. Reinforcement cages are installed immediately after concreting.
Foundation Piling continues to pioneer the development of restricted access auger equipment. The use of Sectional Flight Auger (SFA) techniques in low headroom and restricted access had previously been limited in depth and diameter. Using our restricted access rigs, piles up to 600mm diameter can now be installed in excess of 25 metres and within headroom as low as 4 metres.
Our fleet includes lightweight rigs with short masts and remote power packs for working inside buildings without creating fumes, 38T rigs with shortened masts to construct large diameter piles in 13m headroom, and small footprint (4 x 5m) machines capable of constructing 15m deep piles in a single pass.
The CFA method may be adapted for auger displacement piling (or CHD piling) using a “bullet” type auger. Here, the bullet pushes soil to one side as the auger progresses, with concrete again pumped through a hollow stem.
Further innovations in our fleet include-
- jackup piling rigs which can lift up off their tracks and turn on the spot, avoiding damage to the pile mat on tight sites
- tracked pump and agitator units, which move freely to maximise space on site and shorten concrete hoses for safer pumping
- purpose made lifting tools to assemble auger strings while eliminating work from height hazards
- remote controlled tracking for loading rigs safely from ground level
- dual purpose rigs which rapidly convert between CFA and rotary modes in variable ground conditions or for low cut-off basement piles
Quality control is critical in CFA pile construction. All of our CFA rigs feature in-built computers to monitor the volume of concrete pumped as the auger is extracted. This telemetry allows careful monitoring of pile formation, ensuring stability of the bore and integrity of the pile. Each rig is connected to a mobile network to transmit pile construction data as the pile is built.
Heavy duty twin wall augers are used for contiguous and secant piling, to maintain piling tolerances and maximise the space in a basement or on a sloping site. Where verticality is critical to the design of a structure, our larger rigs can be fitted with a second rotary head and an external casing, known as cased auger or cased secant piling (CAP or CSP piling).
CFA piles are the most economic solution for many sites. Crucially for urban and confined sites, our CFA rigs have minimal environmental impacts in terms of noise and vibration.
Standard Tool Sizes
- Bearing piles
- Retaining walls, including contiguous and secant piling
- Low vibration piling
- Restricted access and low headroom piling
- Diameters from 300mm – 1200mm
- Depths up to 30m
- Rigs from 6-82t operating weight
- Headroom as little as 4m
- Torque up to 271kNm
- Cased CFA options available (CAP/CSP piling)
- Heavy duty augers for high tolerance contiguous and secant piling
- Casing installation to 15m in sectional SFA mode