Cased CFA Pile - An Alternative Piling Methods - A Chance for Technical and Economical Solutions-Paper

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Cased Continuous Flight Auger (CCFA) piling combines a hollow-stem auger with an outer casing, which rotate in opposite directions as they advance into the ground. Spoil travels up the auger and exits through the casing. At the target depth, concrete is pumped through the auger as the tools are withdrawn. The casing improves support and alignment, while controlled spoil-discharge systems and optional compressed air help manage excavated material.<br /><br />CCFA is used mainly for secant and tangent pile walls, though it can also construct foundation piles. Compared with fully cased bored piling, it can reduce installation time and cost; compared with conventional CFA, casing can improve wall quality and verticality. The method is most suitable for cohesive or granular soils that allow spoil transport, generally without boulders. Typical applications reach diameters of about 1.2 m and depths of 25–30 m, depending on equipment and site conditions. Rock socketing is possible in relatively weak rock, but difficult ground may require another method.<br /><br />Project examples demonstrate its productivity. In Bath, UK, a project averaged eight piles per day, with a peak of 14. In New York, a secant wall project averaged five 15–17 m piles per day. Despite encountering boulders, the CCFA rig cut through most of them, and the completed wall met verticality tolerances; a Kelly drilling rig was needed only twice.<br /><br />Successful use depends on matching equipment and tooling to ground conditions, ensuring adequate rig torque and extraction capacity, maintaining a reliable concrete supply, and coordinating and training the crew. CCFA offers substantial schedule and cost-saving potential when site conditions and project constraints are appropriate.

Keywords

cased continuous flight auger

CCFA piling

secant pile walls

tangent pile walls

hollow-stem auger

outer casing

concrete pumping

verticality control

bore pile construction

foundation piles