Made in America:  Continuous Flight Auger (CFA) Piling is the quietest form of piling and is a fast and very economical technique. It is a cast in-situ process, very suited to soft ground where deep casings or use of drilling support fluids might otherwise be needed.

Overview: CFA piles are also commonly known as auger-cast piles or auger-cast-in-place piles. They are constructed by drilling a slender hole into the ground utilizing a hollow stem auger, then pressure pumping grout or concrete through the hollow stem of the auger as it is slowly being retracted. If required, a reinforcing cage or center bar can be installed immediately after the auger is fully withdrawn.

Advantages: CFA piles are a great deep foundation solution for collapsible soils or where the presence of a high water table will have a negative impact on construction. The hollow-stem auger acts as a temporary casing during installation, eliminating the need for costly casing solutions that would be required for other foundation methods. CFA piles are suitable for most soil conditions. The noise and vibration levels are very low compared to other deep foundation methods. The CFA technique has high productivity rates.

Applications: CFA piles are ideal in secant and tangent piling for shoring projects.

Allowing for in-fill construction, they are ideal for projects with limited overhead room.

They are a great deep foundations solution for new construction in commercial, industrial, and infrastructure projects.

Summary from: FHWA-HIF-07-03  Federal Highway Administration  U.S. Department of Transportation

Reinforcing Cage/Specification

Reinforcing cages should be fabricated so that lifting and handling does not cause permanent distortion or racking. For this reason, it is important that wire ties be used on all longitudinal bars at every spiral. Welding is permitted if weldable reinforcement is specified. The use of welded (spiral) cages can assist in handling the cage with a minimum of distortion. Spliced steel cages and/or coupled threaded bars are often necessary to install reinforcement in low headroom applications.

Reinforcement cages are normally specified with (3 in.) clear cover to the outside of the pile. Spacers should be placed at intervals of no more than about (10 ft) along the cage to provide cover. Spacers made of steel may greatly accelerate corrosion of the reinforcing steel, particularly above the groundwater table. Centering guides made of steel, such as a wire “basket” or “football” tied at the base of single-rod reinforcement may be used. A reinforcing cage may be tied together at the bottom to create a “point” to facilitate installation into the pile. If CFA piles are used on a batter, special provisions may be necessary to maintain cover. a continuous PVC pipe may be used on the bottom side of the cage to maintain cover and act as a “runner” to slide the reinforcement cage into position within the grouted pile.

Where a single bar is used for tensile reinforcement, centralizers are used at spacing of no more than (10 ft). Splices may sometimes be used with CFA piles, but it is better to avoid the use of splices. Splices are common for piles supporting tensile forces or for piles reinforced with a single full-length center bar. Mechanical splices are preferred in such cases, and high-strength threaded bars are convenient for this purpose.

Designers should include reinforcement cages that use:

(1) fewer heavy bars instead of many smaller bars;

(2) are no longer than the minimum necessary to provide structural capacity and anchorage; and (3) allow the cage installation proceed with minimum difficulty. The contractor should tie the cage to permit handling without permanent distortion.