CFA - CONTINUOUS-FLIGHT- AUGER PILES by Foundation Specialists , INC.
The continuous Flight Auger Piles or CFA piles are constructed using a hollow shaft with internal diameter 100mm, while the continuous-flight auger’s diameter vary from 300mm to 650mm and can reach depths of up to 30 meters. The system works well in most soil formations, also in the presence of shallow water table. The Continuous Flight Auger is rotated and pressed into the ground to reach the design pile depth. The soil gradually fills the space between the auger stem and the hole’s wall, The build-up of soil within the blades of the continuous auger compressing the soil laterally. the soil filling the auger prevents water from the water table to enter the hole produced by the auger, thus there is no need of drilling fluid and of temporary casing. The bottom of the hollow auger’s stem is plugged with a disposable (sacrificial) plug, usually made of cast iron, which is made to drop off when pouring of the auger pile begins. Concrete usually made with coarse sand (to allow insertion of reinforcing bars cages or other items to be embedded) is pumped thru a rubber hose connecting the concrete pump to the swivel elbow mounted at the top of the rotary, into the hollow auger stem thru the swivel mounted on the stem's top, is conveyed to the auger bottom and into the hole created by the continuous flight auger, which is gradually lifted by the crane’s hoist. In reality the use of an efficient concrete pump will pump the concrete with sufficient pressure to cause the concrete to push the auger upwards. The pouring method prevents cave-in of the hole and also prevents water from the water table to enter the excavation , thus preventing the creation of joints along the pile shaft.. The "Pros" of this system are the rapidity of installation, and low cost of installation. However the system requires the installation of the reinforcing bars cages after the pouring of concrete, which limits the length of the reinforcing bar cage that can be installed.
The CFA piling equipment of FS is mounted on a crawler crane, the power-pack needed to operate the rotary is installed at the back of the crane body, next to the counter-weight. When not in use, the CFA Equipment is disassembled , checked and stored properly.
We show here below a picture of FS CFA Piling Rig, taken at a FS Piling Project Site, and picture taken in our warehouse of the main elements of the CFA equipment, Hydraulic Rotary with two motors , the Mast Elements, Augers, to be assembled and mounted on a crawler crane for the execution of CFA Piles..
Top & BOTTOM VIEWs OF CFA HYDRAULIC ROTARY WITH DOUBLE MOTORS
Side view of the CFA Hydraulic Rotary with double motors
The concrete is pumped, thru a rubber hose, to the hollow built-in swivel at the top of rotary, and from there the concrete is conveyed thru the hollow shaft of the auger to fill the hole created by the auger, while , after completing the boring, the continuous flight auger is gradually lifted upwards.