What is a CFA Pile?
Continuous flight auger piles (CFA piles) are also commonly called augercast, augered cast in place piles (ACIP) or auger pressure grouted piles (APG). They are predominantly used in unstable soil conditions with a high ground water level when conventional drilling would require casing or drilling slurry to stabilize the bore hole.
CFA piles can be installed very efficiently with modern high-torque hydraulic drilling rigs up to a depth of 125 feet and 60 inches in diameter. Crane mounted lead systems extend the installation range beyond 170 feet, however, pile diameters are reduced with depth. Malcolm’s method for installing with the crane mounted lead system is called “CFA Mega Piles.” This method utilizes one continuous auger which is drilled into the ground. The soil on the auger prevents the surrounding ground from caving during the drilling and grouting process.
Close control of auger advancement and soil removal is essential to prevent loosening of the soil by excessive removal during the advancement of the CFA auger. After reaching pile tip, the auger is extracted while fluid concrete or grout is pumped through the hollow stem auger to fill the hole under positive pressure. Rebar is installed into the completed pile after the auger is removed.
CFA installations are highly productive and vibration free. Pile capacities of up to 1,500 tons can be achieved depending on the soil strata. High productivity makes CFA piles most suitable for larger projects. Malcolm has the capability to install CFA piles from 16 to 48 inches in diameter to depths in excess of 150 feet.
All of our drilling units are equipped with a state-of-the-art automated monitoring system (B-Tronics) which controls and records in real time multiple drilling parameters, such as advancement rate, grout volume, drill depth, rotation of the auger and drilling resistance rates. During the auger withdrawal a continuous record is produced including grout or concrete injection rates to verify compliance with all quality control requirements.
Benefits of CFA Piles
- Allows for schedule compression through increased productivity compared to traditional drilled shafts.
- Allows pile construction in unstable soils with high ground water level.
- CFA Piles do not require casing or drilling slurry to stabilize the bore hole.
- Well suited for ground conditions that may cave.
- Efficient/Quick/Cost Effective.