A CFA pile, also known as an Augercast pile, is constructed by drilling to the required founding depth with a full-length hollow-stem auger. The auger has a hollow interior and a steel casing with continuous flights welded the full length along its exterior. Prior to drilling each hole, a plastic plug is placed in the base of the hollow stem of the auger. Once the required depth is achieved, high slump concrete is pumped into the centre of the auger from the top, displacing the drilling plug. The auger is extracted with the rig while the high slump concrete is pumped down the centre of the auger replacing the soil and thus ensuring that the perimeter of the hole remains stable at all times.
To install hole diameters up to 610 mm Anchor’s Bauer BG40’s are capable of achieving drill depths up to 27 metres. For larger hole diameters up to 1000mm these drill rigs are capable of drilling to depths up to 21 metres. As shown below the CFA tooling can also be mounted on Anchor’s Bauer BG28 drill rigs.
In order to verify the capacity of the piles to be used in the design, typically a CFA pile is installed in advance specifically for load testing purposes. It is advantageous to complete installation and testing as early as possible to provide verification of design parameters in the event that modifications that are required as a result of confirmed site conditions.
Installation of the load test pile and every production CFA pile is carefully monitored for rate of auger extraction, concrete pressure and volumes to verify quality of the finished CFA pile. The Bauer rigs used by Anchor Shoring are equipped with monitoring equipment which plot this information on a real-time basis allowing both the operator and the inspector to confirm that there are no issues such as necking or overpouring of concrete during installation, thus ensuring a quality product.