- CFA piles are a type of drilled foundation in which the pile is drilled to the depth required in one continuous process using a continuous flight auger, hence “CFA”. As the auger is drilled into the ground, the flights of the auger fill with soil, providing lateral support and maintaining the stability of the hole. Once the depth is reached, the auger is withdrawn from the hole, concrete or a sand/cement grout is pumped through the hollow center of the auger pipe to the base of the auger. Simultaneous pumping of the grout or concrete and withdrawing of the auger provides continuous support of the hole. Reinforcement for steel-reinforced CFA piles is placed into the hole filled with fluid concrete/grout immediately after withdrawal of the auger
- CFA piling is:
- Vibration free
- Wide range of depth and diameter combinations are available
- Effective retaining wall construction method
- Compatible with most soil types
- For more information:
- Drilling the auger into the ground
- Reaching the required depth
- Pouring in concrete
- Installing reinforcing cage
Drilling with Drilling Fluid
- If the ground water table is high and the soil soft, then the hole will want to collapse.
- A drilling fluid can be used to prevent side wall collapse and prevent water from entering the pier hole.
- As the auger is drilled into the ground, the drilling fluid is pumped into the hole
- Most of the drilling is undertaken under the drilling fluid
- Typically the reinforcing steel cage is placed in the hole once complete
- A caisson is a simple steel tube that is drilled into the ground
- The auger then drills inside the caisson, as the caisson prevents any material from entering the hole
- As the augers drills out the internals of the caisson, the caisson can be advanced to greater depths
- This creates a clear open hole which can be constructed in the same manner as open hole piles above.
- We have successfully used caisson drilling in low headroom and difficult ground conditions.