CFA Piles Melbourne — Vibration-Free Deep Foundation Installation

What Are CFA Piles?

CFA piling (Continuous Flight Auger piling) is an advanced deep foundation method that combines borehole drilling and concrete placement in a single uninterrupted operation. A hollow-stemmed auger is rotated continuously into the ground — without being extracted — until the full design depth is reached. Once at depth, structural concrete is pumped under positive pressure through the hollow auger stem and out at the auger tip. As the auger is slowly and steadily withdrawn, the flowing concrete fills the void left by the retreating auger, forming a continuous concrete column from pile toe to surface.

Once the auger is completely withdrawn and concrete extends to the surface, a steel reinforcement cage is vibrated into the fresh concrete to provide structural strength. The completed pile is a seamless reinforced concrete column formed entirely below ground, with no open borehole at any stage and no casing to extract.

How CFA Piling Works — Step by Step

1. Rig Positioning

   The MAIT HR75 CFA rig is positioned over the pile location and levelled. Alignment is confirmed to the engineer's set-out marks, with horizontal position tolerance typically ±25mm and verticality ±1° per AS 2159-2009. For contiguous pile walls, alignment accuracy directly affects the final wall geometry.

2. Continuous Drilling to Depth

   The hollow-stemmed auger rotates continuously into the ground. Drill cuttings travel up the auger flights to the surface. Drilling continues without pausing or extracting the auger until the full design founding depth is confirmed. The continuous operation is what prevents borehole collapse in soft or unstable ground.

3. Concrete Pumping Commences

   With the auger at full depth, the concrete pump is engaged. High-slump concrete (typically 100–150mm slump, minimum 25MPa at 28 days, to AS 3600-2018) is pumped under sustained positive pressure down through the hollow auger stem and exits at the auger tip. Maintaining positive pressure at all times is critical — any reduction risks soil entering the concrete column.

4. Controlled Auger Extraction

   As concrete pumps, the auger is slowly and continuously extracted at a controlled rate matched to the concrete flow. The extraction rate is managed carefully to ensure concrete always remains ahead of the retreating auger tip. Modern CFA rigs like the HR75 feature automatic extraction rate control for consistent quality across all soil conditions.

5. Reinforcement Cage Installation

   Immediately after the auger is fully extracted, a prefabricated steel reinforcement cage — designed and specified by the structural engineer — is vibrated into the fresh concrete. Installation must be completed within approximately five minutes while concrete remains sufficiently fluid. Cage installation depth and cover are checked against engineer's drawings.

6. Documentation

   For every pile, ASAP Piling records: drilling depth and duration, concrete volume pumped, auger extraction rate, any anomalies or refusals encountered. These records are provided to the engineer for the project quality file.

7. Curing and Pile Head Preparation

   Completed piles cure in place. Pile heads are prepared at the design cut-off level. Where capping beams or ground beams are required, the reinforcement cage is left protruding at the correct embedment length into the beam.

When Is CFA Piling the Right Choice?

CFA piling is the preferred deep foundation method when one or more of the following conditions apply:

CFA vs Standard Bored Piling — Key Differences

The fundamental difference is borehole stability management. Conventional bored piling relies on a temporary steel casing or bentonite/polymer slurry to prevent the borehole walls from collapsing during drilling. CFA eliminates this need by filling the void with concrete before the auger is ever extracted — the borehole is never open at any point during the operation.

Available Specifications

ASAP Piling's CFA Equipment

ASAP Piling operates the MAIT HR75 CFA rig, manufactured by MAIT S.p.A. in Italy and configured specifically for the Australian market. The HR75 features fully automatic extraction rate control during CFA operations, which maintains the consistent withdrawal speed required to produce a uniform, defect-free pile shaft across variable ground conditions. This automation reduces the dependency on operator judgement during the critical extraction phase and produces more consistent outcomes across a working day of high-volume production.