Continuous Flight Auger (CFA) Piles:
CFA piles are a widely used replacement piling solution, replacing the ground with a column of concrete forming the foundation element. The process involves drilling a hollow stemmed continuous flight auger into the ground to the required depth, at which point concrete is injected through the tip of the hollow stem, and the auger is withdrawn from the ground, simultaneously removing the spoil from the ground. When the concreting process is completed, reinforcement is introduced to finish the pile. But what are the benefits and limitations?
1. Speed and Efficiency:
CFA piles are known for their speed and efficiency, making them suitable for projects that require relatively quick installation. The continuous drilling process minimises interruptions and eliminates the need for the casing. Pile depths are generally limited to the length of the auger, which in turn, is governed by the height of the piling rig mast.
2. Reduced Noise and Vibration:
Compared to other piling methods, CFA piles produce less noise and vibration during installation. This is particularly advantageous in urban areas or sites near sensitive buildings and infrastructure where minimising disruption is crucial.
3. High Load-Bearing Capacity:
CFA piles provide wide-ranging load-bearing capacity, subject to diameter and depth, which can be varied relatively easily, making them suitable for a variety of applications, including heavy structures and tall buildings. The continuous concrete column contributes to improved structural integrity and strength.
Sectional Flight Auger (SFA) Piles:
SFA piles are also a replacement piling method that offers unique benefits. The piles are constructed in very much the same way, with the distinct difference being the augers are sectional (typically in 1 – 2m lengths) and are incrementally introduced as the pile advances. Let’s explore the benefits of SFA piles:
1. Restricted Access Capability:
One of the primary advantages of SFA piles is their ability to be installed in restricted access areas. The sectional auger sections can be easily transported and assembled on-site, allowing piling operations in confined spaces or in areas with limited space and headroom. Section lengths are directly related to the speed of installation; short sections take longer to install, but reduce the headroom required to operate.
2. Versatility:
As the auger flights are added in sections requiring only a short mast on the piling rig, this should not always be viewed as a disadvantage. Subject to the piling rig capability, the number of sections added can exceed the depth achievable by a CFA piling rig with one fixed flight.
3. Cost-Effective Solution:
Whilst SFA piles have a slower installation rate than comparable CFA piles, smaller projects are often more cost-efficient due to the smaller plant, and lower plant mobilisation and working platform costs.
When choosing between the two techniques, it’s essential to consider the specific requirements of your project, including factors such as site conditions, accessibility, timeline, and budget. Consulting with experienced professionals, such as the team at Roger Bullivant Limited, will help you make the right choice.