July 20, 2024
CFA Piling

When building a deep foundation, two distinct techniques (cast-in-place or excavation) are utilised: CFA (Continuous Flight Auger) pilings and open drilled piles. These methods are usually employed to support massive structures or transmit structural loads to deeper, more stable soil or rock layers.

What is CFA Piling?

Continuous flight auger piling, or CFA piling, is a type of foundation procedure where reinforcement is inserted into the wet concrete after the drill has been eliminated. Drilling and concreting are done simultaneously.

It is a cast-in-situ method of piling, which means that the concrete is poured and allowed to cure on the spot. It is often used in inner cities and other locations where decreased noise and vibration are crucial.

What are the Applications and Procedures of the CFA Piling?

Where Can CFA Piles Be Used?

  • Fit for well-established sites and structures in inner cities.
  • Very little noise and vibrations during installation.
  • Perfect for both business and residential projects.
  • Suitable for different types of soil.

What is the Procedure for CFA Piles?

  • The hollow stem continuous flight auger is turned down to the intended depth in the soil.
  • As the auger is withdrawn, grout or concrete is injected through the hollow stem to fill the cylindrical void.
  • A cage for reinforcement is inserted through the recently laid concrete.
  • At the very least, a stiff cage of six metres in length is utilised. Longer cages can still be installed in accordance with design specifications.
  • If necessary, specially designed vibrator devices can help locate reinforcing cages precisely.

What is the Cost of CFA Piles?

The prices vary because each type calls for a distinct set of personnel and procedures. For instance, the cost of drilling piling is between £200 and £400 per linear metre. In contrast, sheet piling is roughly £150 to £200 per metre.

What is Open Bored Piling?

Open-bored piles work extremely well in cohesive soils. The revolving auger presses into the strata, reaming out the dirt as it goes. Once the required or desired depth is reached, the drills are removed, leaving an open hole.

Standard pile sizes and bearing capacities are as follows:

150mm diameter with a Safe Working Load (SWL) of 100-150kN, 200mm diameter with a SWL of 150-250kN, 250mm diameter with a SWL of 250-350kN, and 300mm diameter with a SWL of 350-500kN.

After that, steel reinforcement is inserted, and concrete is poured.

What are the Applications and Procedures of the Open Bored Piles?

Open Bored Piles

Where this Piling Can be Used?

  • Borehole piles are drilled into the earth and are a good option for urban locations where vibration reduction is essential.
  • To provide structural stability on cohesive soils with low water tables, open-bore piles are the best option.
  • A pile known as a CFA (Continuous Flight Auger) or SFA (Sectional Flight Auger) is created when concrete is laid prior to auger extraction.

What is the Procedure for this Piling?

  • Open bored piles use a spinning drill, and a hole is created by removing ground until the required depth is attained.
  • In order to create the pile, a steel cage is installed and filled with concrete after withdrawal.
  • Suitable for clay and silty cohesive soils without water tables.
  • Depending on the ground area, different rig sizes are employed; larger rigs are recommended for outdoor or indoor spaces to reduce vibrations.

Conclusion | CFA Piling vs Open Bored Piling

Continuous Flight Auger Piling Open Bored Piling
CFA piling exhibits notable qualities such as swift production rates, minimal noise emissions, and nearly vibration-free installation, rendering it appropriate for inner-city undertakings and settings where minimising disruption is of utmost importance. Open bored piling provides advantages such as fewer stages of excavation, less trench space occupied, and resistance against corrosion and high winds. However, installing it can take longer, and there might be issues with vibrations in the soil and noise pollution when drilling.

In the end, the decision between the two approaches is based on the specifications of the project, the state of the soil, and certain limits like available space and environmental issues.

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