Difference Between CFA Piling and Contiguous Piled Wall

CFA Piling:

In construction and foundation engineering, different piling techniques serve specific purposes depending on ground conditions, structural requirements, and budgetary constraints. Continuous Flight Auger CFA Piling and contiguous piled walls are two popular solutions, often employed in foundation and retaining wall construction. While both involve the use of piles, their methods, applications, and advantages differ significantly.

What is CFA Piling?

Continuous Flight Auger (CFA) piling is a non-displacement method used for creating deep foundations. It involves drilling into the ground using a continuous flight auger, which simultaneously removes soil as it drills. Once the desired depth is reached, concrete is pumped through the hollow stem of the auger while it is being withdrawn, creating a reinforced concrete pile. Steel reinforcement is then inserted into the wet concrete for added strength.

Key Features of CFA Piling

Non-Vibratory Installation:

Ideal for urban areas where minimizing vibrations is critical.

Versatility:

Suitable for various soil types, including soft clays, loose sands, and gravels.

Quick Installation:

The continuous process reduces time compared to other methods.

High Load Capacity:

It can support substantial axial and lateral loads.

Applications of CFA Piling

• Building foundations, including residential and commercial structures.
• Infrastructure projects like bridges and highways.
• Stabilizing slopes or embankments.

What is a Contiguous Piled Wall?

A contiguous piled wall is a retaining wall created by constructing a series of closely spaced piles, leaving small gaps between them (typically 50-150mm). Unlike CFA piles, these walls are designed to act as structural barriers for retaining soil and water. The piles can be bored or driven, and the wall is often combined with additional elements, such as shotcrete or grouting, to reduce permeability.

Key Features of Contiguous Piled Walls

Retaining Wall Solution:

Primarily used for excavation support and slope stabilization.

Intermittent Construction:

Small gaps between piles allow for limited soil movement.

Customizable Depth:

Suitable for deep excavations, with pile lengths adjusted to project requirements.

Water Permeability:

Not fully watertight, but additional measures can reduce seepage.

Applications of Contiguous Piled Walls

• Basement and underground parking structures.
• Retaining walls for deep excavations.
• Stabilizing slopes and preventing soil erosion.

Which One is Favorable?

The decision to choose between CFA piling and a contiguous piled wall depends on the specific requirements of the project. Below are key considerations to help determine the most favorable option:

Choose CFA Piling If:

Foundation Support is the Priority:

CFA piles are excellent for providing deep foundation support for buildings, bridges, and other structures requiring high load-bearing capacity.

Time Constraints Exist:

The continuous process of CFA piling reduces construction time, making it ideal for projects with tight deadlines.

Minimizing Vibrations is Critical:

In urban or sensitive areas, CFA piling’s non-vibratory nature makes it a preferred choice to avoid disturbing nearby structures.

Wide Range of Soil Conditions:

If the site has varied or challenging soil types, CFA piling’s adaptability ensures a stable foundation.

Choose Contiguous Piled Walls If:

Excavation Support is Needed:

Contiguous piled walls are specifically designed for retaining soil and supporting excavations, such as basements or underground parking.

Cost is Secondary to Functionality:

Although generally more expensive, contiguous piled walls provide effective lateral support and can be customized to include waterproofing measures.

Seepage Control is Manageable:

A contiguous piled wall can be an effective solution if small amounts of water seepage are acceptable or can be managed with additional measures.

Steep or Vertical Slopes:

When stabilizing slopes or creating retaining walls for deep cuts, contiguous piled walls offer a robust structural barrier.

Hybrid Solutions

In some cases, a combination of CFA piling and contiguous piled walls may be employed to address both load-bearing and lateral support requirements. For example, CFA piles for deep foundation support alongside contiguous piles are used for retaining walls in basement construction.

Combining CFA piling with diaphragm walls for projects requiring both vertical and horizontal stability.

Conclusion:

Both CFA piling and contiguous piled wall have distinct advantages and are suited to specific construction needs. CFA piling is favorable for projects prioritizing deep foundation support, speed, and minimal vibrations, while contiguous piled walls are ideal for excavation support and retaining soil.

Understanding the project’s requirements, site conditions, and budget is essential to selecting the most appropriate solution. In some cases, combining these methods may provide the optimal balance of functionality, cost-efficiency, and structural integrity.

Southern Foundations & Piling delivers high-quality, efficient, and cost-effective solutions tailored to each project’s specific needs. Their expertise includes Continuous Flight Agglomerator (CFA), mini piling, and other techniques to ensure secure foundations in varying soil conditions. The company prides itself on a strong safety record, timely project completion, and compliance with industry standards.