In the complex realm of piling construction, selecting the appropriate deep foundation method is a pivotal decision that profoundly impacts a project's efficiency, budget, and environmental footprint. Among the most widely used piling types are driven piling and bored piling. While both are crucial for creating robust pile foundations that support the foundations of a building on challenging ground, their methodologies and ideal applications vary significantly. Understanding the key differences between driven piles and bored piles is essential for piling companies and piling contractors seeking to deliver effective and safe solutions.

What are Driven Piles?

Driven piling involves the installation of pre-formed pile elements into the ground using percussive force or vibration. A powerful pile driver (or piling rig) hammers or vibrates the driven pile (which can be precast concrete piles, steel, or timber) into the soil until it reaches the required depth or refusal, indicating sufficient ground bearing capacity. This method is often referred to as pile piling due to the driving action.

Key characteristics of Driven Piles:

• Displacement Method: As the driven pile penetrates, it displaces the surrounding soil laterally, compacting it and often increasing the soil bearing capacity in the vicinity of the pile.

• Pre-formed: The driven pile is manufactured off-site to specific dimensions and strengths, allowing for strict quality control before installation.

• Noise & Vibration: Driven piling can generate significant noise and ground vibration, which is a primary consideration in urban or sensitive environments.

• Minimal Spoil: Since soil is displaced rather than excavated, there is typically minimal spoil (excavated material) to manage on site

What are Bored Piles?

Bored piles, in contrast to driven piles, are cast in situ (on-site). This method involves drilling a hole into the ground, often using a specialized piling rig, and then filling it with concrete and steel reinforcement to form the pile.

Key characteristics of Bored Piles:

• Non-Displacement Method: Soil is extracted during drilling, so there is little to no ground displacement or vibration, making it ideal for sites near existing structures or in congested areas where signs of subsidence from ground movement are a concern.

• Cast In Situ: The pile is formed directly in the ground, allowing for flexibility in length and diameter based on real-time ground conditions.

• Spoil Generation: The drilling process generates spoil that needs to be managed and disposed of.

• Common Types:

  • CFA Piling (Continuous Flight Auger Piles): A very common bored piling method where a hollow-stemmed continuous flight auger drills, and concrete is simultaneously pumped through it as the auger is withdrawn. Also known as continuous auger piles or continuous flight auger CFA piles, this method is fast and minimizes bore instability.

  • Mini Piling: A specific application of bored piling using compact mini piling rig equipment. Mini piles are small-diameter bored piles ideal for restricted access, low headroom, or extensions foundations where larger equipment cannot operate.

  • Rotary Bored Piles: Often used for larger diameters and deeper deep foundation requirements, sometimes involving temporary casing.

    
    

When to Choose Driven Piling

Driven piling remains a strong choice for piling contractors and piling companies when:

• Projects are on large, open sites where noise and vibration are not major concerns.

• Ground conditions are consistent and suitable for displacement (e.g., firm clays, dense sands).

• Speed of installation is a top priority, and a pile driver can operate efficiently.

• There's a need to minimize excavated spoil.

• Pre-manufactured concrete piles offer desired quality assurance.

When to Choose Bored Piling

Bored piling is often preferred by piling companies for:

• Urban or residential areas where noise and vibration restrictions are strict.

• Sites with variable or unstable ground conditions, where the bore needs support during concreting.

• Projects requiring very deep foundations or large diameters that might be difficult to drive.

• When working close to existing structures, where the risk of signs of subsidence due to ground movement needs to be mitigated.

• For specialized applications like mini piling or when continuous flight auger CFA piles offer optimal efficiency.

In Conclusion

Both driven piling and bored piling are proven deep foundation methods that create robust pilings for the foundations of a building. The choice between these two significant types of piling hinges on a thorough understanding of site-specific conditions, structural requirements, and environmental considerations. Whether opting for the percussive power of a driven pile or the quiet precision of a CFA pile or Mini Pile, engaging experienced piling contractors is paramount. Their expertise in assessing the bearing capacity of soil and selecting the most appropriate piling rig and method will ensure your pile foundation is perfectly suited for its purpose, providing a secure and lasting base.