What is the Difference Between CFA Piles and Bored Piles?

When the load-bearing capacity of the topsoil is low or the vertical loads placed are too heavy, a concrete piling base is needed.

There are two main types of concrete piles; the end bearing piles, where the pile serves as a column holding the load down to the bearing strata, and the friction piles, where the load is progressively moved along the length of the pile.

Bored piles are often large in diameter in comparison to traditional continuous flight auger (CFA) piles. They are used to accommodate higher loads, bypass underground impediments, and infiltrate the ground too hard to drill using a continuous flight auger, or to build stacks with a cut-off level below the platform level. On the other hand, the CFA piling methodology is more fitting for lightly-loaded constructs. Let us understand both types of piling in detail and their distinct benefits in the light of individually practical settings

CFA Piling

CFA piles are easy to mount and provide an effective solution for lightly loaded structures. With CFA rigs, contractors can offer the safest and most cost-effective solution for clients. Thorough knowledge and skillset backed by a professional site team and on-board technology ensure to track the quality and efficiency of the work in real-time.

CFA piling method provides the perfect solution for urban developments because it prevents vibration and disruptions in adjacent structures and decreases noise pollution. Besides, continuous CFA piles are ideal for most soil conditions and building projects.

CFA Drilling technique

CFA piles are built by spinning the auger string into the ground by pumping concrete under minimal pressure through the hollow stem of the auger. In one continuous motion, the soil is replaced by concrete, as soon as the auger is removed. After the pile head is cleaned of debris, the steel reinforcement is sunk into the pile of concrete.

The technique does not need external ground support, such as encasing or drilling fluids, since the bore itself is self-supporting. The auger is wheeled to the ground and the concrete holds the bore after excavation.

Land conditions: CFA piling method is ideal for a wide variety of soil conditions— ranging from medium dense sands, gravel to rigid clays to even poor-quality rocks. The technique is not suggested for very soft clays or silts or too loose sand or gravel, though.

Benefits of CFA Piling

  • Higher output rates indicate that piling is commercially viable.
  • A broad range of auger dimensions (300mm – 1200mm diameter) ensures the most efficient use of construction materials.
  • Depth up to 25 meter implies that Continuous Flight Auger piling is efficient for low to mid-range loading and is therefore ideal for most business and residential projects.
  • Low levels of noise
  • Practically vibration-free operation

Rotary Bored Piling

Rotary Bored Piling is conducted through Large Diameter Piling (LDP) rigs that deliver higher power (torque) in comparison to the CFA rigs. As a consequence, the former is more agile and capable of clearing underground obstacles quickly.

When building rotary bored piles, contractors have the opportunity to easily adjust the cutting or digging tools and the auger type to better fit soil conditions. In order to facilitate top-down construction, plunge columns can also be mounted in a pile. Compared to other piling strategies, Rotary Bored Piling offers a higher load capacity and can be deployed at a much greater depth.

Drilling technique

Rotary bored piles are built by rotating an encasing into the field to support weak or granular soil and then extracting the pile bore by means of an auger, bucket, or coring unit connected to the Kelly bar. Once the bore has been thoroughly cleaned to devise depth, the pile of concrete is tremie into the bore, and the casing is removed, leaving the finished pile. Usually, pile support is cast during the concreting process.

Land conditions: 

Rotary Bored Piling technique can be used in almost all soil conditions— ranging from soft ground protected by provisional encasing to high grade, very hard rock cored into open-hole.

Benefits of Rotary Bore Piling

  • Suitable for almost all soil types, including rock drilling.
  • The attainable depth is up to 60 meters with encasing and tool diameters up to 1.8 meters; This ensures that very high load capacity can be accomplished.
  • Minimum ground disruption and vibration, implying the resulting risk to adjacent structures and properties remain minimal.
  • A quick and effective method of installation
  • Ability to build sockets into the rock underneath
  • Available in larger diameters
  • Can be applied to extended depths in comparison to other piling techniques available.