CFA (Continuous Flight Auger) piles are quick to install and they offer an efficient solution for more lightly-loaded structures.
Using our CFA rigs, we can offer the best and most cost-effective solution for our clients’ projects across the UK. Our knowledge and expertise, as well as our experienced site team and on-board technology, means that we can monitor quality and performance real-time.
CFA technology offers the ideal solution for projects in urban locations because it eliminates vibration and disturbance to adjacent structures, and it reduces noise emissions.
Continuous CFA piles are suitable for most soil conditions and construction projects. They are the best and most effective solution when piling is required close to existing buildings, or in built-up areas because this piling approach is virtually vibration free, and it has low noise levels.
CFA Drilling technique: Continuous flight auger piles are constructed rotating an auger string into the ground by injecting concrete under a minimum pressure through the hollow stem of the auger. The soil is replaced with concrete in one continuous movement as the auger is withdrawn. After the pile head is cleared of debris, steel reinforcement is plunged into the pile concrete.
The technique requires no additional ground support, such as casing or drilling fluids, because the bore is self-supporting as the auger is rotated into the ground and the concrete supports the bore after extraction.
Ground conditions: CFA piling is amenable to a broad range of ground conditions from medium dense sands and gravels through to stiff clays and even low grade rock. The technique is not recommended in very soft clays or silts or in very loose sands or gravels.
Advantages of CFA Piling:
- High production rates mean that piles are commercially attractive
- Broad range of auger sizes (300mm to 1200mm diameter) means that the most economical use of construction materials is possible
- Depths of up to 25m means that CFA piling is effective for low to mid-range loading thus suitable for most commercial and residential projects
- Low noise emissions
- Virtually vibration free
Sectors: residential, commercial (multi-storey), urban locations
CFA PILE CONSTRUCTION SEQUENCE
ROTARY BORED PILING
Rotary Bored Piling is carried out by our Large Diameter Piling (LDP) rigs which offer higher power (torque) than our CFA rigs so they are more agile and able to overcome underground obstructions.
When constructing rotary bored piles we have the ability to quickly change coring or digging tools and auger type to best suit soil conditions. We can also install plunge columns in the pile to facilitate top-down construction. Compared with other piling techniques LDP can offer larger load capacities and be installed to far greater depths.
Drilling technique: Rotary bored piles are constructed by rotating a casing into the ground to support poor or granular ground and then removing the pile bore using an auger, bucket or coring unit attached to a telescopic Kelly bar. Once the bore is fully cleaned out to design depth, the pile concrete is tremied into the bore and the casing is extracted leaving a finished pile. Typically, pile reinforcement is cast into the pile during concreting.
Ground conditions: Rotary piling can be employed in almost all ground conditions from soft ground supported by temporary casing through to high grade very strong rock cored in to open-hole techniques.
Advantages of Rotary Bore Piling:
- Amenable to almost all ground conditions including rock drilling
- Depths achievable up to 60m with casing and tool diameters up to 1.8m means that very high capacity loads can be achieved
- Minimal ground disturbance and vibration – resulting risk to adjacent structures and property is limited
- Simple and efficient installation process
- Ability to construct sockets into underlying rock
- Larger diameters feasible
- Can extend to greater depths when compared with any other piling technique
Sectors: commercial (tower), civils, marine
ROTARY BORED PILE CONSTRUCTION SEQUENCE