What does CFA stand for in piling?
07/10/09 Rev 7. The Continuous Flight Auger (CFA) process is virtually vibration free and one of the quietest forms of piling, making it ideal for environmentally sensitive areas. The method enables piles to be formed in water-bearing strata, without the need for casing or bentonite.
When should I use CFA piles?
It is suitable for constructing piles in most strata, including; gravels, sands, silts, clays and soft rocks and in mixtures of strata. CFA is the only acceptable piling method approved by the Environment Agency that does not allow cross contamination of underlying acquifers by contaminated upper soils.
Are CFA piles reinforced?
CFA piles are constructed by rotating a hollow stem continuous flight auger into the soil to a designed depth. Typically, Keller CFA piles are reinforced with a rigid six-meter-long cage as a minimum, but it’s possible to install much longer cages as and when required by the design or specification.
Are CFA piles friction piles?
Continuous flight auger piles are used for places with unstable soil conditions and high level of ground water table. These piles can be terminated in clays, granular soils, in soft rock or can be taken to hard load bearing strata i.e. bearing type of piles or friction piles due to their continuous operation.
What is the difference between driven piles and bored piles?
The fundamental difference between a driven pile foundation and bored pile foundation lies in their point of manufacture. A driven pile is formed off-site under factory-controlled conditions and a bored pile is manufactured on site and in place.
What is driven H pile?
A driven pile is a long, slender column made of preformed material and having a predetermined shape and size that can be installed by impact hammering, vibrating or pushing it into the ground to a design depth or resistance.
Are CFA piles bored?
Continuous flight auger (CFA) piles are drilled and concreted in one continuous operation enabling much faster installation time than for bored piles. Reinforcement is placed into the wet concrete after casting, enabling the pile to resist the full range of structural loading.
What is Rotary Bored piling?
Rotary bored piling (RBP) uses a machine, called a piling rig, with specially designed drilling tools including buckets and augers to remove soil and rock. These tools are used to bore into the ground repeatedly, removing spoil as the pile is progressed, until the design depth is reached.
What is the difference between CFA and rotary bored piles?
Rotary bored piles are often larger diameter than conventional continuous flight auger (CFA) piles. They are used to support greater loads, overcome underground obstructions and to penetrate ground too hard to bore using continuous flight auger techniques.
Why we use bentonite in piling?
Bentonite slurry is used in a simple / crude way along with rotary auger equipment when drilling pile boreholes through sands and gravels to obtain deeper penetration into stiff fine-grained soils. The hole must be augered through the sands and gravels without support, and then the casing is lowered down.
What is the difference between bored and driven piles?
The difference between a driven pile foundation and bored pier foundation lies in the method of construction. Bored pier foundations are typically poured in place and transfer the load only through bearing, while driven piles are driven straight in and transfer the load through friction and/or bearing.