Piling is a form of deep foundation and is generally used for large buildings. It is the process of supporting a heavy load beneath a traditional foundation build. There are many different types of piling and the construction industry has come to use piling for a majority of projects, including farms, commercial and domestic structures.
Usually required when the soil may be affected by water or the deep foundations of a building may be expensive to be removed, piling is a common solution to increasing and strengthening the load capacity of a building.
There is a variety of types of piles used in construction and they mostly involve using wood, concrete or steel. Below we have listed the types of piles that we specialise in here at Dart & Co Foundations.
Rotary Bored & Mini Piling
Rotary bored piles are used to support any structure where the highest load carrying capacity is required. This process is commonly used in factory and town centre environments where it is difficult to have concrete ready to be poured. Due to this, it is possible to have gaps between the concrete and the drilling of the holes.
We provide mini-piling in a diameter as small as 200 mm right up to 450 mm. We can construct mini-piles to suit most terrains and install rotary piles with diameters of 200 mm, 300 mm, 350 mm, 400 mm & 450 mm. The variety, or combination of methods, will depend on the ground’s strata but are generally suitable for sites with limited access.
We also design foundations for areas where shrinkable clay, soft ground or landfill are issues. Our engineers suggest a bespoke solution for piles and ground beams, or piles and raft slab foundations depending on the environment. Piles can be positioned close to existing buildings, or known underground services; their stability will not be impaired as they are constructed with a minimum of vibration.
Our smaller rigs are designed and built to be used in restricted access areas, including back gardens, mine shafts, and enclosed buildings. Our rigs also fit through standard gateways and doorways.
Continuous Flight Auger – The CFA Piling Method
Continuous flight auger is the quietest form of piling and is a rapid and economical construction technique.
CFA piles are formed by drilling a continuous flight auger into the ground when the bore reaches the required depth the temporary plug that is inserted in the lead auger (This prevents soil from entering the auger hollow stem) is then ejected.
Grout or concrete is pumped down the auger’s hollow stem. Soil decompression is almost unavoidable during this phase of the operation, and the rotating auger is re-inserted while the concrete is injected.
When the grout head has been established, the auger is extracted at a speed consistent with grout supply. It is essential that the grout entirely fills the pile’s cross-section, and it is a balance: although the pressure of the grout must be sufficiently high, the auger cannot be removed too quickly or soil may contaminate the pile shaft.
We install 300 mm diameter CFA piles. The process, which is virtually vibration free, is suitable in water-bearing strata; there is no need for casing or bentonite. CFA is suitable for most strata: gravel, sand, clay, soft rock or a combination of these.
Steel Case Driven Piles
Steel cased piles are driven from the bottom of the foundation as opposed to the top, meaning they do not require heavy machinery and can carry loads between 5 and 85 tonnes.
Our driven, cast-in-situ piles are closed-ended, thin-walled steel lining tubes. They are driven into the ground using a cylindrical drop hammer, where they strike a dry-mix concrete plug. The steel tubes, usually two or three metres long, are joined together with full-fillet welding during installation.
The bottom-driven piles have a single bar or cage reinforcement and their casings are filled with high-strength concrete or grout. At Dart & Co Foundations, we can install bottom-driven piles with diameters of 75 mm,100 mm,150 mm,220 mm and 273 mm.