- Pile Types
- Rotary Auger Bored Piles
- Continuous Flight Auger Piles
- Tripod Bored Piles
- Driven Pre-cast Piles
- Driven Steel Tube Piles
- Displacement Piles
- Piled Retaining Walls
- King Post Walls
A description of typical pile types is given in each of the tabs shown above, to view a description click on the relevent tab
Piles are usually classified into two main types which are displacement or replacement.
Displacement piles are where the usually partially piles are driven or jacked into the ground whereas replacement piles are ground is firstly removed, by drilling or augering, and the pile formed in-situ.
The above list does not include all pile types but represents the most frequently used in the United Kingdom. Typical sizes for most conventional replacement piles are between 300mm and 600mm diameter although smaller diameter minipiles or larger, typically bored piles, are also used. Composite piles and those formed of other materials may also be appropriate
Rotary Auger Bored Piles
Rotary auger piles – the pile hole is formed with a rotary auger and after reaching the required depth it is then backfilled with concrete. This technique is ideal in cohesive soils or soft rocks which may stand unsupported during the boring process. Casing or drilling fluids may be used to support the pile hole in unstable soils.
Continuous Flight Auger, CFA, piles – this technique involves boring with a continuous flight auger which is rotated into the ground until the required depth. Concrete is then pumped into the pile hole through a hollow central stem with the auger continuing to rotate as it is withdrawn to the surface. The action supports the sides of the holes as the hole is advanced with the soil removed both during the augering and then during the concreting process as it is displaced. Typical sizes are between 300mm and 600mm although with modern advances in piling equipment larger sizes are also appropriate.
Tripod Bored Piles
Tripod – these use a percussive technique with a heavy clay cutter or bailer, attached to a wire rope and winch, and repeatedly dropped to progress the pile hole. The hole may be supported with a temporary steel casing in unstable soils. On completion the hole is concrete in a similar manner to rotary auger piles. This technique is usually carried out for only a small number of piles, where access is difficult and with a small diameter ( such as 300mm to 600mm ).
Driven Pre-cast Piles
Driven precast - these are usually square section preformed concrete piles which are driven with hammer against the top of the sections. The sections are typically up to 12-15m n length and can be connected with a jointing system. This system is often used through soft deposits on to bedrock. Typical sections are between 200mm and 350mm square. The piles are reinforced to withstand the bending and tensile stresses which occur during transportation and driving.
Driven Steel Tube Piles
Driven thick walled steel tubes – these may be large or small sections and the thick walled tubes allow the installation with top driven piling rigs and accelerated hammers. The tubes are usually open ended with the annulus at the bottom typically plugging during installation. Small section tubes are typically between 110mm up to 340mm diameter with the larger diameter of about 0.8m.
Thin walled steel tubes – this comprises an open cylindrical steel tube which are bottom driven against a closed end or plug. These are small displacement piles and typical sections are 220mm up to 340mm diameter.
Auger displacement – this is a fairly recent technique where a solid steel mandrel is pushed / augered into the ground with only a nominal amount of soil removed from the hole. As the mandrel is removed the hole is filled with concrete to form the pile. The technique relies on a high powered piling rig to allow the mandrel to penetrate the soil.
Piled Retaining Walls
Piled Retaining Walls – these are usually formed with bored cast-in-situ or Continuous Flight Auger piles. Retaining walls may be temporary or permanent and are used to construct a basement or support higher ground during excavation.
King Post Walls
King posts – this technique is mainly used for temporary support and typically involves an augered pile hole with reinforcement comprising a steel beam or column. The holes are more widely spaced, than normal contiguous wall piles which allows concrete or timber panels to be placed between the columns.