Rotary Bored Piling

Rotary bored piles are installed using specially designed digging tools to install piles in highly variable and challenging ground conditions.

What is rotary bored piling used for?

Rotary Bored (or Bored Cast-in-Place) piles are installed using specialist digging tools and bore support equipment / materials. The pile construction, involves progressive soil removal and may require support fluid, or temporary / permanent casing solutions depending on ground stability.

This method is very flexible and, with the right combination of plant, equipment, and materials, can construct piles in most ground conditions.

This method is often used where there are requirements for high structural loads, resulting in deep piles with a large diameter. For this reason, the method is also sometimes referred to as Large Diameter Piling (LDP).

Key capabilities:

Rig loadings: 35–100 tonnes
Pile diameter: 600–2100mm
Maximum depth: 70m
Working load: 400–25,000kN

What are the advantages of Rotary Bored Piling?

Piles can be installed across a wide range of ground conditions
Often used in ground conditions which are too hard or deep for the CFA technique
Pile diameters of up to 3000mm enable much greater loads to be carried without additional piles
The telescopic Kelly bar facilitates the installation of piles up to 65m in depth
Specialist drilling tools including buckets, augers and core barrels are deployed to penetrate some man made obstructions and create rock sockets
Reinforcement cage depths are limited only by length of pile and suited to full length installation
Achieves tight tolerances near boundaries
Allows the addition of advanced monitoring instrumentation, such as O-Cells and fibre optic monitoring

Common Uses

Supports large, complex structures and foundations
Works in all soil types, enhancing pile capacity with rock sockets
Used in secant and contiguous retaining walls, with tighter installation tolerances compared to other techniques.
Stabilises slopes and prevents landslides
Retains deep excavations and basements near structures

Rotary bored piles are constructed using powerful hydraulic piling rigs and a variety of interchangeable digging tools. A temporary cased is firstly installed through unstable upper strata, the soil is then removed using a variety of digging accessories such as augers, cleaning buckets and core barrels depending on the ground conditions.

On reaching the required design depth, the base of the pile is cleaned using a cleaning bucket, the reinforcement is added, and the concrete tremmied from the pile base to a predetermined level above cut-off level. The temporary casing is then removed using the piling rig and reused on the following pile position.

The temporary casing provides support during the boring and concrete process through unstable ground and safe working condition above piling platform level. Single length thin-walled casing are used where the depth of unstable ground is known and relatively shallow. Doubled walled sectional segmental casing is used where ground conditions are variable, and the temporary casing is required to depth.