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

They are installed using hydraulic rigs with interchangeable tools. Temporary casing supports unstable ground, with slip casing used for shallow depths and sectional casing for deeper or variable conditions.

If the casing depth is insufficient or stability is a concern, bentonite or polymer support fluids may be used, with a short casing at the bore top.

After reaching the design depth, the pile base is cleaned, reinforcement is added, and concrete is placed using the free-fall method for dry conditions or the tremie method for wet conditions.