Rotary bored piling

How does the process work?

Specialist tools attached to the telescopic Kelly bar are used to remove pile arisings from within a temporary casing installed by the piling rig.  The temporary/segmental casing provides the required support within the upper unstable ground.  In some instances a combination of casing and support Fluid(Bentonite) is used to support the pile bore to depth.

Once the designed depth has been achieved, prefabricated steel reinforcement cages are placed either on the bore base or suspended at the required depth within the pile. Concreting of the bore then proceeds down a centrally positioned tremie tube from the pile base in order to ensure no mix segregation and adequate final compaction.  After concreting is complete, the temporary casing is removed and reused.

Rotary bored piling techniques have the advantage over CFA bored piles, in that they can be used in more variable and cemented rocks and soils and a number of different coring or digging tools may be used to overcome obstructions.   

Rotary bored piling applications

Bearing piles – ranging from 600 to 3,000mm in diameter as deep foundations for tall buildings and to support a variety of civil engineering structures like bridges.  Foundations loads are transferred to competent soils and or rock head at depth

Pile retention systems – including slope stabilisation  through to permanent basement structures installed as: -

• Contiguous bored pile wall (gap between piles) – no water seal / permanent works 
• Secant piled walls – this includes hard/firm and hard/hard secant pile walls,  – watertight / temporary works

In order to ensure the high verticality tolerances and maximum water tightness; we recommend that secant walls be constructed through concrete guide walls cast ahead of piling works. This is not required with contiguous walls, where water tightness considerations are not relevant. 

A hard/firm secant wall cannot be considered as a permanent water tight structure therefore any basement will require a drained cavity to be provided between it and an internal wall.

Where the retaining wall is to be incorporated within the permanent basement then consideration should be given to either a hard/hard secant (both piles contain reinforcement) or diaphragm wall.

Key capabilities

• Rig Loadings: 30 - 120 tonnes
• Pile Diameter: 600 - 3,000mm
• Maximum depth: 79.5m
• Working Load: up to 50,000 kN