Rotary Bored Piling

Rotary Bored Piling, sometimes referred to as 'Open Bored Piling' or 'Kelly Bored Piling', is one of the oldest forms of bored piling but still caters for specific requirements of the piling market.

A short auger of some 4 or 5 turns of flight, on the end of a telescopic 'Kelly-Bar' is screwed into the ground until fully embedded. It is then pulled to the surface and the spoil on the auger spun off at high revs. The auger is then re-inserted and another 'bite' of ground taken. This bore-pull-spin-off cycle continues until the design depth is reached.

Should the ground be wet, loose or otherwise unstable, temporary casings are inserted to keep the bore open. These casings can be extended as the bore deepens.

When the design depth is reached the reinforcement cage is inserted and concrete poured into the open hole. The casings are extracted once the concreting is complete. If the bore is lined and stable but filled with groundwater, the concrete must be placed by tremmie methods. The processes of temporary casing and tremmie work can be very slow and expensive. Rotary Bored Piling tends not to be cost-effective in ground conditions where CFA piling is viable.

The main advantages of the Rotary Bored System, which have not yet been challenged by conventional CFA processes, are;

Piles up to 1500mm diameter are possible.

Piles over 30 m long are possible.

Extra items such as deep sleeves/liners and H-Sections can be inserted with great accuracy, as can load cells, very long reinforcement cages etc.

Piles with deep cut-offs can be constructed.

In general, unless the above advantages are not going to be exploited, modern CFA techniques have tended to take over significant parts of the Rotary Bored Piling market sector.

Our Rotary Bored piling capabilities are as follows;
400mm - 1500mm diameter
30m deep
Coring, Chiselling, Casing, Tremmie

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