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Bored piles

Bored piles are large-diameter (1 to 2 m) concrete foundation elements that are cast in-situ and can be installed up to great depths.
Very suitable for transferring large concentrated loads (20 MN is feasible) into the soil. These piles are produced using a heavy-duty rig with a rotary drill that rotates a telescopic kelly bar with an auger or bucket drill. The stability of the bore hole is maintained by applying bentonite or water depending on depth and circumstances. 
To guide the drilling equipment and protect the pile head, an auxiliary the topsoil over the first couple of metres.

After cleaning the rebar cage can be positioned and concrete can be poured. This is done using a tremie pipe in order to fill the bore hole from the bottom. During the pouring the tremie pipe is shortened and the bentonite is pumped away. Before curing of the concrete can occur the casing is removed from the top of the pile.

 

 

Application

These piles are used for transferring large concentrated loads at larger depths, such as for tall office buildings, silos, bridges and viaducts. They can also be used as a substitute for multiple piles underneath a column base.
Top-down construction is possible by combining bored piles with prefab concrete columns.

 

Ambient factors

The (auxiliary) equipment that is needed and the resultant footprint are relatively large. These include a bentonite plant, vehicles for transporting the concrete to the pile, and storage for the rebar cages.
 

Pros and cons

  • Vibration-free and low-noise.
  • Capable of absorbing very high loads.
  • Bentonite and soil must be processed removed.
  • Hard layers of soil can be penetrated without problems using special grabs.
  • Work can be carried out close to adjacent structures and foundations.

Applicated

Name of project

Client

Rotterdam Maasvlakte, Construction pit Electrabel powerplant

Visser & Smit Bouw

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