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Drilled Piers

Drilled Piers

Drilled Piers

Are there limitations to the depth that a concrete drilled shaft can be? Is it unheard of to have 100 foot long drilled piers?

RE: Drilled Piers

I've done 90 ft. deep before. Large pier diameters - I think 72" perhaps. Can't recall exactly.

RE: Drilled Piers

A call around to some local, or regional pier contractors would help you get a handle on their abilities.

RE: Drilled Piers

Thank you

RE: Drilled Piers

Definitely see what the local drill rigs available are. That will be your limiting factor for all practical intents and purposes.

RE: Drilled Piers

I might be off a bit but bored caissons (drilled shafts) in Bangkok typically will go to 60 m or more. I'd have to dig up my records to confirm but as they are 8k miles away - that isn't practical.

RE: Drilled Piers

I've just done ~200" (65m) on a major river bridge- Contractor had to import the rigs from Germany. I don't have the specs of the rigs at hand, but they were able to socket into hard rock (>50MPa) at the base of the hole.

All the best,

RE: Drilled Piers

The deeper you go, the fewer contractors will be able to do it, and the more expensive it will be.

RE: Drilled Piers

Going deeper will likely narrow the list of contractors who can do it, but if there's still 3 or 4 in the area that can handle the job, the unit cost (cost per foot of shaft) will probably go down compared to shorter shafts, due to the fixed mobilization and setup costs being being distributed over a larger quantity. Of course, if you get down to only one, or maybe even 2, local contractors, there could be some 'inflation' of the cost.

Rod Smith, P.E., The artist formerly known as HotRod10

RE: Drilled Piers

Caltrans goes that deep and their construction specs are online.

RE: Drilled Piers

There is a paper by Thomas Domanski (Bauer) in a 2019 Conference in Jakarta entitled: "Bored Pile Foudnation fo rthe KLCC Lots LMN, Bored Piles Up to 150 m Deep, Probably the Deepest Bored Piles in the World". The author indcates that for this project at the time of the paper deadline that they had drilled bored piles to depths of 130 m but expect that the depths will, later, go deeper - which is where he probably identifies 150 m. The bored piles were sized at 2 m and 2.5 m diameter.

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