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I know the normal process of how bored piles are normally constructed, but I need to know in case we have a water table at 1.5 m under the surface level and the pile must be at a depth of 25 m. How do they prevent the water from filling into the bored pit. Because when they pour concrete they must remove the water from the drilled pit but if the water keep filling the pit and at very deep depth how could they prevent this ?

One more question I was thinking about is How much does the strength of the concrete get affected in a pile (due to the presence of water and some unwanted soil in it) ?

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    $\begingroup$ Placing concrete under water is a very common procedure using pumps and tremies. Are you mainly concerned about this process or are there other reasons why you do not want water in the hole? $\endgroup$
    – hazzey ♦
    Jun 8 '17 at 12:32
  • $\begingroup$ no only concerned about the process if you have any document could share? I am also concerned for the concrete quality and strength because if I was designing the pile for a strength of 40 MPa for example should I consider in my design a smaller f'c ? $\endgroup$
    – J.Daou
    Jun 8 '17 at 13:58
  • $\begingroup$ Check out how this was solved in the 18/19th C - submersed chambers for the workers etc $\endgroup$
    – Solar Mike
    Jun 9 '17 at 4:57
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    $\begingroup$ Another way this is handled is casing the hole. Can be cost prohibitive though since you can't remove the case. $\endgroup$
    – Rick supports Monica
    Jul 11 '17 at 21:38
  • $\begingroup$ Everyday, somewhere , oil well casing is cemented in in place using cement to displace water/drilling mud, and it cures under water. $\endgroup$
    – blacksmith37
    Jul 27 '19 at 19:52
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Water accumulating in the bottom of the bore is not a concern, as long as concrete is delivered at the bottom of the bore via a hose.

Concrete with the slump of less than 4inches with some plasticizers to minimize cement washing and floating to the surface of concrete will be used and because of its density; it will push the water up and not mix with it.

If the water has impurities or damaging ingredients like sulphates or chloride, then special admixtures must be used, which has to be designed by an specialist in coordination with a testing lab.

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  • $\begingroup$ 4in slump? My typical pumped concrete spec says 7 to 9 inches of slump if it is to be pumped. Any less than about 6 inches and it won't flow around the rebar. $\endgroup$
    – hazzey ♦
    Jul 28 '19 at 12:06
  • $\begingroup$ @hazzey, in many pours of caissons with 30inch bore and say 10- #11 rebars with ties at 12in-oc. I have used 4 inch slump. the independent city inspector must be present continuously and take samples. When you order concrete and ask for strength and slump, they have mix designs and admixtures as per performance you demand. as you know slum directly affects the strength of concrete. these days where concrete of 6 -8 k psi is commonly used it is imperative to keep the water/cement ratio below 40% and that means mix a bit stiff. $\endgroup$
    – kamran
    Jul 28 '19 at 18:09
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One more question I was thinking about is How much does the strength of the concrete get affected in a pile (due to the presence of water and some unwanted soil in it) ?

Strength of concrete improves with water. The crystalline lattice formation rate in concrete is a result of the chemical reaction of cement and water. I would not be too concerned with groundwater water while putting concrete in a pile as it will not harm the overall concrete ultimate strength.

Get advice from a geotechnical engineer for proper treatment.

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  • $\begingroup$ presence of dirt is not acceptable. Water is ok, refer to my answer to the above question. $\endgroup$
    – kamran
    Jul 27 '19 at 18:21

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