Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.


Problem with Dirty Concrete - Bored Piles

Problem with Dirty Concrete - Bored Piles

Currently we are having issues regarding the integrity of our bored piles. Our project is a residential building with 20 floors. We are using dry method when we construct the bored pile since bedrock is very shallow (less than 6 meters from Natural Grade Line)

After subjecting in cross hole sonic logging test, the third party contractor of the tes advise us that our bored piles have issues in the upper layer (2-4 meters). They are thinking that is due to dirty concrete that was not expelled in the construction process. In this light, would like to create a discussion 1) What is the best method of expelling dirty concrete from your experience 2) What is the chance that the cross hole sonic logging test may be receiving bad signals and may not be entirely reliable?

RE: Problem with Dirty Concrete - Bored Piles

Have you considered using a test boring machine and coring down the center f a few for correlation to sonic and other non destructive means.? Even a small diameter rock drilling bit and a log kept of the rate of progress might tell a lot.

RE: Problem with Dirty Concrete - Bored Piles

Some questions:
How large a diameter are your end bearing piles?. Unless you are on granite or something of that ilk, I would think your shafts would be in the order of 900-1000mm dia. How are you inspecting the bearing surface (for a 20 storey building, I'd do that) How heavy are your loads? What is your bearing value? I assume bedrock is 'flat'. How highly stressed is the concrete? How is the contractor cleaning the holes? at bedrock? What is dirty concrete? What is the condition at the pile/bedrock interface?


RE: Problem with Dirty Concrete - Bored Piles

Hi oldestguy, actually that is our course of action at first. But we are having a hard time doing concrete coring due to tight rebar spacing. And if we core rock samples, will it be easy to identify soil inclusions?

RE: Problem with Dirty Concrete - Bored Piles

Hi dik, the diameter is around 2000 - 2500 mm. Length is around 20 meters. We cannot inspect the bottom that much, so we just rely on the tremmie pipe's pressure to expel the dirty concrete. Dirty concrete meaning, concrete with mixed of soil from the boring. The bedrock is severely weathered and poor in strength.

RE: Problem with Dirty Concrete - Bored Piles

With that size of shaft, the bearing pressure would be quite low... Does a little 'mud' in your concrete cause any problems? unless chemical issues, I would think it wouldn't matter. I thought the shafts were only 6m long, not 20m. Are the shafts sleeved prior to casting concrete?


RE: Problem with Dirty Concrete - Bored Piles

Hi Dik Yes, but not all through out. It is sleeved from NGL to 5 m of depth. I am wondering are there any methods/ countermeasures that could secure the release/ flow of dirty concrete?

RE: Problem with Dirty Concrete - Bored Piles

How deep is the shaft? if 6m then increase the 5m sleeve and hand clean...


RE: Problem with Dirty Concrete - Bored Piles

If you have been concreting in a dry hole, it's most mikely the sonic tests that can be questioned. Locate a shallow identified defect and excavate around the pile to expose the defect. If no defect is found you will have your answer.
Check if the sonic tube are mada of steel. PVC should not be used because lack of adherence between concrete and PVC can alter the signal.

RE: Problem with Dirty Concrete - Bored Piles

Hi BigHarvey, why concreting in a dry hole can affect the results of the sonic test? We are currently using B.I. pipes for access tubes.

RE: Problem with Dirty Concrete - Bored Piles

Hi cgseso
You should not have problems concreting dry. I believe the sonic tests can be questioned.
However if the slump value of the concrete is not maintained above 16 cm during the complete concreting section you might have dirty concrete inclusions in the sound concrete. This is because the concrete of the tremie tube goes up alongside the tremie tube instead of being well distributed. At one stage the concrete level is much higher close to the tremie pipe than on the outside of the pile and then can overflow the dirty concrete from the bottom of the excavation.
One way to know is to ask the concrete foreman if he encoutered difficulties with the flow of concrete in the tremie pipe in the last meters of concreting.
Anyway since depth of defects is not that big, you should try to expose alleged defects. If they don't show up, it means that the sonic test contractor proficiency should be questioned. Alternatively you could bring another company (provided you are sure they are working well) to do the tests again.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close