×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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.

Students Click Here

Jobs

Concreting of Friction Caissons

Concreting of Friction Caissons

Concreting of Friction Caissons

(OP)
How long should the hole be left open after drilling  and before concreting?
The job involves a friction caisson with a socket in Shale rock. Shale tends to slake and weather on soaking.  I was told that the practice in some states dictates that an open excavation should not be allowed to stand for more than 4 days or so.In this project, the hole is filled with water to balance the hydrostatic pressures in the hole. We sre going to run some durability tests on Shale.
DocDirt

RE: Concreting of Friction Caissons

Good sense is to concrete as soon as possible after finishing the excavation.However, knowing that you have to install reinforcement and tremie pipe and that you might have a week-end between end of excavation and equipment, 4 days seems a reasonable practical limit.
In practice the bottom should be checked bewore lowering the reinforcement and cleaned if necessary.

RE: Concreting of Friction Caissons

(OP)
Thank you BigHarvey
DocDirt

RE: Concreting of Friction Caissons

For a pile using bentonite as a support fluid most specifications will limit the period to 24 hours. This is sufficient to excavate, install the rebar cage and cast the concrete.   

RE: Concreting of Friction Caissons

(OP)
Based on slake durability tests, we found that there is minimal slaking. However, we have stipulated to the contractor that the holes have to be concreted as soon after drilling. If the hole is left open for more than 12 hours, contractor has to pull ot the rebars, roughen the sides of the socket and clean the bottom again.
DocDirt

RE: Concreting of Friction Caissons

Are you relying on the socket for load?  Stiffness may be that the socket takes 90% and the soil friction is 10%.  I've not often combined the two.

Dik

RE: Concreting of Friction Caissons

(OP)
Thank you dik for your posting.
For determining the load taken in friction and in baring, I use Figure 9.18 b, Page 371, from the text on Rock Mechanics by Goodman.
By the way, I did find some reference from Ohio DOT specifications regarding my question. It states that especially for caissons constructed by the wet method, if the hole is left open for more than 24 hours, hole has to be drilled an additional 6 inches and cleaned before concreting. In a job, I am involved now, where we are using friction caissons, we stipulated that if a hole is left open for more than 24 hours, the sides have to be roughened and the bottom cleaned before concreting.
DocDirt

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!


Resources