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!

*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.

Jobs

Foundation Settlement & Raft on Piles

Foundation Settlement & Raft on Piles

(OP)
Dealing w/ high water table with moderate seismicity here..
Geotech recommended using a raft on pile to bedrock at 40-ft below grade (some at 80-ft)
1. When does it trigger for geotech to recommend using piles over a mat foundation? If a mat settles one or two inches over a large area relative to other corner, does it really affect anything if functionality of the structure is not compromised? Is there a code recommended value?
2. Method of getting an idea of designing the raft on piles: I've read a paper recommending first running an analysis of the raft as a slab-on-grade w/ soil spring or subgrade modulus. Then check for settlement. If the settlement is less than 3 inches, then no need for piles. otherwise use piles and re-iterate the analysis. What is basis of this approach?
I always appreciate any feedback here.

RE: Foundation Settlement & Raft on Piles

Your last question probably can be be answered after more info is provided, such as structural loadings and tolerance for settlement. That also ties in with plumbing beneath and its tolerance. I, for one, question spring constant approach without running laboratory consolidation tests and using that info for settlement estimating.

RE: Foundation Settlement & Raft on Piles

Will you have piles between 40ft and 80ft? Does that mean the site depth to bedrock varies quite a bit across the mat-slab foundation length?
Seems like you would expect a bit of differential settlement if there were no piles or ground improvement
If you use "soil springs" for your soil-structure interaction, you need to consider long term consolidation, as oldestguy has noted. And keep in mind the equivalent soil spring will not be constant for the entire foundation footprint.

RE: Foundation Settlement & Raft on Piles

Perhaps, the piled raft was recommended because you may have liquefaction issues?

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


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