×
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

pad foundation on fill
4

pad foundation on fill

pad foundation on fill

(OP)
I'm asked to design a pad footing of 25 ton working load capacity on a filled ground.
There's no test conducted in the borrow source(from the adjacrnt hill with no ground water detected) but the fill material seems to be stiff clay (light brown color). The compaction seems to achieve 95% MDD according to the contractor eventhough I don't have the density of the fill material. What is the typical settlment value?
Will ther be excessive settlement ?  

RE: pad foundation on fill

3
Settlement will depend on more variables than you have accounted for.  How deep is the fill material?  What is the unit weight of the fill?  What is the stratification just under the footing (upper 1xB)?  What are the subsurface conditions?  Will the fill cause settlement of soft underlying strata?  Is the fill underlain by sand?  What is your anticipated bearing capacity and bearing pressure?  Will there be more than one footing?  Is differential settlement an issue for multiple footings?  If so, how much is tolerable for the construction?

Just a few things you need to consider.

RE: pad foundation on fill

You are flirting with disaster if the fill is very thick at all.  Do not believe the contractor!  Demand to see test results of the density of the fill and inspection reports from independent laboratory.

RE: pad foundation on fill

(OP)
thanks for the response. My friend, a geotech engineer, gave similar advice to me. to find out the settlement,  a consolidation test can be carried out. a plate loading test can be done as well. the problem is my client may not allow it. differential settlement is a concern. I'm worried about tilting of structure if the compaction is not consistent.
what other field test can be used? what about sample plasticity index? Settlement is always related to compressibility.

RE: pad foundation on fill

Listen carefully!!! Compaction is not your issue.  That's easily controlled.  YOU MUST KNOW WHAT THE SUBSURFACE CONDITIONS ARE!  Compaction has only minor implication to settlement.  If the owner is not willing to allow an appropriate investigation of the subsurface conditions, then you might be better served to walk from the job.  If you don't, then I hope you have a good contract and attorney, because if something goes wrong and settlement occurs, guess who gets blamed!!?

RE: pad foundation on fill

(OP)
Thanks for the reminder. I infact checked the borehole log of the initial si before I even bother considering my client's suggestion. the original ground is okay.  

RE: pad foundation on fill

In my experience, uncontrolled fills are exactly what they purport to be, fills without the benefit of engineering control.  Personally I would walk away rather than design a structure on such a fill.  If the underlying soil is acceptable, go for piles but before you do, get the opinion of a geotechnical engineer in writing.

RE: pad foundation on fill

Thanks all of you guys, this is really a valuable discussion

RE: pad foundation on fill

True I see piles the only reasonable solution in such site... and then geotechnical information be logically required. Don't forget negative friction charging more the upper part of the piles when the fill further settles.

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