×
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

Subgrade Stabilization

Subgrade Stabilization

Subgrade Stabilization

(OP)
In a 50 feet continuous footing, if we encountered with 12 feet length of sand fill (SW/SP) in the center of the subgrade, what would be your recommendation to stabilize the subgrade in this location.
The depth of the sand fill is not sure, but it is approximately around 10 feet deep.

Suggestions are greatly appreciated.

Thank you.  

RE: Subgrade Stabilization

Vibrating plate or jumping jack compaction for the length of the footing prior to setting forms.

RE: Subgrade Stabilization

What is the problem with the sand?  Can you give some more info? What kinds of loads are we looking at?  Have you done borings? What kind of structure?  How wide is the footing?  (In strip footing the effective depth is about 4B unlike 2B for retangular and square footing).  Will immediate settlement be a big problem?

Civilperson, I don't think jumping jack is good for compacting sand on a subgrade.  And if he needs deep compacting, the vibrating plate would not do.

RE: Subgrade Stabilization

I'm with Riggly - what's the problem?  What's to either side of the sand, I mean is it soft fat clay?  While not likely the case, there are plenty of foundations that are supported on clean sand, heck just go to the beach for a week!

f-d

¡papá gordo ain't no madre flaca!

RE: Subgrade Stabilization

Maybe it's quick sand...

RE: Subgrade Stabilization

If this just for constructibility, and if the fill is relatively stable and workable, e.g. compact or dense condition, groundwater controllable,etc., and your construction equipment is able to reach the bottom of fill, you may have options as:
1. Engineered fill: dig it out and relay it with engineered fill (check with a geotech engr for local specs).
2. Extended footing: construct a steepsided trench down to contact competent native soil, fill up with flowable, lean mix concrete (unshrinkable fill) to the underside of the footing.  Due to the different supporting characteristics undercross the footing, transitions in subgrade or structure strengthening should be provided in the footing unit.
3. Piers or short piles.
Again, as others indicated, if data shows the fill is engineered, you do not have to remove it, get a geotechnical firm assess the condition (compactness) and if it is considered competent, you may revise you footing design based on a different soil condition and just leave it there and build your foundation over it, provided that no utilities buried within it and surface improvement carried.
Anyway, a geotechnical engineer should be involved for the site condition.

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