×
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

Advice for Tank Foundation on Clay

Advice for Tank Foundation on Clay

Advice for Tank Foundation on Clay

(OP)
I have 4 70ft diameter x 40 ft tall tanks, 4 ft apart, applying 5,000 lbf/ft2 each on clay down to 120 ft. No ringwall. Tanks have sunk 4ft over 40 years and need to be raised and leveled. What type of foundation is recommended?

RE: Advice for Tank Foundation on Clay

I'd suggest consulting your local geotechnical engineer.

If you're planning to put foundations under the existing tanks, that may limit your options considerably.

RE: Advice for Tank Foundation on Clay

I would recommend pilings down to a hard clay or sand layer. Surprised they didn't have pilings to begin with. Most southern Louisiana clays can only handle about 1000 psf

"Look for 3 things in a person intelligence, energy and integrity. If they don't have the last one, don't even bother with the first 2. W. Buffet

RE: Advice for Tank Foundation on Clay

I would think, for what it is worth, that you have achieved a stable condition for these tanks after 40 years of preload. But if you remove the preload for reconstruction, you may allow the material to rebound. You need good geotechnical advice as to how to proceed.

RE: Advice for Tank Foundation on Clay

Coastalforu:
I agree with Hokie, and would like to know the settlement/time frame history of these tanks. Has the settlement settled down over the years, or gotten worse? If this settlement has not done any damage to the tank bottoms, or to the joint btwn. the bottom and the tank shell, what’s the problem? And, to raise the tanks, what is your plan of attack? That can’t be a simple project. You could add a reinforcing plate ring around the bottom of the shell (maybe a rolled, bent, angle) and put small screw/auger type piles at regular intervals around the tank to spread the load out a bit, and to a lower strata of the underlying soils.

RE: Advice for Tank Foundation on Clay

Sounds like you have another leaning tower of Pisa on your hands. With the clays compressing like that I would get foundation recommendations from a geotechnical engineer. I would say your foundation design depends on whether you think you are near the end of settlement or if you expect another 2-4 ft in 40 years.

RE: Advice for Tank Foundation on Clay

There are firms in the business for fixing situations like this. I won't try to list any here, but check for a nation wide firm that has a wide variety of methods of underground improvement. In general I would expect they will be in the compaction grouting field. Do a search for nation-wide geotechnical pressure grouting contractor as an idea. You will need a list of references with a similar problem. Ordinary mudjacking firms likely are not suitable, due to the complexity of this. You will want a form of guarantee, since these methods can cause unintended damage, such as filling sewer lines nearby, lifting the wrong area, etc. While installing piles may be thought of, I question that option, since you might as well tear down the tanks and start over then.

RE: Advice for Tank Foundation on Clay

Don't assuming all the settlement have taken place! Get a soils firm to drill few borings say down to 80 ft or so and ask them to run settlement analysis. If the total settlement is 6 ft, re-leveling will not help you for long. I agree, I am also surprised they haven't used piles or piers on the original design. Further, the circles are too close, so you induce intersecting pressure bulbs. That is is each tank will induce vertical stress to the tank on the left and to the tank on the right. So are the corner tanks leaning inward?

http://www.soilstructure.com/

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