API650 Tank- how to fix failed foundation fill

[J. Ballard]

Hello Everyone,
I've run into a failure I'm unfamiliar with on API650 tanks and could use some advice. The tank was built in 2018 to API650 App.M, 30'dia x 40'h operating at 350F. The bottom is made of 1/4" A36 and tank sits on concrete ring wall with engineered fill and pad sand inside. We recently entered the tank to change out the side mount mixer and found serious settlement issue. The engineered fill and pad sand has subsided by approximately 3". This has produced a noticeable bend in floor plates. So far the tank is not leaking but it's only a matter of time.

How do you replace the engineered fill? I've done floor replacements but those relied on support of the foundation. I'm guessing cutting out the entire floor and putting some sort of support beams attached to concrete ring wall and grillage on top?
Regards,
J. Ballard BSME

 

[JStephen]

3" is not that much, depends on the details. See API-653 for evaluation of bottom settlement.
If you remove the bottom, just add additional sand, I don't know what the beams and grillage would accomplish.
I've heard of, but not been involved with, pumping grout under tank bottoms to fill localized depressions.
That settlement may be due to shrinkage of fill or soils below from drying out with the heat. I don't know if there's any way to reverse or prevent that.

 

[LittleInch]

Agree - Just drill a load of holes and fill the void with grout.

You might want to remove one section at the worst point to try and figure out what has happened and how big the void is.

How do you know the fill has gone down? Could the ring beam and tank have gone up?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IFRs]

I'd get a lot more information on the engineered fill including moisture content and heat transfer from the tank and the geotechnical evaluation of the soils under the tank including their short- and long- term settlement predictions.

 

[J. Ballard]

The shell bends down then rises up at concrete ring around center sump. The API653 B.3.3 equation, only allows 2.36in deformation for distance between ring wall and sump concrete, so I think we have an issue. I'm fairly sure it is loss of pad sand. There are unconfirmed reports of one of the 10 tanks had sand come out from base when installed (before I was hired). The TOC elevations are consistent around edge of tank when using transit off a fixed reference.

 

[Geoff13]

While grout or compacted sand is probably the solution, I'd want to understand why this happened before trying to pick a solution.
[ul]
[li]The zone just inside a ring wall needs very high compaction for the full depth to avoid this sort of settlement. What was specified, and what do the records show was achieved?[/li]
[li]Not sure what kind of engineered fill would be inside the ring wall that would be suffer from shrinkage due to moisture loss. A well-graded granular material has very little moisture to start, and likely wouldn't shrink at all.[/li]
[li]You make it sound like 10 tanks were built in 2018, but only one has this problem. What is unique about this tank? I would discount the rumour of sand loss without documentation. How could 3" of fill flow upwards and over the ring wall?[/li]
[/ul]

Beams and grillage are definitely not the solution.

 

[HTURKAK]

You do not supply a lot of information here..

Apparently this is elevated temperature tank and the content is probably hot bitumen , resid etc.
Having worked with elevated temperature tanks in the past , my first impression is the evaporation of moisture in the supporting soil. Especially if the ground water level is high enough that can happen.

My opinion is , the foundation detail does not comply the requirements and should be reviewed with existing soil data.

The tank should be insulated but still the temperature bulb will build up under the bottom in long term.

My suggestion would be, remove the tank and repair the foundation as per an applicable detail .( Some options, supporting the tank on grillage , replacing the supporting soil with crushed stone and providing some piping to ventilate the foundation...)

In order to get better respond , pls provide more info..









Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[pierreick]

Hi,
Check for isocyanate.

https://www.dalinghausconstruction.com/blog/how-deep-injection-foundation-repair/

Pierre

 

[LittleInch]

Can you post details of the tank floor cross section, depth of fill, type of fill etc?

Is this a cone down into the centre tank?

Any insulation? - If not why not? You'll be loosing a pile of energy into the ground.

Ground water levels or ground water flows?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.