oil storage tank foundations 3

[Lutfi]

Any web sites/details for 100,000 gallon fuel tank foundations. I have seen a few around but did not design any. I need input and ideas for the first.

Regards,

 

[Ron]

Lutfi...is this going to be a concrete tank or a steel tank? Foundations are somewhat different. Does the foundation have to be integral to the containment system?

 

[Lutfi]

Ron, it is a steel tank. 100k fuel 27 foot diameter. It will be on quoqina (hard shell).

I imagine I will need a ring beam, center post footing, layer of sand under bottom of tank, sump, monitoring wells, and layer of compacted fill.

Any step by step or reference would be appreciated.

 

[Lutfi]

Ron,

The containment is separate from the foundation.

 

[JStephen]

You may find a fair bit of information from area tank companies- check them out.

Check out API-650 (and similar related API documents- see their website). It will set you back a couple of hundred bucks or more. But it does have info in one of the Appendices on foundation design and leak-detection system. (Don't get too hung up on their foundation design methodology, which is overkill for most tanks.) See Structural Engineering Handbook for chapter on tanks and foundations. And check out AISI's hand books on tank and steel plate structure design.

If it hasn't been done, at some point, someone needs to check out NFPA-30 or the Uniform Fire Code as they pertain to the tank, and local/state/ federal regulations pertinent to the tank (for example: containment issues, leak detection, venting, setback from property lines, emissions control, etc.)

 

[Ron]

Lutfi...You are on target with your thoughts. As JStephen noted, API 650 is a good reference for this.

The ring wall is designed for confinement of the soil as a retaining wall, with loaded soil. High modulus material under the tank will reduce the load on the wall (shell base or re-compacted coquina works well).

 

[SlideRuleEra]

There is a 3 page paper titled "Oil Storage Tank Foundations" by Irving E. Boberg. This paper was mentioned some time back in another thread as being from 1951, Mr. Boberg seems to have been the chief engineer at Chicago Bridge & Iron at that time.

Best Wishes

 

[SlideRuleEra]

Steve - It's on the way.

Lutfi - You must have changed your hotmail address. The email "bounced" back.

 

[BigH]

There has been much discussion about oil storage tanks in a number of threads. I have been involved with quite a few large diameter tanks and our company did almost all such tanks in Sarnia refineries for years. Basically, the tanks were steel shell and up to 150 ft. diameter. Soil conditions ranged from firm (medium - for the non-Canadians)to stiff clays, shales and sand. To my recollection, we never included any concrete ring foundations. At one refinery where shale was relatively close and overlain by a very stiff till with fill on top, we did put in a granular ringwall for the tank edge to sit on. But generally all tanks were founded on a tank-pad foundation of 1.5m thick topped with 75mm of crushings dust for sitting on the base plates. To my knowledge - we never had any problems with any of the tanks; even one large tank founded on soils with Su values in the order of 750psf initial.

A relevant paper was by Bjerrum on oil storage tank failure in Norway - it was in London's ISSMFE conference 1957. Anyway - just some case histories.

 

[SlideRuleEra]

The paper "Oil Storage Tank Foundations" by Irving E. Boberg is now posted in .pdf format at

http://www.angelfire.com/mech/slideruleera/

 

[Lutfi]

Sliderule.. This is a great idea and service.

Lutfi

http://www.cdeco.com

 

[SlideRuleEra]

Thanks Lutfi, my step-daughter gave me a nice Christmas gift - she taught me the basics of how to build a web page.

 

[fndn]

The book "Theory and Practice of foundation Engineering" by Goodman and Karol, published 1968 has 3 pages on tank foundation design.

the following site has a software and API 650 specs:

http://www.chempute.com/tank.htm#Purchase Online

As for geotechnical end of it, the affected foundation soils would be tank dia^0.75 or 27ft^0.75 = 12 ft. Because the stresses are high, we use 18" compacted crushed rock overlain by 12" mud slab overlain by ring-wall footings. From past experience, allowable bearing capacity of 3ksf yields nearly 3 ft wide footings and ring wall thicknesses ranges from 12" to 18".

If your subsoils are cohesive, use UU triaxial test and FS of 3.0 to get to gross bearing capacity.

A Member of

http://www.civilvillage.com

 

[BigH]

Why do you use concrete ring foundation? The tanks I was referring to above would be about 50 ft. high - so overall bearing pressure of about 3000psf - we never used concrete ring foundations. And why such a thick mud-mat? - the mud mat is just a leveling course and to ensure no disturbance - so, if you do use one, why not 3 to 4 inches or so? - it's not structural. Just interested - perhaps differences due to "company's historical past"????

 

[fndn]

In the winter, specially in Clayey sites, with equipment, construction movements, stockpiling formwork and the like, we use thick mud-slab so as to avoid subgrade pumping. Another advantage of the 30" of crushed rock and mud slab, is that we reduce the applied pressure to the soil nearly by half(nearly 3ft footing width and 2.5 ft of stress diminishing depth.) Now, if the soils are sandy and the water table is close to the bottom of the footings, then we recomment mat foundations-but still with always a ring wall. As for the use of a ring wall, when you have a beam on elastic foundation, we assume that the deflections are uniform over the width of the tank, and to keep the twisting of the shell to a minimum-we have to resort to ring wall.

If you have taller tanks, say nearly 75 ft, then we are forced to jump to pile foundations due to wind and larger loads.

A Member of

http://www.civilvillage.com

 

[BigH]

fndn - are your tanks sitting on pedestals on individual footings ? . . . or are they flat bearing throughout the whole area of the tank bottom - this is one point that many (including me ) don't usually point out in the threads. All our storage tanks were flat-bottom steel plate so we didn't have footings per se to hold up the tank - and our undrained shear strengths except for a small desiccated crust was in the range of 1000 psf - typical for Sarnia Ontario. If you use ring wall of granular, again, use 36 inches of crushed, then a few inches of mudmat for laying on steel for ring-wall foundation and get the same thing. The paper by Bjerrum is really quite a good one for tanks on clays. I have it - would be glad to pass on. My em is in other threads - (95% Compaction, for example).

 

[fndn]

BigH-The exterior of the tanks is on the ring wall foundation, but the center is a steel plate on concrete slab with a gravel cushion. Now mind you, all my experience is in the midwest, and that might be very different from say practices in Florida or Ontario.

I remember now that Foundation Engineering book by Jumikis 1987 edition also had special foundations coverage-just am not sure how much tank foundation was included.

Yes, I would appreciate the paper on tanks on clay, and would search for your email.

A Member of

http://www.civilvillage.com

 

[flamby]

From Slide-Rules to Web-Pages! Impressive!!


Ciao.

 

[BigH]

Oh Swamy SlideRuleEra - teach us how!!
(wished my daughter would teach me!)

 

[SlideRuleEra]

flamby - Thanks for the comment; it has been, and continues to be an interesting journey.

BigH - Good idea, I'll write up a draft version of what I was taught (it's not hard, and the way we did it, it's free) and post it on my page in a few days (will ask step-daughter to refine the document).

Happy New Year