ringwall question

[texeng88]

I have a questions regarding ringwall foundations that has been driving me nuts. I am working on a project where the process engineers have requested a slab under a tank that will be supported by a ringwall. They will be putting grooves in the slab to allow drainage of any leaks so the slab will have to sit on top of the ringwall. My questions is whether this will have an effect on the distribution of weight that is supported by the ringwall. Typically the only vertical forces being supported by the ringwall would come from the walls and roof of the tank and bottom pressure for the area of tank bottom sitting directly on the ringwall. In this situation where we have the slab between the bottom of the tank in the soil..will this cause a portion of weight on the bottom of the tank to be transferred to the ringwall? If this doesn't make any sense let me know and I will provide a sketch. Thanks.

 

[kylesito]

I think I am following what you are saying...

In my mind, it depends...

If you provide adequate fill below the slab (contained by the ringwall) then this is essentiall nothing more than a slab on grade in which the load of the liquid 'passes through' the slab. You would need to ensure that the fill that is used has an appropriate modulus to it and then it's just about designing it like a slab on grade. In this case, I would design the wall for the normal vertical force and maybe add some additional load to account for the weight of the slab + some of the liquid weight transferring over to the wall but nothing else. And of course, you would need to check the horizontal (hoop stress) in the wall too.

If you don't provide a fill under the slab then yes, this would significantly impact the vertical force at the wall because it would then be a suspended slab with all weight being transferred to the wall.

Question though...if they want a slab anyway, why not support the tank on a mat foundation and be done with it. Why use the ring wall? And I know there is a whole debate on whether you should use them anyway but if they are already building a slab in this case, maybe you can get it to work for you.



PE, SE
Eastern United States

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