Concrete slab for tanks

[prmmel]

I am doing a slab for (2) 20K concrete tanks. The tanks are 10'6" diameter each and total weight with water is about 25,000# each.

I need to design the slab to support the weight. The slab will be 37'x37'x6" thick, but I was going to do an interior support that is about 24' x 12' x 9.5" thick to support the tanks. I am thinking that this may not be substantial enough...not sure how to calculate.

I will lay down 6" of crush/run as a base first.
I am planning on a 3000psi mix and using 6x6 wire mesh.

Attached is a detail drawing. Any help is appreciated.

 

[JAE]

nothing attached...

 

[dik]

What type of soil? Do you have to keep it from floating?

Dik

 

[prmmel]

Sorry
Try this

 

[prmmel]

The existing soil is sandy/silty clay and has very good compaction. There is not a concern for floating up as the slab will be above grade.

 

[Ron]

It looks like the majority of your slab area is for containment. The thicknened section holding the tanks will have a shear issue relative to the other "unloaded" slab.

The contact stress on the ground is relatively low, bearing is not an issue. I would thicken the perimeter of the 12x24 section and isolate it from the unloaded slab. Develop a good joint configuration and seal it at the perimeter isolation joint.

 

[prmmel]

Our concern was how to calc. the thickness requirements of the concrete directly under the tanks.

 

[Ron]

Shear at the perimeter of the tanks will likely control. Given that, figure the amount of shear area you need to keep the factored shear stress within code limits, divide by the perimeter length (or circumference of the tank, if they are circular), and the result will be the required thickness.