How do I anchor an underground tank?

[TonyES]

I have a large underground concrete tank that is designed to be water tight. The water table could be above the lid resulting in extremely high bouyancy forces. To help get an idea the tank has about 3,000 ft^3 of volume - I would need a 7' thick x 20' x 12' concrete deadman to anchor it too to resist the bouyancy. There is no bedrock nearby to anchor to either. One thought was to pour a skirt - concrete wall that extends around the tank such that the soil above this wall helps keep the tank from floating - this skirt would be 8" tall and as wide as needed to resist the force - but will this work? If I have to assume the water table is above the tank than will there be any soil to help resist the uplift?
Any thoughts?
thanks

 

[HeavyCivil]

hokie - okay, I was thinking you were just making the mat thicker... even still, maybe just the top layer of bar needs to satisfy crack control?

msquared - like paddingtongreen said, we call it flowable fill or CLSM. Yes, I've seen it poured. In our area its $90/yd... barly cheaper than 3000psi, so it rarely is used. No kidding, its that expensive.

My point- which may be moot - was that the less yardage and complexity in anything that must be monolithic the better. 5 minutes to unload 10 yds is fast but if it will be a couple hours before he can come back with 10 more we can have issues.

 

[msquared48]

VTEIT:

You do not have to waqit for the first poir to set, but can make the second, third, etc immediately after, depending on the batch plant and the pumper capacity...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[HeavyCivil]

msquared - yes that is pretty clear. The couple hours I was talking about weren't for the concrete or CLSM to set, but were symptoms of using small batch plants in rural areas far from the tank site. I think this is straying from the original questions - just wanted to clarify that was not what I was saying.