anchoring a RC tank base to rock
anchoring a RC tank base to rock
(OP)
Hello,
I'm wondering if there's an easy and cheap way to anchor a reinforced concrete base of a tank to underlying rock,to resist flotation.
I'm designing a Washwater Recovery Tank. The Site Investigation shows a water table upto 1m below ground close to the site. Using this as my level for flotation, I have to increase the weight of the tank.
The Contractor says he is excavating down at least 4m before he gets any ground water. And of course he doesn't want any extra concrete on his bill just for flotation.
Any suggestions for a cheap anchoring system please?
I'm wondering if there's an easy and cheap way to anchor a reinforced concrete base of a tank to underlying rock,to resist flotation.
I'm designing a Washwater Recovery Tank. The Site Investigation shows a water table upto 1m below ground close to the site. Using this as my level for flotation, I have to increase the weight of the tank.
The Contractor says he is excavating down at least 4m before he gets any ground water. And of course he doesn't want any extra concrete on his bill just for flotation.
Any suggestions for a cheap anchoring system please?






RE: anchoring a RC tank base to rock
These would need to be tested though.
csd
RE: anchoring a RC tank base to rock
RE: anchoring a RC tank base to rock
csd
RE: anchoring a RC tank base to rock
Drile007
RE: anchoring a RC tank base to rock
RE: anchoring a RC tank base to rock
I was looking at grouting rebar into the rock. Unfortunately the Contractor and I disagree on the likelyhood of the water table rising above 4m below ground. But it's his bill and his risk. And I know nobody will get hurt if the tank lifts. Still, I don't like the idea of a tank I've designed setting sail sometime in the next few years, all for the sake of a few extra loads of concrete.
Anyway, I will be instructing a good drainage material for backfill so the water has a choice to move on if possible.
RE: anchoring a RC tank base to rock
RE: anchoring a RC tank base to rock
I've included a 'skirt' except I call it a toe, some others call it a heel.
It does help, but the tank is 20m x 15m (about 66' x 49') on plan so this leaves the base resisting uplift in bending and shear. I've got this to work with a 475mm base and some hefty rebar.
RE: anchoring a RC tank base to rock
RE: anchoring a RC tank base to rock
Can you provide a groundwater monitoring well and in the O&M manual state "do not de-water the tank when groundwater exceeds XX elevation"?
RE: anchoring a RC tank base to rock
RE: anchoring a RC tank base to rock
Relief valves have a history of failing, thus causing your tank to leak out into the soil, and if you drawdown the tank quickly, can actually contribute to uplift forces.
I think anything other than mass or rock anchors is getting too technical.
RE: anchoring a RC tank base to rock
But, as they use some weird and wonderful materials for the aggregate(metal based typically)you would need to be certain that it was applicable for tank containing liquid.
Alternatively consider a hybrid where the heavyweight provides mass only and does no structural work?
RE: anchoring a RC tank base to rock