Tank Pad above soil - Is frost depth a concern?
Tank Pad above soil - Is frost depth a concern?
(OP)
I am a structural engineer and we are proposing to build a 13 foot diameter by 2 foot thick concrete tank pad. We are placing it 6 inches below grade on top of 6 inches of clean gravel. My question is does it need to go to the frost depth to resist upheaval? In other words won't the weight of the concrete (13' dia x 2' thick - total weight is 40,000 pounds) tank pad with the tank (8,000 pounds) on top resist any type of upheaval in the soil? Is thier a way I can calculate how much weight is needed to resist upheaval?





RE: Tank Pad above soil - Is frost depth a concern?
I used to work in the North Slope of Alaska. The concern of water tanks was that they would melt permafrost. To mitigate this concern, "cryoanchors" would be installed beneath the tank to keep the soil frozen and minimize the thermal affect (i.e., thawing) below the tank.
Hope this helps.
f-d
¡papá gordo ain’t no madre flaca!
RE: Tank Pad above soil - Is frost depth a concern?
Unless this pad is heated and insulated - I would at least propose a footing going down to below frost line
By the time you form all that up - the few extra cubic yards of concrete to get to the frost line might be cheaper. Of course, then you might have to worry about exceeding the soil capacity
Good luck
RE: Tank Pad above soil - Is frost depth a concern?
RE: Tank Pad above soil - Is frost depth a concern?
I asked our chief geotech if it was overkill and if I could put it higher. He said heaving was still possible even with the heavy load.
RE: Tank Pad above soil - Is frost depth a concern?
Take a clean sand for instance. It has low moisture content (low heat of fusion per c.f.). Thus frost can go very deep. But the stuff is not frost susceptible, so who cares about frost depth, unless if is for necessary depth of buried water pipes.
For a clay however, it probably is frost susceptible, but has lots of water so frost penetration is not deep. The amount of heave within that "depth" depends on permeability. High plasticity means low frost heave.
The worst stuff is silt or silty clay.
As a side to this, how deep is frost depth at a lake? Not 4 feet, but why? Lots of heat of fusion to offset that cold penetration.
To get real crude about it,going to "frost depth" as locally defined will do it, but it may not be needed.
RE: Tank Pad above soil - Is frost depth a concern?
RE: Tank Pad above soil - Is frost depth a concern?