an alternative to these might be a tank with an entrance door/welded onto it.
Used Stainless Steel Storage Tanks : Pipe Culverts : Carbon Steel Tanks : Pressure Vessels : D & K Tanks
But that is probably somewhere in the 10k ballpark, maybe less plus shipping.
This one here looks room size
tem #185 & Item 186
Sidewall: 1 - 2" coupling low ~ 1 - 1" coupling low
Roof: 2 - 2" couplings ~ 1 - 18" loosebolt manway ~ 2 lifting eyes
$3,500.00 each plus freight from Robinson, IL
This one is 9'
Steel tank on skids
8 feet diameter by 27 feet long
Overall - 9 feet tall - 32 foot long skid
Skid is 5 feet wide
Located in Robinson, IL
$4,500.00 plus freight
As mentioned elsewhere is to build multple layers to hold dirt above the object to divert structural load beraing back to the earth I posted the mult layer shelter model in another thread
What you can do is slope the wall downward you could create boxes on the layer to hold the dirt, if it colapses it shuold collapse to the space left to the size of the shelter rather than ontop of the shelter. You should have air intakes and outlets that are covered to protect from cloging on your air intake.
3 layers provides for 3 separate 1 ft surfaces to hold.
3ft of soil provides for 99.9% of blocking. this allows you to have multiple layers all your layers shold be sloped for drainage. having them plastic sealed should provide water accumulation prevention. the key is to make sure you have room for drianage, a drainage well and that you divert surface water away from the shelter to keep soil weird low as possible.
This allows you to have multiple layers of load bearing so it isn't all supported by your object.
Instead of having 10 ft of dirt on your home, you have multiple levels each supporting a smaller amount of dirt.
This one looks pretty good too
6,360 gallons approximately
Carbon steel tank
18'8" overall height
1 - 18" manway
1 - 3" emergency vent
2 lifting eyes
Sump with 2 - 2" flanges
1 -1-1/2" coupling
1 - 18" manway
8" flange mixer on sidewall
$4,000.00 plus freight
You could actually instead of having air between layers put insulation between the layers which fills up greater volume but is much lighter than dirt.
Even a natural insulator like leaves in garbage bags could be used.
just attempted to explain in more detail