If you just make sure that your subgrade (stone, sand, whatever) is properly compacted and level, it has no problem supporting anything. My concrete guy suggested I add a couple inches to the floor in case I wanna pull the tractor in the shop. 7000 lb Farmall 560...
Type V XPS has a compressive strength of 100 psi. I'll probably go with Type VII, at 60 psi which is plenty strong. Tractor with concrete would only be about 30 psi or less...
If we took your 7000# tractor and divided the weight into the 4 point loads (bearing points at the tire contact patch) we would get 1750# per tire (this is not an accurate distribution of the weight, but good enough for discussion).
OK, a 1750# load onto a 100 psi max support would require a minimun of 17.5 sq inches of even distribution...or...a contact patch of 3.5" x 5"
minimum. This all assumes that you are pulling the tractor right on top of the insulation and the point load is evenly distributed across the contact patch. I don't know what the contact patch size is for your tires, but I bet it exceeds the 17.5" min at all 4 corners. This is good, but it illustrates just how close you are to exceeding the support capacity. Now...let's add the concrete and reinforcing. Yes, it adds some weight to the foam support, but it is relatively negligible. It all comes back to the lateral distribution of the point load by the reinforced concrete; just how far it pushes the load out radially. I don't know what that calc is, but it illustrates how vital it is in the big picture of load support for this application.
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...did I get that right?
