Dow Hi Load Insulation

[nicholi]

I have question about choosing the correct dow hi load insulation. Insulation is required under a mat foundation for a unheated warehouse to minimize frost penetration in northern Canada.

The question is in choosing the correct type of insulation, hi -40, hi-60 or hi-100 for the warehouse loading conditions and respective soil under the warehouse. Looking at the dow table of engineering properties and some additional literature from dow I have been given values of k for the different types of insulation. Dow calls k the foundation modulus. Related to the foundation modulus (fm) is the compressive modulus (cm), where fm = cm / thickness of insulation.

First question, what is compressive modulus and how do use that and other engineering values (some are obvious) to choose the correct hi load insulation?

Second question, is tied to the firt and is in picking a correct insulation that has a correct foundation modulus. In choosing the insulation I want to understand how it will work and I picture this in my mind. Point loads or distributed loads, concrete slab, insulation and then a soil structure. How will the insulation react in that sandwich layer? There are two site situations, see below.

Note that there are two sites (same client), one on good gravels, with the soil modulus of subgrade reaction,k = 200 + pci, and the second in an low lying area with high water table. The second site has a low k = 55 pci. The construction is mat foundation over top of a 1.0 m gravel pad overlain by a compressible dirty sand with potential for severe frost lenses, with water table potential of migrating into the sand layer. A woven geotextile fabric will be placed between the sand and gravel layer.

Thanks in advance for your advice. Note that the geotech eng did not know (or care to give an answer) and suggested that I talk to suppliers (which will only lead me back to dow's tech support) and dow tech support only kwow what is in front of them on printed paper.

 

[BigH]

nicholi - this is only intuitive; the foundation modulus appears to be a stiffness measurement of how much the particular geofoam will compress under the various weights given; i.e., each of the types of geofoam (40, 60, 100) apparently have a compression modulus. Given, then, the thickness of the geofoam, you can get the stiffness modulus for use in your mat design. I may be off base, and will follow the threads.
I've worked in Northern Ontario previously and in a few instances, I have founded very high up - say with only 1 m of embedment even though frost levels would go down to 3 m. Why? For a soil to be affected by frost (and therefore the foundation), it needs to be frost susceptible and needs to have access to water and needs to have requisite permeability to move the water (homogeneous non-laminated fat clays are not nearly as frost susceptible as lean clays or silty clays). In my case, and perhaps your gravel case, I was on non-frost susceptible coarse sand with water table down about 4m - no way (as no capillary rise) for water to be within the frost zone - hence no need for frost protection. Your gravel site may be similar. The other site with the high water level is a different story. You will need protection.