Perhaps the stress strain data at
www.beaver plastics - DYNAFLEX, from one of the calculators
would be helpful , if you know what the wall can handle for lateral load, and you can make a guess at how much strain (soil face movement) you think you should provide for.
I was going to add to the above: Yes I work for Beaver Plastics. No this is not necessarily a commercial message. I like this stuff, and that's the reason why I worked with geotechnical engineers to develop the calculators. Once you have determined the maximum stress that your slab/piles can...
Determining the necessary thickness of any foam plastic "solid void" material (yes, I know, that's contradictory)to absorb subgrade uplift is a difficult calculation. Stress climbs rapidly with strain, so the thickness required for even a small amoount of freezing or clay swelling can be...
