msucog...I agree...the plastic modulus we use in structural has no relevance to a soil modulus of any sort. Soil doesn't have a "plastic" range in the same sense as the structural "plastic" range.
If you're right about them trying to adapt structural software to accommodate soil parameters directly, they are probably in for a surprise. We can model soil response in structural analysis software, but we usually do so by using springs or similar tools to replicate soil behavior.
Yeah, the only term I could equate to it as well was resilient modulus..thus my question above about pavements.