Hence for very large deformations, say above 10 percent or so, don't use such geometrical linear analysis. This model accounts for permanent plastic deformations under high pressures for granular materials. First a deviatoric stress measure and hydrostatic stress measure are defined See above for and . The parameter follows from where the hydrostatic compression yield stress is to be defined with an table of volumetric plastic strains versus with . As always, positive strain denote extension whereas negative strains denote compression.
Associative flow is used, so the flow rule is taken equal to the yield rule.
Each of these is only incorporated if it is a compression stress. The model now reads This plasticity surface limits the allowed compression stresses. Each of these is only incorporated if it is a tension stress. The model now reads This plasticity surface limits the allowed tension stresses. A simple model for concrete can be obtained as follows.