A new hardening interpolation rule for the dynamic behavior of soils using Generalized Plasticity framework

In soil mechanics, it is of major interest to distinguish the soil behavior under cyclic or transient loads from that of monotonic ones. Most cyclic plasticity models require accurate predictions of irreversible strains computed through a flow rule in virgin loading and during stress reversals which is typically performed using a plastic hardening modulus. In bounding surface models, hardening modulus is calculated using an interpolation rule essentially relating the location of current stress tensor to its projection on the bounding surface. It is important that the interpolation rule used to obtain the plastic modulus through stress tensor is consistent with the hardening law. In this study, a new interpolation rule for the computation of plastic hardening modulus during stress reversals of soils is proposed within the Generalized Plasticity Theory. The rule is used in the calculation of plastic strains during unloading-reloading cycles requiring a single material parameter to be defined as a function of accumulated deviatoric plastic strain. Firstly, a bounding surface is embedded in the generalized plasticity framework and a number of static and cyclic triaxial tests are simulated. Then the effect of the new interpolation rule on the cyclic behavior of cohesive and cohesionless soils is investigated.