Double‐Yield‐Surface Model. II: Implementation and Verification

A double‐yield‐surface constitutive model for the stress‐strain‐time behavior of cohesive soils is implemented into a nonlinear finite element program based on Biot's three‐dimensional consolidation theory. The coupled soil deformation‐fluid flow model allows creep effects to be modeled concurrently. The soil's hydraulic conductivity is considered a state variable, which varies with the void ratio so that it decreases as the soil compacts. Parametric, laboratory, and field‐case studies are performed on various cohesive soils such as Weald clay, undisturbed bay mud, and Boston blue clay to validate the model. Numerical simulations include drained, undrained, consolidation, creep, stress‐relaxation, and combined stress‐relaxation and creep tests under triaxial and plane‐strain stress conditions. The constitutive model is shown to predict the stress‐strain‐time behavior of “wet” clays more accurately than did an earlier version based on a single‐yield‐surface criterion.