Three-Dimensional Modeling of Strain-Softening Soil Response for Seismic-Loading Applications

A three-dimensional (3D) incremental plasticity constitutive model is developed for simulating the strain softening behavior of soil materials. The constitutive model extends an existing multiyield surface (MYS) plasticity formulation with a new strain softening logic. Formulation of the model is presented, and calibration is undertaken to match an available data set. Implementing the model into OpenSees, finite element (FE) simulations are conducted to highlight the underlying response mechanisms. Strength and stiffness degradation due to the strain softening mechanism is shown to play a substantial role in terms of accumulated deformation and influence on the resulting ground accelerations. For that purpose, computed results with and without the strain softening effect are compared and discussed. As such, incorporation of strain softening is an important consideration for a wide range of scenarios involving sensitive clays, cemented, over-consolidated, very dense, or frozen soils among others. Overall, the derived insights are of significance for seismic loading in such soil formations.