Response Prediction of Granular Materials at Low Effective Stresses

Abstract

Analysis of laboratory experiments and model structures on cohesionless granular materials conducted at very low effective stress levels have shown that their response to loading differs significantly from that observed at higher stress levels. These differences may be attributed both to intrinsic material properties and external factors such as boundary conditions. The gravity induced self‐weight stresses that occur in typical laboratory specimens are often of the same order of magnitude as the externally applied tractions or stresses that result from displacement controlled modes of loading at very low confinement levels. A three stress invariant elastoplastic constitutive model recently proposed may be used to simulate the nonlinear stress‐strain‐strength behavior of granular soils at low stress levels. The constitutive equations have been integrated via a fully implicit technique. The model parameters are calibrated via an optimization scheme. In this study the model is implemented in a finite‐element code in order to study nonlinear boundary value problems. The optimization scheme is used (at the finite‐element level) as an inverse‐identification procedure that is used to better identify the constitutive model parameters (without the influence of external forces, such as gravity) from triaxial experiments at very low as well as high confining stress levels.