New Viscoplastic Bounding Surface Subloading Model for Time-Dependent Behavior of Sands

Abstract

This research focuses on experimental and constitutive time-dependent modeling of sands considering rate dependency, fabric, and stepwise sudden frequency changes during loadings. Several cyclic triaxial undrained tests were performed on Toyoura sand having various void ratios, while the deviatoric stress was applied by changing the frequency in a successive number of cycles. In order to predict the viscoplastic behavior of sands, a bounding surface model accounting for fabric changes that could predict sands cyclic behavior was employed as a reference model. A subloading surface model accounting for time-dependent behavior was incorporated into the bounding surface model to develop a new viscoplastic model. A linear integration method combined with the explicit method integrates the elastoplastic part and viscoplastic part of the model. Performance of the model was verified with the experimental data obtained from triaxial undrained tests in which a good agreement was observed.