Bounding Surface Plasticity Model Incorporating the State Pressure Index for Rockfill Materials

The critical state line of Tacheng rockfill material (TRM) was described by a pressure-power function. A simple bounding-surface plasticity model, combining the dilatancy stress ratio and peak-failure stress ratio pertaining to the state pressure index, was developed for TRM within the framework of critical-state soil mechanics and the bounding surface plasticity. Detailed investigations of influences of design parameters on the model predictions were carried out. The developed model, using a set of model constants, captured well behaviors such as strain hardening and volumetric contraction for TRM in a loose state (e.g., at a large initial void ratio or a high initial confining pressure) and strain softening and volumetric expansion in a dense state (e.g., at a small initial void ratio or a low initial confining pressure).