Modeling and behaviours of rockfill materials in three-dimensional stress space

A bounding surface model incorporating a unified nonlinear strength criterion is proposed. The proposed bounding surface model contains 9 model parameters, which can be determined from the conventional triaxial tests. The bounding surface model can reproduce such behaviours as the strain hardening, the post-peak strain softening, and the volumetric strain contraction and expansion. Based on the comparisons between the predictions and the test results, the proposed strength criterion and model can well reproduce the experimental results of the strength and stress-strain behaviours of rockfill material in three-dimensional stress space. The strength behaviour of rockfill material is summarized as: (a) the failure stress ratio decreases with the initial confining pressure on the meridian plane; (b) the failure deviatoric stress decreases with the Lode angle from 0° to 60° on the deviatoric plane. The stress ratio decreases with increasing one of such factors as the initial void ratio, the intermediate principal stress ratio and the minor principal stress at the same strain when the other factors are given.