Abstract:

By using Lode angle, a shape function is proposed to describe the curve of strength criterion in octahedral plane, and then the Mohr-Coulomb criterion is revised to predict the influence of the intermediate principal stress ratio on the peak friction angle of soils correctly. The revised strength criterion is shown to be able to produce the same curve with Lade-Duncan’s criterion in octahedral plane, while it is suitable for predicting the strength of loose sands under true triaxial condition. In the loading process, the deformation of soil body often accompanies with strain localization, which makes the mobilized strength of soils to be reduced. The reducing effect on the strength of soils by strain localization is justified by bifurcation analysis. By comparing to the experimental results, it is shown that the mobilized strength of dense sands can be correctly predicted by the bifurcation analysis of non-coaxial plasticity under different intermediate principal stress ratio conditions.

Key words: strength, strain localization, intermediate principal stress ratio, true triaxial condition