Abstract: The mechanical properties of coarse granular material are not only depending on effective confining pressure, but also closely related to compaction degree. The effects of confining pressure and density on mechanical properties of coarse granular material under critical state were investigated using large-scale triaxial consolidation and drainage shear tests on specimens with four different initial dry densities. The deviatoric stress at failure state for softening stress-strain curve is larger than that at phase transformation state which is closer to the deviatoric stress at critical state. The stress ratio of deviatoric stress to mean normal stress gradually approaches the stress ratio at critical state. The curve of stress ratio for softening stress-strain test displays a single hump shape, while the curve of stress ratio for hardening stress-strain test shows a climbing shape. The critical void ratio decreases with the increase of mean normal stress under critical state, and basically increases linearly with the increase of initial void ratio.

Key words: coarse granular material, critical state, mechanical properties, phase transformation state, density, confining pressure