Abstract: Dry density has an important influence on strength properties of coarse granular material, especially in three-dimensional stress state. In this study, the effects of dry density on strength properties of coarse granular material were investigated using large-scale true triaxial tests under equal intermediate principal stress coefficient (b=0.25) loading condition with equal minimum principle stress and large-scale triaxial tests at different dry densities. The results show that the stress-strain curve of large-scale true triaxial test presents basically of climbing shape which is higher and steeper than that of large-scale triaxial test and shows strong hardening behavior. The strength of coarse granular material increases linearly with the increase of initial dry density or minimum principal stress. The strength of large-scale true triaxial test increases by 20%–97% compared with that of large-scale triaxial test, and the smaller the minimum principal stress, the greater the strength increase. If the cohesion of coarse granular material is 0, the internal friction angle increases linearly with the increase of initial dry density and decreases with the increase of minimum principal stress. The failure stress ratio linearly increases with the increase of initial dry density and decreases linearly with the increase of minimum principal stress. The failure stress ratio of large-scale true triaxial test is smaller than that of large-scale triaxial test.

Key words: large-scale true triaxial test, coarse granular material, dry density, intermediate principal stress, strength, internal friction angle, failure stress ratio