Friction and Dilatancy Angles of Granular Soils Incorporating Effects of Shearing Modes

The strength–dilatancy relationship, which is significantly influenced by the shearing mode, is of great importance in modeling evolution of the mobilized strength and predicting deformations of granular soils. In this paper, the effects of the shearing mode on the strength–dilatancy relation were investigated by performing the multiaxial tests on gravelly soils. It was interestingly found that the gradient of the fitting line for the relationship between the peak–failure friction angle and maximum dilatancy angle increased with increasing the intermediate principal stress ratio b. In particular, for b = 0, the gradient of the fitting line was 0.44 (which was smaller than the Bolton dilatancy index of 0.48). In addition, a strength–dilatancy equation incorporating the effects of shearing mode was proposed for this gravel soil. Thereafter, a general equation between peak friction–failure angle and maximum dilatancy was obtained by using experimental data from the literature and current work for different shearing modes. The two equations were then validated by other independent test data on sands and gravels. It was observed that the general strength–dilatancy equation could well capture the strength–dilatancy relationships on various granular soils, including sands and gravel under different shearing modes.