Shear banding and cross-anisotropic behavior observed in laboratory sand tests with stress rotation

Shear banding in Santa Monica beach sand deposited by dry pluviation in hollow cylinder specimens is studied in 34 drained torsion shear tests with rotation of principal stress directions. The effect of the specimen height on the soil behavior was investigated by testing specimens with heights of 40 and 25 cm. Each test was conducted with the same, constant inside and outside confining pressure, σ r , thus tying the value of b = (σ 2 – σ 3 )/(σ 1 – σ 3 ) to the inclination, β, of the major principal stress. Shear bands can develop freely without significant restraint from the soft rubber membranes. Strain localization and shear banding were observed in the hollow cylinder specimens, and this created failure conditions in plane strain and in tests with higher b-values. The results clearly indicate the influence of the cross-anisotropic fabric on the stress–strain behavior, on the shear band inclination, and on the shape of the failure surface.