Experimental study of drained anisotropy of granular soils involving rotation of principal stress direction

A series of drained tests were conducted on the medium dense Toyoura standard sands using a hollow cylinder apparatus, including both F tests (sheared with a fixed principal stress direction) and R tests (sheared with a constant deviatoric stress but rotating the principal stress directions). The effects of anisotropy on the deformation characteristics were examined, including both the inherent anisotropy that formed in the process of sand sample preparation and the anisotropy which induced due to the 'inclined' consolidation. The results of F tests showed that the effect of the inherent anisotropy was significant on the stress-strain behaviour and failure strength of sand. It was also seen that the deformation characteristics of R tests, including the development of strain components, the nominal strain increments and the degree of non-coaxiality, were considerably dependent on both the 'inclined' consolidation directions and the deviatoric stress level. It was also noted that the development of nominal strain increments and volumetric strain was affected by the number of cycles due to the densification of the sand under cyclic rotation of principal stress axes under drained conditions.