Comparison of True Triaxial and Hollow Cylinder Tests on Cross-Anisotropic Sand Specimens

Experiments have been performed in true triaxial equipment and in hollow cylinder equipment on dense Fine Nevada sand to study and compare the influence of the intermediate principal stress on the behavior observed in the two types of apparatuses. By suitable application of outside and inside pressures in hollow cylinder tests performed on cross-anisotropic sand deposits with horizontal bedding planes (without application of shear stresses), generated stress states are comparable with those applied in true triaxial tests on oriented specimens in Sector I and III of the octahedral plane. Stress non-uniformities occur in the hollow cylinder specimens and they may affect the results of these tests. The experiments showed good comparison in Sector I, but those in Sector III were not comparable because the hollow cylinder tests showed effects of buckling instability, failure in the σ2-direction, and effects of stiff versus flexible boundaries through which the pressures were applied.