Simple Shear Testing on Sand in a Torsional Shear Apparatus

Abstract

A method for simple shear simulation using a hollow cylindrical specimen is described. Drained tests at controlled axial stresses were performed automatically by means of a servosystem consisting of a micro-computer and a pneumatic-controlling system. For undrained tests on saturated specimens the simple shear simulation was achieved only by a mechanical means. The torsional simple shear behavior of Toyoura sand is described. This is well comparable with that from the Cambridge simple shear apparatus reported in the literature ; i. e., the major part of the rotation of principal stresses takes place only at the early stage of shearing keeping a stress ratio σ1'/σ3' close to the initial value 1/K0. Strains associated with the principal stress rotation were found very small. It was found that the strength and deformation properties of Toyoura sand at relatively large strains in torsional simple shear are very similar to those by the plane strain compression test in which the directions of principal stresses with respect to the deposition direction and the value of σ3' are similar to those at failure in the torsional simple shear test. It is likely that the effect of principal stress rotation on simple shear behavior during monotonic loading has often been considerably over-exaggerated.