Lateral Stresses Observed in Two Simple Shear Apparatus

Abstract

Two simple shear apparatus (SSA), the Cambridge University SSA Mk7 and an NGI type, were used to compare the radial stresses developed in the NGI‐type SSA with the horizontal normal stresses on the plane perpendicular to the plane of shear deformation and the intermediate principal effective stresses as measured in the Cambridge University SSA Mk7. These stresses are often assumed to be equal. Monotonic and cyclic simple shear tests were conducted on dense and loose Leighton Buzzard sand at constant applied vertical load. Comparison of results from these tests in the two SSA shows that the radial stresses are equal to neither the horizontal normal stresses nor the intermediate principal effective stresses. These radial stresses do not appear to be valuable in calculating the stress state of a specimen in the NGI‐type SSA. The values of intermediate principal effective stress ratio and the horizontal stress ratio reached at peak stress ratio (maximum shear stress/vertical) in monotonic tests on sand in its initial densest state represent threshold values for cyclic simple shear tests.