Effects of Cyclic Rotation of Principal Stress Axes and Intermediate Principal Stress Parameter on the Deformation Behavior of Sands

Four series of drained tests on sands were performed with a hollow cylinder apparatus in order to investigate the fundamental deformation behavior of sands and the effects of the intermediate principal stress parameter b during cyclic rotation of principal stress axes. The test condition that principal stress axes rotated cyclically from 0° to 180° relative to vertical under constant effective principal stresses was maintained. The experimental results indicated that strains were accumulated steadily with the increasing number of cycles, while b had considerable influences on their changes during the process of cyclic rotation. The increase rate of the maximum contractive volumetric strain within each cycle was lowered with its progressive accumulation. It was found from four test series that the magnitude of the volumetric strain at the same number of cycles increased with the increase of b. The hysteretic loop in shear stress-strain curves was observed to be unclosed for the first several cycles but tend to become closed with the increase of the number of cycles. The test results in this paper also demonstrated the significant effects of the density, the effective mean normal stress and deviatoric stress on the deformation behavior of sands under cyclic rotation of principal stress axes.