DEFORMATION BEHAVIOR OF ANISOTROPIC DENSE SAND UNDER PRINCIPAL STRESS AXES ROTATION

ABSTRACT In order to investigate the fundamental deformation behavior of sand under the more general stress condition involving the rotation of principal stress axes, a series of drained tests was carried out on a dense anisotropic sand using a hollow cylinder torsional shear apparatus. The hollow cylindrical specimens have an anisotropic fabric formed by the parallel alignment of particles induced during deposition, and are tested under the principal stress axes rotation keeping the values of three principal stresses constant. The experimental results showed that the shear deformation of sand due to the rotation of principal stress axes are not negligible as compared with that due to the shear with fixed principal stress axes and the effects of inherent anisotropic fabric on the shear deformation and volume change behavior are considerably large. The mode of anisotropic effects on the deformation characteristics depends strongly on whether the rotation of principal stress axes are involved or not. It was also indicated that the anisotropic deformation characteristics under the principal stress rotation can be explained by taking account of the predominant sliding occurring on the bedding plane, irrespective of whether the principal stress axes rotate or not. This consideration is supported by the fact that the bedding plane has the lowest value of the resistance against shear stress according to the horizontal alignment of subelongated sand particles.