Effect of Intermediate Principal Stress Parameter on Cyclic Behavior of Sand

Soils have an anisotropic response and changing the inclination (α) and magnitude of the major principal stress will affect the collapse potential and brittleness as well as the shear strength and shear stiffness. In this paper the effect of stress path with changing in intermediate principal stress on the dynamic behavior of Babolsar sand is studied. A series of undrained monotonic and cyclic tests on loose sand with induced anisotropy were conducted using automatic hollow cylinder apparatus. Special attention was paid to the significant role of the intermediate principal stress parameter (b) in the deformation behavior of sand during cyclic loading. Results show that at constant α, confining stress and fabric; variation ofb has significant effect on the strain amplitudes but it would not change contractive or dilative behavior of specimens. The variation of b has high effect on liquefaction resistance but has no effect on the mobilized friction angle at steady state. It is shown that confining stress has significant effect on soil response (the strain development, excess pore water pressure generation and shear modulus and damping ratio). Moreover by increasing the confining stress, the effect of b value on cyclic behavior will be more pronounced.