Effects of mean net stress and cyclic deviatoric stress on the cyclic behavior of normally consolidated unsaturated kaolin

Experimental study of the cyclic behavior of unsaturated materials is more complex than that of the saturated materials due to the required equipment, experience and time. Furthering investigations in the field of unsaturated materials is necessary to better understand its complexity and sensitivity of unsaturated cyclic parameters to different determinants such as suction path, stress path, loading speed, deviatoric stress amplitude, physical specifications, and etc. To this end, the main focus of this study has been to analyze the effects of factors such as mean net stress and deviatoric stress levels in fast cyclic loading on the cyclic behavior of a normally consolidated unsaturated fine-grained trade soil, namely the Zenoz kaolin. Various unsaturated tests were performed in three mean net stress levels and three amplitudes of cyclic deviatoric stress levels. Results showed that increase of suction in the same strain level leads to increase in stiffness in normally consolidated samples (i.e. increase in elastic modulus and shear modulus and decrease in damping ratio). Also, in the same suction value and strain level, increase of the mean net stress during the isotropic consolidation causes to the denser normally consolidated samples and results to increase of elastic modulus and shear modulus, and decrease of damping ratio.