Effect of Microfabric on Undrained Static and Cyclic Behavior of Kaolin Clay

Microfabric plays an important role in the engineering behavior of soils. Although many studies are available in the literature on the effect of microfabric on the static behavior of soils, the effect on the cyclic behavior is less understood. In the present study, samples with different microfabric were prepared in the laboratory by reconstituting commercially available kaolin clay with different pore fluids under a consolidation pressure of 100 kPa. Consolidated undrained triaxial tests were carried out on these samples under static and cyclic loading conditions. Dispersed samples were found to have monotonic stress-strain behavior with a peak deviatoric stress and higher peak undrained shear strength than the flocculated samples. However, the dispersed samples were found to offer less resistance to cyclic loading. When subjected to cyclic loading, dispersed samples failed within a few cycles under a cyclic stress ratio (defined as the ratio of cyclic deviatoric stress to the undrained shear strength) close to 0.6, whereas in flocculated samples, sudden failure was not observed even at a higher cyclic stress ratio of 0.9, although strains and pore pressures accumulated to higher values. Postcyclic monotonic tests conducted on samples that did not fail under cyclic loading showed an apparent overconsolidation effect caused by cyclic loading in a similar manner, as reported in the literature.