Undrained Shear Behaviors of High Plastic Normally K0-Consolidated Marine Clays

Isotropic normally consolidated-undrained and K0-consolidated-undrained triaxial compression tests were carried out in order to investigate the effects of K0-consolidation and secondary consolidation on the undrained shear behavior of undisturbed marine clay with varying plasticity index in this study. The deviator stress ratio M* mobilized at the maximum deviator stress qmax of normally K0-consolidated young clays at the end of primary consolidation became smaller than the critical stress ratio M due to stress induced anisotropy caused by the K0-consolidation, this ratio M/M* was 0.85 regardless of plasticity index. On the other hands, the effective stress path for normally K0- consolidated young clays was parabolic curves with plastic softening beyond the maximum deviator stress, which became more marked as the plasticity index increased. It was clearly showed that the shape of the curve will strongly depend on the plasticity index. Furthermore, it was found that experimental effective stress path of high plastic normally K0-consolidated young clays showed remarkable plastic softening beyond the maximum deviator stress, and this phenomenon could be modeled using a quadratic equation and the parameters M* and initial deviator stress ratio after K0 consolidation, η0, modified by an anisotropic kinematical hardening rule.