Constitutive Modelling and Determination of Soil Parameters for Anisotropically Consolidated Clay

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1. On the stress-strains-time behavior of normally consolidated clay ;A series of undrained triaxial stress relaxation tests on four saturated clays consolidated under isotropic stress condition and constant rate of strain triaxial compression test on a saturated clay consolidated under isotropic and anisotropic stress conditions were performed. Experimental results show that the principal stress difference versus logarithm of time relationship during stress relaxation test is approximated by the two straight lines independent of strain level, strain rate and mode of stress application in the preceding undrained shear process. Stress ratio versus strain relationship is not affected by the rate of strain during shear, and the porepressure during shear decreases with the increase in the rate of strain.2. On the stress-strain-time equation for anisotropically normally consolidated clay ;Based on the test results mentioned above, a new elasto-viscoplastic constitutive equation for anisotro … More pically consolidated clay was proposed. It was found that the proposed equation can predict fairly well the effect of rate of strain on the undrained stress-strain behavior, stress relaxation and also undrained creep behavior of anisotropically consolidated clay.3. On the elasto-plastic constitutive model for anisotropically overconsolidated clay ;A series of drained stress probe tests along six stress paths for the specimens consolidated and rebounded under anisotropic stress condition were conducted to investigate the influence of anisotropic stress history and stress path on the stress-strain behavior of overconsolidated clay.From the test results, it was found that the shear strain during shear depends not only on the change of stress ratio but also on that of mean effective stress, and that K_ overconsolidated clay exhibits negative dilatancy at the beginning of loading even on the "dry side", and then significant positive dilatancy is observed on the stress path moving towards the Hvorslev surface on the dry side. Based on the test results, a constitutive model for anisotropically overconsolidated clay was proposed. Stress-strain behavior for the stress path moving towards the critical state line and also for the stress paths directed from the overconsolidation state to the normal consolidation zone can be well predicted by the model. Less