Constitutive Modelling and Determination of Soil Parameters for Anisotropically Consolidated Clay

1.关于正常固结粘土的应力-应变-时间特性，进行了四种饱和粘土在各向同性应力条件下的不排水三轴应力松弛试验和饱和粘土在各向同性和各向异性应力条件下的恒应变三轴压缩试验。实验结果表明，应力松弛试验中的主应力差与时间关系的对数可以用两条直线近似，与前一次不排水剪切过程中的应变水平、应变率和应力施加方式无关。剪切过程中的应力比-应变关系不受应变率的影响，剪切过程中的孔压随应变率的增大而减小。各向异性正常固结粘土的应力-应变-时间方程基于上述试验结果，建立了新的各向异性…弹粘塑性本构方程人们提出了更坚固的粘土。结果表明，该方程能较好地预测应变率对各向异性固结粘土的不排水应力应变行为、应力松弛和不排水蠕变行为的影响。基于各向异性超固结粘土的弹塑性本构模型，对各向异性应力状态下的固结回弹试件进行了一系列沿6个应力路径的排水应力探头试验，研究了各向异性应力历史和应力路径对超固结粘土应力应变行为的影响。试验结果表明，剪切过程中的剪切应变不仅取决于应力比的变化，还取决于平均有效应力的变化；K_超固结粘土在加载初期甚至在“干侧”也表现出负的剪胀性，然后在干侧向Hvorslev表面移动的应力路径上观察到显著的正剪胀性。根据试验结果，提出了各向异性超固结粘土的本构模型。该模型可以很好地预测应力路径向临界状态线移动以及从超固结态到正常固结区的应力路径的应力应变行为。较少

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