饱和超固结黏性土的三剪弹塑性本构模型研究

针对饱和超固结黏性土现有下加载面修正剑桥模型中破坏应力比为定值、土体黏聚力为零，以及不能准确反映不同应力状态下土的强度差异这些问题，基于三剪统一强度准则以及应力坐标平移法得到了扩展破坏应力比，其特点是能更好地反映应力状态变化以及土体黏聚力的影响。在此基础上提出了饱和超固结黏性土的三剪弹塑性本构模型，该模型的特点是能描述土体受力时的中间主应力效应，应力区间效应和拉压差影响，同时也能更好地考虑土体黏聚力的影响。基于该模型对ABAQUS软件进行了二次开发，并利用其模拟了饱和超固结黏性土在排水和不排水条件下的真三轴和常规三轴压缩试验特性。对常规三轴压缩条件下土体力学特性作了模拟和试验结果对比。结果表明所提模型能很好地反映不同超固结比下土体的变形、剪胀、孔隙水压力变化特性。

The triple-shear elasto-plastic constitutive model for saturated over-consolidated clay

The extended failure stress ratio connecting with the different stress state and the cohesion is given out based on the triple-shear unified failure criterion and coordinate translation for the saturated over-consolidated clay, in order to overcome the shortcomings of the original sub-loading yield surface modified cam-clay model with the definite failure stress ratio without considering the soil cohesion, which can't reflect the practical differences of strength properties under different stress states and cohesions for soils. The advantage is that the extended failure stress ratio could show the practical effects of different stress states acting on the saturated over-consolidated clay with different cohesions better. Depending on the viewpoint above, a new triple-shear elasto-plastic constitutive model for the saturated over-consolidated clay is set up. Its features are that it can describe the effects of intermediate principal stress, rang changes of stress, difference between tension and compression and different cohesions. In addition, the ABAQUS is developed secondly based on the new constitutive model and the mechanical properties are simulated under the true and the conventional triaxial tests in the drainage and the undrained conditions for the saturated over-consolidated clay. Comparisons between the numerical simulations and experimental results under conventional triaxial tests show that the proposed model could reflect the changes of deformations, shear dilatations and pore water pressures for the saturated over-consolidated clay with different OCR.