超固结饱和黏性土的弹塑性本构模型及三轴试验模拟

The elasto-plastic constitutive model and tri-axial numerical simulation for saturated over-consolidated clay

针对饱和超固结黏性土现有的下加载面修正剑桥模型破坏应力比为定值,不能反映土体在不同应力状态下强度特性存在差异这一问题,为了更好地反映应力状态变化对破坏应力比的影响,基于三剪统一强度准则确定超固结土的破坏应力比。在此基础上得到了超固结土的弹塑性本构模型,该模型的特点是能够描述土体受力时的中间主应力效应、应力区间效应、拉压差影响。基于该本构模型作了常规三轴压缩条件下超固结饱和黏性土的模拟结果与试验结果对比,结果表明:该模型能够反映不同超固结比下土的变形、剪胀、孔隙水压力变化特性和规律。利用该本构模型模拟了排水和不排水条件下的真三轴压缩试验,得到了相应的应力-应变特性曲线。

The original modified cam-clay model with subloading yielding surface cannot reflect the practical difference of failure properties under different stress states for the saturated over-consolidated clay due to the definite failure stress ratio. In order to overcome the above shortcomings, the failure stress ratio connecting with the different stress states is given out based on the triple-shear unified failure criterion. The advantage is that the proposed failure stress ratio exposes better the practical effects of different stress states on the saturated over-consolidated clay. Depending on the viewpoint above, a new elasto-plastic constitutive model for the saturated over-consolidated clay is set up. It features that it can describe the effects of intermediate principal stress, range of stress and difference between tension and compression. Comparisons between the numerical simulation and experimental results under the conventional tri-axial tests show that the proposed model reflects the changes of the deformation, the shear dilatancy and the pore water pressure for the saturated over-consolidated clay with different OCR. Additionally, the proposed constitutive model is also used to simulate the mechanical characteristics of the saturated over-consolidated clay in true tri-axial tests under the drainage and undrained conditions.