基坑放坡开挖破坏性状大变形有限元分析

Large deformation finite element analysis on excavated slopes

基于任意拉格朗日–欧拉(ALE)有限元方法,采用理想弹塑性本构模型(不考虑软化)和考虑应变软化的本构模型以及Mohr-Coulomb屈服准则,对平面应变条件下软土均质地基上的基坑放坡开挖进行数值模拟,并对非软化及软化模型的结果进行对比。研究表明:考虑应变软化分析的结果同非软化分析的结果有较明显的不同,在基坑开挖达到一定深度后,土体剪切带发展方向不同,考虑应变软化时基坑顶部比基坑底部早达到塑性状态,而非软化分析中则是基坑底部早达到塑性状态;同时从图形化分析角度讲,非软化分析中剪切带的贯通过程较为明显,而软化分析中其剪切带的贯通过程则要复杂。非软化分析得到的结果是偏不安全的。

Based on the arbitrary Lagrangian-Eulerian finite element method combined with Mohr-Coulomb yield rule, numerical analysis on the excavated slopes was presented by using ideal elasto-plastic model or that considering strain-softening of soils. The results were quite different by using these two different models. The top of the slop reached the plastic state earlier than the bottom for the model considering strain-softening, and contrariwise, the bottom reached earlier for the ideal elasto-plastic model. From the point of view of graphic analysis, the development of shear-band was more obvious for the ideal the elasto-plastic model, and was more complex for the model considering strain-softening. The results calculated by the ideal elasto-plastic model will lead to unsafety.