边坡变形破坏过程的大变形有限元分析

Large deformation fem analysis of slopes fallure

在用有限元法分析边坡稳定性时,引入计算大变形问题的更新的拉格朗日方法,推导了边坡大变形弹塑性有限元分析的方程式。采用边坡某一幅值的等效塑性剪应变区,从坡脚到坡顶贯通前的折减系数作为边坡安全系数。在此基础上,采用弹塑性大变形有限元分析软件计算了均质土坡不同坡角的安全系数,将其与小变形分析的结果进行了对比分析,结果表明:用弹塑性大变形有限元分析边坡失稳破坏的过程中,既考虑了岩土材料的非线性,又考虑了边坡的几何非线性,使计算结果更趋合理。并结合东深供水改造工程BIII2边坡进行了大变形有限元分析,计算结果与勘查到的实际边坡的滑动面分布位置比较接近。研究表明:该方法尤其适宜于软土类边坡或基坑的稳定性分析。

The updated Lagrangian method of large deformation for the stability analysis of slopes is introduced; and then the equation of elasto-plastic large deformation FEM for the large deformation of slopes are presented. The strength reduction coefficient before a well-defined equivalent plastic shear strain (EPSS) running through from the bottom to the top of a slope is considered as its safety factor. The safety factors of homogeneous soil slope with different gradients are calculated by elasto-plastic large strain FEM method. The results are well coincident with the results calculated by small strain FEM; The elasto-plastic large strain(EPLS) FEM analytical results show that not only the nonlinearity of soil material but also the geometric nonlinearity in the process of failure stability is considered. So, the calculation results of EPLS is more reasonable. the large deformation method is applied to analysis of BIII2 landslide in the water supply reconstruction project from Dongjiang to Shenzhen. The results show that calculation EPSS is more similar to the actual sliding area given by geotechnical survey. The large deformation method is more suitable for the calculation of soft soil(rock) slopes or the wall of foundation pits.