Masashi NAMBA

Rigid Plastic Finite Element Analysis of Landslide Stability and Stabilizing Method

Satoru OHTSUKA

Landslide takes place along the existent slip line even though gentle slope. The shear strength of slip line is remarkably lower than that of soil in slope. It is widely estimated by inverse analysis in practice due to the difficulty to predict the strength parameters of slip line. The limit equilibrium method is generally employed in inverse analysis, however, the accuracy of the method is not so high in stability assessment. This study introduces the rigid plastic finite element method into inverse analysis.
This study aims to develop the stability method to take account of low strength discontinuous line inside slope. Based on contact friction a constitutive equation was developed for three-dimensional RPFEM. It provides rational stability assessment for various slopes such as landslides and slopes with thin weak layer. It was employed to identify the strength parameters of slip line for past landslide. The applicability of the developed method was investigated through three-dimensional analyses of natural slope. In addition, the stabilizing method with anchors was examined by three-dimensional slope stability analyses. The following conclusions were obtained.
1)Stabilizing effect of anchors was rationally estimated by rigid plastic FEM. Three-dimensional RPFEM analyses of slope stability showed the two-dimensional analyses generally overestimated the factor of safety.
2)Failure mode of slope greatly depended on the existence of thin weak layer. It caused the failure mode wider and deeper in case studies. The applicability of developed method with constitutive equation for contact plane was examined for various conditions of boundary value problem.
3)Inverse analyses for strength parameters of slip line were conducted for landslides where circular and non-circular arc slip lines constituted. It provided the possible strength parameters not uniquely, but dependent of shear strength of soil in slope. It affords a new understanding of inversed strength parameters and future subject in design practice.