Sensitivity analysis of slope stability using finite element method

Stability analysis of earth slopes can be carried out by either limit equilibrium method (LEM) or finite element method (FEM). The LEM has inherent limitations as it does not consider the stress – strain relation of the material, whereas the FEM for slope stability analysis is widely used because it accounts stress – strain behaviour of soil, the formation of failure zone based on the limiting soil properties and is considered more accurate and reliable. While using the FEM it is necessary to quantify the various parameters affecting the stability of slope. These parameters include the material properties of soil, geometry of slope and the soil constitutive model. In this study, the finite element (FE) sensitivity analysis is performed for a homogenous slope with c – ϕ soil to evaluate various parameter affecting the stability of slope. The analysis is carried out considering the strength parameters (c and ϕ), unit weight of soil (γ), Young’s modulus (E), Poisson’s ratio (ν), slope angle (i), slope height (H), depth of foundation layer below the slope (D). The soil is assumed as linear elastic perfectly plastic with Mohr–Coulomb failure criterion and follows the non-associative flow rule. The results of sensitivity analysis are presented as factor of safety vs. displacement plots for various parameters and also represented as spider plot and tornado plot. The results of FE analysis are compared with the limit equilibrium method and solutions available in the literature. The study also examines the effect of different constitutive models on the FoS of slope. The material models considered are Mohr–Coulomb (MC) model and Hardening Soil (HS) model. It is found from the results that the factor of safety (FoS) of slope is sensitive to slope angle, slope height, unit weight, friction angle and cohesion of soil while it is least sensitive to deformation parameters of soil (E and ν), depth of foundation layer and constitutive models used in the study. Based on the study few suggestions are also given in regard to the FE analysis of slope stability problems.