Reliability of Probabilistic Finite Element Method Over Deterministic and Traditional Probabilistic Method in Slope Stability Analysis

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Addis Ababa University


Slope Stability is one of the crucial topics in geotechnical engineering to be investigated well because oftentimes slope exists naturally or formed artificially during construction of various civil engineering structures which needs to be at equilibrium. For that matter, there are various methods of analysis. For the last couple of decades, it is observed hard for Engineers to use Probabilistic Slope Stability Analysis due to many reasons. But these days, technological advancements which led to having more rigorous software packages made it be possible to use in the analysis and its merit. The aim of this thesis is to show the use of more reliable method of slope stability analysis for hypothetical back slopes in Addis Ababa where red clay soil is dominant and that is achieved by comparing methods based on a factor of safety, probability of failure, and reliability index. Limit Equilibrium Method (LEM) and Numerical Method are used for this purpose. Both deterministic and probabilistic analyses are carried on by modeling seven slope geometries with different input parameters from Addis Ababa ring road III project and hypothetical slopes using a two-dimensional Slope Stability analysis software called SlideV6.0. A Global Minimum type of analysis are carried on by using the Slide software. For finite element analysis and probabilistic finite element analysis, RS2 software from Rocscience is used. Uncertainty is accounted for in a better way in probabilistic analysis by defining parameters as a random variable in link with other features. It is shown by this study that, Probabilistic Finite Element Analysis (PFEA) seeks out the most critical slip surface than that of the finite element method. In addition, even if the factor of safety found from the deterministic analysis is greater than one still a probability of failure is observed. Moreover, it is attested that the factor of safety is not the only measure for slope stability, but other measures exist while using probabilistic analysis.



Slope, Probabilistic analysis, FEM, PFEA, Slope Stability