Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Civil Engineering

Reliability of safety factor in slope stability problems is a major issue in geotechnical engineering. The research goal is to study the reliability of the factor of safety of a slope stability calculated by LE and FE methods. Simple slope rested on granular soil and cohesive soil with different soil states was studied. A comparison between limit equilibrium using SLIDE software and finite element using PLAXIS 2D was done. Among LE methods, Bishop simplified, Janbu simplified and Morgenstern-Price methods were utilized. Also, three constitutive models for FE analyses were applied. Statistical analysis was performed to predict the coefficient of variation of shear strength parameters. The research indicates that FS alone is misleading and reliability analysis provides a logical framework. Bishop and Morgenstern limit equilibrium methods were almost the same results while using Janbu method gave quite different than the other two methods. Different levels of complexity in soil models produce almost the same values of FS and reliability index. While using simple constitutive model results in a smaller value of PF% than sophisticated one for granular soil. FS calculated using FE method is less than using LE approach results. Accordingly, LE produces results in higher reliability index than (FE). Finally, LE approach is preferable for granular soil

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