Probabilistic Assessment of Commercial Design Guides for Steep Reinforced Slopes: Implications for Design

Abstract

Deterministic procedures are still the predominate methods used in reinforced slope design. These procedures generally use limit equilibrium methods based on accepted factors of safety. This paper presents a method of probabilistic analysis which is easily adapted to existing deterministic methods. The method is used to analyze the reliability of a two steep reinforced slopes designed using commercially published guidelines. The reliability of internal failure modes (passing within the reinforced zone) and composite failure modes (passing mostly outside of the reinforced zone) are computed and compared. The results indicate that internal and composite failure modes may be nearly equally likely leading to a total probability of failure of twice that of either mode. The paper present a design process to ensure that the probability of failure is controlled by composite failure modes and the reliability of internal modes is sufficiently high that they do not significantly reduce the total reliability of the slope.