Reliability analysis applied on lebanese slopes subjected to seismic loads

Abstract eng:
In this paper, a reliability-based analysis and design of earth slopes situated in seismic areas is performed. Two failure or unsatisfactory performance modes are considered in the analysis. Both of them concern the ultimate limit state ULS. The first one refereed to as ‘Pseudo-static Stability Analysis Model’ involves the safety margin of the slope against ovearall soil mass failure. The second one referred to as ‘Permanent displacement assessment model’ emphasizes the safety margin against a maximal prescribed permanent displacement. Both modes of failure make use of the same rotational log-spiral failure mechanism. The Hasofer-Lind reliability index is used for the evaluation of the slope reliability index and the corresponding failure probability for both modes of failure. The random variables considered in the analysis are the soil shear strength parameters c and ϕ . It was shown that the pseudo-static stability approach is more conservative than the permanent displacement approach. For the same seismic loading, different level of reliability may exist depending on the soil variability. A reliability-based design procedure is carried out for the calculation of the height of a slope situated in seismic area to achieve a target reliability index. At the end of the paper, a case study of typical Lebanese slope illustrates this approach.

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