Observations on Probabilistic Two-Layer Undrained Slope Stability Analysis

In geotechnical engineering a two-layer undrained slope may be encountered in which an embankment or levee rests on a different foundation soil. This paper will use the random finite-element method (RFEM) to conduct probabilistic stability analyses of two-layer undrained slopes in which each layer has different statistical properties. The RFEM results show that, if both layers of the slope consist of spatially variable soil, the critical failure mechanism may go through the lower foundation layer, which would not occur in a deterministic analysis. This is explained by the "seeking out" effect of RFEM, which permits the deeper failure mechanisms to form naturally because of possible lower undrained strengths in the foundation layer. The RFEM results also demonstrate the worst-case phenomenon and show that the worst-case effect becomes less obvious as the mean strength ratio of the two layers increases.

Keywords: RFEM, Two-layer, Undrained strength, Failure mechanism, Worst-case, Probabilistic anaysis.