A simplified approach for modeling spatial variability of undrained shear strength in out-plane failure mode of earth embankment

•A simplified study of soil slope stability incorporating spatial variation is presented.•The out-of-plane failure mode (in 3-D) of an earth embankment is investigated by probabilistic analysis.•A comparison between spatial-averaging and spatial-autocorrelation approaches is illustrated.

This paper presents a probabilistic study of the out-plane failure mode of long embankments by first-order reliability method (FORM) and limit equilibrium method (LEM). The uncertainty and longitudinal spatial variability of soils that are deemed the most important factors producing the 3-D failure modes are considered in the probabilistic analysis. The longitudinal (out-plane) spatial variation of undrained shear strength is modeled by both spatial-averaging approach and spatial-autocorrelation approach. Comparisons are made between the two methods. For a long earth embankment, the local 3-D failure with a probabilistic critical width is investigated.