Simplified slope reliability analysis considering spatial soil variability

Due to inherent spatial variability, soil properties vary from one location to another even within one soil layer. Such spatial variability of soils gives rise to scale-dependency in slope safety evaluation. This paper presents a simplified reliability method for slopes considering spatial soil variability. In this method, equivalent homogeneous random soil parameters are used in a single random variable (SRV) method (e.g., the first-order reliability method) to evaluate the slope reliability. Spatial variability is considered by using the equivalent parameters such that a SRV method with these equivalent parameters produces a comparable failure probability as that calculated using a more rigorous random finite element/difference method (RFEM/RFDM) with the original spatially variable parameters. Empirical equations for determining the statistics (mean value and standard deviation) of the equivalent parameters are derived through extensive RFDM analyses. The proposed method is found to be valid for both single-layered and two-layered slopes.