Probabilistic Seismic Displacement Hazard Assessment of Earth Slopes Incorporating Spatially Random Soil Parameters

Abstract

Permanent sliding displacement is a parameter that is used widely to evaluate the seismic performance of earthen slopes, and the inherent variability of soil strength parameters is considered simply using a logic tree in current practice. This study thus proposes a fully probabilistic framework to assess the seismic displacement hazard of earthen slopes by quantifying the inherent spatial variability of soil strength parameters. The framework incorporates the random field theory and a multiple quadratic response surface (MQRS) model into the fully probabilistic seismic sliding displacement hazard analysis. Random field theory was employed to characterize the spatial variability of soil parameters, and the MQRS model is proposed to estimate the yield acceleration (ky) of slopes in an efficient way. The performance of the proposed framework was demonstrated by slope examples. The results indicated that (1) the predicted ky values of the MQRS model are comparable with those computed by the traditional pseudostatic procedure, validating its accuracy in applications; (2) slope strength parameters exhibiting a weaker spatial variability (larger scale of fluctuation) yield a larger dispersion of ky and a larger displacement hazard; and (3) a larger displacement hazard is produced for soil parameters exhibiting weaker correlation between cohesion and friction angle. The proposed framework enables assessment of the probabilistic seismic displacement hazard of earthen slopes with proper consideration of the spatial variability of soil parameters.