Reliability analysis of backward erosion piping in an embankment dam considering the spatial variability of soil properties.

Abstract

The spatial variability of soil seepage parameters is an essential component of the uncertainty of earth dams. This paper presents a method for backward erosion reliability analysis that considers the spatial variability of seepage parameters in earth dams to assess the distribution of the Factor of Safety (FoS) and the initiation probability (P_f). In this study, the Karhunen-Loeve method is used to generate Random Fields (RFs) of soil hydraulic properties, and Monte Carlo simulations (MCS) are used to generate realisations of these RFs, which are then introduced into the numerical model to assess the spatial variability of the seepage analysis results. The hydraulic gradient distribution is compared with the critical hydraulic gradient to assess the FoS and the P_f due to backward erosion at each point of the dam. This study also presents the effect of water level H, permeability anisotropy coefficient ξ, and RFs parameters (coefficient of variation COV_Ks, correlation length L_h & L_v) on the FoS and P_f of Backward Erosion Piping (BEP). The results illustrate that the initiation probability P_f increases with H, COV_Ks and ξ. The initiation probability P_f is not sensitive to the vertical correlation length, but may decrease with the horizontal correlation length. Furthermore, the study discusses the potential initiation locations of internal erosion and presents results based on criteria using both local and global hydraulic gradients.