Effects of spatial variability of soil properties and ground motion characteristics on permanent displacements of slopes

The seismic performance of earth slopes is a problem of great importance in geotechnical earthquake engineering associated with various sources of uncertainty. This research investigates the effects of two important causes of such uncertainty: (a) the spatial variability of soil properties and (b) the variability of the temporal and frequency characteristics of the earthquake excitation. The former is investigated based on a series of detailed dynamic numerical simulations using stationary random fields of both cross-correlated and spatially autocorrelated soil properties. The latter is explored by conducting incremental dynamic analysis at various levels of excitation intensity using (a) a total of forty historic earthquake and synthetic records, modified to match the Eurocode 8 design spectra for rock sites, and (b) thirty original historic earthquake records. The results demonstrate the significant effect of the spatial variability of soil properties on the permanent slope displacements. Moreover, they show that the effect of the uncertainty associated with the variability in the temporal and frequency characteristics of excitations is more important compared to the effect of the spatial variability of soil properties. • The spatial variability of soil properties affects the size and location of the failure surface. • The effect of spatial variability of properties on the permanent displacements of a slope is significant. • The effect of the temporal and frequency characteristics of the excitation is more significant than that of spatial variability. • The use of original records results to higher permanent displacements than those obtained from records modified to match Eurocode design spectra. • Slope performance may be evaluated using the mean value plus one standard deviation of permanent displacements from a minimum of 7 excitations.