American Society of Civil Engineers

Probabilistic Slope Stability Analysis with Stochastic Soil Hydraulic Conductivity

by Shengxiang Gui, (Dept. of Renewable Resour., Univ. of Wyoming, Laramie, WY 82071-3354), Renduo Zhang, (Dept. of Renewable Resour., Univ. of Wyoming, Laramie, WY), John P. Turner, (Dept. of Civ. and Arch. Engrg., Univ. of Wyoming, Laramie, WY), and Xuzhang Xue, (Dept. of Civ. and Arch. Engrg., Univ. of Wyoming, Laramie, WY)

Journal of Geotechnical and Geoenvironmental Engineering, Vol. 126, No. 1, January 2000, pp. 1-9, (doi:

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Document type: Journal Paper
Discussion: by Robert D’Andrea    (See full record)
Discussion: by Zouhair Mrabet    (See full record)
Closure:(See full record)
Abstract: The effects of stochastic hydraulic conductivity on the slope stability of an embankment dam are investigated using a combination of random field simulation, seepage analysis, and slope stability analysis. The hydraulic conductivity distribution is treated as a spatially stationary random field following a lognormal distribution. The turning band method is used to generate the spatial variability of the saturated hydraulic conductivity K\ds in the domain. Different standard deviations of log hydraulic conductivity σlnKsare investigated. For each value of σlnKs various realizations of hydraulic conductivity were generated and combined with a numerical model to simulate water flow in an earth dam with variable Ks The first-order second-moment reliability index β was employed to characterize the influence of the variability of Ks and hence, pore-water pressures, on the stability of the downstream slope. A linear relationship between σlnKs and the standard deviation of the factor of safety σ\dF was obtained from the simulation results. A relationship between β and σlnKs in which every 0.1 increment of σlnKsresults in a decrease of 1.0 in β, is deduced based on the simulation results. Results of a Shapiro-Wilk test for goodness-of-fit indicate that the factor of safety can be assumed to be normally or lognormally distributed when the saturated hydraulic conductivity follows a lognormal distribution and σlnKsis small (< or = 0.5). When σlnKsis large (>0.5), neither normal nor lognormal distributions provide a reasonable approximation of the factor of safety. Simulation results show that nether standard deviation nor coefficient of variation of the factor of safety is constant when only the variability of hydraulic conductivity is considered. While the results presented are directly applicable only to the particular earth dam geometry and boundary conditions studied, the methodology is general and may be extended to embankments with different boundary conditions.

ASCE Subject Headings:
Embankment dams
Hydraulic conductivity
Pore water
Slope stability
Water pressure