Seepage analysis of earth dams considering spatial variability of hydraulic parameters

To investigate the influence of spatial variability of hydraulic parameters on the flow in earth dams, saturated-unsaturated seepage is numerically simulated combining Monte Carlo simulation and random field theory. The van Genuchten model is adopted to represent soil-water characteristic curve (SWCC). The SWCC fitting parameters (a, n) and the saturated hydraulic conductivity parameter (ks) are considered as lognormal random fields. An approach of logarithmic translation is used for generating lognormal variables with lower limits greater than zero. The influence of the coefficient of variation (COV) and autocorrelation distance of hydraulic parameters on the flow rate is studied and compared. Sensitivity analysis indicates that the COVs of SWCC parameter n and saturated hydraulic conductivity ks have a larger effect on the flow rate than that of SWCC parameter a. A larger horizontal autocorrelation distance corresponds to a larger mean and COV of the flow rate. Neglecting the spatial variability of hydraulic parameters leads to overestimation of the mean and COV of the flow rate in earth dams, which could lead to conservative design of dams.