EXTREME HYDRAULIC-GRADIENT STATISTICS IN STOCHASTIC EARTH DAM

The existence of large hydraulic gradients in regions of an earth dam where fine-grained soils are inadequately filtered can sometimes lead to internal erosion and piping failure. This paper investigates the st ochastic nature of hydraulic gradients through two different earth dam cross sections, both with simple drains. In particular the magnitude and location of maximum hydraulic gradients are studied via Monte Carl o simulation to derive their probability distributions and assess thei r variability. These results can be used to guide designers with respe ct to minimizing the risk of internal erosion in the presence of uncer tain soil permeability. The effect that the stochastic nature of the p ermeability field has on the hydraulic gradient distribution is compar ed to hydraulic gradients obtained in the deterministic case. This ena bles an evaluation of the importance of considering permeability rando mness in the design process.