Influence of the Unsaturated Flow Domain on Seepage Through Earth Dams

Publisher Website
Google Scholar
Abstract
This paper presents an integrated analysis of flow through earth dams in which the entire porous domain is considered. The mathematical model provides a finite difference solution to two‐ or three‐dimensional problems involving transient or steady state flow in the saturated and unsaturated domains of nonhomogeneous, anisotropic dam sections. In general, the water table is not a streamline; in many zoned cross sections, a significant proportion of the stream tubes may take unsaturated flow routes for some part of their traverse. In addition, the position of the water table may be quite different from that determined from the classic saturated‐only analysis. Unsaturated flow components take on greater importance in small dams rather than in large, in dams with sloping cores and downstream filter blankets rather than more homogeneous sections, and in the fine‐grained, well‐graded soils common to internal cores rather than in the more permeable and more uniform soils of the external sections. A simulation of the transient initial advance problem shows that the rate of growth of the saturated zone is highly dependent on the unsaturated properties of the soils and on the initial moisture contents. In the early stages of seepage following a rapid rise in the upstream reservoir level, inflow rates into the dam may be as much as 100 times the steady state seepage rate. Consideration of the unsaturated zone in the analysis of seepage through earth dams involves added mathematical complexity and requires data on unsaturated soil properties that are not commonly available.

This publication has 14 references indexed in Scilit: