Abstract
An embankment structure such as an earth dam or a river bank should be designed to ensure its stability under various reservoir or river stages. The stability of an earth slope subjected to the effects of changing external water levels depends on, among other factors, stresses induced within the earth mass due to transient seepage. By using the finite element procedure which combines a saturated-unsaturated seepage analysis, a stress-deformation analysis including a sequential construction analysis and a slope stability analysis, the interaction between transient seepage, effective stress and the stability of earth dams or river banks subjected to storms accompanied by changing external water levels in the reservoir or the river is investigated.
Two main findings are identified in this study:(1) The instability of an embankment structure such as an earth dam or a river bank can be explained fairly well through the stress changes which are induced by transient seepage; and (2) two counterblows which deteriorate earth slopes should be recognized in evaluating the stability of embankment structures subjected to storms, one of which attacks the downstream slope of the embankment structure as the external water level begins to rise after rainfall and the other attacks the upstream slope during the drawdown of the external water level. It will be shown that the numerical procedure developed can offer a tool for analyzing, designing and understanding the behavior of embankment structures subjected to transient seepage conditions. Although the study is only concerned with a hypothetical and simple hydrograph of a storm and an homogeneous cross-section of the earth structure, it is possible to apply the procedure to more complicated problems involving two or more storms or a zoned cross-section of an embankment dam.
