Analysis of Global Backward Erosion in Embankment Dams: Case Study the Val d'Orléans dam, France.

Abstract

Global backward erosion is a progressive type of internal erosion when soil particles are eroded and transported downstream, forming cavities within the subsurface that can retrogressively move in the upstream direction. This process has the potential to undermine the structural stability of embankment dams through settlement, deformation, and potential collapse. Although several studies have examined internal erosion and cavity formation in embankment dams, most of these works primarily focused on local erosion mechanisms or simplified cavity geometries without investigating the combined effects of cavity position, diameter, and depth on the overall deformation behavior of the dam. Both experimental testing for verification of the numerical model using a permeability tank and numerical modeling with ABAQUS are integrated into this study. In this research an extensive finite element analysis to evaluate the influence of different cavity geometries (location upstream and downstream, diameter, and depth) on the deformation response of embankment dams was conducted. This approach provides new insights into the mechanisms controlling backward erosion for assessing dam behavior and safety. The numerical results show that the downstream transition zone (  = 0.7:0.9) is the most critical cavity location. Settlement along the downstream side exceeded that near the crest by 60–85%, whereas it decreased by more than 90% toward the upstream boundary. Increasing the cavity diameter from  = 5:60%) increased the maximum settlement by approximately 170%, while increasing the cavity height reduced settlement, leading to improved dam stability. Design charts and empirical equations were also developed for practical engineering applications.