Advanced numerical simulation of collapsible earth dams

Abstract

This paper presents a methodology for advanced numerical analysis of earth dams, considering all design stages. It also includes transient analysis of safety factors and can be applied to general three-dimensional conditions, considering unsaturated materials and the interrelation between hydraulic and mechanical phenomena by simultaneously solving equilibrium and continuity conditions. The methodology has been successfully implemented in a finite element program and applied to the analysis of earth dams with sections composed of soils at optimum, dry of optimum, and mixed compaction conditions. The dry section is intended to simulate the so-called “Alka-Seltzer” dams, constructed with poorly compacted and dry material, thus resulting in a meta-stable and collapsible structure. The results show that it is possible to design a less expensive mixed section with approximately the same behavior and in some cases even better performance when compared with the homogeneous section at optimum conditions. This is achieved by strategically placing the optimum materials in the most stressed zones of the earth fill. The safety factor analyses show the importance of considering coupled effects in collapsible dams. In such cases, failure can be simulated in the upstream slope during the first reservoir impounding, as has been observed in some actual cases.