Etude hydraulique et geotechnique de la formation de breches dans un barrage en terre

To analyze the risk of dam failure it is necessary to understand thoroughly the failure process. The validity the dam failure studies is linked to importance that we grant to the choices of the breach parameters for failure evaluation and consequences. Thus physical and mathematical studies were used to obtain the necessary parameters for the numerical models used to evaluate the formation and the development of breach.;Our research concerns the formation and the development of a breach in an earth-fill dam or an rock-fill dam at the time of a overtopping flood. Among our objectives, the principal one was to develop a realistic numerical model for the anticipation of breach. It is known since several decades that the reliability of the breach flood prediction of the valley depends on the reliability of the failure hydrograph made before construction.;This model will be therefore be based on hydraulic, geometric and geotechnical considerations and will simulate the gradual erosion of the breach without having to specify its development, form and width. The model is based on the physical process of development of the breach by the coupling of the hydraulic flow over a dam and the erosion mechanism of expansion of the breach canal. The opening of the breach and the erosion of the canal are functions of the transport of sediments and characteristics geotechnical of the materials of the dam. What interests is the surface erosion at the crest of the dam or to the slope and which propagates itself by surface erosion. To arrive to the fixed objective it was necessary: (1) To review the existing methods and models. Five of the inventoried methods were kept and analyzed each in its study context, then grouped together in a predictive computer program (BRECHE) that was applied to a rupture case observed in the Saguenay area in July 1996. (2) To better understand the complex process the breach formation, an experimental study of rupture by overtopping in laboratory was done on a homogenous moraine dam. This showed the breach erosion very different from the mechanisms used in existing models for failure calculation for the dam. (Abstract shortened by UMI.)...