Études des mécanismes d'érosion du roc à l'aval des évacuateurs de crues par des simulations expérimentales à grande échelle

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Hydroelectric dams are generally equipped with spillways excavated in rock. A serious concern is that erosion caused by flowing water reaches the immediate dam foundation. Cases of such erosion, with no serious consequences to date, have been observed at the site of some Hydro-Québec dams. Hydro-Québec is very interested in methods for the prediction of erosion, in order to ensure the sustainability of its works. Some existing methods to determine the state of erosion of these works are based on experience feedback. The application of these methods on several new dam cases in the world have shown significant gap between the observed erosion and the forecasts obtained by these methods. Their empirical nature makes it difficult to identify conditions for which the method does not yield a correct prediction; In particular, it is impossible to study the combined effects of several geomechanical parameters on the erosion.The objective of this project is to develop a new approach to erosion prediction better adapted to rock mass conditions. First of all, it is necessary to identify which geomechanical parameters have the greatest impact on the erosion level and to determine the relative importance of each of the parameters in the erosion process. For this, two instrumented evacuators, the first one at the laboratory scale, the second one, at a field Pilot-Plant scale, will be set up as part of this project. This equipment will make it possible to study experimentally the effects of several geomechanical parameters of the rock mass and the relative importance of each parameter in the erosion process. Experimental test results and the observed erosion database will be used to calibrate numerical models to determine the effects of geomechanical parameters on erosion on a real scale. The final results of these studies will lead to the development of a new model for predicting rock mass erodability at rock spillways.