Grant: Collaborative Research and Development Grants

Core overtopping occurs when the water level rises over the impermeable core, into the filter of zonedembankment dams. It can lead to internal erosion at the interface between core and filter, and eventually to damfailure. Core overtopping can be avoided by maintaining a low water level in the upstream reservoir. However,low reservoir levels can have economic consequences for dam owners. Experimental data on the progression ofcontact erosion during core overtopping for complex dam geometries, transient flow and widely graded corematerials are scarce. As a consequence, it is important for dam owners to get a better understanding of the realimpact of core overtopping. The main objectives of this project are to gather experimental data on coreovertopping for realistic geometries, materials and flow conditions, and to develop a numerical model for thisphenomenon. In the first phase of the project, core overtopping will be replicated experimentally with alaboratory model for different core and filter grain size distributions. The tested materials will be chosen so thatsome combinations fail to respect the accepted design criteria for stability against erosion. Combinationsrepresentative of Canadian embankment dams with a widely graded core will be tested. In the second phase ofthe project, a numerical model will be programmed to replicate the experimental results. The continuummodels that are widely used in practice perform poorly when modelling phenomena that are dependent onmicroscale behaviour, such as internal erosion. The numerical model will be based on a novel multiscaleapproach. It will combine particle scale modelling with the discrete element method, where the displacement ofindividual particles is modelled (software YADE), and large scale modelling with the finite element method,where the soil is modelled as a continuum (software COMSOL). There are currently more than 10,000 dams inCanada. A practical multiscale model and experimental data on erosion threshold and rate of erosion forrealistic geometries and materials will allow appropriate actions to be taken in case of core overtopping. It willalso help design new structures.