Numerical Simulation of Dam Breach with XBeach

Abstract

A dam breach is defined as the uncontrolled release of material retained in the impoundment. The resulting flow of water, or mine waste can be catastrophic to the environment, local infrastructure, and human life. Engineered dams and sand dunes are studied by different academic communities. This thesis recognizes that breaching in coastal environments is an analogous problem to overtopping engineered dam failures and proposes that similar tools can be used in both scenarios. The goal of this project is to determine if the XBeach model, traditionally used by the coastal engineering community, is a reliable tool in simulating overtopping dam breach failure by validating breach simulation outcomes against the physical laboratory conditions of Walsh (2019). The first objective of this study was to explore the model parameters necessary for overtopping failure simulation. Results indicate that breach is most accurately simulated when the Soulsby – van Rijn sediment transport formulation is selected and the avalanching module of the model is turned on. Using these conditions, the model could accurately simulate the upstream erosional control and define the outflow hydrograph for four upstream slope angles ranging from 10.0o to 30.0o. After validation, five simulations of dams with beach intersection heights ranging from 0.50 cm to 0.90 cm were conducted to determine whether XBeach can capture the outflow hydrograph and quantify the volume of eroded material with the presence of a tailings-style beach. Through the quantitative comparison of physical and numerical model outcomes, it was concluded that XBeach can reproduce the bulk characteristics of a tailings style dam breach failure. Considering the peak outflow value of the breach hydrograph, XBeach results saw most cases within 25% of the physical laboratory observations. Focusing on a cross-sectional centreline of the physical and numerical studies, it was found that both models produce a similar magnitude of eroded material with the percent difference of eroded material being less than 10% in all test configurations. Overall, this investigation supports a growing case for the use of XBeach in field-scale numerical simulation and to extend the capabilities of the model.