| The objective of this project is to develop a physical model capable of analysing the behaviour of a hybrid dyke, featuring an embankment and a structural core wall, when it is subjected to an overflow. Based on the Multiple Wedge Analysis Method developed by the U.S. Army Corps of Engineers, the model combines both geotechnical and structural elements. The geotechnical element creates slip planes secant to the core wall, while the structural element calculates the bending and shear stresses generated within this component which acts as a cantilever beam. Together, these two elements enable the model to predict the dyke's minimum safety factor.;Simulations employing the physical model and in the laboratory were conducted using the Moncouche dyke's 1995 characteristics as well as it's projected 2002 characteristics featuring an elevated crest. The erosion depth, breach width, nappe thickness, breach discharge and time scale were all adapted and incorporated into the behavioural model. It was thus possible to express the safety factors, structural core wall failure time and breach hydrograph as a function of the ongoing erosion. An analysis of the gain in security achieved by elevating the dyke's crest was also completed.;In spite of it's limitations, the model constitutes a new insight into the comprehension and prediction of the behaviour of hybrid dykes when they are subjected to overflows, priming, highwater or variable exploitation levels. Considering the dyke's characteristics and the corresponding breach hydrograph leads to better suited and safer management techniques.;The model is verified using data obtained during flume tests conducted in the hydraulics laboratory of l'Ecole Polytechnique de Montreal, where a model of the Moncouche dyke was built. A unit section of this hybrid structure, situated on Lake Kenogami in the Province of Quebec, was constructed in such a way as to permit an overflow and the progressive erosion of its leeward side. The dyke's core was reproduced using an aluminum plate installed at the structure's center. Strain gauges measured it's deformation. Linking the stresses acting on the plate with the observed strain using Hooke's Law, made it possible to compare the model predictions with the measurements obtained. It is concluded that the behavioural model adequately predicted the results observed during the flume tests and could furthermore be used for in situ forecasting. |
