Étude expérimentale des mécanismes d'érosion durant le franchissement de noyau dans les barrages en remblai

Abstract

Core overtopping in embankment dams is an important issue that may lead to contact erosion along the core/filter interface. This erosion can cause instabilities or reduce filter effectiveness within the dam. This project presents new experimental data regarding erosion mechanisms at the core/filter interface during core overtopping. The effects of particle size distribution of the filter and cyclic variation of upstream water level on erosion progression are studied. The experimental results were obtained with a reduced-scale model. Digital image correlation (DIC), microcomputed tomography (µCT) and sediment collection at the outlet were used to quantify the erosion. Four experimental runs were conducted with a till core and different filters. Three of the four filters did not fulfill the appropriate filter criteria. The fourth filter was representative of real Northern Quebec dam configurations. No contact erosion occurred during the test for the more realistic till-filter combination. The filters that did not respect the criteria did not protect the core adequately. Piping appeared along the downstream slope within the core when the water level reached its crest. A selfhealing process within the core material was observed and is responsible of the decay of the erosion rate with time as the hydraulic gradient increased. Erosion decayed with time as the upstream water level was varied cyclically. DIC and µCT results showed that contact erosion occurred continuously, but it appeared less significant than piping. Deformation rates obtained with DIC are directly dependent on measured erosion rates. Comparing experimental results with COMSOL simulations allowed sources of errors to be identified. The results for this project can be relevant to detect and monitor contact erosion in real embankment dams more adequately. The author suggests putting more emphasis on downstream slope stability of the core material during core overtopping for upcoming research projects. The effect of unsaturated conditions on erosion mechanisms is also a promising area of study.

Date	3 Feb 2017
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	François Duhaime (Supervisor) & Yannic A. Éthier (Co-supervisor)