Erosion monitoring during core overtopping using a laboratory model with digital image correlation and X-ray microcomputed tomography

Core overtopping in embankment dams is an important phenomenon that may lead to contact erosion along the core–filter interface. This paper presents new experimental results regarding erosion mechanisms at the core–filter interface during core overtopping. The experimental results were obtained using a reduced-scale model with a variable upstream water level. Digital image correlation (DIC), microcomputed tomography (μCT), and sediment collection at the outlet were used to quantify erosion. Four experimental runs were conducted with a till core and different filters. Only one of the four filters satisfied the filter criteria that were applied. No contact erosion occurred during this test. For filters that did not respect the filter criteria, piping occurred within the core along the downstream slope when the water level reached the top of the core. As a result of the self-healing process within the core material, the erosion rate decayed with time as the hydraulic gradient increased. Results for DIC mainly reflected settlements within the filter due to erosion and a soil arching effect. The magnitude of the displacement vector obtained with DIC is directly proportional to the volume of till eroded. μCT showed that contact erosion occurred continuously.