Author(s): Masoumeh Ebrahimi; Nathan Delpierre; Catherine Swartenbroekx; Didier Bousmar; Sandra Soares-Frazao

Linked Author(s): Masoumeh Ebrahimi

Keywords: Earthen embankments; Breach outflow; Levee overflowing; Experimental modelling

Abstract: A series of medium-scale dike breaching experiments were conducted to study the breach evolution of homogenous sand dikes subject to overtopping. The testing platform consists of a basin area of 190 m2, enabling the testing of frontal dikes up to 1 m high. A uniform sand soil, with median grain diameter of 0.31 mm was used to construct the dikes. To reproduce frontal breaching processes in laboratory experiments, the reservoir should ideally be sufficiently large or supplied with a variable inflow discharge to maintain a constant water level. In the present experiments, two different inflow conditions were investigated: (i) a variable inflow discharge aiming at maintaining a constant water level in the reservoir, and (ii) a constant inflow discharge. It was observed that the inflow conditions impact the breach outflow discharge significantly, but the breaching process and the final breach shape were found to be much less impacted. Close-range photogrammetry was employed to monitor and capture the morphological evolution of the breached dike. While photogrammetry effectively captured the exposed dike topography, including the breach channel and, under specific conditions, the water surface, it could not accurately detect submerged portions of the dike. Factors such as water turbidity and light refraction pose challenges to estimating the underwater geometry, making it difficult or even impossible to measure it. Therefore, small plastic balls embedded in the dike were used as breach bottom-level indicators to further monitor the erosion process. Reproducibility of experiments was confirmed through sufficient replications of each test case. The experiments provided valuable insights into breach formation and development in sand dikes at a scale closer to the reality than usual small-scale experiments, confirming the influence of major physical processes such as surface erosion and mass blocks failure during different phases.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1865-cd

Year: 2025