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During overtopping, water runs over the downstream wall, which creates staircases that act like a succession of mini waterfalls generating erosion. In some cases, this process is likely to lead to the failure of the structure.
The Jet Erosion Test has been developed in order to represent this overtopping erosion phenomenon on cores. It consists in applying a vertical water jet on the axis of the core and monitoring the depth of the generated hole. The test quantifies the resistance to erosion of the soil..
The JET carried out at geophyConsult is derived from the American standard ASTM D5852. It enables to determine :
- the position of the soil in the Hansion classification of soil erosion rates (which varies from « Very erodible » to « Very resistant ») ;
- the τc parameter, which addresses the hydraulic conditions required to initiate the erosion process ;
- the κd parameter, which, associated with τc in an erosion model (windam, hr-breach…), enables to estime the kinetic of a possible breach.
The test has been carried out all around the world on very different types of soil. It gives first rough estimate of the erodibility whatever the erosion process (overtopping as well as other types of erosion). This is why it can be used to compare various types of possible refilling, or to compare the erodibility of different layers of a given soil.
The test can be made on intact soils, provided they do not contain gravels of size greater than 5 mm, and provided they are delivered in cores of diameter greater than 8 cm and of height greater than 10 cm. It can also be carried out on reworked soils (provided at least 1.5 kg of soil is provided with).
The can be carried out in situ, provided the tested soil does not contain gravels of size greater than 5 mm.
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