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Communication Dans Un Congrès Année : 2015

Laboratory experiments on silt infiltration into a gravel bed

Expériences de laboratoire d'infiltration de sédiments fins dans un lit de graviers

A. Herrero
Céline Berni
B. Camenen

Résumé

River habitats are among the most important environmental issues at stake in recent years. Indeed, they have a strong impact on biodiversity. The numerous structures that are built in rivers such as dams, hydroelectric plants, dikes, etc. have dramatically changed the sediment dynamics in some rivers. This fact sometimes causes the clogging of the river bed, i.e. the infiltration of very fine sediments within the coarser matrix forming the bed. It is essential to understand the dynamic of fine sediments above and within the bed to quantify how clogging develops. We propose to analyze fine sediment fate in infiltration experiments in the tilting flume of the Hydraulics and Hydromorphology Laboratory (HHLab) of Irstea Lyon-Villeurbanne. This flume is 1 m-wide and 18 m-long, with transparent side-walls. Fine sediment (median diameter of 15 and 66 microns) laden-flows with different discharges recirculate over a gravel bed. Bed shear stress is lower than the critical shear stress for gravels incipient motion. Measurements of velocity and turbidity are handled with an ADV (Acoustic Doppler Velocimeter) and turbidimeters. Water samples relate turbidity to fine sediment concentration in suspension. Fine sediment content within the bed is estimated both analyzing lateral pictures and bed sampling. Fine sediments progressively infiltrate within the bed at a rate which seems mainly to depend on concentration and sediment properties (fall velocity). The evolution of fine sediment concentration along the flume reveals that fine sediment infiltrates all along the flume and that for high sediment concentration, the suspended concentration decreases significantly along the flume which needs to be taken into account to compute fine sediment infiltration rate.

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Dates et versions

hal-02603635 , version 1 (16-05-2020)

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A. Herrero, Céline Berni, B. Camenen. Laboratory experiments on silt infiltration into a gravel bed. 13th International Conference on Cohesive Sediment Transport Processes, Sep 2015, Leuven, Belgium. pp.2. ⟨hal-02603635⟩

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