Distribution des sédiments cohésifs en relation avec la vitesse de la phase solide dans l’estuaire de la Loire

Abstract

b) U.M.R. 6143, Esplanade de la paix, 14032 Caen. RésuméCette note concerne une approche globale de la vitesse de la phase solide des sédiments cohésifs de l'estuaire de la Loire couvrant la très large gamme de concentrations observée in situ. La vitesse de chute W des matières en suspension est étudiée comme une variable stochastique, il est constaté qu'elle suit une loi de probabilité en accord avec la loi gamma. La vitesse de tassement V de la crème de vase est caractérisée par un scalaire puisque les sédiments à l'intérieur d'une couche de crème de vase descendent sans vitesse différentielle. Enfin, il est montré que la vitesse de chute entravée caractérise une transition entre la vitesse de chute des matières à l'état dispersé et la vitesse de tassement correspondant aux suspensions très concentrées. AbstractThis paper presents a global approach of the distribution of the cohesive sediments in the estuary of the river Loire in terms of the velocity of the solid phase. The study covers the large range of concentrations observed in situ. It deals with the settling velocity of suspended matter, the hindered settling velocity of intermediate concentration suspensions and the settlement velocity of fluid mud. The settling velocity W is studied as a stochastic variable and it is observed that it is gamma distributed. The settlement velocity V is scalar as the sediments in a layer of fluid mud fall with no differential velocity. Finally, the hindered settling velocity is a transition between W and V.

Coupled 3d Modeling of Turbidity Maximum Dynamics in the Loire Estuary, France

“…The transfer between the bottom layer of the water column and the top layer of the bed is carried out when the suspended sediment concentration exceeds 40 g/l. The parameter 'a' was calibrated with laboratory measurements performed by Sanchez et al (2004). A validation of the model was carried out against settling tube measurements.…”

Evaluation of an Offshore Disposal Site in the Loire Estuary Through Field Monitoring and 3d Numerical Modeling

“…• New law of erosion (M. Sanchez and D. Levacher,2008) • New law of consolidation (M. Sanchez et al,2004) • Flocculation effects on fall velocity • Sliding effect • Development of a multilayer mixing length for a better calculation of stratification effect (R. Walther et al,2009) • Morphodynamic coupling of bottom roughness and fluid mud (L. Hamm and R. Walther,2008) The model proved to be able to reproduce a full annual cycle of the dynamics of the maximum turbidity in the Loire estuary without any assumption regarding the bathymetric state of the estuary (R. Walther et al ,2012).…”