Author(s)

N.-E. Boudjenane, M. Mekkaoui, M. Belhadri, L. Abdelkrim & A. Magnin

Abstract

Silting of dams is an important economic concern in Algeria. This phenomenon considerably reduces the capacity of water reserves. The control of hydraulics and unsilting techniques, as well as the valorization of collected silts, pass by the rheometric comprehension of their behavior and the relationships to their physicochemical characteristics. For this purpose, five samples taken at selected places at the reserve of the Fodda Wadi dam will be studied. A granulometric study shows that we are in the presence of a mud whose particle size varies between 0,1 and 40µm and whose argillaceous fraction is about 50%. A study of the potential zeta of the silts shows a stability zone for pH between 6 and 10. Flow yield stress, which is a very important characteristic in unsilting of dams was studied. The effects of volumetric concentration, of pH and rest period on the flow yield stress, were studied. The yield stress increases considerably with the volumetric fraction. Scale laws according to concentration and sampling places are identified. A correlation is established between the evolution of the yield stress of flow and the evolution of the pH. Flow properties of the silts were studied on a wide range of shearing speed. An important preliminary work to control the disturbing effects (sedimentation, fracturing, etc) of rheometric characterization was carried out. Several geometries of measurements and visualizations of deformation fields were implemented. The influence of the concentration of the dry matter is presented. Keywords: silt, dam, rheometry, granulometry, yield stress.

Keywords

silt, dam, rheometry, granulometry, yield stress.