Author(s): R. Gaudio; G. Dodaro; A. Marion
Linked Author(s): Roberto Gaudio
Keywords: No Keywords
Abstract: Laboratory tests were performed on scouring of a mixtures of cohesive and incoherent sediments downstream of a fixed bed. A 9. 66m-long, 48. 5cm-wide rectangular tilting flume was used, with a PVC bottom and a glass side-wall. The bed was artificially roughened by gluing a uniform sand with median diameter d50=1 mm. The mobile bed was made up in a50cm-long recess box, in which a mixtures of cohesive and incoherent sediments was placed (87% sand, 11. 5% silt and1. 5% clay), with d50, m=0. 35 mm. Instruments consisted of an electrically-driven point gauge for the measure of water depth and bed elevation, a Thomson weir for the measure of discharge and a 3-D Laser Scanner for the measure of the eroded bed surface. Two test series were carried out: series A, with longitudinal bottom slope S0=0. 5‰, and series B, with S0=5‰. In each series, liquid discharge varied from test to test. In each test, the eroded bed surface was measured at different time instants. Eroded bed surfaces, cross-sections and profiles were obtained over time, and both average and maximum scour depths were analysed. Results were interpreted in dimensionless form, showing that the ratio of the maximum scour depth over the water depth can be expressed through an empirical power law; discharge and slope increase the scour extent; the difference with respect to a classical predictive formula for incoherent sediments (Breusers, 1966, 1967) increases up to 70% in long-term conditions.
Year: 2010