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Index of Figures
Index of Figures
1. Introduction 1
Fig.1.1: Hydraulic scale model of the Reuss River, Gurtnellen, Switzerland [Kuster et al., 1992] 2
2. State of the art 5
Fig.2.1: Flow structure around a bridge abutment 13
3. Theoretical considerations 21
Fig.3.1: Layers in a coarse gravel bed river submitted to armoring 22
Fig.3.2: Approximation of a sediment grain by an ellipsoid 23
Fig.3.3: Time averaged boundary shear and velocity distribution in an idealized channel for uniform
flow and 28
Fig.3.4: Definition of the boundary shear stress as a gravity component 30
Fig.3.5: Shields diagram [Günther, 1971, Fig. 6] 36
Fig.3.6: Definition sketch; situation and cross-section 40
Fig.3.7: Location of scour holes by means of the shock pulse surface theory [Williams 1899, Fig.
4 and 5] 41
Fig.3.8: Forces acting on a grain on an inclined plane 42
Fig.3.9: Comparison of with laboratory and field data 46
Fig.3.10: Velocity distribution at the location of the average flow depth 48
Fig.3.11: Velocity components of the flow and of the grain 49
Fig.3.12: Comparison of computed maximum scour depth with experimental data 60
Fig.3.13: Comparison of corrected computed maximum scour depth with experimental data 62
Fig.3.14: Comparison of different formulae with the measured bed topography (upstream, downstream)
65
4. Experimental setup and test procedure 67
Fig.4.1: Schematic view of the testing facility with definition of locations 68
Fig.4.2: Sediment inlet (left) and sediment sampling at the outlet (center and right) 69
Fig.4.3: Testing facility during construction 69
Fig.4.4: Operational experimental set-up 70
Fig.4.5: Different types of sediment supplies 71
Fig.4.6: Scheme of the used sediment supply 72
Fig.4.7: Sediment supply machine (explanations see Fig. 4.6) 73
Fig.4.8: Inlet box with perforated cylinder and assembly of small pipes 74
Fig.4.9: Outlet box with tilting gate and sediment sampling device 75
Fig.4.10: Pictures of the sediment filtering basket 76
Fig.4.11: Scheme of the macro-roughness elements and picture of the flow around ribs 78
Fig.4.12: Macro-roughness on the protection wall, Reuss River in Gurtnellen (Switzerland) 78
Fig.4.13: Scheme of the experimental setup with circulations 79
Fig.4.14: Computed backwater curve in the outlet reach - difference between computed water level
and normal water depth 81
Fig.4.15: Grain size distributions of some mountain rivers and of the used sediment mixture 82
Fig.4.16: Scheme of the data acquisition 83
Fig.4.17: Picture of the data acquisition system and the used probes 84
Fig.4.18: Data flux between the central command unit and the data acquisition programs 85
EPFL Ph.D thesis 2632 - Daniel S. Hersberger November 9, 2002 / page 219