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Chapter 4 - Experimental setup and test procedure
4.3 Properties of the used sediment mixture
a) Grain size distribution
The bed of the flume was composed of a coarse sediment mixture. The mixture was selected
according to common grain size distributions of alpine rivers (see Fig. 4.15) with the following
characteristics:
d min d max d mean d 10
d 35
d 50
d 75
d 90
[mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm]
2 32 8.5 3.2 4.4 5.3 9.1 14.8
Table 4.2:
Characteristics of the used sediments
The part of fine sediments was left out for practical reasons (to reduce suspended load in the
general water circuit of the laboratory and to keep the water transparent) and due to the fact that
the fine parts are not significant for the bed load transport in the case of a wide grain size distribution
in gravel bed rivers.
100%
80%
Donau
Traun
60%
Inn
Mean curve
Gait
Ill
40%
Hasli-Aare
Rhein
Aare Rupperswil
20%
Mean curve
Used mixture
Used mixture
0%
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
di/dm [-]
Figure 4.15: Grain size distributions of some mountain rivers and of the used sediment mixture
b) Other parameters
Other parameters related to the sediment mixture like the density of the sediments, the porosity
and the friction angle can be found in § 3.1.1.
page 82 / November 9, 2002
Wall roughness effects on flow and scouring