1887

oa Civil Engineer in South Africa - Absolute roughness of concrete-lined channels

 

Abstract

Observations on absolute roughness and Manning values have been done in concrete-lined canals at four major schemes (Gamtoos, Hartbeespoort, Lower Orange River and Vaalharts) of the Department of Water Affairs, Forestry and Environmental Conservation.


Manning values which are still being used extensively by the Directorate of Water Affairs for open channel flow calculations were first obtained by means of flow measurement and then determined independently by linear roughness measurements of the canal surfaces during off-periods. The correlation between these two methods was found to be very satisfactory, 92 per cent of the observations yielding similar results.
During the investigations a number of important advantages of the method using roughness measurements to determine friction coefficients such as Manning values have been observed on site.

Waarnemings tov die ruheidsmaat - en Manning -waardes van betonkanale is op vier groot skemas van die Departement van Waterwese, Bosbou en 0mgewingsbewaring uitgevoer, nl by Gamtoos, Hartbeespoort, Benede Oranjerivier en Vaalharts.


Manning -waardes wat tans nog vry algemeen deur die Direktoraat van Waterwese vir oop-kanaal stromingsberekeninge aangewend word is eers dmv vloeimetings bepaal en is daarna onafhanklik met behulp van liniêre metings van die kanaalwandruhede tydens droë periodes vasgestel. Die korrelasie tussen hierdie twee metodes was besonder bevredigend; 92 persent van die waarnemings het identiese resultate opgelewer.
Tydens die proefnemings het 'n aantal belangrike voordele van die metode om wrywingskoëffisiënte soos Manning -waardes mbv liniêre ruheidsmetings te bepaal aan die lig gekom.

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/content/civeng1/23/7/EJC24852
1981-07-01
2016-12-06
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