Selective transport and armouring of non-uniform alluvial sediments (1980)
Type of ContentTheses / Dissertations
Thesis DisciplineElectrical Engineering
Degree NameDoctor of Philosophy
PublisherUniversity of Canterbury
The armouring process resulting from the selective transport of non-uniform sediments is experimentally examined. Aspects include the change, with time, of the bed-surface composition, the eroded material composition and the sediment transport rate, for a particular starting mixture, and the influence on the final bed composition of changing the starting mixture or the applied flow.
As a necessary preliminary, the non-equivalence of surface and volume samples is examined. Experimental practicalities require different sampling methods for the beginning and end of each run. This has contributed to the conflicting results of earlier research into armouring. A conversion is developed to enable the comparison of the initial volume-by-volume sample type with the final area-by-volume sample type.
The selective sediment transport process is examined by assuming the source of the eroded material is known at two times - the beginning of each experimental run, when the original bed material is the source, and the end of each run, when the armour layer is the source. The resulting range of data is used to develop a correction to allow for the effect that varying exposure has on the transport of the different sizes in the mixture.
Two armour layer prediction approaches are explored. The experimental results indicate that the reliance, of some previous work, on two parameter composition descriptions, is not adequate when used with a regression analysis type of approach. To use the results of this and other studies, an alternative form of regression analysis is described in the first approach, using a more detailed description of the original and armoured beds.
The second approach is a numerical parallel degradation scheme, based on the concept of an active layer subjected to the erosion forces of the flow, the influence of the flow on each size being modified by the exposure correction.
KeywordsBed load; Sediment transport
RightsAll Right Reserved
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