Armouring and Its Effects on Local Scour around a Bridge Pier in Non-uniform Sediments
International Journal of Engineering and Technology
Bridges constitute an important part in the infrastructural development of any nation by connecting the regions and parts separated by water bodies and by providing access to inaccessible areas. Scour around bridge elements is one of the major causes of bridge failures and approximately 60 % of the bridge failures take place due to scour and other hydraulic related issues. Researchers have devoted significant time and attention towards this issue, but the research work is mainly concentrated
... nly concentrated towards uniform sized sediments. However, in nature no stream exists with truly uniform sized sediments. Therefore it is essential to carry out research work in non-uniform sediments. The main feature associated with non-uniform sediments is the formation of an armour coat which differentiates the non-uniform sediments from the uniform sized sediments. The armour coat by its presence prevents the scour up to certain velocity but once the armour layer is dislodged, the scour depth starts increasing again and becomes nearly equal to that of scour in uniformly sized sediments. As evident from the open literature, the correlation between the velocity of flow and stability of armour layer is yet to be established. Thus, an experimental investigation has been planned and experiments are being carried out in uniform flow, unsteady flow in discrete steps and some non-uniformity in the flow in the form of hydrographic run. The sediments used in the study were collected from River Yamuna and nonuniformity was generated by artificially mixing of sediments in different proportions. The results of the experimental investigation are being presented in this paper. Index Terms-Armour layer, hydrographic run, nonuniform sediment, unsteady flow.