SCOUR AROUND BRIDGE PIER IN GRAVEL BED

Abstract

The deteriorating effects that river flow can have on the stability of piers, abutments that support a bridge founded in river is significant. The primary cause of concern in stability of bridges is the lowering of river bed level caused by river flow around bridge members due to scouring. Scouring is defined as the erosion caused by flowing water resulting in removal of sand, earth, or silt from the bottom of the river. The research in the field of scour is very vast but still there is a lagging in some specific areas. Large number of researchers worked on scouring in non cohesive sediments (primarily alluvial sand bed) but scour phenomenon in cohesive sediment and other non-cohesive sediment (gravel bed) still needed attention for active research. In the case of gravel bed, the magnitude of scour depth is changed due to some other factors like change in bed roughness and formation of armor layer. As the flowing water carries out the scouring, the particles which are smaller in size is scoured away and the remaining larger size sediment particles result in forming a protective layer over the flow called the armor layer. Bridge located across streams having gravel bed still don’t have any scienific & rational formula for determining the scour depth.