Reduction of local scour at a bridge pier fitted with a collar in a 180 degree flume bend (Case study: oblong pier)

Local scouring around the bridges pier occurs because of flow separation and developing several vortexes around the bridge pier. Such scour hole can cause failure of the bridge especially during the river floods. In this study, the use of oblong collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. The study was conducted using in a 180 degree laboratory flume bend. Tests were conducted using one oblong pier in positions of 60degree under one flow conditions. In this study, the time development of the local scour around the oblong pier fitted with and without collar plates was studied. The effects of various sizes of collars fitted on the temporal development of scour depth at the oblong pier were also studied. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. It was observed that, as the size of a collar plate increases, the scour decreases. So minimum depth of scour is dependent on the 3D collar.