Effects of bridge pier position in a 180 degree flume bend on scour hole depth

Abstract

Local scouring around the bridge 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. Because of this several researches, have been conducted during the past three decades in straight flumes. For the case when the bridge piers located in river bend, little information is available. In this study, a series of experimental tests have been conducted in a 180 degree laboratory flume bend with a relative curvature of bend of 4.67. One oblong model pier of width 60 mm and length 180 mm was used for the study in seven different positions of 0, 30, 60, 90, 120, 150 and 180 degree under three different flow conditions were tested. Natural sand with uniform graining of d50 = 2 mm and uniformity factor of 1.7 were used as bed materials. The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. The depth of the scour hole increases as with increasing duration of flow. The extent of scour observed at the pier also increases as the duration of the tests increases. The results of this study showed that, while oblong pier is placed in the bend, the maximum scouring depth is occurs in position of 60 degrees. Also, it was observed that in all positions, increasing the Froude number increases the scouring depth. Measuring depth of scouring based on experimental observation, an empirical relation is developed with high regression coefficient 94%. © 2010 Asian Network for Scientific Information.