Effects of Bridge Pier Location and Debris Accumulation on Equilibrium Morphology

Scour at bridge piers is one of the most studied and challenging problems for hydraulic engineers. Many researchers analyzed such scour phenomenon, focusing on the effect of hydraulic conditions and geometric configurations. In particular, previous analyses focused on the scour evolution and equilibrium configuration under both clear- and live-bed conditions, providing useful design criteria, accounting for the effect of hydraulic conditions and pier geometry. On the contrary, only a few studies deal with the effect of debris accumulation on scour evolution and equilibrium configuration. But, to the best of authors’ knowledge, none of them analyzed the effect of debris accumulation for an isolated pier located at different transversal positions with respect to the channel bank. In order to fill this gap of knowledge, we conducted experimental tests by varying the transverse position of the pier within the channel. Furthermore, we tested different debris accumulations varying the percentage blockage ratio. Experimental results revealed that scour equilibrium configurations are affected by the tested parameters. Therefore, the aim of this paper is to present a preliminary analysis of the scour hole features, highlighting similitudes and differences in terms of scour characteristics caused by the pier location in the presence of debris accumulation

Prediction of Scouring Depth at the Outlet of Partially Blocked Box Culvert

© 2014 American Society of Civil Engineers. Culverts are built at a location in a waterway that crosses a road or railway. The narrowing cross section of waterway creates a limitation to flow passage and therefore blockage occurs during flood events with accumulation of debris at the inlet. The blockage of the culvert can accelerate bed scouring and consequently causes failure of the culvert. It subsequently produces high damage to private properties and public assets. This article concerns scouring at the outlet of partially blocked culverts. In this context the blockage of culverts is studied as an important factor in the scouring pattern of culverts. Therefore, experimental tests were conducted to investigate the effects of culverts blockage on scouring downstream of a culvert. The experimental program was designed to investigate the relationship between the maximum scour depth, blockage ratio of the culvert, and flow characteristics. The experimental tests were carried under nonblocked and partially blocked conditions. The sediment material used in this study was uniform noncohesive sand particles. Results showed that the scoured area and maximum scour depth increases in partially blocked condition compared with the nonblocked condition. The results were compared with the previous developed models, and it was found that the previous model predicts scouring depth less than the scouring depth at blocked condition