Effect of Flow Intensity and Collars on Scour Depths Around Bridge Abutments

Date

2023-5-05

Author

Gökmener, Serkan

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In this experimental study, the temporal development of the local scour was studied around semi-circular end and rectangular bridge abutments under unsteady-state clear-water flow conditions in a rectangular sediment channel. Six different abutment lengths having constant width with uniform sand as bed material were tested for 3 different successive flow intensities each applied continuously for 2 hours. Effects of the abutment length, flow intensity and temporal variation on the scour depths around semi-circular end and rectangular bridge abutments were investigated. According to the results, it was shown that flow intensity is the most important parameter in scour development and the maximum scour depth always occurs at the front noses of the abutments. Then, the performance of collars on reducing local scour depth around semi-circular end and rectangular bridge abutments under unsteady-state clear-water flow conditions was examined. Three different abutment lengths having constant widths were tested with varying sizes of collars that are located at different elevations relative to the bed level. The effect of abutment length, collar width, collar elevation, flow intensity and temporal variation on local scour reduction performances of collars were tested. According to the experimental results, it can be stated that the application of collars around semi-circular end and rectangular bridge abutments decreases the local scour depth by up to 72%. Best collar performances were generally achieved for the largest collar width located around bed level. Also, semi-circular end collars gave more efficient results in reducing the scour depths than rectangular collars. Finally, additional experiments were carried out in order to understand the effect of flow depth on scour reduction efficiencies of the collars and it was observed that the flow depth had no significant effect in reducing the scour depth for longer abutments but had a significant effect for shorter ones.

Subject Keywords

collar, rectangular abutments, scour, scour countermeasures, semi-circular end abutments, unsteady-state flow conditions

URI

https://hdl.handle.net/11511/103252

Collections

Graduate School of Natural and Applied Sciences, Thesis