Experimental Investigation for the Effect of the Presence of Bridge Piers on the Outer Bank Erosion of a River's Bend

The effect of the oblong-shaped bridge piers on the erosion of the outer bank has been experimentally investigated when it is present in the river bend. Two Oblong Piers are installed at two sections of the straight reach of a flume (before the bend), then at each ۶۰ °, ۹۰ °, ۱۲۰ °, and ۱۸۰ ° of the central angle inside the U-bend. The novelty of this work lies in experimentally investigating, under specified geometric and hydraulic conditions, how the presence of bridge pier, affects the morphological characteristics and the amount of erosion that occurs at the outer bank. The experiments are conducted under clear water conditions and a uniform grain size distribution of sand bed material. For all experiments undertaken, the flow intensity was fixed at V/Vc=۰.۹۸. The results show an appreciable increase in erosive length at the outer bank with the presence of a bridge as compared to that occurring with no bridge at the same flow condition. The percentage increase in erosion length with piers installation is: ۴۹%, ۵۵.۴%, ۷۷.۵%, ۵۵.۴%, ۲۰.۵% and ۶۱.۷۵%, respectively. Furthermore, the results exhibit that the scour depth along the line of erosion generally decreases compared with the result with no bridge.

کلیدواژه ها:

Oblongs Piers ، Scour Depth ، Streamwise Velocity ، Uniform Sand Bed ، U-shape Bend