» Research Note «Impact of Channel Contraction on the Abutment Scour and Application of Submerged Vanes in Scour Prevention and Control

When a bridge pier or abutment is built on a river bed, a contraction in the river flow section occurs. Under this condition, in addition to local scour at pier and abutments, contraction scour also takes place on the river bed. The objective of the present study is to investigate the effect of channel contraction on abutment scour and application of submerged vanes to prevent or control it. For this purpose, four different contraction sections, of 0.833, 0.667, 0.500 and 0.333 relative width are installed in an experimental flume furnished with non-cohesive materials with median size of 0.78 mm. In this research, three double vanes were tested. Vanes were arranged with three angles of attack namely, 10, 20 and 30 degrees with respect to the channel center line. All experiments were repeated for 3 discharges, 20, 30 and 40 lit/sec. Results of this research showed that the maximum reduction in the bed elevation due to scouring was 75 percent for relative width of, 0.833 of angle of attack of 20̊ and relative flow equal to 0.5.