Effect of repositioned submerged vanes on local scour variations around a pier in a bend: experimental investigation

Bridge pier local scouring has forever been under consideration as an unwelcome phenomenon that threatens the safety of bridges. Hence, an investigation into methods of scour reduction around piers is of great importance regarding the hydraulic and environmental aspects. This study mainly focused on the role of submerged parallel vanes' positioning across the channel width in decreasing the depth of scouring around the pier. This experiment was conducted in a channel made of a 180 degrees sharp bend. The bridge pier was positioned at the 90 degrees cross section, while the submerged vanes were located upstream of the pier in different arrangements. The results demonstrated that placing the submerged vanes at the channel's central axis caused the greatest reduction in scouring depth compared to the tests with no vanes. With the minimum scour hole volume around the pier, a 51% scour reduction resulted compared with the test without submerged vanes. In addition, the maximum scour reduction occurred with the submerged vanes placed at 2.5 times the pier diameter away from the pier's centerline and at intervals of 1 and 1.5 times the pier diameter. This pattern resulted in 30% and 25% local scour reductions around the pier. Moreover, the lowest and the highest sedimentation values were, respectively, larger than the pier diameter by factors of 6.1 and 2.2, occurring at distances of 9 and 24% of channel width away from the inner bank. These results led to the proposed experimental equations with an acceptable accuracy in calculating the maximum scouring depth.

Automated summary

This study mainly focused on the role of submerged parallel vanes' positioning across the channel width in decreasing the depth of scouring around the bridge pier. The results showed that placing the submerged vanes at the channel's central axis caused the greatest reduction in scouring depth, with a reduction of 51% compared to the tests without vanes. Additionally, placing the submerged vanes at specific distances from the pier's centerline resulted in local scour reductions of 30% and 25%.