Author(s): Youichi Yasuda; S. Suzuki

Linked Author(s): Youichi Yasuda

Keywords: Assembled boulders; Seepage flow; Local scouring; Velocity fields; Refuge space; Flood stage

Abstract: The authors recommended the installation of the consecutively assembled boulders downstream of the concreate apron instead of the protection blocks. The experimental investigation on the flow passing the movable weir was conducted by 1/10 scale model under Froude similarity law. The deflected flow due to the impingement of the main flow to the pier was confirmed, and the main flow was located near the bottom at the downstream of the protection blocks. Also, local scouring was formed. On the other hand, the installation of consecutively assembled boulders downstream of the apron was observed to cause the main flow to rise toward the water surface. In this case, an installation area of at least 1.5 times the apron length should be recommended. After 30 hours of experiment, local scouring downstream of the protection region could be minimized. The velocity measurement downstream of the apron is helpful for the explanation of the protection against local scouring. The authors found that the formation of seepage flow inside the assembled boulders was effective for the reduction of the mean velocity including turbulent intensity and the rising of the mainstream of the protection area. The installation of assembled boulders could lead to the role of habitat for aquatic animals and shelter from predation damage during normal stages. This effectiveness was confirmed at a river site for another use.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024