Author(s): Yang Wenjie; Chen Qigang
Linked Author(s): Qigang Chen
Keywords: Guide bank; Scour; Plane layout; Attack angle; Blockage ratio
Abstract: Many transportation routes in the northwest region of China, which traverse wide and shallow river reach in front of mountains, often use a multi-bridge approach to cross the river. These routes need straight-closed guide banks to guide the upstream flood flow smoothly through the bridge openings. However, this practice can lead to damage of the road embankments approaching bridges due to excessive scour at the foundation of guide banks. However, existing scour formulas are primarily designed for curved guide banks with low blockage ratio and small attack angle. They are not applicable to the straight-closed guide banks with high blockage ratios and large flow attack angles. This study employs generalized physical model experiments to investigate the impact of attack angle and blockage ratio on the scour of guide bank. The results revealed that the attack angle of the guide bank affects both the maximum scour location and scour depth. As the attack angle increases from 10° to 90°, the maximum scour location gradually moves upstream from the outlet of the bridge opening to the head of the bank. Regarding the impact on scour depth, the overall trend indicates that the maximum scour depth of guide bank increases with the enlarging of the attack angle. The maximum scour depth increases quickly when the attack angle of guide bank is less than 60°, while the influence diminishes notably when it surpasses 60°. Similarly, an increase in blockage ratio also leads to an increase in the scour depth. Furthermore, it is found that when the attack angle exceeds 30°, the blockage ratio affects both the contraction scour depth and the local scour depth. Therefore, it is recommended that for guide banks with large attack angles, the total scour depth should be calculated directly. The findings can provide references for the design of straight-closed guide banks and similar structures.
Year: 2023