Investigation approaching flow to bridge and prediction of bridge pier scour with floodplain vegetation in compound channels under pressurized flow conditions

Abstract

Abstract The local scouring around the pier, is one of major cause of the bridges failure worldwide. Compared to the flow hydraulics in single channels, the flow pattern in compound channels is completely different with flood plains covered with vegetation and this issue can affect the amount of scouring in the area of bridge piers. However, the combined effect of these factors has not been systematically investigated. Therefore, due to the complex nature of the local scouring phenomenon and the absence one of an accurate prediction model, in this research, an experimental study on the hydraulic characteristics of the flow approaching the bridge deck in compound channels with floodplain vegetation in pressurized flow conditions, has been done. It was found that increasing vegetation density on average will reduce scour depth by 15% for the same floodplain width and relative depth. In free-flow conditions, increasing the vegetation density on average will increase the scour depth. The aim is to develop an optimized model to estimate the bridge pier scour in consideration of the combined effect. The newly developed relationship shows a good correlation coefficient of more than 92% with the experimental data and yielded better results than the previous equations. The finding of this study will have potential applications for the prediction of the bridge pier scour in clear water conditions.

Keywords

• Bridge pier scour
• Vegetation
• Compound channel
• Pressured flow