Numerical Simulation With Characteristics Of Flow Field And Scouring And Deposition In Daling River Of Yixian Bridge Group Segment

Due to the serious destruction of ecological environment in Daling River Yixian section, building the Daling River ecological wetland park between Potaizi Bridge and urban area in Yixian County effectively protects the river ecological environment. And with the completion of the Beijing-Shenyang passenger line in urban section, there has formed bridge group in the section, having an impact on flood control safety during the flood season; at present, research on the influence of flow and scouring and silting within the bridge group river section is relatively few. In this paper, aiming at Daling River Yixian urban bridge group section, the numerical simulation of the different bridge spacing, pier shape, the angle between main stream line and bridge axis, flow and sediment particle size on the flow and scouring and silting characteristics before and after the bridge building of Beijing-Shenyang passenger line is studied.In this paper, the software Mike21 is used in the two-dimensional numerical simulation of Daling River Yixian urban bridge group section. Hydrodynamic module and sediment module in the software are used to create a different unstructured triangular mesh and carry out the numerical simulation. Main research content and results are:1. Numerical calculation of the change of the flow and scouring and silting characteristics before and after the bridge building of Beijing-Shenyang passenger line is conducted. The result shows:the backwater of Beijing-Shenyang passenger line and Xinyi Railway Bridge superimposes, backwater level significantly increases and the change of the flow and scouring and silting is obvious, having an impact on upstream flood control safety.2. The reasonability of the distance between Beijing-Shenyang passenger line and Xinyi Railway Bridge is analyzed. On the basis of the original bridge spacing, the Beijing-Shenyang passenger line is respectively built at the 300m and 600m downstream Xinyi River Bridge. The result shows:building bridge at 300m downstream Xinyi River Bridge, it is relatively small of the backwater level before the completion of Beijing-Shenyang passenger line to generally affect the change of coupling and flow; building bridge at 600m downstream Xinyi River Bridge, influenced by the backwater of downstream Beiguan Bridge, it results in the cumulative effect on the backwater level, and flow rate reduces and siltation increases; therefore, the current construction location of Beijing-Shenyang passenger line is not the best choice from the flow and scouring and silting characteristics.3. The flow and scouring and silting characteristics of different pier shape are different and the influence on front pier and back pier changes with the difference of the pier shape. Different angles between main stream line and bridge axis affect the distribution change of the flow and scouring and silting around the pier. With the increase of the flow, water level and flow rate both increase, the siltation of upstream and downstream bridge increases and the scour between piers increases. In the case of different suspended sediment particle diameter, with the increase of the diameter, the water level and flow rate increase and the scouring area increases.