Experimental Study On Flood Control Safety Of Beiminghe Bridge

With the rapid development of economy,in recent years,the country has increased the construction of roads and Bridges.At present,building Bridges across rivers is one of the most economical and effective methods for human beings to overcome the water barrier to solve the problem of land transportation and river connection and expand the scope of social activities.The construction of Bridges across rivers plays an important role in economic development.But,after the building of the bridge on the river,bridge pier severely compressed river flood discharge section,flow direction change of discharge per unit width between bridge piers,cause the bridge pier local scour near the river bed,high water level of harmony and uneven distribution of flow velocity,and the flow regime inside of the river near the bridge pier,the riverbed evolution becomes very complex,at the same time,the flow velocity increases under the bridge,to change,the bank also can produce,scouring the result is bound to the bridge safety,river flood control safety pose a serious threat.Therefore,it is of great engineering application value to study the influence of bridge engineering on river flood discharge and river bank protection.Beiming River originated in Qiushuping Village,Wu'an City.It is a seasonal river with a total length of 59 km.Beiming River Bridge belongs to the construction project of West Second Ring Road in Wu'an City.The bridge is located in the north of Gaocun Village,Shangtuancheng Township.The bridge crosses the main stream of Beiming River and is arranged in an arc to cross the river.Geographical location,it is necessary to conduct flood control safety test research.This paper simulates the completion of Beiming River Bridge through physical model tests,and analyzes the test results of the water level,velocity,river bed erosion and deposition changes and flow patterns of the studied river section and near the bridge piers.The main results are as follows:(1)Based on the results of physical model tests,this paper proposes an optimal layout plan for the piers of the Beiming River Bridge,that is,to optimize the working conditions and adjust the angle between the No.7 pier and the water flow direction to be 9.9°,and the right bank pile number 18+248 to The bottom of the 18+464 riverbed is protected by gabion cages,with a length of 216 m and a width of 36 m.(2)The water level of piers 5 to 7 is obviously high,and the water level increases with the increase of flood flow.The water level of the optimized working condition is smaller than the original design working condition.When there is a flood in 100 years,the water blocking area of the bridge piers accounts for 6.39% of the total water passing area.The optimal working condition bridge pier front backwater range is 0.05 m ? 0.19 m,and the backwater length is 45m;the original design working condition bridge front backwater range 0.08 m ? 0.37 m,the length of backwater is 60 m.The construction of the cross-river bridge caused the water level in the river to change.The original design conditions aggravated the water level on the right bank,and the optimized conditions reduced the erosion on the right bank.(3)When a flood occurs in the study section,the flow velocity distribution in the river channel changes.Due to the diversion of the bridge piers,the original design conditions of the flood mainstream deviate to the right bank of the river channel,resulting in an increase in the speed of the right bank and causing certain erosion to the right bank embankment.Not conducive to the stability of the dike on the right bank.The flood mainstream gradually approached the middle of the river course under the optimized working conditions,reducing the riverbed erosion on the right bank and protecting the stability of the embankment on the right bank.From the point of view of water flow pattern and river regime,under the optimized conditions,the water flow in the river course is smooth,the flow velocity is evenly distributed,and the river regime is stable.(4)After the construction of the bridge,compared with the condition without piers,the original design conditions except for the siltation of the river bed near the No.2 pier,the No.1 pier and the No.3 ? 7 piers all have different degrees of erosion,and the flood occurs once in 100 years.When the scouring range is 0.35 m ? 5.45 m,the average depth is 3.27 m.Optimized working conditions Siltation occurred near pier No.2 and No.7 pier,and the river bed near pier No.1 and No.3 to No.6 had different degrees of scour.When there was a flood in 100 years,the scour range was 1.59 m ? 5.12 m,and the average scour depth was 2.00 m.The scouring depth increases with the increase of flood flow,and the scouring depth of the optimized conditions is smaller than the original design conditions.(5)After the adjustment of the bridge,the riverbed erosion and sedimentation situation has changed to varying degrees.When flood flow occurs once in 100 years and once in 50 years,the impact range of bridge pier layout on the downstream riverbed is 300 m and 260 m respectively.The arrangement of large-angle piers under the original design conditions caused an increase in the scour area of the river bed on the right bank downstream of the bridge area,threatening the stability of the right bank embankment,and not conducive to the safety of flooding on the right bank of the river.Optimize working conditions to protect the river bed on the right bank,adjust the angle between the No.7 pier and the water flow to 9.9°,the flood mainstream in the river course gradually shifts to the middle of the river course,and the river bed erosion on the right bank is reduced,which protects the flood discharge safety of the right bank dike.