| With the construction of a bridge in the river,the compression of bridge pier for the river crossing section will cause excessive local damming,flow pattern disorder,speed up,which can not be ignored on the river flood,water delivery and river bed stability.For the river course with many Bridges and not far apart,the Bridges will have more intricate influences on each other due to the water level,river regime,river gradient,water and sediment characteristics,and geological conditions.In this paper,the proposed National Highway 233 Jiajiang Bridge as the research object,on the basis of the full collection of the bridge and its river reach data,through numerical simulation,from many aspects of the proposed National Highway 233 Jiajiang Bridge impact on the flood channel,the calculation and analysis results have direct guiding significance for engineering design and construction.The main conclusions are as follows:(1)In the once-in-a-century flood period,the calculated flow field of the river channel changes little on the whole before and after the construction of the bridge,and the pier has little influence on the flow field of the whole reach.At the same time,the height of the bridge front and the height of the pier front thrust are both small,and the overall influence of the super large bridge on the river at the downstream Wufengshan Bridge is also small.(2)The height of backwater in front of cofferdam is 2.18cm under the water level condition during the construction period once in five years,and the impact range of backwater is large.The water level in front of the bridge is raised by 2.0cm within 3km.(3)Under the reverse water transfer condition,the water level of the main channel at Bajiangkou downstream of the bridge site changes within 0.001m,and the velocity changes within 0.005m/s.The changes are very small.The construction of the bridge has no effect on the water transfer capacity of the river.(4)According to the measured data for many years,the shoreline of the project reach is stable,the deep pool swing is small,the section shape is basically unchanged,and the river regime is relatively stable.After the construction of the bridge,the river flow field changes little,and the river regime will continue to maintain a basically stable state.(5)A11 the piers located in the river channel meet the safety standard of the buried depth of the bridge base.The influence of bridge scour on the river regime of the Jiajiang River is very small.(6)Under the condition of once-in-a-century design water level and discharge,the stability indexes of longitudinal and transverse riverbed are 1.24 and 1.42 respectively,and the river phase relation of the section at the bridge site is 2.08.The river section where the proposed bridge is located is relatively stable and difficult to impact the river. |
