| According to the ministry of water resources "the notification of examination and approval about on further strengthening and standardizing of the river management area construction project "(Water connecting No.[2001])and"The water of the People’s Republic of China""The People’s Republic purposes""River management area the relevant provisions on the administration of construction projects"(Published by The ministry of water resources and the state development planning commission water administration in No.7[1992]), within the scope of river that may affect people’s life safety and the safety of property of construction projects and important construction projects, etc, must be given flood control impact assessment. The role of the flood control impact assessment mainly includes two aspects, one is the construction project within the scope of river management give the flood safety evaluation calculation of itself, on the other hand is given the flood control evaluation calculation of the river after the construction project will be built and have been built that might to the whole river flood control, and through the evaluation calculation results, put forward Suggestions to decrease the flood control effect. Mainly includes research and calculate the situation of buildings hinder water and backwater and scour, deposit, river regime of river way, and the influence of river channel stability after the construction project built.YangJaWan Yellow River bridge belongs to the railway which under Construction that from LanZhou to ChongQing. Setting for the freight transport of LanZhou hub which connecting the station of SangYanZi and QingBaiShi to cross the Yellow River. Taking viaduct and whole bridge across, locating in YangJiaWan village of the town of QingBaiShi, about600meters far away from the Yellow River bridge which belongs to downstream BaoLan railway of the town of DongGang. The included angle between bridge normal and mainstream is about25degrees. The mainly river channel in the bridge location is about250meters, and the flow is more gentle because of near the backwater tail end of XiaoXia hydropower station.River flow restricted by piers and the cross-sections of river are compressed due to the river bridge building, the water flow direction also be changed. The unit discharge between the bridge pier increases relatively, locality water gradient and water velocity increasing, leading to increased riverbed scouring near the pier. At the same time, complex flow structure was formed near the bridge piers and watercourse, local scour around bridge pier was produced. And because the flow regime changed, effective water area reduction, bridge and flow velocity increasing, the bank also produces erosion.There are no dike projects in the scope of1.5Kilometers of YangJiaWan yellow river bridge from the upstream and downstream, in the left bank of downstream is the YangJiaWang pump station which belongs to the YangJiaWan village used to agricultural irrigation.Because near the backwater tail end of XiaoXia hydropower station, it is necessary to predict the influence of superposition backwater to the pump; Meanwhile,Analysis of stability of river channel and flood current under different flood frequencies, especially the existing levee project, flow channel regulation project and other water conservancy project’s impact analysis under the once-in-a-hundred time flow; Finally through the water with sand or not, study the law of the river sediment transport after the bridge built and the deposit law of DongGang bridge and XiaoXia reservoir, focuses on put forward the reservoir reasonable operation mode, and the manner of sluice open.Through the similar theory, using the moving bed hydraulic model test to imitate the section of the Yellow River in LanZhou before and after the bridge built, and analyzes the relevant test data, we got that:In the design flood of once-in-a-hundred time standard, the span length and the clearance under bridge meet the requirements of specification, river flood via safely; Consider from river regime, the position of navigation hole setting reasonable.Due to the piers occupy the river way and making the river water area reduced, suggesting to make river dredging upstream and downstream to the pier of6#to8#, especially6#to8#, and transport waste of the right bank meanwhile. The downstream main stream move up65meters after the bridge built because of the effect of river diversion coursed by piers, making the right bank deposit produced, while more scour on the left bank, so suggest to strengthen the left bank of this paragraph and entrench structures nearby.There will be produced backwater about18centimeters after bridge built, so suggest related departments when build BinHe embankment, considering the adverse effect of the flood control. |
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