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输水渡槽对河道行洪风险的影响分析

Research on Aqueduct′s Effect on the Flood Risk of River Course

  • 摘要: 涉水工程可能导致原有的河道水动力条件改变,进而影响河道行洪能力。研究有无涉水建筑物下河道的行洪风险,对工程维护、河道治理及保障地区防洪安全具有重要意义。基于对河道洪峰流量、初值水位、糙率以及堤防高程4种不确定性因子的随机模拟,分析修建在河流上的输水渡槽在洪水作用下的受力情况,结合河道水面线计算结果,采用常规蒙特卡罗法和基于拉丁超立方抽样的蒙特卡罗法分别计算在有无渡槽情况下的河道行洪风险。结果表明:(1)在渡槽内水位分别为0.5,1.0,1.5,2.0 m的4种工况下,清丰山溪行洪能力相较设计流量1 200 m3/s分别下降了36.68%、27.87%、19.00%、10.05%;(2)在无渡槽的情况下,河道行洪风险为0.007;在有渡槽情况的下,上述4种工况对应河道行洪风险依次为0.34、0.045、0.016、0.012;(3)令渡槽内水位处于安全范围内最高值,当清丰山溪流量超过1 600 m3/s时,河道行洪风险仍随洪水流量增大显著增加,应考虑报废渡槽以保证河道行洪;(4)常规蒙特卡罗法和基于拉丁超立方抽样的蒙特卡罗方法均适用于评估渡槽对河道行洪风险的影响,后者具有更好的收敛性。综合而言,在河道中修建渡槽对河道本身的行洪能力有负面影响,致使河道的行洪能力低于设计值,河道行洪风险增加,提高渡槽内水位可以在一定程度上减少河道行洪风险。

     

    Abstract: Wading projects are likely to bring about changes of the original hydrodynamic conditions of the river, and this may further affect the flood discharge capacity of the river course. Thus, it is of great significance to study the flood risk of the river course with or without the wading projects, so that we can well maintain the project, regulate river course and ensure regional flood control security. Based on the random simulation of four uncertain factors, namely peak flood discharge, initial water level, river course roughness and dike elevation, this paper analyzed the stress of aqueduct under flood action, and then calculated the water surface line of the river. Combined with theforce conditions and water surface line calculation results, the conventional Monte Carlo method and the Monte Carlo method based on Latin hypercube sampling were both used to calculate the flood risk of river course with or without an aqueduct. The results show that:(1) When the water level in Gangqian Aqueduct is 0.5, 1.0, 1.5 and 2.0 m, the flood discharge capacity of Qingfeng Mountain stream, compared with its designed discharge of 1 200 m~3/s, respectively decreases by 36.68%, 27.87%, 19.00% and 10.05%.(2) In the case of having no aqueduct in its river course, the flood risk of Qingfeng Mountain stream course is 0.007. In the case of having Gangqian Aqueduct in its river course, when the water level in the aqueduct was 0.5, 1.0, 1.5 and 2.0 m respectively, the flood risk of Qingfeng Mountain stream course is 0.34, 0.045, 0.016, 0.012 in turn.(3) Keep the water level in Gangqian Aqueduct at the highest value within the safe range. When the discharge of Qingfeng Mountain stream exceeds 1 600 m~3/s, the flood risk of its river course still rises significantly with the increase in the flood flow. Therefore, in this case, Gangqian Aqueduct would have to be scrapped to ensure the flood discharge capacity of Qingfeng Mountain stream.(4) Both the conventional Monte Carlo method and the Monte Carlo method based on Latin Hypercube Sampling are suitable for assessing the influence of aqueduct on flood risk of river course, and the latter has better convergence. In summary, building adueducts in river courses would have a negative impact on the river courses’ flood discharge capacity. It results in the flood discharge capacity of the river course being lower than the designed discharge, and further, led to the flood risk of river course increasing. To a certain extent, raising water level in the aqueduct can reduce the flood risk of river course.

     

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