桥梁堵塞对河道洪水影响的三维数值模拟

Effect of bridge blockage on flood flow by three dimensional numerical simulation

摘要

【目的】暴雨山洪中往往含有浮木、树枝等漂浮物,导致桥梁堵塞,影响河道行洪能力,增加山洪灾害风险,已有规范在进行山洪灾害风险评价时不考虑桥梁堵塞的影响,这会低估洪水风险等级。【方法】以甘肃省华池县的某河道为例,采用三维水动力数值模型开展了河道桥梁不同堵塞率条件下的洪水淹没风险研究,分析了100 a、50 a、20 a和10 a一遇不同设计暴雨条件以及桥梁堵塞率对洪水风险的影响。【结果】研究表明:在无堵塞情况下,该河道防洪能力大于50 a一遇。然而,随着堵塞率的增加,河道的洪水位增大。特别是,当堵塞率达到80%,50 a一遇洪水条件下的桥梁的过流能力系数下降了60%,而10 a一遇洪水条件下桥梁的过流能力系数下降了22%。建立了桥梁过流能力修正系数与堵塞率的经验关系。【结论】桥梁堵塞显著降低了河道的行洪能力,增加了洪水风险,在山洪灾害风险评价中,有必要考虑桥梁堵塞的潜在影响。提出的过流能力修正系数经验公式可为一维模型中堵塞条件下桥梁断面内边界条件的设置提供参考。

Abstract

[Objective] Flash floods often contain floating debris such as driftwood and branches, which can cause bridge blockages, affecting the river' s flood-carrying capacity and increasing the risk of flash flood disasters. Existing standards for evaluating the risk of flash flood disasters don' t consider the impact of bridge blockages, underestimating the risk level.[Methods] takes A river channel in Huachi County, Gansu Province was took as an example, and a three-dimensional hydrodynamic numerical model was used to carry out research on the flood inundation risk under different bridge blockage rates.It analyzed the impact of different design rainstorm conditions such as 100-year, 50-year, 20-year, and 10-year return periods, as well as the bridge blockage rate on the flood risk. [Results] The research indicates that under no blockage conditions, the river's flood prevention capacity is greater than a 50-year return period flood. However, as the blockage rate increases, the floodwater level in the river rises. Notably, when the blockage rate reaches 80%, the bridge's flow capacity coefficient under a 50-year return period flood decreases by 60%, and under a 10-year return period flood, it decreases by 22%. An empirical relationship between the bridge's flow capacity correction coefficient and the blockage rate has been established. [Conclusion] Bridge blockages significantly reduce the river's flood-carrying capacity and increase the risk of flooding. In the assessment of flash flood disaster risk, it is necessary to consider the potential impact of bridge blockages. The empirical formula for the flow capacity correction coefficient proposed in this study can provide a reference for setting the boundary conditions within the bridge section under blockage conditions in a one-dimensional model.

关键词

桥梁堵塞 / 洪水风险 / 过流能力 / 壅水高度 / 数值模拟

Key words

bridge blockage / flood risk / the flow capacity / backwater height / numerical simulation

基金资助

国家自然科学基金项目(52079106)

西安市科技计划项目(23GXFW0050)