河道糙率和桥墩壅水对宽浅河道行洪能力影响的研究

为研究宽浅型河道糙率和桥墩壅水对行洪能力的影响,本研究采用了物理模型试验、数值模拟和经验公式方法分别模拟其水力特性并进行比较分析。通过物理模型试验给出了河道糙率的模拟方法,分别采用4种材料模拟河道护坡:无植被、稀疏植被、稀疏植被中间种植灌木和密集植被。其中,糙率最大的密集植被和糙率最小的无植被护坡条件下各断面水位差均值为0.03 m。结果表明:对于宽浅河道,护坡糙率较大范围的变化对河道行洪能力影响不显著。复杂边界条件和水力条件下桥墩壅水模拟结果表明:二维数学模型比经验公式和一维数学模型能较真实地反映河道边界条件、桥梁长度、桥墩形状对桥墩壅水高度的影响,模拟结果同物理模型试验值较为接近。本研究为宽浅河道安全行洪中糙率评估和桥墩壅水计算提供可靠的参数和依据。

Influence of roughness and backwater of bridge piers on flood carrying capacity in a wide-shallow river

The roughness and backwater of bridge piers are the key parameters, which effect on the flood carrying capacity in a wide-shallow river. In this study,these two parameters are analyzed by physical model test,numerical simulation and empirical formula. The slope protection is simulated by four kinds of materials,namely,no vegetation,sparse vegetation,sparse vegetation and shrub,and dense vegetation. The average water level difference is 0.03m under the condition of no vegetation and dense vegetation. The results show that the impact on the flood carrying capacity is not significant with the obvious roughness changes in the wide-shallow river. The simulation on the backwater of bridge piers shows the results of the two-dimensional mathematical models, which can reflect the boundary conditions of the river and characteristics of the bridge more really than the empirical formula and one-dimensional mathematical model, are close to the physical model experiments. This study provides a reliable basis for the evaluation of the roughness and the calculation of the pier backwater in the wide-shallow river.