混凝土面板砂砾石坝漫顶溃坝模型研究

基于沟后面板砂砾石坝溃坝案例调研资料及溃坝离心模型试验的反馈分析,提出了一个可描述混凝土面板砂砾石坝漫顶溃决过程的数学模型。该模型的特点是选择可反映高速水流作用下推移质与悬移质运动的坝料输移公式描述宽级配砂砾料的运动特征,以及建立可模拟面板坝每块钢筋混凝土面板在各种变化荷载作用下破坏过程的表达式。选择沟后面板砂砾石坝溃坝案例对建立的模型进行验证,计算结果与实测结果的对比表明:溃口峰值流量、堆石体溃口的顶宽与底宽、折断的面板的数量和各面板的破坏长度、溃坝历时等输出参数的相对误差均控制在±15%以内;由于溃坝过程中面板不断折断,溃口流量过程呈锯齿状抬升。另外,参数敏感性分析的结果表明坝料的冲蚀率和级配特征对溃坝流量过程具有重要的影响。

Numerical model for breach of concrete face sand-gravel dams due to overtopping

Based upon the data of field investigations and back analysis of centrifugal model tests for the beach case of the Gouhou concrete face sand-gravel dam (CFSGD), a numerical model for breach of CFSGD is developed. The major highlights of the model are the adoption of soil erosion equation which can consider the erosion of bed load and suspended load to depict the erosion process of sandy gravels with a wide range of gradation, and the establishment of analogy to simulate the failure process of concrete face slabs under varying loads during the dam breach. The analysis of the case study of the Gouhou dam breach is used to testify the proposed model, and the comparison between the calculated and measured results shows the relative errors of less than ±15% for the output of breach parameters, which contain the peak breach flow, breach top and bottom widths of the rockfill body, numbers of the failed concrete face slabs and their failure lengths, as well as the failure time of dam breach. Owing to the bending of concrete face slabs, the breach hydrograph has a serrated increase. In addition, the sensitivity analysis indicates that the soil erodibility and grain-size distribution significantly affect the prediction of the breach flow of the dam.