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针对当前堰塞坝溃决试验粒径取值偏低和粒径相差不大的现状,采用两组粒径差别明显的砂样进行了堰塞坝垭口漫顶溃决试验。试验表明,同条件下粗、细两种颗粒坝体的溃决现象有着较明显的不同。垭口挡板提起后,细颗粒坝体以下切侵蚀为主,冲刷强度比较剧烈,坝体较容易发生溃决;而粗颗粒坝体则是以渗流出流形成的溯源冲刷为主,冲刷强度较低,溯源面逐渐向上发展,只有当其发展到垭口下端附近时坝体才有可能迅速发生溃决。试验还发现,下游坝坡对溃决过程的影响比较显著,坝坡越陡,坝体越易溃决,溃口的平均展宽速率也越大。此外以deVries输沙率公式为基础建立了具有物理意义的概念性溃口出流计算模型,并采用试验实测数据对该模型进行了验证,结果表明该模型具有良好的适用性。
In view of the present situation that the particle size of the dam test is small and the difference of the particle size is not big, the sand-dam sample with obvious difference in particle size has been used to carry out the test of the overhang collapse of the dam dam. Experiments show that, under the same conditions, coarse and fine particles of two kinds of grain collapse phenomenon has a more significant difference. Pass baffle lifted, the fine-grained dam under the main cut, relatively intense erosion intensity, the dam more prone to collapse; and coarse-grained dam is formed by the erosion of seepage erosion-based, low erosion intensity , The source of trace gradually upward development, only when it is developed to near the bottom of the pass when the dam may collapse quickly. The experiment also found that the impact of the downstream dam slope on the collapse process is more significant. The steeper the dam slope, the easier the dam body will collapse and the larger the average extension rate of the breach. In addition, based on the formula of deVries sediment transport rate, a conceptual fracture flow calculation model with physical meaning is established, and the experimental data are used to verify the model. The results show that the model has good applicability.