不同推移质输沙模型在溃坝洪水模拟中的对比分析

Comparison of Sediment Transport Model in Dam Break Simulation

溃坝洪水模拟分析中,溃口的侵蚀过程对溃口展宽和洪峰流量有直接影响,决定溃坝洪水模拟的准确性.在对圆弧滑裂面溃口展宽模型简化的基础上,将16组推移质输沙方程换算为侵蚀率,发现基于经验输沙方程的"侵蚀率—剪应力"均呈指数形式.结合唐家山堰塞湖溃决过程,对比多组经验输沙方程和指数形式的侵蚀率模型对溃坝洪水分析的影响,结果表明,采用Einstein-Brown(1950)输沙方程和指数模型中a=5,b=1.3时,模拟结果与实测资料较为相符,验证了指数模型的可行性,并通过参数率定指数模型可替代经验输沙模型.但指数模型中b值对计算结果极为敏感,甚至会导致计算不收敛,因此基于土石料最大可能冲刷率的概念提出双曲线模型,解决了这一问题,对准确模拟土石坝和堰塞坝的溃决提供一定的参考.

The process of soil erosion has a direct impact on the dam breach width and flood peak discharge in dam break analysis that to decide the accuracy of simulation results. This paper converts 16 bed load transport formulas to erosion rate and finds that the relations of erosion rate and shear stress of those experience equations are exponential, which are based on a simplified model of arc slip surface breach extension. The experiential formulas are compared to the exponential by Tangjiashan Barrier Lake for dam break analysis. It turned out that the calculated results from the Einstein-Brown (1950) equation and a=5, b=1.3 in the exponential model are consistent with the measured data. This should verify the feasibility of exponential model that could instead of the experiential models. However, the value of b in exponential model is extremely sensitive for dam break and may leads to no-convergence. The hyperbolic model can resolve this problem that is based on the concept of erosion rate of earth and stone. It provides a reference for accurate simulation of earth dam barrier dam break process. © 2015, Editorial Board of Journal of Basic Science and Engineering. All right reserved.