通过土石坝溃决的特征,建立了土石坝体溃决模型,并预测溃口流量过程和溃口拓展过程.模型溃口假定为梯形,且在坝体溃决过程中底宽和溃口边坡不发生变化.根据水量平衡和坝体物质守恒,模拟溃口的拓展过程；溃口水力过程用宽顶堰流表示,并使用经验公式计算溃口不同水头条件下的冲蚀量.针对这些差分方程为隐性格式,难以直接求解,提出了特殊的迭代解法,且较少的迭代次数即可收敛.通过模型对四川北川唐家山堰塞湖的溃决过程进行了反演,结果显示:坝体溃决相关参数包括溃决持续时间,溃决峰值流量和出现时刻、坝体最终几何形状以及堰塞湖溃决排出总水量,当计算参数选择合理时,预测值与实测值比较吻合.从模拟计算结果来看,模型预测具有一定的可行性,可以为堰塞坝的安全预警和应急处置提供数据支持.%A mathematical model to simulate the dam break process by overtopping and to forecast the flood hydro-graph in the breach is developed in this paper. Hie breach is assumed trapezoidal, coupling with the bottom width and side slope angle keeping constants during the overall process of dam breach. Simulation of dam breach evolution is based on the conservation of mass of reservoir capacity and sediment transport capacity. Particularly, broad - crest weir relation is utilized to simulate the outflow in the breach, and an empirical equation is used to compute the rate of erosion in the breached section. Because of the implicit form of these equations, an iterative solution is proposed with convergence achieved in a few iterations. The dam breach process of Tangjiashan dam had gained many detailed information supporting datum for dam breach modeling. The model is used to calculate the dam breach processes of Tangjiashan Dam, results show that: the forecasting dam breach parameters including breach lapsed time, peak discharge and corresponding time, final breach geometry, and the total volumes of water exhausted accord measured values. The calculation method of natural dam breach could be useful for the purpose of hazard assessment and emergency mitigation setting.
展开▼
