无粘性土堤漫顶溃决溃口区域水力参数变化过程数模研究

Study of breach hydraulic parameters variation of noncohesive embankment overtopping breach process

结合物理模型试验建立平面二维水流数学模型,采用高分辨率有限体积格式计算漫顶溃堤洪水演进过程,并针对不同时段溃口形态建立三维几何模型进行水力参数变化规律数值模拟.研究结果发现,堤防溃决属溯源冲刷,与流速密切相关;溃决过程外江水位平稳下降,内江水位先上升后逐渐稳定,内外江水位差随溃口展宽逐渐减小;壁面剪切应力及动水压力较大区域集中在溃口内江侧与河底连接处,且随溃决过程逐渐减小.

Based on the flume experiments, a 2D unsteady flow numerical model which adopts high precision finite volume method is established to simulate flood evolution of embankment breach process. According to experiments data and simulation results of the 2D numerical model, 3D geometrical models of the breach at different breach development phases are established to investigate hydraulic parameters variation of the breach. The result implies that embankment overtopping breach is backward erosion and flow velocity is the most important factor affecting the breach development. During the breach process, the water level of outer river declines gradually and the water level of inner river rises up at first then keep stable; the water level difference between inner river and outer river decreased step by step. Peak values of wall shear stress and pressure turn out at the connection of breach surface and inner river bottom and gradually decrease in the process of the embankment breaching.