堰塞坝漫顶溃决机理与溃坝过程模拟

Breach mechanism and numerical modeling of barrier dam due to overtopping failure

堰塞坝作为自然作用的产物,由于其自身特点,极易发生漫顶溃决.基于小比尺堰塞坝溃决模型试验与唐家山泄流现场实测资料揭示的堰塞坝漫顶溃决机理,建立了一个堰塞坝漫顶溃坝过程数学模型.模型基于堰塞坝的几何特征和坝料物理力学特性,统一分析坝顶与下游坡溃口的发展,并充分考虑堰塞体沿河流运动方向的形态变化;模型可考虑坝体的单侧与两侧冲蚀、不完全溃坝与坝基冲蚀等溃坝模式.选择唐家山堰塞坝泄流案例对模型的合理性进行验证,通比对峰值流量、溃口最终宽度、峰值流量到达时间等参数发现,模型计算结果与实测值的相对误差在10%以内;另外,计算获取的溃口流量过程和库水位变化过程与实测值基本吻合,验证了模型的合理性;参数敏感性分析结果显示,残余坝高、冲蚀系数等参数对溃坝过程具有重要影响,单侧或两侧冲蚀对溃坝过程影响较小.

As a production of natural process, the barrier dam has its own features, and is easily to fail due to overtopping. Based on the breach mechanism revealed by small-scale model tests and the draining case of Tangjiashan Barrier Lake, a numerical breach model for barrier dam due to overtopping failure is put forward. In terms of the geometrical characteristics, physical and mechanical properties of barrier dam, a unified approach is developed to model the evolution of breaches in the dam crest and downstream slope, as well as the morphological change of the barrier dam in streamwise. Furthermore, different failure modes, such as one-and two-sided erosion,incomplete and base erosion are taken into account. The draining of Tangjiashan Barrier Lake is adopted to testify the present model,and the comparison of measured and calculated results indicates the rationality of the present model with the relative errors are less than 10% for peak discharge, final breach widths, and time to peak; in addition, the calculated breach discharge hydrograph and the changing process of water level are in accord with the measured data. The sensitivity analysis shows that the residual dam height after breaching and soil erodibility affect the breach flow prediction of the barrier dam significantly, whereas the one-or two-sided breach mode is less sensitive.