堰塞坝漫顶溃决过程数值模拟及应用

堰塞坝作为自然形成的天然坝体,其结构不稳定性强,绝大多数的堰塞坝最终都将发生漫顶溃决,一旦溃决,将会对下游带来巨大的生命和财产损失。因此,有必要合理预测堰塞坝的溃决流量过程,为溃坝应急预案的编制提供理论与技术支撑。本文充分考虑堰塞坝的形态特征及坝料的物理力学特性,建立了一个可合理模拟堰塞坝漫顶溃坝过程的数学模型。该模型可较好地反映水动力条件下的溃口发展过程和下泄流量过程。选择西藏易贡堰塞坝溃坝案例对模型进行验证,通过计算结果与实测资料的对比发现:计算得到的溃口峰值流量、最终溃口宽度、峰值流量到达时间等参数的最大相对误差均在±15%以内;溃口流量过程与实测资料也吻合较好,有效地验证了模型的合理性;参数敏感性分析结果显示,残留坝高、冲蚀模式(单侧与两侧冲蚀)、冲蚀系数等参数对溃坝过程均有重要影响。

Numerical modeling of breach process of landslide dams due to overtopping and its application

As a production of natural process, the landslide dam has poor structural stability, and most of which will finally fail due to overtopping, which will pose tremendous risks to the people and property in the inundated area. Therefore, it is of significant importance to predict the discharge hydrograph for the breach process of landslide dams so as to provide theoretical and technique supports to the dam emergency plan for dam breaching. In this study, based on the geometrical characteristics, physical and mechanical properties of a landslide dam, a numerical model for the breach process of the landslide dam due to overtopping failure is developed. This model can reasonably reflect the evolution and discharge hydrograph of the breach under the hydrodynamic condition. Meanwhile, the dam breach case of Yigong landslide dam is chosen as the representative to testify the proposed model. The comparison of the measured and calculated results shows that, the relative errors for the peak discharge, final breach widths, and time to peak are within ±15%; furthermore, the breach discharge hydrograph is in accordance with the measured one. Thus, the rationality of the model is verified effectively. The sensitivity studies show that the dam breach process is sensitive to the residual dam height, the erosion mode (one- or two- sided breach), and the soil erodibility.