堰塞体漫顶溃决模式的离心模拟及数值模拟研究

Barrier dams have been widely distributed in the world,especially in China. 61% of the barrier dams after they are formed will break within one month. In the 20th century, the breaking of barrier dams only in China has killed 13520 people and caused direct economic losses of 260 million yuan. The occurrence and development of a barrier dam directly determines the peak flow of dambreak flood and downstream affected areas. Most of the previous research on the mechanism of dam breach was based on small physical models of artificially filled dams, thus two important factors, the structure composition of a barrier dam and stress state, influencing the breaching process had not been fully considered. Based on the investigation result of the barrier dams caused by Wenchuan earthquake, this study will re-estabilish the physical model of the dams with the typical composition using the soil and rock samples gathered from Tangjiashan barrier dam. The prototype stress state will be applied to the small physical model by means of centrifugal simulation, and the overflow breaking mode of the typical barrier dam will be studied by the same method. Additionally, the scour characteristics of the soil and rock samples of the barrier dams will be tested by the large-scale testing device developed by ourselves. Then, on the foundation of the testing results, the scour equations of drainage channel and the lateral collapse stability equations will be established, and the theoretical breach model of barrier dams will be improved, moreover, a program for simulating the breaching process of a barrier dam will be developed. The research achievements of this project will provide a reliable method for forecasting the breaking of barrier dams and the theoretical and technical support for emergency disposal schemes.

堰塞体在世界范围内尤其我国有着广泛的分布，61%的堰塞体在形成的1 个月内都会发生溃决，仅20 世纪我国因堰塞体溃决造成的死亡人数达13520 人，直接经济损失达2.6 亿元。堰塞体的溃决发生发展过程直接决定着溃坝洪水洪峰流量及下游波及范围，以往对溃坝机理研究多基于人工填筑坝小物理模型，并未充分考虑堰塞体结构组成及应力状态这两个重要因素对溃决过程的影响。本研究拟基于汶川地震震后堰塞体调研结果，利用取自唐家山堰塞体土石料，重塑典型结构组成的堰塞体模型。应用离心模拟方法还原堰塞体真实应力状态，针对典型堰塞体漫顶溃决过程进行研究，应用自行研制的大尺寸土体抗冲蚀测定装置对土石料抗冲蚀特性进行试验。综合试验结果建立引流槽冲刷及溃口侧向崩塌数学方程，完善堰塞体溃决理论分析模型，并编制计算程序应用于堰塞体溃决过程数值模拟。本项目成果将为堰塞体溃决过程预测提供可靠方法，为应急处置方案制提供理论和技术支撑。

本项目针对漫顶条件下土石坝溃坝流量不易准确评估的背景，针对土石材料的冲刷特性、土石坝溃决流量的计算模型以及土石坝抗溃决防护措施进行研究。采用大型圆筒冲刷试验方法对唐家山、易贡等堰塞体的土石材料的启动流速以及冲蚀速率进行研究，提出了土石料冲蚀速率的双曲线模型。开发了溃坝洪水计算程序IWHR-DB，该程序克服了众多溃坝程序都需进行迭代求解，数值求解稳定性不高的缺点，而且将岩土工程中的边坡稳定分析方法应用于溃口边坡的稳定性分析中，使得溃坝流量计算更加准确。采用IWHR-DB程序，对唐家山堰塞体的溃决过程进行了反演分析研究，验证了程序的可行性以及对相关计算参数进行率定。采用物理模型试验方法对土工格栅加筋对土石坝抗溃决的作用方式及效果进行研究，初步分析了土工格栅加筋的抗溃决作用机理。2014年8月3日，云南鲁甸地震形成红石岩堰塞体，其堰塞湖最大库容达到2.6亿m3，堰塞湖属于极高危风险。项目组在陈祖煜院士带领下对红石岩堰塞体在漫顶条件下产生的溃决洪水流量及历时进行研究，对开挖不同宽度、深度引流槽对降低溃决洪水洪峰流量的作用效果进行研究。同时，还对红石岩堰塞体溃决后可能造成连锁溃决洪水进行研究。