不同粒组含量下堰塞坝溃决过程的试验研究

Experimental study on the breaching process of landslide dams with different particle contents

【目的】堰塞坝结构松散、颗粒级配范围宽,易发生漫顶溃决,严重威胁上下游人民的生命财产安全。为进一步探究相同粒径范围内不同粒组含量条件下堰塞坝的溃决过程,【方法】以“11.3”金沙江白格堰塞坝为参考原型,开展了溃决模型水槽试验。【结果】结果显示,堰塞坝的溃决过程可以划分为渗流与过流、溯源侵蚀、溃口发展及衰减平衡四个阶段。溃口流速与溃决流量均呈现先增大后减小的过程,但峰值流量滞后于峰值流速。另外,溃决水流冲击力在溃口发展阶段持续增大,在衰减平衡阶段开始下降,而水流重度在溃口发展阶段表现出一定范围内的波动。随着中值粒径的增大,溃决流量峰值减小、峰现时间延迟、溃决水流冲击力峰值减小,下游泥沙淤积区长度变短、厚度变大。【结论】研究结果进一步揭示了相同粒径范围内的不同粒组含量对堰塞坝稳定性、溃决过程和溃决参数的影响,可为堰塞坝灾害的风险评估和应急处置提供参考。

[Objective]Landslide dams are usually with loose structure and wide range of particle gradation and prone to overtopping failure,which seriously threatens the life and property safety of up and downstream people.In order to further understand the breaching process of landslide dams under the condition of different particle contents within the same particle size range,[Methods]several breaching tests models by flume were carried out by using the“11.3”Baige landslide at Jinshajiang River as a reference prototype.[Results]The result show that the failure process of landslide dams can be divided into four stages,including seepage and overflow,backwater erosion,breach development and attenuation equilibrium.Both the rate and discharge of the breach flow first increase and then decrease with time,but the peak flow rate lags behind the peak flow rate.In addition,the impact force of the flow increases continually in the stage of breach development and begins to decrease in the stage of attenuation equilibrium,while the flow severity shows a certain range of fluctuation in the stage of breach development.With the increase of the median particle size,the rate of breaching peak flow decreases,the appearance time of peak flow delays,the peak of the impact force of the breaching flow decreases,and the length of the sediment deposition downstream becomes shorter and the area larger.[Conclusion]This paper further reveals the influence of different particle contents within the same particle size range on landslide dam stability,breaching process and parameters,which would likely contribute to risk assessment and emergency response.