梯级水库群溃坝洪水风险分析——以澜沧江上游为例

Dam-break Flood Risk for Cascade Reservoirs:A Case Study of the Upper Lancangjiang River

梯级水库的建设是开发利用我国丰富水能资源、保障国家能源安全、实现减排目标的重要途径.但是由于部分水库结构老化、地势险峻以及近几年极端天气频发等原因,极有可能造成单坝溃决,继而引起梯级连溃,最终使整条流域系统瘫痪,为下游城镇带来不可估量的经济和生命损失.为准确预测梯级连溃发生后的危险程度及影响范围,基于心墙坝漫顶溃坝数学模型和HEC-RAS软件提出了梯级连溃地貌特征演变及洪水演进计算方法,并应用于澜沧江流域梯级水库RM-XW水电站大尺度连溃分析.结果表明,在遭遇1.4倍超标准洪水的情况下,RM水电站发生漫顶溃决,溃决过程中,心墙发生四次折断,并伴随溃口迅速扩张以及溃决流量激增,最高峰值流量达699986.5 m^(3)/s,溃决洪水演进至下游,使WNL-XW水电站相继发生漫顶.河道距离、坝型特征和坝体物理参数是影响梯级连溃过程中溃决流量大小的重要因素.

The construction of cascade reservoirs is a crucial means for developing and harnessing China’s abundant hydroelectric resources,ensuring national energy security,and achieving emission reduction goals.However,due to factors such as the aging of certain dam structures,the rugged terrain,and the increasing occurrence of extreme weather events in recent years,there is a significant risk of isolated dam failures.These isolated failures can subsequently trigger cascading dam failures,ultimately leading to the paralysis of the entire river basin system which could bring incalculable economic and human losses to the downstream town.To accurately predict the level of danger and the extent of impact following cascade dam failures,this paper proposes a methodology based on the mathematical model for core dam overtopping breaches and the HEC-RAS software.This methodology is applied to conduct a large-scale cascade breach analysis at the RM-XW Hydropower Station in the Lancang River Basin.The results indicate that,when subjected to a flood 1.4 times higher than the standard,the RM hydropower station experienced overtopping failure.During the breach process,the core wall ruptured four times,accompanied by rapid expansion of the breach and a significant increase in breach flow.The peak flow reached 699986.5 m^(3)/s.As the breach flood propagated downstream,it led to subsequent overtopping failures at the WNL-XW hydropower station.It is evident that river channel distance,dam type characteristics,and physical parameters of the dam body are crucial factors influencing the magnitude of breach flow during the cascade failure process.