全球气候变化背景下越来越频繁的极端水文事件严重威胁堤坝防洪安全,2016年、2020年长江流域均发生大洪水并伴有堤防溃决;2024年7月5日湖南洞庭湖团洲垸堤发生溃决,给人民生命财产安全带来极大威胁。为人民群众早日返回家园并防止次生灾害,溃堤发生后通常会尽早抢险封堵合龙。此时圩垸堤内外水位相平,溃口合龙条件下圩垸内应急快速抽排,水位骤降对主堤及二道防线堤防安全的影响备受关注,甚至制约应急抢险。为分析洞庭湖团洲垸应急抽排对堤防安全的影响,并为应急抢险方案制定提供支撑,以洞庭湖水位维持不变为背景,结合地质和设计资料,构建团洲垸临溃口主堤和钱团隔堤非稳定渗流和稳定分析模型,在团洲垸溃口合龙条件下,重点分析应急抽排过程中垸堤内水位极端骤降速率0.3、0.6 m/d工况下,堤防渗透稳定和边坡安全。分析结果表明,各工况下堤防最大渗透坡降和边坡稳定均满足3级堤防规范要求。综合考虑诸多影响因素,提出了相关降速的建议,为应急抢险和二道防线守护等提供了技术支撑;也可为水位骤降条件下堤坝边坡安全分析提供参考。

Under the background of global climate change, extreme hydrological events with increasing frequency pose severe threat to dam safety. Large floods in the Yangtze River Basin, accompanied by levee breaches, occurred in 2016 and 2020. On July 5, 2024, the embankment of Tuanzhou township in Dongting Lake area, Hunan Province, collapsed, endangering the safety of people’s lives and property. To expedite the return of residents to their homes and prevent secondary disasters, early emergency closure measures are typically implemented post-breach. At this stage, with equalized water levels inside and outside the polder, rapid emergency drainage is conducted under breach closure conditions. The impact of sudden water level drops on the safety of the main embankment and the secondary embankment has attracted significant attention, even constraining emergency rescue operations. To assess the effects of emergency drainage on embankment safety in the Tuanzhou polder of Dongting Lake area and aid in the formulation of emergency response plans, we constructed non-steady seepage and stability analysis model for the main embankment and the Qianlianghu-Tuanzhou interval embankment near the breach with Dongting Lake water level remaining unchanged. The analysis focuses on the seepage stability and slope safety of the embankment under extreme sudden water level drop rates of 0.3 m/d and 0.6 m/d during emergency drainage during breach closure. The results indicate that the maximum seepage gradient and slope stability of the embankment meet the standards for third-level embankment safety under various conditions. Additionally, we propose rapid drainage measures in comprehensive consideration of multiple factors to provide technical support for emergency rescue and shed new insights for safety analysis under similar conditions.