库水升降及降雨引起库岸地下水动态变化,地下水动态升降是顺层碎裂岩质滑坡变形破坏的直接诱发因素之一。通过三峡库区木鱼包滑坡近7 a监测数据、勘察资料等,研究了降雨、库水位与地下水位之间的定量关系,以及坡体变形对地下水的响应机制。研究表明:①地下水升降明显先于坡体变形,由降雨和库水位来预测地下水位,可进一步判断坡体变形情况,这为滑坡预警预报提供了有力依据。② 当坡体前部地下水位超过最高库水位(175 m)时,坡体变形在浮托减重效应影响下,动水压力作用逐渐增强。③获得了降雨抬升地下水位的阈值,持续降雨10 d降雨量达150 mm,坡体前部地下水位抬升3.22~6.88 m;30 d内降雨量300 mm,坡体前部地下水位抬升10 m左右。④2017年10—12月,前部平台QSK1钻孔地下水位高达184.2 m,比库水位(175 m)高近10 m,72 d坡体位移量为88.5 mm。该研究成果为库区顺层岩质滑坡监测预警、防灾减灾和库水调度提供理论支撑。

[Objective] Since the impoundment of the Three Gorges Dam in 2003, many cataclastic bedding landslides in the reservoir area have been reactivated due to the influence of external factors such as reservoir water level fluctuations, variations in groundwater levels, and rainfall. These landslides are typically large in scale, exhibit complex deformation mechanisms, and pose significant challenges for early warning and disaster prevention. This paper attempts to establish an interaction model linking rainfall, reservoir water, and groundwater with groundwater as the main triggering factor of landslide deformation, and to further reveal the dynamic migration patterns of groundwater under the coupled effects of reservoir water level fluctuations and rainfall. [Methods] The study took the Muyubao Landslide, a cataclastic bedding landslide in the Three Gorges Reservoir area, as a case study. By integrating data statistics with field investigations, a statistical analysis was conducted on nearly seven years of manual and automated monitoring data, field investigation materials, and hydrometeorological information to investigate the quantitative relationship among reservoir water level, rainfall, and groundwater level, as well as the interaction between groundwater level and slope displacement and deformation. [Results] The research results indicated that: (1) A groundwater level of 175 meters at the front platform of the slope served as the critical threshold for the initiation of landslide deformation. When the groundwater level at the front platform approached 175 m, deformation began under the influence of buoyancy-induced weight reduction. When the groundwater level at the front platform exceeded 175 m, both buoyancy-induced reduction and dynamic water pressure acted on the slope, with the effect of dynamic water pressure intensifying as the groundwater level rose.(2) Statistical analysis of monitoring data revealed thresholds for rainfall-induced groundwater level rise. Ten consecutive days of rainfall totaling 150 mm increased the groundwater level at the front of the slope by 3.22 m to 6.88 m. In the case of 300 mm of cumulative rainfall within 30 days, the groundwater level at the front of the slope increased by approximately 10 m. A “lag effect” was observed in groundwater response to rainfall, typically lasting 3 to 13 days.(3) From October to December 2017, rainfall occurred on 27 out of first 32 days, totaling 310.6 mm. As a result, the groundwater level in borehole QSK1 at the front platform of the slope rose to 184.2 m, nearly 10 m above the highest reservoir water level (175 m). Over the 72-day period, the slope displacement totaled 88.5 mm. [Conclusion] (1) Groundwater level fluctuations significantly precede slope deformation. Given known reservoir water levels, it is possible to forecast groundwater level based on reservoir water level and rainfall data, and further predict slope deformation based on the groundwater level. This approach provides a strong basis for landslide early warning and prediction.(2) The effective contribution of rainfall to groundwater recharge varies with different types of rainfall. Compared to intense rainstorms, prolonged and continuous rainfall causes a more significant rise in groundwater levels, especially around periods of high reservoir water levels, posing greater risks to slope stability. Therefore, in landslide disaster prevention, the role of rainfall and groundwater should be carefully considered. It is crucial to optimize the layout of monitoring points, enhance real-time automated groundwater monitoring capacity and service quality, and better understand the impact of groundwater dynamics on slope deformation.