Abstract:

The rise and fall of reservoir water and rainfall cause dynamic changes in groundwater in the Three Gorges Reservoir area. The dynamic rise and fall of groundwater levels is one of the most direct factors inducing the deformation and damage of cataclastic bedding rock landslides. This paper studys the response mechanism of landslide deformation to groundwater and the quantitative relationship among rainfall, reservoir water level, and groundwater level using monitoring data, investigation data from the Muyubao landslide in the Three Gorges Reservoir area over the past 7 years. Research shows that: (1) Groundwater rises and falls significantly earlier than landslide deformation. Predicting groundwater levels from rainfall and reservoir water levels can judgement landslide deformation, which provides a strong basis for landslide warning and forecasting. (2) When the groundwater level in the front of the landslide exceeds the maximum reservoir water level (175m), the deformation of the landslide is affected by the the floating weight-loss effect, and dynamic water pressure gradually increases. (3) The threshold value for rainfall to raise the groundwater level was obtained. Continuous rainfall for 10 days, the rainfall reached 150mm, and the groundwater level in front of the landslide increased by 3.22m-6.88m; when rainfall reached 300mm in 30 days, the groundwater level in the front of the landslide increased by about 10m.(4) From October to December 2017, the groundwater level in the QSK1 borehole on the front platform was as high as 184.2m, nearly 10m higher than the reservoir water level (175m). The landslide displacement in 72 days was 88.5mm. The research results provide theoretical and technical support for monitoring, early warning, disaster prevention and mitigation, reservoir water regulation of bedding rock landslides in the three Gorges Reservoir area.

Key words: groundwater level, rainfall, reservoir water level, cataclastic bedding landslide, deformation mechanism