Transient seepage triggered by rainfall and water level changes has a significant impact on embankment stability. To investigate the effects of rainfall and water level changes on the seepage field of embankments, numerical comparative experiments were conducted based on the Shu River embankment project. The influence of key factors such as rainfall, water level rise and fall rate, and rainfall-coupled water level rise and fall on the internal seepage field of the embankment was analyzed, and the main factors affecting the stability of the embankment slope were identified. The relationship among permeability coefficient, lag rate of the phreatic line, and embankment slope stability factor is explored, and fitting equations are developed. The results show that rainfall infiltration increases the pore water pressure of the soil, leading to a decrease in the effective stress of the soil and a decrease in the slope stability factor. The stability factor of the embankment slope is positively correlated with the rise and fall of the water level, and the faster the rate of rise and fall, the higher the rate of change in pore water pressure. The stability factor of the embankment slope showed a trend of decreasing and then increasing with the decrease in water level, and when the water level had decreased by 70%, the lag rate of the phreatic line was the largest, and the stability factor of the embankment slope was the lowest. The established equations for fitting the stability factor of the embankment slope to the lag rate of the phreatic line can be used as a reference for the safety assessment of similar embankment projects.

Reservoir impoundment induces a large amount of cumulative deformation of landslide body, leading to damage to the geological environment. Due to many yearly cycles of reservoir water fluctuation, the cumulative deformation of landslides tends to be stable, showing a self-adaptive deformation phenomenon. The study of the self-adaptive deformation mechanism is very important for evaluating landslide stability and achieving the safe operation of hydropower stations. To study the mechanism of self-adaptive deformation, two sets of physical models were used to monitor the groundwater, earth pressure, and cumulative deformation of landslide under periodic fluctuations of the reservoir water level. The results showed that the soil consolidation compaction, release of sliding stress, and increase in permeability are the three main factors of the self-adaptive deformation of landslide accumulation. The overall permeability decreased first and then increased, the front permeability increased greatly, and the middle and rear permeability decreased. The main factors that affected the permeability change were deformation and seepage force.