Since 2008, the water level of the Three Gorges Reservoir has been periodically fluctuating between 175 and 145 m. The rise and fall of the reservoir water level result in changes in the seepage field in the slopes on both banks of the reservoir. Groundwater is an important factor affecting the stability and reactivation of landslides. Developing a method to accurately determine the location of the groundwater saturation line is crucial to the evaluation and prediction of landslide stability. In this paper, the phreatic line under the condition of steady seepage is used as the initial value for unsteady seepage, and the analytical solution for the phreatic line on the bank’s slope under the action of reservoir water level changes is mainly modified based on two assumptions about the rate of change in the reservoir water level and the slope of the bank. In addition, through a large number of indoor tests, the relationship between the water yield, the permeability coefficient, and the porosity of the landslide in the Three Gorges Reservoir area is studied in detail, and a formula for the water yield of a soil–rock mixture is proposed. Finally, the modified analytical solution is used to determine the phreatic line in the Shiliushubao landslide, and the results are compared with the numerical analysis and monitoring results. The results show that the modified analytical solution is closer to the actual situation of the phreatic line in the reservoir water level fluctuation zone.

2008年以来，三峡水库水位在175～145m之间周期性波动。水库水位的上升和下降导致水库两岸边坡渗流场发生变化。地下水是影响滑坡稳定性和再活化的重要因素。开发一种准确确定地下水饱和线位置的方法对于滑坡稳定性的评估和预测至关重要。本文采用稳态渗流条件下的潜水线作为非稳态渗流的初始值，水库水位变化作用下的岸坡潜水线解析解主要基于水库水位变化率和岸坡坡度两个假设进行修正。此外，通过大量的室内试验，详细研究了三峡库区滑坡的产水量、渗透系数和孔隙度之间的关系，并给出了土壤产水量的公式——建议使用岩石混合物。最后利用修正解析解确定了十六树堡滑坡的潜水线，并与数值分析和监测结果进行了对比。