Estimation of the residual strength of the soil on the landslide sliding surface is essential for analyzing reactivated landslides. This study investigated the influence of over-consolidation ratio (OCR) and shear rate on the residual strength of SM-type (silty sand) landslide soils in the Three Gorge Reservoir using ring shear tests under drained conditions. A series of ring shear tests were conducted to measure the drained residual strength under over-consolidation ratios of 1–12 and shear rates of 0.06–30.00 mm/min. Test results showed that residual strengths of SM-type landslide soils were not affected significantly by the over-consolidation process. The effect of shear rate on residual strength did not exhibit a regular pattern at shear rates of 0.06–10.00 mm/min, and behaved negatively at a high shear rate of 30 mm/min. The reduction in residual strength at higher shear rates may be attributable to increases in the water content of the shear zone and the amount of finer particles, due to particle breakage and/or larger grains being pushed from the shear zone.

Landslide hazard prediction for the Three Gorges area is necessary for mitigating geohazards, especially under extreme rainfall conditions. A method for calculating rainfall in the extreme rainfall return period was first proposed. Then, geological conditions of the Baishuihe landslide on the reservoir shore were modelled, along with soil parameters. Four geological profiles were chosen, and the phreatic line of the landslide was simulated in the SEEP/W programme. The profiles were then divided into slices, and, the long-term stability and failure probability of each slice was calculated using the uncertainty of the soil parameters and the Monte Carlo method. An Empirical Bayesian Kriging (EBK) method in ArcGIS was used to obtain a hazard distribution map for the landslide’s active area and the deeper landslide. The standardized extreme rainfall for different return periods were then used to predict the hazard of the active area and determine the relationship between the unstable area within the active area and the rainfall return period. The stability of the Baishuihe landslide shows a periodic trend and a strong relationship with the reservoir water level and the rainfall distribution, while the stability of the deeper landslide is less affected. With an increase in the rainfall return period, the unstable area of the active area expands. The ratio of the unstable area in the active area and the rainfall return period show a logarithmic correlation. This paper solves the standardization problem of rainfall return period in the field of geological hazards, and realizes the visualization of local stability in the landslide area, which can promote to enhance the ability of preventing and controlling landslide hazards.