Currently, the destabilization mechanisms of slopes due to rainfall infiltration are not fully understood. We conducted physical model tests to measure displacement and pore water pressure from rainfall, using the data to validate numerical models. This study explores how rainfall intensity and duration affect these measures across loess slopes with varying steepness. The goal is to understand slope responses to different rainfall conditions. Our findings indicate that steeper gradients see modest increases in displacement and pore water pressure at the top and mid-slope, but these increases are more pronounced at the toe. The changes at the toe and mid-slope are driven by infiltrated rainwater volume and soil compressive behavior, while top-slope displacement is primarily due to infiltration. Continuous deformation was observed during and after the rainfall events. Post-rain, pressure from saturated soil at the slope's apex amplifies pore water pressure at the toe, influenced by gravitational forces and retained water pressure. This underscores the complex interactions affecting slope stability in wet conditions. Understanding loess slopes' responses can improve predictive models and mitigation strategies, reducing infrastructure and safety risks in these vulnerable areas.

Understanding the rainfall-triggering mechanisms influencing loess landslides and developing targeted prevention and control strategies are critical challenges in engineering. This study focused on a representative landslide-prone area in Huxian County, Xi'an, China, and field experiments involving artificial rainfall simulations were conducted. Utilizing the annual rainfall statistics for Huxian County, three distinct rainfall scenarios-light, moderate, and heavy-were established. The aim was to explore the correlation between internal pore water pressure and temporal and depth-related changes during the postrainfall stage. At the same time, reflective patches were placed on the slope and total stations were used to monitor the impact of different rainfall intensities on slope displacement. Based on the field data, a three-dimensional simulation validation was executed using Surfer software. Our findings suggest that increasing rainfall intensity directly correlates with higher internal pore water pressure. As the rainfall persisted, the daily amplitude of pore water pressure initially surged before moderating, ultimately exhibiting a logarithmic trend with depth. The effective influence depths of the daily amplitude of pore water pressure during light, moderate, and heavy rainfall stages were found to be 1.6, 2.2, and 5.0 m, respectively. Following cessation of the rainfall, the surface pore water pressure underwent substantial change, and the daily amplitude rapidly declined before stabilizing. Slope displacement consistently increased from the summit to the base throughout the rainfall stages, with the base being most susceptible to sliding instability. The maximum displacement at the foot of the slope was in Columns 3-5, with a maximum displacement value of 1,158 mm. Proximity to the slope's base correlated with greater gravitational and downward forces. Specific maximum displacement values were recorded at different locations along the slope, revealing the most significant changes along the slope's centerline. This work will contribute to the effective management and landslide prevention of loess slopes.

The hydrological response of groundwater to rainfall plays a key role in the initiation of deep-seated bedrock landslides; however, the mechanisms require further investigation due to the complexity of groundwater movement in fissured bedrock. In this study, an active translational landslide along nearly horizontal rock strata was investigated. The hydrological response of groundwater to rainfall was analyzed, using the data from a four-year real-time field monitoring program from June 2013 to December 2016. The monitoring system was installed along a longitudinal of the landslide with severe deformation and consisted of two rainfall gauges, nine piezometers, three water-level gauges, and two GPS data loggers. Much research effort has been directed to exploring the relationship between rainfall and groundwater response. It is found that both the pore-water pressure (PWP) and groundwater level (GWL) responses were significantly influenced by the rainfall pattern and the hydrological properties of the underlying aquifer. The rapid rise and fall of PWP and GWL were observed in the rainy season of 2013 with high-frequency, long-duration, and high-intensity rainfall patterns, especially in the lower of the landslide dominated by the porous aquifer system. In contrast, a slower and prolonged response of PWP and GWL to rainfall was observed in most monitoring boreholes in 2014 and 2015 with two rainstorms of short duration and high intensity. In the lower of the landslide, the peak GWL exhibited a stronger correlation with the cumulative rainfall than the daily rainfall in a single rainfall event whereas the peak groundwater level fluctuation (GWLF) exhibited a strong correlation with API with a half-life of 7 days. In the middle of the landslide, however, relatively lower correlation between rainfall and groundwater response was observed. Three types of groundwater flow were identified based on the recession coefficients of different segments of water-level hydrographs in the landslide area, corresponding to the quick flow through highly permeable gravely soil and well-developed vertical joints in the bedrock, the slow and diffuse flow through the relatively less-permeable bedrock, and the transition between them in the aquifer system.