The destabilization mechanism of loess landslides induced by intermittent rainfall: from laboratory tests and field application

To explore the triggering mechanism and disaster process of loess landslides under intermittent rainfall, this study focuses on a loess landslide in the Ili River Valley in Central Asia and employs physical model test and microscopic testing methods to investigate the destabilization mechanism of intermittent rainfall-induced loess landslides. The research findings reveal the following: The deformation evolution of loess landslides triggered by intermittent rainfall primarily unfolds in three stages: the expansion of surface fissures, followed by surface runoff and foot-of-slope erosion, culminating in sudden landslides precipitated by a sharp rise in pore water pressure. As rainfall infiltrates, fine particles in the upper soil layer migrate downward through pores, coalesce, and form pore throat blockages. This leads to a sustained increase in pore water pressure within the slope that cannot dissipate, generating excess pore water pressure and thereby reducing effective stress. Ultimately, as the eroded zone at the slope toe continues to expand, the stress imbalance culminates in sudden landslide initiation. By comparing physical model monitoring data with field observations, it is evident that intermittent rainfall triggers a sequence in earthen slopes: fluctuating moisture content increases - cumulative rise in pore water pressure - non-linear acceleration of landslide deformation. This process diminishes slope stability, precipitating landslide disasters. Moreover, the deformation exhibits hysteresis, significantly influenced by the time required for moisture infiltration. This study provides a theoretical foundation and scientific basis for the monitoring, early warning and prevention of loess landslide disasters triggered by intermittent rainfall.