Triggering mechanism and reactivation probability of loess-mudstone landslides induced by rainfall infiltration: a case study in Qinghai Province, Northwestern China

Rainfall, especially rainstorm, is a major factor in inducing loess-mudstone landslides and plays an essential role in landslide reactivation. The aim of the paper is to study the triggering mechanism and reactivation probability of a loess-mudstone landslide induced by rainfall infiltration in Qinghai Province, Northwestern China. According to the numerical model of elastic–plastic mechanics, the triggering mechanism of loess-mudstone landslides was revealed. Then, the reactivation probability of the potential landslide was evaluated by the combination of the limit equilibrium and Monte-Carlo methods. For one thing, the relationship between water content and shear strength of media was analyzed based on the mechanical test of materials. For another, the effects of rainfall conditions were analyzed on the distribution of water content in the aerated zone with the two-dimensional coupling model of unsaturated–saturated seepage. The results show that the shear strength of media is very sensitive to water content because of water–rock interaction including hydration and dissolution. Besides, the water content significantly increases at the interface between the loess and mudstone after the rainstorm occurring owing to the permeability heterogeneous of media and topographic feature, which leads to the strength deterioration. Although the whole landslide is stable in the rainstorm conditions, its middle part can be reactivated along the original sliding zone with high probability by a geomechanical model of sliding-tension. Therefore, the landslide reactivation is controlled by the water sensitivity of media, the permeability heterogeneous of media, the topographic feature and the original sliding zone, especially the original sliding zone. This research provides a valuable reference for the occurrence and reactivation of similar landslides.