ABSTRACT
In unsaturated shallow deposits, rainfall infiltration is the most common cause of landslides. This paper focuses on landslides involving coarse-grained soils and, in particular, analyses the mechanisms that cause the evolution of slides into flow-slides. This study provides an alternative explanation for the initiation of these phenomena, suggesting that they may result from a combination of two unstable processes: the first occurring when the soil is still in the unsaturated regime, the second taking place when full saturation is reached. This hypothesis is based on the analysis of the numerically observed response of an ideal infinite slope to rainfall events. Beyond illustrating the initiation of the unstable process, the study investigates its causes and provides an analytical criterion for capturing the onset of the instability and monitoring local slope stability.
