engleski

Importance of the unsaturated zone in landslide reactivation on flysch slopes: observations from Valići Landslide, Croatia

Field investigations and back-analyses of (re)activated landslides in the Rječina River Valley indicate prolonged intense rainfall and the rise of the groundwater table, often to the slope surface, which are common prerequisites for the occurrence of landslides in the valley. However, previous studies have never considered the transient process of rainfall infiltration in the unsaturated zone of the slope, quantified the infiltrated volumes, or determined its effect on the stability of a slope over time. This study presents a numerical model capable of determining the transient pore-water pressure distributions on a flysch slope subjected to a realistic rainfall event and how rainfall affects the stability condition over time. This investigation presents a case study of the Valići Landslide that was reactivated on 13 February 2014 after several months of intense, mostly uninterrupted rainfall. Under certain constraints and working assumptions, 10-min rainfall data collected at the site are used to study the hydraulic response of the slope during 167 days of the simulation, as well as the changes in the slope that led to the reactivation event. The results obtained quantitatively confirm rainfall duration to be a crucial factor in landslide reactivation. On the other hand, an analysis performed using synthetic rainfall data suggests that the time required to reach failure remained unaffected for rainfall intensities greater than 8 mm/day. This study suggests that the unsaturated zone plays a crucial role in maintaining the stability of a slope during prolonged rainfall, with a strong correlation between the antecedent rainfall and time to failure.

Deep-seated landslides, flysch deposits, rainfall infltration, slope stability analysis, unsaturated soil

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