Early warning of fast landslides triggering based on instrumented slope data analysis

The results of laboratory infiltration experiments on instrumented small scale model slopes are presented. Loose granular pyroclastic soils from the mountainous area north-eastern of Napoli have been examined. The experiments aimed to reproduce the simple case of a homogeneous indefinite slope, for a better understanding of the hydraulic processes leading to slope failure. With this respect, useful information was provided by the results of coupled measurements of soil suction and volumetric water content, respectively carried out by minitensiometers and Time Domain Reflectometry. The obtained results indeed showed how soil wetting during rainfall infiltration took place under matric suction values around 5kPa smaller than what could be predicted by equilibrium water retention curves estimated in laboratory. Since steep slopes equilibrium is often guaranteed by cohesion increment due to suction under unsaturated conditions, the obtained result indicates that effective early warning of fast landslides should rely on direct monitoring of soil suction and water content in the field