Ramondini, Massimo

Fallout volcanic deposits of Somma- Vesuvius (Campania, southern Italy), characterized by the presence of layers with contrasting textural and hydraulic properties, are frequently affected by shallow landslides during rainwater infiltration. The soils of the stratigraphic sequence present intra- particle pores, originated by the gases escaped during magma decompression in the volcanic conduit, thus are characterized by double porosity (i.e., intraparticle and interparticle pores), which is expected to affect their hydraulic behaviour, and to play a key role in rainwater infiltration through layered deposits. To understand the effect of double porosity on the hydraulic behaviour of the involved soils, controlled experiments have been carried out in an infiltration column. The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry (TDR) probes, not buried in the investigated soil layers so as to minimize disturbance to the flow, allowing water content measurement during vertical flow processes. Specifically, transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices, both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius, featuring double porosity with different pore size distributions, that were estimated by X-ray tomography and Mercury Intrusion Porosimetry. The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes, mainly related to the different dimensions of intraparticle pores.

Land subsidence due to underground resources exploitation is a well-known problem that affects many cities in the world, especially the ones located along the coastal areas where the combined effect of subsidence and sea level rise increases the flooding risk. In this study, 25 years of land subsidence affecting the Municipality of Ravenna (Italy) are monitored using Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques. In particular, the exploitation of the new Sentinel-1A SAR data allowed us to extend the monitoring period till 2016, giving a better understanding of the temporal evolution of the phenomenon in the area. Two statistical approaches are applied to fully exploit the informative potential of the A-DInSAR results in a fast and systematic way. Thanks to the applied analyses, we described the behavior of the subsidence during the monitored period along with the relationship between the occurrence of the displacement and its main driving factors.