A. Pochini

Zoning and Mapping Landslide Hazard in the Castelnuovo di Garfagnana Region (Tuscany, Italy)

ISPRA and Tuscany Region Administration recently funded a project aimed at assessing and mapping landslide hazard of the area of the n. 250 “Castelnuovo di Garfagnana” map (1:50,000 scale). The area includes the upper Serchio River basin (Tuscany, Italy) and exhibits peculiar geological and geomorphological features and severe climatic conditions, which cause high landslide hazard. The project proceeded as follows: 1:10,000 geomorphological survey and landslide inventory map; Physical and mechanical properties of rocks (discontinuities, strength, rock mass classification) and soils (grain size, consistency); GIS oriented organization of the spatial distribution of the considered factors; GIS supported statistical analysis (spatial analysis, conditional and multivariate analyses, neural network technique); Landslide hazard map, where landslide hazard is subdivided into five classes based on instability probability; Final products: landslide hazard map at 1:50,000 scale, together with other related maps (landslide map, structural sketch, geotechnical sketch, isohyet map, etc.); explaining booklet; database.

Processi gravitativi di instabilità in rocce molto fratturate: il metodo alle differenze finite in un caso applicativo nella provincia della Spezia

The Marinasco-Strà village is involved in wide instability phenomena in rock masses, determining a high landslide risk. In this area a geological-technical, kinematic and geomechanical characterization of the landslides and rock masses was carried out. Moreover, a monitoring system concurred in collecting important data on rainfall, piezometric response and deformation of the slopes. This integrated approach allowed the realization of a model of the landslide mass, regarded as a multiphase system and based on the physical-mechanical characterization of soil and rock. The determination of the state of stress and deformation and the location of actual or possible zones of failure inside the slope were among the main aims. In particular, the finite-difference method was applied, in order to estimate the stressstrain response of the slope to the variations of tensional state; in fact, this method fits better the instability phenomena in intensely fractured rock masses. A deformation model, consistent with the results of the investigations, was performed. In the analysed model, the shear strain concentrates along the main discontinuities deriving from plastic deformation of the mass causing the slope failure. Key terms: landslide, DGSD, numerical modelling, La Spezia, northern Apennine Termini chiave: frana, DGPV, modellazione numerica, La Spezia, Appennino Settentrionale