D. Marchetti

DP Test in Geotechnical Characterization of Shallow Landslides Source Area: Results and Perspectives

Aiming at improving the knowledge on the source areas of shallow landslides, this research deals with the geotechnical characterization of the debris slope cover of arenaceous formations, by means of low cost dynamic penetration tests (Dynamic Probing – DP).

Slope Stability Modelling of a Sandstone Cliff South of Livorno (Tuscany, Italy)

This paper will examine a sandstone cliff south of the town of Livorno Italy, between the Rio Maroccone mouth to the north and the Leone cove to the south, in its most dangerous area, between the sea and the main road Aurelia. The aim of this paper is to divide the area into homogenous hazard classes and assess the possible kinematic evolution. The paper refers to an evaluation of parameters that may trigger rock falls on the cliff, which could constitute dangers for tourists. The identification of critical areas has been achieved through the elaboration of landslide susceptibility maps. The geotechnical study was carried out on the Macigno Fm at the site. Field surveys and indirect tests for classifying rock masses and estimating the uniaxial compression strength (UCS) were performed. Some numerical analyses were executed to study the static and dynamic behavior of the slope. The results confirm the vulnerability of the areas, demonstrating the dynamic instability of the analyzed sections and a precarious equilibrium is also in static conditions. These analyses, compared with the site surveys, show poor data and in some cases alarming results; some portions of the cliff are under limit equilibrium conditions or close to it, especially in some of the areas appreciated by tourists and bather. Through the numerical modeling the critical situation of these slopes becomes even more evident, confirmed by some rock falls of small blocks occurred during the geomechanical survey period. To make the situation even worse, the whole area is constantly subject to exogenous agents such as strong winds and the wave action, which determine a rapid deterioration of the mechanical characteristics of strength in the Macigno Sandstone.

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