The valley of the River Marecchia (Northern Apennines, central Italy) is characterised by the presence of competent fractured formations outcropping in isolated and dismembered slabs, overlying argillaceous soils with a prevalent plastic-ductile behaviour. This particular geological situation has favoured in the past the construction of castles, strongholds and villages since from their privileged strategic position they could better control the communications and movements at the bottom of the valley. Nevertheless, the superimposition of geological formations characterised by extremely different mechanical parameters has determined the activation of several mass-movements, which for many centuries have threatened the stability of these urban centres. Most of these landslides, which had previously been interpreted as surficial movements, have now been ascribed to deep-seated gravitational deformations, thanks mainly to new evidences deriving from detailed field and laboratory data. In fact, the presence of numerous geomorphological elements, such as sagging of the rigid slabs' central parts along structural discontinuities and bulging of the ductile substratum, lead toward this interpretation. In this paper the slabs of Pennabilli and San Leo are being considered, since on them two of the most important historical towns of the valley are placed. The situations studied correspond to two different kinds of slabs: Pennabilli belongs to a tabular-type slab, whilst San Leo is ascribable to an arcuate-type slab. Moreover, both cases differ not only for the structural elements but also for the characteristics of the substratum. The two slabs are interested by dense fracture network systems that control their dismemberment and the kinematics of the mass-movements, with different patterns of evolution according to the diversity of the structural elements and of the clayey substratum. In particular, the relationships between the mineralogical and geotechnical properties of the substratum, the structural characteristics and the evolution of the landslides have been investigated. On these sites, monitoring systems have also been installed and consolidation and upgrading works have been enterprised. Notwithstanding this, the interventions carried out so far have not solved the problems related to slope movements, that by now involve a large number of buildings, since they were not based on a correct and thorough interpretation of the instability causes.
|Data di pubblicazione:||1993|
|Titolo:||Some cases of landslides affecting urban areas in the Marche (central Italy)|
|Autori:||Conti, Stefano; Tosatti, Giovanni|
|Data del convegno:||7-11 February 1993|
|Nome del convegno:||Environmental Management|
|Luogo del convegno:||Wollongong (AUS)|
|Titolo del libro:||Environmental Management: Geo-Water and Engineering Aspects|
|Appare nelle tipologie:||Relazione in Atti di Convegno|
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