Geological-geomorphological characterisation and monitoring activities of a large slope instabilities in Upper Graveglia Valley (Ligurian Apennine, Italy)

摘要

Large slope instabilities is a recent research field with significant implications either for scientific knowledge or
\nfor the most engineering issues.
\nThe landforms and processes recognition that characterize large slope instabilities requires a multidisciplinary
\napproach, from basic geology to applied geomorphology, from thematic mapping to geotechnical engineering.
\nThe new techniques of remote sensing have allowed in recent years a better identification of these large slope
\nphenomena, which can feature different degrees of hazard and risk for the inhabited areas and infrastructures.
\nIn this research we present the geological-geomorphological study and the monitoring activities of the large-scale
\nlandslides on which the villages of Arzeno and Prato di Reppia in Upper Graveglia Valley are settled. This
\nis a well-known territory from the Earth Sciences researchers as the Upper Graveglia Valley is internationally
\nrecognized for its exceptional ophiolitic sequence with its sedimentary covers and for the mining activity.
\nThe Upper Graveglia valley, in the part between the Biscia Pass, Mt. Chiappozzo and the Reppia stream, which
\nincludes the villages of Prato di Reppia, Arzeno and Case Soprane, shows several morphological evidences that
\ncould be linked to a Mountain Slope Deformation.
\nIn the upper sector, remarkable wetlands can be observed in flat areas, which can be associated with trench filled
\nby swampy deposits.
\nFor decades there have been reports of slope instability phenomena in the villages of Arzeno, Prato di Reppia and
\nCase Soprane, which are outlined by several indirect kinematic indicators.
\nAs a result of a project funded by Regione Liguria with the 2015 yearly geohydrological risk mitigation works
\nregional program, drilling activities were carried out to identify the stratigraphic sequence and to set up monitoring
\nnetwork.
\nIn 2015, a first geognostic survey was carried out in the village of Arzeno, characterized by n. 4 boreholes with
\npiezometric cases, which showed a complex stratigraphy and hydrogeology.
\nIn 2016, an extensive geophysical survey was launched in order to properly plan the second geognostic survey
\ncarried out in 2017 and composed by 6 boreholes: n. 2 inclinometer cases were installed (one with robotized
\nsystem) and n. 4 piezometric cases.
\nThe monitoring instrumentation was completed with the installation of a weather station and n. 2 GPS benchmarks,
\nto make a crosscheck of the displacements.
\nThe monitoring activities also included the damage degree of buildings survey by measurement of cracking in
\nfacades and the use of the PSInSARTM displacement rate data delivered by the National Environmental Remote
\nSensing Project.
\nThe field survey and monitoring activities show a complex situation for the studied slope: an evolution of the large
\nslope instabilities in several compartments with different kinematics and hydrogeological set-up is recognized, as
\nwell as a good convergence between satellite, GPS and inclinometric monitoring data