|
Alessandro Pasuto, IRPI-CNR (Italy)
Kazunori Fujisawa, PWRI-MLIT (Japan)
Gianluca Marcato, IRPI-CNR (Italy)
Kei Higuchi, PWRI-MLIT (Japan)
|
|
A deep seated movement is located on the left flank of the Tagliamento River valley some 50 km NW of Udine (Eastern Italian Alps). The slope of Mt. Tinisia involved in the landslide is mainly constituted by dolomitic and calcareous Triassic formations underlying a thick Quaternary cover made up by morainic and scree slope deposits. The landslide can be defined as a rotational rock-block slide with a sliding surface at a depth of more than 200 m. It develops from an altitude of 1200 m a.s.l. to the Tagliamento river bed at 600 m a.s.l. The possible damming of the valley is a serious threat. The mass movement involved a road tunnel that is going to be finished and the N.R. 52. For this reason the evolution of the phenomenon is of paramount importance for the local communities and for the Friuli-Venezia Giulia Region which is going to fund the monitoring activity. Due to this high-risk situation the Civil Defence Department has already made some investigations using conventional techniques (e.g. inclinometers, LIDAR surveys, TDR, Ground Based InSAR, topographic and GPS networks). The results highlighted displacements of several centimetres per year. Moreover, after a geomorphological analysis based on aerial photograph interpretation and detailed fieldwork, a wide instability involving the entire flank of Mt. Tinisia has been detected. From the data collected and the study of the stratigraphic sequence, it appears that the slope was interested by mass movements since the retreat of the Wurmian glaciers: in fact the course of the Tagliamento River is diverted by a huge post-glacial landslide deposit.
Finally, in order to assess the hazard of the whole area an innovative monitoring system, based on optical fiber sensing technology with early warning purposes has been designed. This technology, employing Brillouin optical time domain reflectometer method, allows continuous measurements over long distances. This is extremely useful when the areas to investigate are huge and risk location is difficult to determine in advance.
|
