Event Scenario Analysis for the Design of Rockslide Countermeasures

The Torgiovannetto quarry(Assisi municipality,central Italy) is an example of a site where the natural equilibrium was altered by human activity,causing current slope instability phenomena which threaten two roadways important for the local transportation.The quarry front,having a height of about 140 m,is affected by a 182,000 m3 rockslide developed in intensely fractured limestone and is too large to be stabilized.In 2003 some tension cracks were detected in the vegetated area above the quarry upper sector.From then on,several monitoring campaigns were carried out by means of different instrumentations(topographic total station,extensometers,inclinometers,ground-based interferometric radar,laser scanner and infrared thermal camera),allowing researchers to accurately define the landslide area and volume.The latter's major displacements are localized in the eastern sector.The deformational field appears to be related to the seasonal rainfall.The landslide hazard associated with the worst case scenario was evaluated in terms of magnitude,intensity and triggering mechanism.For the definition of the possible runout process the DAN 3D code was employed.The simulation results were used in order to design and construct a retaining embankment.Furthermore,in order to preserve both the safety of the personnelinvolved in its realization and of the roadways users,an early warning system was implemented.The early warning system is based on daily-averaged displacement velocity thresholds.The alarm level is reached if the prediction based on the methods of Saito(1969) and Fukuzono(1985) forecasts an imminent rupture.

Monitoring Landslide-Induced Displacements with TerraSAR-X Persistent Scatterer Interferometry (PSI): Gimigliano Case Study in Calabria Region (Italy)

This work provides a detailed detection of landslide-induced displacements at local scale on Gimigliano site (Italy), by means of PSI (Persistent Scatterers Interferometry) analysis, exploiting TerraSAR-X data acquired in November 2010-October 2011. In February-March 2010, several landslides affected Gimigliano, following high-intensity precipitation, and causing damages to structures and roads. In order to assess any spatial and temporal patterns of deformation, the present X-band PS data were compared with historical motion rates derived from ERS1/2 and ENVISAT satellites, and with geological and geomorphological evidences resulting from auxiliary data such as landslide databases and orthophotos referred to different dates, finally validated with recent field checks. The PSI analysis of the historical ground motion rates highlighted that the modern built-up area located downhill was already affected by surface ground deformation since 1993. A significant enlargement of the instability phenomena is detected across time. The recent PS data analysis and the in situ observations permitted us to accurately update the ground movements in the investigated site: their evidence allowed assessing a reactivation of the large deep-seated landslide zone on which the new urbanized area had built-up, with an average deformation rate of about 8 - 9 mm/yr. The higher instability phenomenon is affecting the eastern part of Gimigliano old village, with a mean displacement velocity reaching up values of -30 mm/yr, in the radar temporal acquisition of only 10 months. These outcomes can be taken into account for further hazard-reduction analysis and to support risk mitigation design within the investigated area.