Use of GIS Techniques in the Study of Land Stability

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By Carmela Buono

In the Emilian Appennines of northern Italy there was a great deal of excavation work done to make space for high-speed railway tunnels from 2002 to 2007. This site for excavation is located in the Pianoro territory which is highly known for hydro-geological instability due to shallow soils. A study was conducted to observe and analyze the causes of instability in this area which caused property damage after a landslide occurred. Primarily, this study used archived aerial survey photographs to confirm geotechnical stability.

The creation of the high-speed railway included three tunnels which all connected. During this excavation there was a large landslide that damaged three facilities located on the Emilian Appennines hillside. The instability of the land was at too large of a scale for individual scientists to examine so the use of GIS science was introduced to the project to help get a better spatial understanding of the cause of the instability that led to the landslide. Since the area is historically known for being naturally unstable due to the soil types naturally occurring, there was still the question as to whether this landslide was the result of more than just natural causes. The excavation caused a great deal of stress on the landscape and the exact effects of the disturbance are not known. Instead, evidence from historical photogrammetry and digital surveys allowed for analysis to be performed.

Surveys were performed in 1998, 2004, and 2007 using archived multi-temporal digital photographs with an average scale of 1:8,000. Black and white stereo pairs for each survey were created and scanned with a Wehrli Raster Master RM2 to document them and digital images were also created with a ground resolution of about 9-10 cm. Using GPS methodology, the points of focus for the surveys were confirmed. The data matches the time frame from which the damage began, the excavation of the tunnels began, and overall helped to show that the hillside increased in vulnerability due to the increased stress on the landscape. Using digital aerial photographs, the damage and displacement of the three facilities was monitored. The final result used the roof tops of the buildings to identify the displacement directions of the landslide and indicated that the excavation was linked to the unstable ground.

3D representation of automatic DEM of the studied area (the black dots indicate the damaged buildings).

3D representation of automatic DEM of the study area (the black dots indicate the damaged buildings).

References:

Achilli, V., Carrubba, P., Fabris, M., Menin, A., & Pavanello, P. (2015). An archival geomatics approach in the study of a landslideApplied Geomatics7(4), 263-273.

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