The Assisi landslide monitoring: a multi-year activity based on geomatic techniques
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ORIGINAL PAPER
The Assisi landslide monitoring: a multi-year activity based on geomatic techniques Guido Fastellini & Fabio Radicioni & Aurelio Stoppini
Received: 23 April 2010 / Accepted: 29 December 2010 / Published online: 29 January 2011 # Società Italiana di Fotogrammetria e Topografia (SIFET) 2011
Abstract A wide area of the Assisi town, in Umbria (central Italy), is interested since its first edification (1950–1960) by an extensive landslide. The rate of motion is very slow (around 1 cm/year), but the deformations accumulated for almost 60 years have produced considerable damage to many private and public buildings, including the civic hospital and an important Franciscan monastery. The University of Perugia established in 1995 a geodetic monitoring network over the Assisi landslide, connecting a number of control points inside the moving area to an external reference network with markers placed on stable geological formations. The monitoring has been based since the beginning on GPS satellite positioning with static observations, aiming to obtain a three-dimensional accuracy of about 1 cm level. From 2001 onwards, GPS+GLONASS receivers have been used for all measures, and more control points have been added in 2006, for a better description of the field of movements. Since 1999, a high precision levelling network has been set up over the landslide area, in order to improve the accuracy of the height component, increasing its monitoring sensitivity to a few millimetre level. During the years, observation campaigns have been repeatedly performed on both networks, accumulating a consistent and increasing quantity of data. Such database permits to carry out a series of analyses (coordinate time series, annual and accumulated displacement vectors, deformation velocity and deformation field) leading to a better comprehension of the landslide phenomenon and its evolution, helpful for the design of technical interventions. G. Fastellini : F. Radicioni : A. Stoppini (*) DICA, Università degli Studi di Perugia, Via G. Duranti 93, 06125 Perugia, Italy e-mail: [email protected] URL: http://labtopo.ing.unipg.it
Keywords Landslide . Deformation monitoring . GPS . GNSS . Precision levelling
The Assisi landslide The landslide under research interests a urban area of Assisi town, whose edification started in the years 1950–1960, as a planned expansion towards East of the historical town centre. The area is located on a slope (average inclination 21%) where no signs of motion where noticed at the time of the first building activity, albeit no in-depth analysis was performed. The urbanization of the area caused relevant changes to the flow regimen of the surface waters, deviating and in some cases closing existing ditches and streams. Around 1970, the first phenomena connected with an active landslide started to show, in the form of growing damage to buildings (initially attributed to local foundations failures), but also retaining walls, pipelines and street paving. From then on, the area was thoroughly investigated from a g
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