GeoActa Special Publication 1
2008
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GeoActa
an international Journal of Earth Sciences
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Francesca De Rienzo, Giuseppe Nardi
Dipartimento di Scienze della Terra, Università Federico II, Largo S.Marcellino, 10, 80138 Napoli, Italy.
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New geological data on the subsurface of Turin city centre derived by high-resolution stratigraphic analysis
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Abstract
The aim of this paper is to present the geological results of a stratigraphic analysis based on subsurface data concerning the subsurface of Turin urban area (Northern Italy), as a technical support during the underground opera project.
The analysis of about 400 stratigraphic description from boreholes has led up to achieve a geological three-dimensional model of subsurface stratigraphy in the Turin urban area, showing the spatial distribution of Pliocene to Quaternary sediments (from the bottom: Pliocene marine sands, Villafranchian clays and gravel lenses, Quaternary alluvial sediments).
The alluvial sediments are characterized by a marked variability in cementation. A spatial distribution of the cementation has been performed by means of the identification, in the alluvial horizon, of three classes: C1, C2 and C3 (poorly-, medium- and highly-cemented sediment). The cementation classes have been defined through description of existing boreholes and in-field tests, and testified by the different geotechnical parameters coming from newly performed data (laboratory test and a back analysis carried out on monitoring measures). The resulting 3D-geological and geotechnical model has been managed by a Geographical Information System, and recently applied to engineering studies carried out in the Turin city to evaluate i) the value of surface settlements during excavation of the metro line, ii) the effect on the building stability, due to the intersection of the metro line and the railway junction below the city surface, iii) sites along the metro route where sediment consolidation treatments are required to avoid surface settlement due to the tunnel excavation.
Keywords: Turin, 3D-geological model, Cementation, Urban Geology.
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