3D geo-mapping based on surface data for preliminary study of underground works: A case study in Val Topina (Central Italy)

This paper reports a geological modelling procedure suitable for the reconstruction of three-dimensional models and for applications in preliminary tunnelling studies. The geological modelling is based on field survey data stored and organized in a database using a Geographic Information System (GIS) and then exported in a Computer Aided Design (CAD) software system, which is used to create the geometrical model. The main steps of the elaboration are: 1. reconstruction of the Digital Terrain Model; 2. calculation of elevation for the 2D geological data; 3. reconstruction of geological cross-sections oriented perpendicular to the geo-structural (fold) axis (geological profiles) by means of down-plunge projection; 4. modelling of the geological surfaces via NURBS interpolation. A model built in this way can be used to automatically create sub-horizontal geological cross-sections at tunnel level or vertical cross-sections along the alignments in order to define accurately the geo-lithological characteristics along each underground segment during excavation and to calculate the segments lengths in every geological formation along the tunnel. The authors delineate the procedure through a simple, and yet exhaustive, case study carried out in order to choose the optimal path for the Foligno-Nocera Umbra railway (mainly in tunnel) to be realised in Val Topina (Umbria Region, Italy). (c) 2008 Elsevier B.V. All rights reserved.