The “A12—Tor dè Cenci” Motorway: Geological Reference Model and Design Solutions in Presence of Soft Soils

Abstract

The link that connects the A12 “Roma-Civitavecchia” with the “Roma (Tor de ‘Cenci)—Latina” motorway (today designed but not built) is a road infrastructure of considerable size and importance. It needs a very detailed Geological Reference Model, defined in each design phase through the analysis of numerous geological surveys and site investigation data. In the preliminary phase of the plan we found very useful to keep account of the considerable amount of data concerning the area surrounding the designed motorway. At a later stage we realized a very detailed geological survey and site investigation activity, especially referred to the scale of the main viaducts. This study has allowed us to define the sequence of the different lithofacies and their geometric relationships. The presence, in the subsoil, of highly deformable organic soils, with peat layers, characterized also by a low shear strength, has influenced the design solutions. In fact, throughout the development of the road axis, different interventions were used with the aim to reduce the settlements of the road body. So, the study of the plan was marked by the reduction of the applied load, kee** as low as possible the project level and the height of the embankments. At the same time it was necessary to design some embankments providing the use of very light materials (expanded clay, Polystyrene) and particular solutions for the foundations design of the main bridges and viaducts.