Evolution of Design and Construction Approaches in the Field of Tunnelling: The Results of Applying ADECO-RS When Constructing Large Underground Works in Urban Areas

Abstract In the last 25 years in Italy, over 1000 km of tunnels have been constructed in urban and extra-urban areas. Despite being constructed in very complex and difficult grounds; generally these were completed (from the design stage to the construction and actual opening of activity) with industrial methods, and within the technical times and costs foreseen by the design laid out by the tenders. This extraordinary result has been made possible since the public administrations have adopted modern design and construction approaches in their contract specifications, based on strictly scientific criteria and which leave nothing to the typical vagueness of those design and construction systems from the twentieth century, which remedied cavity instability solely by means of partitioning the excavation face. Today we know that full-face advancement is all the more necessary the more difficult the excavation conditions are. Memory serves to illustrate the criteria that helped define modern design and construction concepts and an example of their application for constructing a great twin tunnel (258 m2 + 258 m2 in section) in the urban area of Rome.