ABSTRACT
The world's cities today are closed networks of transportation systems, utilities, and residential and industrial buildings. Millions of people live and work in such major cities, often in restricted and congested spaces. In fact, underground spaces have historically been created in urban areas and mainly used to host traffic ways (streets, subways, railways) and public-service utilities (water supply ducts, sewers). In the case of interurban links, long-length tunnels are justified by saving time and reducing costs, maximizing safety and minimizing environmental impacts". Indeed, in an urban environment, it is also necessary to take into account a set of completely distinct elements or factors that frequently influence the choice of the design and construction. Applications of mechanized excavation to other transport systems, which are less frequent today but surely of great interest in prospect, concern the construction of road penetrations and by-passes in urban areas, obviously when they are sufficiently long to justify recourse to mechanized tunnelling.
