Buenos Aires, Argentina, is expanding its metro network. Some 17 km of new tunnels have been excavated between 1998 and 2009, and some 20 km are scheduled for construction in the near future. Many major improvements have been implemented during these years in the fields of design and construction procedures of NATM tunnels. Some of the achievements and lessons learned are described in this paper, including: characterization of Buenos Aires soils for the numerical modeling of NATM tunneling, description of the design and construction procedures in use and some comments on the observed ground behavior during construction. The paper is an update of (Sfriso 2008).
