Metro Santiago - Design and Construction of Shallow Tunnels

In the early year 2000, the Santiago's subway network was comprised of not more than 40 km and 46 stations with only about a half of its network being underground construction, mainly cut and cover boxes. Nowadays, with the additional 17.5 km of new line extensions (Line 1 and 5), the subway network will achieve a considerable expansion reaching a total length of 104.5 km and 108 stations, with over 60 km of shallow mined tunnels and more than 70 underground stations. The construction of the new extensions of Line 1 (3.3 km) to the East and Line 5 to Maipu/West (14.2 km) have started in the beginning of 2007 and are planned to be completed in 2009. The mined tunnel sections of both lines include twelve large shallow underground stations and several intermediate ventilation and emergency exit shafts and tunnels. The present article describes some relevant aspects associated to the design and construction of shallow tunnels for the Metro Santiago and gives an insight into the current ongoing construction works of the new Line 5 extension.