The construction of the Vivaceta Tunnel (Santiago de Chile)
The tunnel of Vivaceta is located at Santiago de Chile and has a total length of 525 m, involving also an intermediate shaft, and the crossing under the Mapocho River using a cut and cover tunnel. The tunnel is being excavating in the well-known gravels and pebbles of the second and first deposition of the Mapocho River. At the South side of the river fill materials cover these alluvial. The construction method follows the NATM, in top and benching sequence, using systematically micropile forepoles. The whole tunnel alignment has a very reduced overburden in an urban environment with several surface and subsurface structures, which have required a very strict control of the induced deformations and subsidence during construction.