María de Molina Tunnel joins Paseo de la Castellana and Velázquez Street with the N-II highway (Madrid - Barcelona) is the largest municipal underground work in Spain. The tunnel is 2171 meters long and it wills absorbe traffic of 30000 vehicles going out every day.
The initial part of the tunnel has been designed as false tunnels made with foundation walls and slabs. The concrete has been cast over the ground and the tunnel has been excavated afterwards in order minimize the effect of the work on Madrid traffic. Once a sufficient depth has been reached, two different construction systems have been proposed, depending on the conditions the tunnel finds in each case.
The project presents some singular points in which the solutions adopted are structurally extraordinary.