Proyecto y construcción del túnel de Guadarrama

The article describes the background of this tunnel right up to the adopted solution of a 28.4 km base tunnel under the Sierra de Guadarrama. The design consists of two independent tubes with an 8.50 m internal diameter, spaced 30 m between centrelines and with cross passages. The tunnels pass through igneous and metamorphic rock formations, predominantly formed by gneiss (62%) and granites (23%) and entail numerous structural problems due to the tectonics of the area. The tunnels will be bored by 4 "double shield" tunnelling machines and the assembly of the TBMs has recently been started and the main tunnel is now expected to be completed in 2005.