The Guadarrama Tunnel is the longest railway tunnel in Spain and the fifth longest railway tunnel in the world. It is a railway tunnel across the Sierra de Guadarrama, along the high-speed route Madrid–Valladolid in Spain.
The tunnel has two tubes. The western tube is 28,407 m long and the eastern tube 28,418 m long. The twin-tube tunnel passes through the Sierra de Guadarrama Mountain range, about 45km north of Madrid.
The tunnel is used by the AVE high-speed trains travel at a maximum speed of 310km/h. The journey time between Madrid and Segovia is reduced to just 22 minutes with the use of Guadarrama tunnel. The travel time between Madrid and Valladolid is reduced to just 55 minutes.
Detailed geological mapping was conducted to evaluate the rock mass before the tunnel construction. The rock mass excavated for the tunnel contained crystalline rocks such as granite and gneiss.
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