Gibraltar Strait Tunnel • Spain - Morocco

The Gibraltar Strait Tunnel represented a big challenge in underground engineering, both from the design and from the technological point of view. It is a highly complex engineering work that had no precedent in the world as regards the depth at which the tunnels will be excavated: between 400 to 500m beneath the sea level, with 100-150m of overburden at the deepest location. The exceptional magnitude of the Gibraltar Project imposed feasibility limits for the available technology in terms of potential hydrostatic pressures to be encountered by the tunnel boring machines.

Owner/Client:   SECEG (Spain) – SNED (Morocco)
Cost of works:   US$ 5,000 to 6,000 million (estimated)
Period of Activity:   2006 - 2007
Project Description:   The project includes a 38.7km-long twin tunnel linking Spain to Morocco, out of which 28km will run below the sea, with an intermediate safety/service tunnel, similar to the well-known connection under The Channel. Recent investigations highlighted the presence of two deep (more than 600m under the sea level) paleo-channels intersecting at two locations the selected tunnel alignment, which are filled with deposits of clayey breccias, of flysch origin. The geological and hydro-geological conditions along the route still represent a source of uncertainty, despite the extensive investigations already done. The railway tunnel will carry both passenger and goods trains, as well as high-speed and special trains.
Description of Services:   Updating of the “APP-Avant Projet Primaire” - preliminary design – and preparation of the Environmental Impact Study.