The Tunnel under the Strait of Gibraltar it is an ambitious project, discussed for decades, which aims to connect Europe to the African continent. If on paper the two continents seem very close, the geological reality tells a different story: between seabeds that descend to over 400 meters and unstable terrain, creating this connection is a very complex engineering challenge. However, a work of this magnitude has never gone beyond the theoretical phase, held back by technical difficulties, high costs and political implications. Here is the history of the project and the obstacles that have held it back since the 1930s.
The idea of a connection between Europe and Africa
From a design point of view, the underwater tunnel should extend for a length of between 38 and 40 kilometersreaching a depth greater than 400 meters: a choice dictated by the geological conformation of the area. Numerous proposals have been put forward over the years. The first project, conceived by the Spanish government, dates back to 1930but almost immediately encountered enormous engineering obstacles. In fact, feasibility studies revealed that the seabed was composed of extremely hard rocksimpossible to penetrate with the technologies available at the time. To try to get around the problem, the possibility of building a prefabricated tunnel to be placed on the seabed, composed of modules connected to each other and stabilized by sturdy anchoring cables. This idea, however, was soon shelved.
The Tunnel project under the Strait of Gibraltar today
In March 2009 a collaboration was started between the Moroccan company Société Nationale d’Études du Détroit de Gibraltar (SNED) and its Spanish counterpart Sociedad Española de Estudios para la Comunicación Fija a Través del Estrecho de Gibraltar (SECEGSA), with the aim of studying and developing a connection system between the two countries. The project would have been financed by the two publicly owned companies, with the economic support of theEuropean Union; while it is not yet known whether the initiative will fall within the Interreg Euro-MED programme, or will be carried forward through the establishment of a commercial consortium.
The engineering challenges and pitfalls
At this point, however, a question arises spontaneously: what would be the main ones engineering challenges to face to create such a complex work? The first concerns the depth. The Strait of Gibraltar, especially at its narrowest point, reaches great depths (900 meters). For this reason, according to the studies available to date, the possible tunnel should pass further west, corresponding to the so-called Judge’s Thresholdwhere the seabed stands at around 400 metres. This choice would make it possible to simplify, at least in part, the excavation and construction operations. A further critical issue is then linked to nature of the soil along the route considered most favourable. The area that the tunnel would cover is in fact characterized by clayey and unstable sediments, which would make the use of TBMs, the Tunnel Boring Machines, a reference technology for tunnel excavation complex.
