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The Mont d'Ambin Base Tunnel, also known as the Mont Cenis Base Tunnel, is the largest engineering work of the Lyon–Turin rail link project. Once completed, it will facilitate the principal high-speed rail link between Italy and France, conveying both high-speed passenger trains and rail freight between the two countries. At , that tunnel will be the longest rail tunnel in the world, ahead of the
Gotthard Base Tunnel The Gotthard Base Tunnel (GBT; , , ) is a railway tunnel through the Alps in Switzerland. It opened in June 2016 and full service began the following December. With a route length of , it is the world's longest railway and deepest traffic tunn ...
. It represents one third of the estimated overall cost of the project and is the only part of the line where work has started. Crossing the
Alps The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia. ...
between the
Susa Valley The Susa Valley (; ; ; ; ) is a valley in the Metropolitan City of Turin, Piedmont region of northern Italy, located between the Graian Alps in the north and the Cottian Alps in the south. It is one of the longest valleys of the Italian Alps. ...
in
Piedmont Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...
and
Maurienne Maurienne (; ; ) is one of the provinces of Savoy, corresponding to the arrondissement of Saint-Jean-de-Maurienne in France. It is also the original name of the capital of the province, now Saint-Jean-de-Maurienne. Location The Maurienne val ...
in
Savoie Savoie (; Arpitan: ''Savouè'' or ''Savouè-d'Avâl''; English: ''Savoy'' ) is a department in the Auvergne-Rhône-Alpes region, Southeastern France. Located in the French Alps, its prefecture is Chambéry. In 2019, Savoie had a population o ...
. It has an estimated cost of
The euro sign () is the currency sign used for the euro, the official currency of the eurozone. The design was presented to the public by the European Commission on 12 December 1996. It consists of a stylized letter E (or epsilon), crossed by t ...
8 billion. During September 2016, a key agreement towards the tunnel's construction was reached by France and Italy. Three years later, competitive tenders to perform packaged elements of the construction work were sought. As of late-2022, the expected completion date for the base tunnel was 2032.


History

During 2002, reconnaissance work commenced on the French side. Initially, access points were excavated at
Modane Modane (; ) is a Communes of France, commune in the Savoie Departments of France, department in the Auvergne-Rhône-Alpes Regions of France, region in southeastern France. The commune is in the Maurienne Valley, and it also belongs to the Vanoise ...
; excavations commenced in Saint-Martin-de-la-Porte during 2003, and at La Praz two years later. During 2011, excavations in support of the survey work started on the Italian side at La Maddalena. Between 2016 and 2017, while full-rate construction of the tunnel had not officially commenced, a reconnaissance gallery had been tunnelled from Saint Martin de la Porte towards Italy; it was bored along the intended axis of the South tube of the tunnel and was driven at its final diameter. It will comprise the first eight percent of the tunnel's final length. During September 2016, it was announced that France and Italy had reached a mutual agreement for the construction of the tunnel. Furthermore, the tunnel has been approved and part-financed by the European Union, which has stated its intention to finance 40 % of the tunnel construction costs, and has indicated its willingness to increase its contribution to 55 %, as well as to help fund its French accesses if those go beyond mere adaptations of the existing infrastructure. In January 2017, a treaty was ratified between the two countries, confirming the project's approval. During March 2019, the Italian government issued a formal request for proposals (RFP) for the construction of the French portion of the base tunnel; in July 2019, a second RFP was released for the Italian portion of the tunnel. During July 2020, it was announced that a consortium headed by the French civil engineering firm Vinci Construction Grands Projets had been awarded a contract for the construction of several major elements of tunnel, including four Avrieux shafts of up to depth, and the conventional excavation of multiple galleries and seven caverns at the foot of the Villarodin Bourget–Modane decline. All four of the access tunnels, three in France and one in Italy, have been completed and work began in early 2019 on the artificial tunnel that will be the entrance to the base tunnel on the French side. In September 2019, the first of eight
tunnel boring machine A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. TBMs are an alternative to drilling and blasting methods and "hand mining", allowing more rapid excavation through hard rock, wet or dry so ...
s (TBMs) to be used on the project finished excavation of the first of the southern tube of the base tunnel, reaching the La Praz access
adit An adit (from Latin ''aditus'', entrance) or stulm is a horizontal or nearly horizontal passage to an underground mine. Miners can use adits for access, drainage, ventilation, and extracting minerals at the lowest convenient level. Adits are a ...
. The diameter hard rock single shield TBM started its journey in the summer of 2016 from the Saint-Martin-de-la-Porte access adit and managed to maintain an average speed of /day. This first €390 million lot of the base tunnel was constructed by a joint venture of Batignolles TPCI, Eiffage TP, Ghella, CMC, Cogeis and Sotrabas. Egis and Alpina provided project management Contracts for the Mount Cenis Base Tunnel were awarded in July 2021: *Lot 1 (€1.47 billion) for between Villarodin-Bourget/Modane and the Eastern (Italian) portal; expected to take 72 months *Lot 2 (€1.43 billion) for between Saint-Martin-de-la-Porte/La Praz and Modane; expected to take 65 months *Lot 3 (€228 million) for between Saint-Martin-de-la-Porte and the Western (French) Portal at Saint-Julien-Mont-Denis; the shortest, but with difficult geology requiring all blasting; expected to take 70 months The approach routes are less advanced; planning is under way on the French side, but on the Italian side the proposed route has had fierce controversy, particularly in the Susa Valley the location of the Eastern portal, with a ''No TAV'' (no to high-speed rail) movement. The 2016 approval legislation could require extension of the tunnel by to reduce the impact on the local landscape.


Characteristics

The Mont d'Ambin Base Tunnel is the principal engineering challenge of the in-development
Turin–Lyon high-speed railway The Turin–Lyon high-speed railway is an international rail line under construction between the cities of Turin and Lyon, which is intended to link the Italian and French high-speed rail networks. It will be long, of which over will be t ...
. During 2019, it was stated that the tunnel's construction phase had been projected to take approximately ten years to complete. Opposition to the project is mostly organised under the loose banner of the ''No TAV'' movement. As a result of protests against the original alignment of the tunnel in the Susa valley, it was decided to increase its length from . Upon opening, the tunnel will be the longest rail tunnel in the world, followed by the Gotthard Base Tunnel (), the
Brenner Base Tunnel The Brenner Base Tunnel (; ) is a railway tunnel under construction through the base of the Eastern Alps beneath the Brenner Pass. Once completed, the Brenner Base Tunnel will rank as either the second or third longest railway tunnel in the wor ...
(, currently under construction), the Seikan Tunnel in Japan (), the
Channel Tunnel The Channel Tunnel (), sometimes referred to by the Portmanteau, portmanteau Chunnel, is a undersea railway tunnel, opened in 1994, that connects Folkestone (Kent, England) with Coquelles (Pas-de-Calais, France) beneath the English Channel at ...
(), and the
Yulhyeon Tunnel The Yulhyeon Tunnel () is a railway tunnel in South Korea, which opened in 9 December 2016, and is currently the world's fourth longest railway tunnel at . The tunnel, which consists of a double-track tube, is part of the Suseo–Pyeongtaek high ...
in South Korea (). The tunnel portals will be in
Saint-Jean-de-Maurienne Saint-Jean-de-Maurienne (; or ''Sant-Jian-de-Môrièna''; ) is a Subprefectures in France, subprefecture of the Savoie Departments of France, department, in the regions of France, region of Auvergne-Rhône-Alpes (formerly Rhône-Alpes), in south ...
on the French side and
Susa Susa ( ) was an ancient city in the lower Zagros Mountains about east of the Tigris, between the Karkheh River, Karkheh and Dez River, Dez Rivers in Iran. One of the most important cities of the Ancient Near East, Susa served as the capital o ...
on the Italian side. The geology adjacent to the French portal is heavily composed of fractured and sheared coal-bearing
schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...
s, as revealed by test drilling, which is poorly suited for using
tunnel boring machine A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. TBMs are an alternative to drilling and blasting methods and "hand mining", allowing more rapid excavation through hard rock, wet or dry so ...
s; thus, conventional
drilling and blasting Drilling and blasting is the controlled use of explosives and other methods, such as gas pressure blasting pyrotechnics, to break rock for excavation. It is practiced most often in mining, quarrying and civil engineering such as dam, tunnel ...
has to be used for the corresponding section. The cost of the joint Franco-Italian section (from Saint Jean de Maurienne to Val Susa) has been estimated at 8 billion euros (in January 2018 value). This cost will be borne by the French and Italian governments, as well as drawing upon European Union (EU) funds. The EU has agreed to provide 40 % of the financing, but has indicated its willingness to increase its contribution to 55%, as well as to conditionally partially fund its French accesses. However, a 2012 report by the French Court of Audit questioned the reliability of the estimated costs of the tunnel, as well the projected traffic volumes. The tunnel will be used by both freight trains and freight shuttles running at , as well as by higher speed passenger trains operating at ; this design speed of slightly below the threshold used by the European Commission to define
high-speed railway High-speed rail (HSR) is a type of rail transport network utilising trains that run significantly faster than those of traditional rail, using an integrated system of specialised rolling stock and dedicated railway track, tracks. While there is ...
s. A stated aim of the project is a modal shift from road to rail for freight traffic over the Alps, as well as more passengers travelling by train rather than airliners, both of which achieve a reduction in emissions.


See also

*
Lyon Turin Ferroviaire Lyon Turin Ferroviaire (LTF), a subsidiary of Réseau Ferré de France (RFF) and Rete Ferroviaria Italiana (RFI), was the early developer of the joint French-Italian part of the future rail link between Lyon and Turin. It has now been replaced i ...
*
NRLA The New Railway Link through the Alps (NRLA; , , ), is a Swiss construction project for faster north–south rail links across the Swiss Alps. It consists of two axes with several improvements along these rails including three new base tunnels s ...
*
Turin–Lyon high-speed railway The Turin–Lyon high-speed railway is an international rail line under construction between the cities of Turin and Lyon, which is intended to link the Italian and French high-speed rail networks. It will be long, of which over will be t ...
*
Lists of tunnels A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, but ...


References


External links

*
Lyon-Turin rail link official site
{{DEFAULTSORT:Mont D'ambin Base Tunnel Railway tunnels in France Railway tunnels in Italy Transport in Piedmont Proposed railway tunnels in Europe Base tunnels France–Italy border crossings Tunnels in the Alps