Pajares Base Tunnel
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The Pajares Base Tunnel is a twin pair of
railway Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...
tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...
s beneath the Puerto de Pajares pass in the
Cantabrian Mountains The Cantabrian Mountains or Cantabrian Range () are one of the main systems of mountain ranges in Spain. They stretch for over 300 km (180 miles) across northern Spain, from the western limit of the Pyrenees to the Galician Massif ...
,
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
. The length tunnel forms a key portion of the
high-speed rail 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 ...
line between León and
Gijón Gijón () or () is a city and municipality in north-western Spain. It is the largest city and Municipalities of Spain, municipality by population in the autonomous communities of Spain, autonomous community of Asturias. It is located on the coa ...
, and can be used by both high speed passenger trains as well as by slower freight trains. Work commenced on the Pajares Base Tunnel following its authorisation in 2003. During the construction process, multiple setbacks were incurred on the part of the geological conditions present, particularly the copious ingress of water into the tunnels. Despite multiple years of remedial work and the deployment of unique engineering solutions, the infiltration issue has proved to be difficult to address, and questions have arisen as to if its electrification is even practical. As a result, the fitting-out of the tunnel has been delayed by several years. Early on, the through route was expected to be open in 2010. Finally, the tunnels were opened to passenger traffic 30 November 2023.


Construction

During the early decades of the 21st century, Spain allocated a large proportion of
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
-supplied infrastructure funding into the expansion of its
AVE is a Latin word, used by the Roman Empire, Romans as a salutation (greeting), salutation and greeting, meaning 'wikt:hail, hail'. It is the singular imperative mood, imperative form of the verb , which meant 'Well-being, to be well'; thus on ...
high speed rail network. On 1 March 2002, it was announced that Gestor de Infraestructuras Ferroviarias (GIF) had awarded a €5·18m contract to Ineco and Geoconsult for the design of a new 50 km high speed railway between
La Robla La Robla is a municipality located in the province of León, Castile and León, Spain. According to the 2020 census ( INE), the municipality has a population of 3,752 inhabitants. The area around La Robla was once an important mining community. T ...
and Pola de Lena, forming a part of the main line between Madrid - Oviedo main line. The most prominent civil engineering work of this line is the twin-bore Pajares Base Tunnel, which necessitated a length of to traverse the Pajares pass of the
Cantabrian Mountains The Cantabrian Mountains or Cantabrian Range () are one of the main systems of mountain ranges in Spain. They stretch for over 300 km (180 miles) across northern Spain, from the western limit of the Pyrenees to the Galician Massif ...
. It was reportedly regarded as being one of the largest and most challenging civil engineering projects anywhere in Europe at that time. The tunnel would replace a relatively steep and winding conventional route through the mountains that had limited train speeds to a maximum speed of 70 kmph, while the new line was envisioned to facilitate speeds of up to 300 kmph. During 2003, the Public Works Ministry awarded a €1.8 billion contract for the Pajares Base Tunnel's construction to a consortium involving the majority of Spain’s major civil engineering firms, including FCC,
Acciona Acciona, S.A. () is a Spanish multinational conglomerate dedicated to the development and management of infrastructure (construction, water, industrial and services) and renewable energy. The company, via subsidiary Acciona Energía, produces 21 ...
, Dragados, Ferrovial, Sacyr, and Constructora Hispánica. As originally planned, both bores of the Pajares Base Tunnel would have been furnished only with
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), international gauge, UIC gauge, uniform gauge, normal gauge in Europe, and SGR in East Africa. It is the ...
high-speed rail 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 ...
; however, mid-way through construction, it was decided that a
dual gauge Dual gauge railroad track has three or four rails, allowing vehicles of two track gauges to run on it. Signalling and sidings are more expensive to install on dual gauge tracks than on two single gauge tracks. Dual gauge is used when there i ...
arrangement would be installed instead, as it was thought that the presence of Iberian gauge would make the tunnel particularly useful to freight trains as well. It had been anticipated that the completed tunnel would facilitate a journey time of 2 hours and 12 minutes between
Madrid Madrid ( ; ) is the capital and List of largest cities in Spain, most populous municipality of Spain. It has almost 3.5 million inhabitants and a Madrid metropolitan area, metropolitan area population of approximately 7 million. It i ...
and
Oviedo Oviedo () or Uviéu (Asturian language, Asturian: ) is the capital city of the Principality of Asturias in northern Spain and the administrative and commercial centre of the region. It is also the name of the municipality that contains th ...
by 2010. Its execution began with five TBMs (four for the large tubes and the fifth for the gallery from Buiza) between July and September 2005 on the León slope and between April and July 2006 on the Asturian slope. The tunnel boring machines extracted 4.3 million m³ from the tunnels. The bulk of the excavation work for the Pajares Base Tunnel was performed by
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). The construction soon encountered substantial amounts of underground water, the presence of relatively porous
karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...
in the vicinity of the bores had been previously identified by surveys undertaken in the 1980s; accordingly, vast quantities of water continuously infiltrated into the bores. It has been alleged by construction workers that management had prioritised maintaining a high rate of progress over properly sealing the tunnel against water infiltration. Furthermore, the geological conditions surrounding the tunnel featured multiple areas of high compressive tectonic stress regimes, such as thrust faults, which necessitated greater levels of support to be installed in the tunnel than had been originally anticipated. Despite this, the boring process was completed eight months ahead of schedule. On 11 July 2009, a ceremony was held to mark the completion of the tunnels. However, despite this milestone being attained, the fitting-out of the tunnel proceeded at a very slow rate due to the water infiltration issue; up to 2,200 liters of water was reportedly entering the tunnel every second, much of it via cracks in its concrete walls. Conventional waterproofing measures, such as polymeric paste injection and polymeric membranes, proved insufficient, while additional excavation was prohibitively expensive due to the walls being largely complete already. Instead, engineers turned to unorthodox means of channeling the water by installing a first-of-its-kind composite lining. After four years of work, the rate of water infiltration had been reduced by 40 percent. By 2014, the difficulties of constructing the Pajares Base Tunnel had become thoroughly apparent. Over the course of one decade, the initial plans of the tunnel were altered on 15 occasions. The costs of its construction has overrun substantially, rising to €3 billion against the originally budgeted price of €1.8 billion. During June 2020, it was announced that
Administrador de Infraestructuras Ferroviarias ADIF (, an acronym of ) is a Spanish state-owned railway infrastructure manager. This state owned company reports to the Ministry of Development (Spain), Ministry of Transport and Sustainable Mobility. ADIF is charged with the management of m ...
(ADIF) had awarded a €53m contract to a consortium of
Alstom Alstom SA () is a French multinational rolling stock manufacturer which operates worldwide in rail transport markets. It is active in the fields of passenger transportation, signaling, and locomotives, producing high-speed, suburban, regional ...
,
Indra Indra (; ) is the Hindu god of weather, considered the king of the Deva (Hinduism), Devas and Svarga in Hinduism. He is associated with the sky, lightning, weather, thunder, storms, rains, river flows, and war.  volumes Indra is the m ...
and the San José Construction Group to supply tunnel safety and security systems for the 12 tunnels of the Pajares New Line project, including the Pajares Base Tunnel. Despite plans for the tunnel to be electrified by
25 kV AC Railway electrification systems using alternating current (AC) at are used worldwide, especially for high-speed rail. It is usually supplied at the standard utility frequency (typically 50 or 60Hz), which simplifies traction substations. The dev ...
throughout its length, questions have been raised if electrification is feasible due to the high level of water infiltration present.


See also

* León-Gijón railway line


References


External links


Description

Basic facts
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