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A base tunnel is a type of tunnel, mainly a railway tunnel, that is built through the base of a mountain pass. This type of tunnel typically connects two valleys at about the same altitudes.^[1]

When originally constructed, classical railway lines through mountainous terrain tried to minimize tunnelling, due to technical limitations and also expense, and therefore required long and steep gradients and many curves, or even spirals. Such tunnels are sometimes also called culmination tunnels, especially in the presence of a base tunnel through the same mountain massif.

The base tunnels take the opposite approach, eliminating, or at least, minimizing gradients and eliminating curves with the consequence of having longer tunnels on a route, but shorter total distances to travel, allowing higher speeds and lower energy costs. Usually, there is an already existing culmination tunnel, and it would not have been possible or reasonable to build a tunnel at an even lower altitude.

Schematic representation of a normal base tunnel construction method in Europe; they have two tubes connected every few hundred meters in order to enable evacuation in case of emergency
[image shows an evacuation station of the base tunnel Gotthard, the longest railway tunnel in the world – 57 km (35 mi)]

Some of the best-known base tunnels are (length and opening):

Gotthard Base Tunnel (57.1km, 2016), Switzerland
Mont d'Ambin Base Tunnel (57km, not projected yet), France and Italy
Brenner Base Tunnel (55km, proj. 2025), Austria and Italy
Lötschberg Base Tunnel (34.6km, 2007), Switzerland
Semmering Base Tunnel (27.3km, proj. 2025), Austria
Pajares Base Tunnel (24.7km, not projected yet), Spain
Zimmerberg Base Tunnel (20km, not startet yet), Switzerland
Apennine Base Tunnel (18.5km, 1934), Italy
Ceneri Base Tunnel (15.4km, proj. 2020), Switzerland
Furka Base Tunnel (15.4km, 1982), Switzerland

Base tunnels through the San Gabriel Mountains have been proposed as part of the California High Speed Rail system.^[2]

References

^ "LZMK: tunel" (in Croatian). enciklopedija.hr. Archived from the original on June 2, 2016. Retrieved June 2, 2016. ... prema dubini u terenu: niskoležeći (bazni) tuneli, tuneli koji spajaju dvije doline približno iste nadmorske visine, visokoležeći kratki vododijelni tuneli s usponima s obiju strana i prijelomom nivelete u sredini tunela te niskoležeći dugi vododijelni tuneli s jednim nagibom. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ Latest plan for California’s high-speed rail calls for tunnel into San Fernando Valley, Los Angles Daily News, 2016-4-11

[LZMK-1] "LZMK: tunel" (in Croatian). enciklopedija.hr. Archived from the original on June 2, 2016. Retrieved June 2, 2016. ... prema dubini u terenu: niskoležeći (bazni) tuneli, tuneli koji spajaju dvije doline približno iste nadmorske visine, visokoležeći kratki vododijelni tuneli s usponima s obiju strana i prijelomom nivelete u sredini tunela te niskoležeći dugi vododijelni tuneli s jednim nagibom. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[2] Latest plan for California’s high-speed rail calls for tunnel into San Fernando Valley, Los Angles Daily News, 2016-4-11

[1]

[2]

Revision as of 17:36, 11 July 2016 edit 24.190.116.30 (talk) Translate stray French word to English. ← Previous edit		Revision as of 14:18, 7 August 2016 edit undo 88.98.85.216 (talk) linking Next edit →
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	A '''base tunnel''' is a type of [[tunnel]], mainly a [[railway ~~tunnel~~]], that is built through the base of a [[mountain pass]]. This type of tunnel typically connects two [[valley]]s at about the same [[altitude]]s.<ref name="LZMK">{{cite web \|url=http://www.enciklopedija.hr/natuknica.aspx?ID=62681 \|title=LZMK: ''tunel'' \|language=hr \|publisher=enciklopedija.hr \|accessdate=June 2, 2016 \|quote=... prema dubini u terenu: niskoležeći (bazni) tuneli, tuneli koji spajaju dvije doline približno iste nadmorske visine, visokoležeći kratki vododijelni tuneli s usponima s obiju strana i prijelomom nivelete u sredini tunela te niskoležeći dugi vododijelni tuneli s jednim nagibom. \|archiveurl=https://web.archive.org/web/20160602151538/http://www.enciklopedija.hr/natuknica.aspx?ID=62681 \|archivedate=June 2, 2016 \|deadurl=no}}</ref>		A '''base tunnel''' is a type of [[tunnel]], mainly a [[Rail transport\|railway]] tunnel, that is built through the base of a [[mountain pass]]. This type of tunnel typically connects two [[valley]]s at about the same [[altitude]]s.<ref name="LZMK">{{cite web \|url=http://www.enciklopedija.hr/natuknica.aspx?ID=62681 \|title=LZMK: ''tunel'' \|language=hr \|publisher=enciklopedija.hr \|accessdate=June 2, 2016 \|quote=... prema dubini u terenu: niskoležeći (bazni) tuneli, tuneli koji spajaju dvije doline približno iste nadmorske visine, visokoležeći kratki vododijelni tuneli s usponima s obiju strana i prijelomom nivelete u sredini tunela te niskoležeći dugi vododijelni tuneli s jednim nagibom. \|archiveurl=https://web.archive.org/web/20160602151538/http://www.enciklopedija.hr/natuknica.aspx?ID=62681 \|archivedate=June 2, 2016 \|deadurl=no}}</ref>

	When originally constructed, classical railway lines through mountainous terrain tried to minimize tunnelling, due to technical limitations and also expense, and therefore required long and steep gradients and many curves, or even spirals. Such tunnels are sometimes also called ''culmination tunnels,'' especially in the presence of a base tunnel through the same mountain massif.		When originally constructed, classical railway lines through mountainous terrain tried to minimize tunnelling, due to technical limitations and also expense, and therefore required long and steep gradients and many curves, or even spirals. Such tunnels are sometimes also called ''culmination tunnels,'' especially in the presence of a base tunnel through the same mountain massif.