{{Short description|Construction 20 meters or more below ground, using methods other than cut-and-cover}} {{Distinguish|Deep underground (Japanese law)}} {{More citations needed|date=January 2026}} '''Deep level underground''' is construction that is {{Convert|20|m|ft|abbr=on}} or more below ground and not using the [[Tunnel|cut-and-cover]] method, especially train stations, air raid shelters and bunkers, and some tunnels and mines. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support structure that is strong enough to carry the load of what is to be built above the tunnel.
==History== ===Mining=== Although some deep mining took place as early as the late Tudor period (in North-East England, and along the Firth of Forth coast in Scotland) deep shaft mining in Britain began to develop extensively in the late 18th century, with rapid expansion throughout the 19th century and early 20th century when the industry peaked. Before 1800, a great deal of coal was left in places as extraction was still primitive. As a result, in the deep Tyneside pits (300 to 1,000 ft deep) only about 40 percent of the coal could be extracted. The use of wooden pit props to support the roof was an innovation first introduced about 1800.
===Transit systems=== {{main article|London Underground infrastructure#Subsurface versus deep-level tube lines}} Before any plans were made for transit systems with tunnels and stations, several railway operators had used tunnels for freight and passenger trains, usually to reduce the grade of the railway line. Examples include Trevithick's Tunnel from 1804, built for the Penydarren locomotive, the [[Crown Street railway station|1829 Crown Street Tunnel at Liverpool]] and the {{convert|1.13|mi|m|abbr=off}} long 1836 [[Liverpool Lime Street railway station|Lime Street Tunnel]] also at Liverpool, of which a part is still used today making it the world's oldest used tunnel.
The world's first urban underground railway was the Metropolitan Railway, which opened on January 10, 1863. It was built largely in shallow tunnels (see more at cut and cover) and is nowadays part of the London Underground. It was operated using steam trains, and despite the creation of numerous [[ventilation shaft]]s, was unhealthy and uncomfortable for passengers and operating staff. Nevertheless, its trains were popular from the start and the Metropolitan Railway and the competing [[District Railway|Metropolitan District Railway]] developed the [[Circle line (London Underground)|Inner Circle]] around central London (completed in 1884) and an extensive system of suburban branches to the northwest (extending into the adjoining countryside), the west, the southwest and the east (mostly completed by 1904).
[[Liverpool James Street railway station]], together with Hamilton Square underground station in Birkenhead are the oldest deep level underground stations in the world, while London's underground stations were just below the street surface built by means of the cut-and-cover method. The stations were so deep they required [[elevator|lifting]] to access easily, this gave another world's first in having the first lift-accessed stations. The lifts were hydraulically operated. For the first deep-level tube line, the [[City and South London Railway]], two {{convert|10|ft|2|in|m}} diameter circular tube tunnels were dug between King William Street (close to today's [[Bank and Monument stations|Monument station]]) and Stockwell, following under the roads above to avoid the need for an agreement with owners of property on the surface. This opened in 1890 with [[electric locomotive]]s that hauled carriages with small opaque windows, nicknamed "[[padded cell]]s".
==Construction== Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support structure strong enough to support the load of what would be built above the tunnel. Modern deep level construction is usually done by using [[tunnel boring machine]]s.
In London, the [[Circle line (London Underground)|Circle]], [[District line|District]], [[Hammersmith & City line|Hammersmith & City]], and [[Metropolitan line|Metropolitan]] lines are services that run on the sub-surface network that has railway tunnels just below the surface and built mostly using the "cut-and-cover" method. The tunnels and trains are of a similar size to those on British main lines. The Hammersmith & City and Circle lines share all their stations and most of the track with other lines. The [[Bakerloo line|Bakerloo]], [[Central line (London Underground)|Central]], [[Jubilee line|Jubilee]], [[Northern line|Northern]], [[Piccadilly line|Piccadilly]], [[Victoria line|Victoria]] and [[Waterloo & City line]]s are deep-level tube lines, using smaller trains that run through two circular tunnels with a diameter of about {{convert|11|ft|8|in|m}}, lined with cast iron or precast concrete rings, which were bored using a [[tunnelling shield]]. These were referred to as the tube lines, although since the 1950s the term "tube" has come to be used to refer to the whole London Underground system.
==Deepest train stations== Many metro systems in [[post-Soviet states]] (particularly [[Ukraine]] and [[Russia]]), as well as some [[London Underground]] lines, have deep level stations.<ref>{{Cite web|url=http://www.ianvisits.co.uk/blog/2011/07/01/how-deep-is-every-tube-station-on-the-underground/|title=How deep is every tube station on the Underground?|date=July 2011 }}</ref><ref>{{Cite web|url=http://underground-history.co.uk/deeplevel.php|title = London Underground History - Deep Level Disused Stations}}</ref> The deepest [[high-speed rail]] station in operation, the [[Badaling Great Wall railway station]] in [[Beijing]], China, has platforms {{convert|102|metres|ft}} below street level.<ref>{{Cite news |title=China to build world's deepest high-speed rail station under Great Wall |last= |first= |date=2016-09-26 |url=https://www.theguardian.com/world/2016/sep/29/china-to-build-worlds-deepest-high-speed-rail-station-under-great-wall |work=[[The Guardian]]}}</ref><ref>{{Cite news |title=Beneath the Great Wall of China lies the world’s deepest high-speed railway station |last=Hiufu Wong |first=Maggie |date=2022-02-02 |url=https://edition.cnn.com/travel/article/badaling-great-wall-station-high-speed-railway-intl-hnk |work=[[CNN]]}}</ref> The world's deepest metro station is [[Hongyancun station]] of [[Chongqing Rail Transit]], at {{convert|116|m}} below street level,<ref>{{Cite web|last=Ong|first=Edwin|title=[Video] Chongqing's Hongyancun now the deepest metro station in China|url=https://www.thinkchina.sg/society/video-chongqings-hongyancun-now-deepest-metro-station-china|access-date=2024-06-21|website=ThinkChina|language=en}}</ref> followed by [[Arsenalna (Kyiv Metro)|Arsenalna]] on the [[Kyiv Metro]], which is {{convert|105|m}} below street level.<ref>{{cite web | last=O&apos | first=Feargus | title=As Thousands Shelter in Stations, Kyiv’s Metro Is Still Running Trains | website=Bloomberg.com | date=March 14, 2022 | url=https://www.bloomberg.com/news/articles/2022-03-14/how-kyiv-transformed-its-subway-into-a-bomb-shelter | access-date=June 21, 2024}}</ref>
==Deepest mines== {{main|List of deepest mines}} * The deepest mines in the world are the [[TauTona]] (Western Deep Levels) and Savuka [[Gold mining|gold mines]] in the [[Witwatersrand]] region of [[South Africa]], which are currently working at depths exceeding {{cvt|3900|m}}.<ref>{{Cite web|year=2009 |title=TauTona, Anglo Gold, South Africa |url=http://www.mining-technology.com/projects/tautona_goldmine/ }}</ref> There are plans to extend [[Mponeng Gold Mine|Mponeng mine]], a sister mine to TauTona, down to {{cvt|4500|m}} in the coming years.{{Citation needed|date=May 2009}} * This region is also the location of the harshest conditions for hard rock mining, where workers toil in temperatures of up to {{convert|45|C}}. However, massive refrigeration plants are used to bring the air temperature down to around {{convert|28|C}}. * The deepest hard rock mine in [[North America]] is [[Agnico-Eagle|Agnico-Eagle's]] LaRonde mine, which mines [[gold]], [[zinc]], [[copper]] and [[silver]] [[ore]]s roughly {{cvt|45|km|mi}} east of Rouyn-Noranda in [[Cadillac, Quebec|Cadillac]], [[Quebec]]. LaRonde's Penna shaft (#3 shaft) is believed to be the deepest single lift shaft in the Western Hemisphere. The #4 shaft bottoms out at over {{cvt|3000|m|ft}} down. Their LaRonde mine expansion sees open stopes down to a depth of over {{cvt|3000|m|ft}}, the deepest long hole open stopes in the world. * The deepest mine in Europe is the 16th shaft of the uranium mines in [[Příbram]], [[Czech Republic]] at {{cvt|1838|m|ft}},<ref name="DeepestEurope">{{cite news |title=Mineral deposits: from their origin to their environmental impacts |date = January 1995|url=https://books.google.com/books?id=o-WkCSk4jbkC&q=uranium+mines+in+P%C5%99%C3%ADbram+1838&pg=PA400 |publisher= Taylor & Francis|isbn = 9789054105503}}</ref> second is Bergwerk Saar in [[Saarland]], [[Germany]] at 1,750 meters. * The deepest hard rock mines in [[Australia]] are the [[copper]] and [[zinc]] [[lead]] mines in [[Mount Isa]], [[Queensland]] at {{cvt|1800|m|ft}}. * The deepest [[platinum]]-[[palladium]] mines in the world are on the [[Merensky Reef]], in [[South Africa]], with a resource of 203 million [[troy ounce]]s, currently worked to approximately {{cvt|2200|m|ft}} depth. * The deepest tourist level mine is [[Guido Mine and Coal Mining Museum]] in [[Zabrze]], [[Poland]]. * The deepest [[borehole]] is [[Kola Superdeep Borehole]] in [[Murmansk Oblast]], [[Russia]]. At {{cvt|12,262|m|ft}}, it is the deepest artificial [[Extreme points of Earth|extreme point of Earth]]. <!--This is not a mine at all, but interesting for comparison-->
==References== <references/>
[[Category:Tunnels]] [[Category:Civil engineering]]