Seikan Tunnel

The tunnel was constructed using conventional construction methods, including blasting with the New Austrian tunneling method (NATM), and tunnel boring machines (TBMs). The construction cost of the tunnel itself was 538.4 billion yen at the planning stage, but it actually cost 745.5 billion yen. The construction cost of the strait line, including the attachment line, was 689 billion yen at the planning stage, but ended up costing 900 billion yen. During the construction, 34 workers were killed in the Seikan Tunnel, mostly in transportation accidents.{{Cite news |last=Haberman |first=Clyde |date=1985-03-19 |title=JAPANESE SEE NO LIGHT AT END OF LONGEST TUNNEL |url=https://www.nytimes.com/1985/03/19/world/japanese-see-no-light-at-end-of-longest-tunnel.html |access-date=2025-03-20 |work=The New York Times |language=en-US |issn=0362-4331}}

Unlike the start of construction during the heyday of the Seikan route, even in eastern Japan, passenger traffic to Hokkaido was already dominated by aircraft, and the construction of the Hokkaido Shinkansen was frozen when it was completed. On the freight side, due to the deterioration of labor-management relations at the JNR at the time, including the frequent strikes and legal compliance struggles, freight transportation continued to stagnate as it lost market share to ferries and coastal shipping. In addition, the tunnel faced criticism for its high maintenance costs, the need to pump a large amount of spring water even after completion, and that the large investment to build it is regarded as a sunk cost, and it is said that it is more economical to abandon it. It was ridiculed variously as "Showa's Three Idiots Assessment", "useless long things", and "quagmire tunnel".

However, after its opening, it has played an important role in freight transportation by JR Freight between Hokkaido and Honshu, and has made 21 round trips (regular trains) a day. Including special trains, there are about 50 freight trains up and down. The effect of being able to achieve stable and safe transportation that is not affected by the weather has been significant, and in particular, the transportation volume of agricultural products, which are a key industry in Hokkaido, has increased dramatically.

File:Location TsugaruPeninsulaJp.jpg in Japan]]

File:青函トンネル開通記念500円白銅貨.jpg

File:Inside seikan tunnel.JPG, in July 2008]]

The idea to connect the islands of Honshu and Hokkaido by a fixed link was proposed by the Imperial Japanese Army in the late 1920s for strategic reasons and was part of the army's idea of linking the Japanese main islands with Japanese-held Korea and Sakhalin Islands, the latter then being divided with Japan and the Soviet Union.

The tunnel plan was handed over to the Ministry of Railways in 1946, with preliminary geological surveys and feasibility studies beginning on 24 April of that year,{{cite news |title=World's longest tunnel to link Japanese islands |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/straitstimes19800507-1.2.106.23?qt=seikan,%20tunnel&q=seikan%20tunnel |work=The Straits Times |date=7 May 1980}} induced by the loss of overseas territory at the end of World War II and the need to accommodate returnees. In 1954, five ferries, including the Tōya Maru, sank in the Tsugaru Strait during a typhoon, killing 1,430 passengers. The following year, Japanese National Railways (JNR) expedited the tunnel feasibility study. Also of concern was the increasing traffic between the two islands. A booming economy saw traffic levels on the JNR-operated Seikan Ferry double to 4,040,000 passengers/year from 1955 to 1965, and cargo levels rose 1.7 times to 6,240,000 tonnes/year. Inter-island traffic forecast projections made in 1971 predicted increasing growth that would eventually outstrip the ability of the ferry pier facility, which was constrained by geographical conditions.{{cite journal| author=Matsuo, S. | title=An overview of the Seikan Tunnel Project Under the Ocean | journal=Tunnelling and Underground Space Technology | year=1986 | volume=1 | issue = 3–4 | pages=323–331| doi=10.1016/0886-7798(86)90015-5}}

On 22 March 1964, the Japan Railway Construction Public Corporation was established, and excavation work began that year. In September 1971, the decision was made to commence work on the tunnel. Drilling began in 1972 from both sides {{endash}} Hamana on the northern tip of Honshu and Yunosato in Hokkaido. To avoid danger from earthquakes, the tunnel goes through dense volcanic rock. A Shinkansen-capable cross section was selected, with plans to extend the Shinkansen network. Arduous construction in difficult geological conditions proceeded despite multiple challenges including drilling difficulties, tunnel floodings and the 1973 oil crisis which caused the completion of the tunnel to be delayed. Thirty-four workers were killed during construction.{{cite news| url=https://www.newspapers.com/image/141085840 |via=Newspapers.com |title = Japan Opens Undersea Rail Line|agency = Associated Press|page = 6B|newspaper=St. Louis Post Dispatch|date = 14 March 1988}}

The necessity for the project was questioned at times during construction, as the 1971 traffic predictions were overestimates. Instead of the traffic rate increasing as predicted to a peak in 1985, it peaked earlier in 1978 and then proceeded to decrease. The decrease was attributed to the slowdown in Japan's economy since the first oil crisis in 1973 and to advances made in air transport facilities and longer-range sea transport.{{cite news|first = Peter |last = Galloway |title = Japan's super tunnel a political nightmare |work = The Globe and Mail |page = 15 |date = 25 February 1981}}

By mid-1982, the tunnel had only {{Convert|1000|m}} to complete.{{cite news |title=Coming up — world's longest rail tunnel |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/biztimes19820703-1.2.24?qt=seikan,%20tunnel&q=seikan%20tunnel |work=Business Times (Singapore) |agency=Financial Times |date=3 July 1982}}

On 27 January 1983, Japanese Prime Minister Yasuhiro Nakasone pressed a switch that set off a blast that completed the pilot tunnel. Following this, on 10 March 1985, Minister of Transport Tokuo Yamashita symbolically bored through the main tunnel{{cite news |title=Japanese finish world's longest rail tunnel |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/straitstimes19850311-1.2.12.3?qt=seikan,%20tunnel&q=seikan%20tunnel |work=The Straits Times |agency=United Press International, Associated Press |date=11 March 1985}} by detonating a dynamite charge on the last few meters of the earth.

The tunnel was opened on 13 March 1988,{{cite news |title=Longest undersea tunnel opens in Japan |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/straitstimes19880314-1.2.10?qt=seikan,%20tunnel&q=seikan%20tunnel |work=The Straits Times |agency=Reuters |date=14 March 1988}} having cost a total of ¥1.1 trillion (US$7 billion) to construct, almost 12 times the original budget, much of which was due to inflation over the years.{{cite book|last1=Langmead|first1=Donald|last2=Garnaut|first2=Christine|title=Encyclopedia of Architectural and Engineering Feats|url=https://archive.org/details/encyclopediaofar0000lang|url-access=registration|access-date=11 March 2018|year=2001|publisher=ABC-CLIO|isbn=9781576071120|page=[https://archive.org/details/encyclopediaofar0000lang/page/301 301]}} To commemorate the event, a commemorative 500 yen coin depicting the tunnel was issued by the Japan Mint in 1988.{{cite web|title=青函トンネル開通記念500円白銅貨幣|trans-title=Seikan Tunnel opening commemoration 500 Yen White Copper Coin|url=https://www.mint.go.jp/popup/data_kinen_page13.html|work=Japan Mint|language=ja|access-date=29 April 2020}} Once the tunnel was completed, all railway transport between Honshu and Hokkaido used it, particularly conventional express trains. Similarly, the commuter ferry service between the two islands run by Japanese National Railway{{cite news |title=Gloomy future for world's longest tunnel |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/biztimes19860408-1.2.23.2?qt=seikan,%20tunnel&q=seikan%20tunnel |work=Business Times (Singapore) |agency=UPI |date=8 April 1986}} had also ended.{{cite news |title=An engineering marvel for the 21st century |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/straitstimes19880424-1.2.97.13.4?qt=seikan,%20tunnel&q=seikan%20tunnel |work=The Straits Times |date=24 April 1988}} However, for passenger transport, 90% of people use air travel due to the speed and cost. For example, to travel between Tokyo and Sapporo by train takes eight hours (Tokyo station and Shin-Sapporo station), with transfer from Shinkansen to narrow-gauge express train at Hakodate. By air, the journey is 1 hour and 45 minutes, or 3 hours and 30 minutes including airport access times. Deregulation and competition in Japanese domestic air travel has brought down prices on the Tokyo-Sapporo route, making rail more expensive in comparison.

The Hokutosei overnight train service began after the completion of the Seikan Tunnel;{{cite web |url=http://www.jreast.co.jp/train/express/24hokutosei.html |publisher=JR East |title=北斗星 |trans-title=Hokutosei |archive-url=https://web.archive.org/web/20141221070924/http://www.jreast.co.jp/train/express/24hokutosei.html |archive-date=21 December 2014 |language=ja}} a later and more luxurious Cassiopeia overnight train service was often fully booked. Both were discontinued following the commencement of Hokkaido Shinkansen services in March 2016, with freight trains being the only regular service utilising the narrow-gauge line since that time.{{Cite news |url=https://mainichi.jp/english/articles/20160326/p2a/00m/0na/021000c |title=Passengers on Aomori to Hokkaido bullet train enjoy smooth, speedy ride |date=26 March 2016 |work=Mainichi Daily News |access-date=11 March 2018 }}{{cite web |url= http://rail.hobidas.com/rmn/archives/2015/08/jrjr_140.html|script-title=ja: 寝台特急〈北斗星〉ラストラン|trans-title= Last run of Hokutosei sleeping car limited express |date= 24 August 2015|work= RM News|publisher= Neko Publishing Co. Ltd.|location= Japan|language= ja|access-date= 2 September 2015}}{{cite web |url= http://railf.jp/news/2016/03/21/201000.html |script-title=ja: 寝台特急"カシオペア"運転終了|trans-title= "Cassiopeia" sleeper services end |date= 21 March 2016|work= Japan Railfan Magazine Online|publisher= Koyusha Co., Ltd.|location= Japan|language= ja|access-date= 22 March 2016}} JR Hokkaido is exploring the use of "Train on Train" technology to remove the threat that the shock wave created in front of Shinkansen trains traveling at full speed poses to freight trains operating on Japanese standard narrow-gauge track in a tunnel setting. If successful, it will allow the Hokkaido Shinkansen to travel at full speed inside the tunnel in the future.{{cite news | script-title=ja:独自の研究開発 人と物流 高速化に活路 |trans-title=Own R&D leading to increased speed| newspaper = Hokkaido Shimbun | location = Japan | language = ja | publisher = The Hokkaido Shimbun Press | date = 20 December 2008 | url = http://www.hokkaido-np.co.jp/cont/shinkansen/45633.html | access-date = 30 September 2009}}

As of March 2019, Shinkansen trains operate through the tunnel to Shin-Hakodate-Hokuto Station in Hakodate, connecting Tokyo and Shin-Hakodate-Hokuto stations in 3 hours and 58 minutes. Their maximum speed is {{Convert|160|km/h|mph|abbr=on|round=5}} within the tunnel, {{Convert|260|km/h|mph|abbr=on|round=5}} outside it, and {{Convert|320|km/h|mph|abbr=on|round=5}} to the south of Morioka.{{cite news |date=16 April 2014 |title=東京―新函館４時間10分 北海道新幹線、16年春開業 |language=ja |newspaper=Nihon Keizai Shimbun |url=http://www.nikkei.com/article/DGXNASDG16047_W4A410C1CC1000/ |access-date=16 April 2014}} It was expected that by 2018 one daily service will be run at {{Convert|260|km/h|mph|abbr=on|round=5}} through the tunnel. The final stage is proposed to open to Sapporo Station in 2031 and is expected to shorten the Tokyo-Sapporo rail journey to five hours. The Hokkaido Shinkansen will be operated by JR Hokkaido.

File:Seikan Tunnel 3d cross section 1a.svg

File:Seikan Tunnel profile diagram.svg

Surveying started in 1946 and construction began in 1971. By August 1982, less than 700 metres of the tunnel remained to be excavated. First contact between the two sides was in 1983.{{cite journal| author=Morse, D. | title=Japan Tunnels Under the Ocean | journal=Civil Engineering |date=May 1988 | volume=58 | issue = 5 | pages=50–53}} The Tsugaru Strait has eastern and western necks, both approximately {{convert|20|km|0|abbr=on}} across. Initial surveys undertaken in 1946 indicated that the eastern neck was up to {{convert|200|m|0|abbr=off}} deep with volcanic geology. The western neck had a maximum depth of {{convert|140|m|0|abbr=off}} and geology consisting mostly of sedimentary rocks of the Neogene period. The western neck was selected, with its conditions considered favourable for tunnelling.{{cite journal| author1=Tsuji, H.|author2=Sawada, T.|author3=Takizawa, M. | title=Extraordinary inundation accidents in the Seikan undersea tunnel | journal=Proceedings of the Institution of Civil Engineers – Geotechnical Engineering | year=1996 | volume=119 | issue= 1 | pages=1–14 | doi=10.1680/igeng.1996.28131}}

The geology of the undersea portion of the tunnel consists of volcanic rock, pyroclastic rock, as well as sedimentary rock of the Neogene period.{{cite journal| author=Paulson, B. | title=Seikan Undersea Tunnel | journal=Journal of the Construction Division | year=1981 | volume=107 | issue= 3 | pages=509–525| doi=10.1061/JCCEAZ.0000983 }} The area is folded into a nearly vertical syncline, which means that the youngest rock is in the centre of the strait and encountered last. Divided roughly into thirds, the Honshū side consists of volcanic rocks (notably andesite and basalt); the Hokkaido side consists of sedimentary rocks (notably Tertiary period tuff and mudstone); and the centre portion consists of Kuromatsunai strata (Tertiary period sand-like mudstone).{{cite journal|author1=Kitamura, A. |author2=Takeuchi, Y. |name-list-style=amp | title=Seikan Tunnel | journal=Journal of Construction Engineering and Management | year=1983 | volume=109 | issue= 1 | pages=25–38| doi=10.1061/(ASCE)0733-9364(1983)109:1(25)}} Igneous intrusions and faults caused crushing of the rock and complicated the tunnelling procedures.

Initial geological investigation occurred from 1946 to 1963, which involved drilling the sea-bed, sonic surveys, submarine boring, observations using a mini-submarine, as well as seismic and magnetic surveys. To establish a greater understanding, a horizontal pilot boring was undertaken along the line of the service and main tunnels. Tunnelling occurred simultaneously from the northern end and the southern. The dry land portions were tackled with traditional mountain tunnelling techniques, with a single main tunnel. However, for the {{Convert|23.3|km|adj=on}} undersea portion, three bores were excavated with increasing diameters respectively: an initial pilot tunnel, a service tunnel, and finally the main tunnel. The service tunnel was periodically connected to the main tunnel with a series of connecting drifts, at {{Convert|600-1000|m|sigfig=2|adj=on}} intervals. The pilot tunnel serves as the service tunnel for the central five-kilometre portion. Beneath the Tsugaru Strait, the use of a tunnel boring machine (TBM) was abandoned after less than two kilometres ({{convert|2|km|abbr=off|disp=output only}}) owing to the variable nature of the rock and difficulty in accessing the face for advanced grouting. Blasting with dynamite and mechanical picking were then used to excavate.

A 2002 report by Michitsugu Ikuma described, for the undersea section, that "the tunnel structure appears to remain in a good condition."{{cite journal| author=Ikuma, M. | title=Maintenance of the undersea section of the Seikan Tunnel | journal=Tunnelling and Underground Space Technology | year=2005 | volume=20 | issue= 2 | pages=143–149| doi=10.1016/j.tust.2003.10.001| bibcode=2005TUSTI..20..143I }} The amount of inflow has been decreasing with time, although it "increases right after a large earthquake".

In March 2018 at 30 years of age, maintenance costs amounted to 30 billion Yen or US$286 million since 1999. Plans are to increase speed and provide mobile communication at the full track.{{cite news |last1=Abe |first1=Hiroaki c.s. |title=At 30, undersea tunnel requires maintenance, need for speed |url=http://www.asahi.com/ajw/articles/AJ201803270007.html |access-date=29 September 2018 |publisher=The Asahi Shimbun |date=27 March 2018}}

Initially, only {{Track gauge|1067 mm}} narrow-gauge track was laid through the tunnel, but in 2005 the Hokkaido Shinkansen project started construction which included laying dual gauge track (providing standard gauge track capability) and extending the Shinkansen network through the tunnel. Shinkansen services to Hakodate commenced in March 2016, and are proposed to be extended to Sapporo by 2031. The tunnel has {{convert|52|km|0|abbr=on}} of continuous welded rail.{{cite web |title=Seikan Tunnel Museum |url=http://seikan-tunnel-museum.com/museum.html |url-status=dead |archive-url=https://web.archive.org/web/20060501153308/http://seikan-tunnel-museum.com/museum.html |archive-date=1 May 2006 |access-date=8 May 2006 |work=記念館案内 青函トンネル記念館 公式ホームページ |language=ja |df=dmy-all}}

Two stations used to be within the tunnel—Tappi-Kaitei Station and Yoshioka-Kaitei Station. Both closed with the construction of the Hokkaido Shinkansen, but continue to serve as emergency escape points. In the event of a fire or other disaster, the stations provide the equivalent safety of a much shorter tunnel. The effectiveness of the escape shafts at the emergency stations is enhanced by having exhaust fans to extract smoke, television cameras to help route passengers to safety, thermal (infrared) fire alarm systems, and water spray nozzles. Before the construction of the Hokkaido Shinkansen, both stations contained museums detailing the history and function of the tunnel that could be visited on special sightseeing tours. The museums are now closed and the space provides storage for work on the Hokkaido Shinkansen.{{cite web | title= March 2006 | work=jrtr.net | url=http://www.jrtr.net/topics/mar2006.html | access-date=24 May 2006}} The two were the first railway stations in the world built under the sea.{{Teishajo|II|830}}{{cite news |url=http://www3.nhk.or.jp/nhkworld/english/news/20131110_24.html |title=World's first undersea station ends operation |publisher=NHK |archive-url=https://web.archive.org/web/20131111062005/http://www3.nhk.or.jp/nhkworld/english/news/20131110_24.html |archive-date=November 11, 2013 | df=dmy-all}}

File:Seikan_Tunnel_entrance_-_dual-gauge_track.jpg|Entrance to the tunnel from Honshu side. The dual gauge tracks are visible

File:Seikan-tunnel-yoshioka.jpg|Yoshioka-Kaitei Station platform in the Seikan Tunnel

• Seikan Tunnel Tappi Shakō Line
• Train on Train, an experimental concept for conveying freight at higher speeds through the tunnel
• JR Freight Class EH800, AC freight locomotives used to haul trains through the Seikan Tunnel
• Sakhalin–Hokkaido Tunnel
• Bohai Strait tunnel

{{reflist|30em}}

{{commons category|Seikan Tunnel}}

• [https://web.archive.org/web/20060503142919/http://www.pref.aomori.jp/newline/shinkan/shinkan/newline-e/sin-e08.html The Seikan Tunnel], Aomori Prefecture Government, version of 3 May 2006 at the Internet Archive
• [https://www.pbs.org/wgbh/buildingbig/wonder/structure/seikan.html BUILDING BIG: Databank: Seikan Tunnel]

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Category:Coastal construction

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Category:Tunnels in Aomori Prefecture

Category:Tunnels in Hokkaido