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Seikan Tunnel
Map of the Seikan Tunnel.
Location Beneath the Tsugaru Strait
Coordinates 41°11′36″N 140°09′09″E / 41.1932°N 140.1525°E / 41.1932; 140.1525Coordinates: 41°11′36″N 140°09′09″E / 41.1932°N 140.1525°E / 41.1932; 140.1525
Status Active
Start Honshū
End Hokkaidō
Opened 13 March 1988
Owner Japan Railway Construction, Transport and Technology Agency
Operator Hokkaido Railway Company
Track length 53.85 km (23.3 km undersea)
Electrified Yes

The Seikan Tunnel (青函トンネル Seikan Tonneru or 青函隧道 Seikan Zuidō) is a 53.85 km (33.46 mi) railway tunnel in Japan, with a 23.3-kilometre (14.5 mi) long portion under the seabed. Track level is about 140-metre (460 ft) below seabed and 240-metre (790 ft) below sea level.[1] It is the longest undersea tunnel in the world, although the Channel Tunnel between the United Kingdom and France has a longer under-sea portion. It travels beneath the Tsugaru Strait — connecting Aomori Prefecture on the Japanese island of Honshū and the island of Hokkaidō — as part of the Kaikyo Line of Hokkaido Railway Company. Although it is the longest traffic (railway or road) tunnel in the world, faster and cheaper air travel has left the Seikan Tunnel comparatively underused. Its claim to the record for the longest tunnel will be taken when the Gotthard Base Tunnel, a European railway tunnel, is completed in around 2018. It is also the deepest rail tunnel in the world.[2]



Connecting the islands of Honshū and Hokkaidō by a fixed link had been considered since the Taishō period (1912–1925), but serious survey only commenced in 1946, due to the loss of overseas territory at the end of World War II and the need to accommodate returnees. In 1954, five ferries, including the Toya Maru, sank in the Tsugaru Strait during a typhoon, killing 1,430 passengers. The following year the Japanese National Railways (JNR) expedited the tunnel investigation.[3]

1946-04-24 Geological surveying begun
1954-09-26 Train ferry Toya Maru sank
in the Tsugaru Strait
1964-03-23 Japan Railway Construction
Public Corporation established
1971-09-28 Main tunnel construction begun
1983-01-27 Pilot tunnel holed through
1985-03-10 Main tunnel holed through
1988-03-13 Tunnel opened

Also of concern was the increasing traffic between the two islands. A booming economy saw traffic levels on the JNR-operated Seikan (a contraction of principal cities Aomori and Hakodate[4]) Ferry doubled to 4,040,000 persons/year from 1955 to 1965, and cargo levels rose 1.7 times to 6,240,000 tonnes/year. In 1971, traffic forecasts predicted increasing growth that would outstrip the ability of the ferry pier facility, which was constrained by geographical conditions. In September 1971, the decision was made to commence work on the tunnel. A Shinkansen-capable cross section was selected, with plans to extend the Shinkansen network.[3]

Arduous construction in difficult geological conditions proceeded. 34 workers were killed during construction.[5]

On 27 January 1983, Japanese Prime Minister Yasuhiro Nakasone pressed a switch that set off a blast that completed the pilot tunnel. Similarly on 10 March 1985, Minister of Transport Tokuo Yamashita symbolically holed through the main tunnel.[3]

The project's success was questioned at the time, with the 1971 traffic predictions being 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.[6]

Commemorative 500 yen coin

The tunnel was opened on 13 March 1988, having cost a total of ¥538.4 billion (US$3.6 billion) to construct.[7]

Once the tunnel was completed, all railway transport between Honshū and Hokkaidō used the tunnel. However, for passenger transport, 90% of people use air due to the speed and cost. For example, to travel between Tokyo and Sapporo by train takes more than ten hours and thirty minutes, with several transfers. By air, the journey is three hours and thirty 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.[8] The Hokutosei overnight train service, which began service after the completion of the Seikan Tunnel, is still popular among travellers. The newer and more luxurious Cassiopeia overnight train service is frequently fully booked.

Shinkansen trains currently do not run through the tunnel, although the Seikan Tunnel was built to accommodate Shinkansen trains. The JR East company decided to extend the Tohoku Shinkansen to Aomori and then to make connections to the future Hokkaido Shinkansen line. From Aomori, the Hokkaido Shinkansen would continue on to Shin-Hakodate Station in Hakodate, Hokkaido by 2015 and then eventually to Sapporo Station. The future Hokkaido Shinkansen would be operated by JR Hokkaido.

Surveying, construction and geology

Tsugaru Strait traffic data
Year Passengers
Freight (T/yr) Mode
1955 2,020,000 3,700,000 Seikan Ferry[3]
1965 4,040,000 6,240,000 Seikan Ferry[3]
1970 9,360,000 8,470,000 Seikan Ferry[3]
1985 9,000,000[t 1] 17,000,000 1971 Forecast[3]
1988 ~3,100,000 Seikan Tunnel[8]
1999 ~1,700,000 Seikan Tunnel[8]
2001 >5,000,000 Seikan Tunnel[8]
  1. ^ This may be a typographical error in the source
Typical tunnel cross section. (1) Main tunnel, (2) service tunnel, (3) pilot tunnel, (4) connecting gallery.
Profile diagram of the underwater section of tunnel.

Surveying started in 1946 and in 1971, twenty-five years later, construction began. By August 1982, less than 700 metres of the tunnel remained to be excavated. First contact between the two sides was in 1983.[7]

The Tsugaru Strait has eastern and western necks, both approximately 20 kilometres across. Initial surveys undertaken in 1946 indicated that the eastern neck was up to 200 metres deep with volcanic geology. The western neck had a maximum depth of 140 metres and geology consisting mostly of sedimentary rocks of the Neogene period. The western neck was selected, with its conditions considered favourable for tunnelling.[9]

Geology of the undersea portion of the tunnel consists of volcanic rock, pyroclastic rock, and sedimentary rock of the late Tertiary era.[4] The area is folded into a nearly vertical anticline, 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 (andesite, basalt etc); the Hokkaidō side consists of sedimentary rocks (Tertiary period tuff, mudstone, etc); and the centre portion consists of Kuromatsunai strata (Tertiary period sand-like mudstone).[10] Igneous intrusions and faults caused crushing of the rock and complicated the tunnelling procedures.[9]

Initial geological investigation occurred from 1946–1963 which involved drilling the sea-bed, sonic surveys, submarine boring, observations using a mini-submarine, and seismic and magnetic surveys. To establish a greater understanding, a horizontal pilot boring was undertaken along the line of both the service and pilot tunnels.[9]

Tunnelling occurred simultaneously from both the northern and southern ends. The dry land portions were tackled with traditional mountain tunnelling techniques, with a single main tunnel.[9] However, for the 23.3-kilometre 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 shafts, at 600- to 1,000-metre intervals.[10] The pilot tunnel serves as the service tunnel for the central five-kilometre portion.[9]

Beneath the Tsugaru Strait, the use of a tunnel boring machine (TBM) was abandoned after less than two kilometres owing to the variable nature of the rock and difficulty in accessing the face for advanced grouting.[4][9] 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".[11] The amount of inflow has been decreasing with time, although it "increases right after a large earthquake".[11]


Train approaching Tappi-Kaitei Station, in July 2008

Originally only narrow gauge track was laid through the tunnel, but in 2005 the Hokkaidō Shinkansen project started construction has included laying dual-gauge track and linking the tunnel into the Shinkansen network. Shinkansen trains will be able to traverse the tunnel to Hakodate from 2015 and eventually Sapporo. The tunnel has 52 kilometres of continuous welded rail.[12] Two stations are located within the tunnel itself: Tappi-Kaitei Station and Yoshioka-Kaitei Station. The stations serve as emergency escape points. In the event of a fire or other disaster, both stations provide the equivalent safety of a much shorter tunnel. The effectiveness of the escape shafts located 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.[7]

Previously, both the stations contained museums detailing the history and function of the tunnel and which could be visited on special sightseeing tours. Only Tappi-Kaitei remains as a museum, the museum function at Yoshioka-Kaitei was closed on 16 March 2006 to provide a storage room for work on the upgrades related to the Hokkaidō Shinkansen service.[13]

The two stations were the first railway stations in the world built under the sea.

See also


  1. ^
  2. ^
  3. ^ a b c d e f g h Matsuo, S. (1986). "An overview of the Seikan Tunnel Project Under the Ocean". Tunnelling and Underground Space Technology 1 (3/4): 323–331. doi:10.1016/0886-7798(86)90015-5.  
  4. ^ a b c Paulson, B. (1981). "Seikan Undersea Tunnel". American Society of Civil Engineers, Journal of the Construction Division 107 (3): 509–525.  
  5. ^ "Japan Opens Undersea Rail Line". Associated Press. 14 March 1988. p. 6B.  
  6. ^ Galloway, Peter (25 February 1981). "Japan's super tunnel a political nightmare". Special to The Globe and Mail: p. 15.  
  7. ^ a b c Morse, D. (May 1988). "Japan Tunnels Under the Ocean". Civil Engineering 58 (5): 50–53.  
  8. ^ a b c d Takashima, S. (2001). "Railway Operators in Japan 2: Hokkaido (pdf)". Japan Railway and Transport Review 28: 58–67.  
  9. ^ a b c d e f Tsuji, H., Sawada, T. and Takizawa, M. (1996). "Extraordinary inundation accidents in the Seikan undersea tunnel". Proceedings of the Institution of Civil Engineers, Geotechnical Engineering 119 (1): 1–14.  
  10. ^ a b Kitamura, A. & Takeuchi, Y. (1983). "Seikan Tunnel". Journal of Construction Engineering and Management 109 (1): 25–38. doi:10.1061/(ASCE)0733-9364(1983)109:1(25).  
  11. ^ a b Ikuma, M. (2005). "Maintenance of the undersea section of the Seikan Tunnel". Tunnelling and Underground Space Technology 20 (2): 143–149. doi:10.1016/j.tust.2003.10.001.  
  12. ^ "Seikan Tunnel Museum". 記念館案内 青函トンネル記念館 公式ホームページ. Retrieved 2006-05-08.  
  13. ^ "March 2006". Retrieved 2006-05-24.  

External links


Simple English

File:Seikantunnel - Tsugaru street
The Seikan Tunnel (in red)
Seikan Tunnel(Ja:青函トンネル)is a railway tunnel in Japan. It connects Hokkaido to Aomori. This is the longest tunnel in the world. The tunnel is 53.85 km (33.49 miles) long. 23.3 km (14.5 mile) of the tunnel is underwater. There are two stations in a tunnel.
  • Yoshioka-kaitei-station
  • Tappikaitei-station

These stations are used in case of emergency.


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