Seikan Tunnel

Name	Seikan Tunnel青函トンネル
Caption	Map of the Seikan Tunnel.
Location	Beneath the Tsugaru Strait
Coordinates
Status	Active
Start	Honshu
End	Hokkaido
Open	13 March 1988
Owner	Japan Railway Construction, Transport and Technology Agency
Operator	Hokkaido Railway Company
Tracklength	53.85 km (23.3 km undersea)
Notrack	double track rail tunnel
Gauge	Mixed
El	Yes

The Seikan Tunnel (青函トンネル Seikan Tonneru or 青函隧道 Seikan Zuidō) is a railway tunnel in Japan, with a long portion under the seabed. Track level is about below seabed and below sea level. It travels beneath the Tsugaru Strait—connecting Aomori Prefecture on the Japanese island of Honshu and the island of Hokkaido—as part of the Kaikyo Line of Hokkaido Railway Company. The name Seikan comes from combining the on'yomi readings of the first characters of and , the nearest major city on the Hokkaido side.

Seikan is both the longest and the deepest operational rail tunnel in the world, although the Gotthard Base Tunnel in Switzerland will be longer when it opens to traffic in 2016. It is also the longest undersea tunnel in the world, although the Channel Tunnel between the United Kingdom and France has a longer undersea portion.

History

Connecting the islands of Honshu and Hokkaido by a fixed link had been considered since the Taishō period (1912–1925), but serious surveying only commenced in 1946, 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 Toya Maru, sank in the Tsugaru Strait during a typhoon, killing 1,430 passengers. The following year, Japanese National Railways (JNR) expedited the tunnel investigation. |- | 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 breakthrough |- | 1985-03-10 || Main tunnel breakthrough |- | 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

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.

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

Once the tunnel was completed, all railway transport between Honshu and Hokkaido 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. || 17,000,000 || 1971 Forecast |- | 1999 || ~1,700,000 || — || Seikan Tunnel

Geology of the undersea portion of the tunnel consists of volcanic rock, pyroclastic rock, and sedimentary rock of the late Tertiary era. 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 Hokkaido side consists of sedimentary rocks (Tertiary period tuff, mudstone, etc); and the centre portion consists of Kuromatsunai strata (Tertiary period sand-like mudstone). Igneous intrusions and faults caused crushing of the rock and complicated the tunnelling procedures. The amount of inflow has been decreasing with time, although it "increases right after a large earthquake". 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.

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

See also

Channel Tunnel, an undersea railway tunnel connecting Great Britain and France.

Seikan Tunnel Tappi Shako Line

Train on Train, an experimental concept for conveying freight at higher speeds through the tunnel

Bering Strait crossing

References

External links

The Seikan Tunnel, Aomori Prefecture Government, version of 3 May 2006 at the Internet Archive

Category:1988 architecture Category:Coastal construction Category:Railway tunnels in Japan Category:Undersea tunnels