A Japanese rail tunnel beneath the Tsugara Strait, linking Tappi Saki, Honshu, with Fukushima, Hokkaido; constructed 197288; longest railway tunnel in Japan, length 54 km/34 mi.
The Seikan Tunnel (青函トンネル Seikan Tonneru or 青函隧道 Seikan Zuidō) is a 53.85 km (33.49 mile) railway tunnel in Japan, with a 23.3 km (14.5 mile) portion under the seabed. Although it is the longest railway tunnel in the world, faster and cheaper air travel has left the Seikan Tunnel comparatively underutilized.
History
|
Timeline |
|
|---|---|
| April 24, 1946 | Geological surveying commenced |
| September 26, 1954 |
Toya Maru sank in the Tsugaru Straight |
| March 23, 1964 |
Japan Railway Construction Public Corporation established |
| September 28, 1971 | Main tunnel construction commenced |
| January 27, 1983 | Pilot tunnel holed through |
| March 10, 1985 | Main tunnel holed through |
| March 13, 1988 | Tunnel opened |
| Source: | |
Connecting the islands of Honshū and Hokkaido by a land route 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.
| Tsugaru Strait traffic data | |||
|---|---|---|---|
| Year |
Passengers (persons/yr) |
Freight (T/yr) | Mode |
| 1955 | 2 020 000 | 3 700 000 | Seikan Ferry |
| 1965 | 4 040 000 | 6 240 000 | Seikan Ferry |
| 1970 | 9 360 000 | 8 470 000 | Seikan Ferry |
| 1985 | 9 000 000 † | 17 000 000 | 1971 Forecast |
| 1988 | ~3 100 000 | — | Seikan Tunnel |
| 1999 | ~1 700 000 | — | Seikan Tunnel |
| 2001 | — | >5 000 000 | Seikan Tunnel |
| † This may be a typographical error in the source | |||
Once the tunnel was completed all railway transport between Honshū and Hokkaido utilised the tunnel.
Geology of the undersea portion of the tunnel consists of volcanic rock, pyroclastic rock, and sedimentary rock of the late Tertiary era. However, for the 23.3 km 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 - 1000 m intervals. The pilot tunnel served as the service tunnel for the 5 km centre portion.
Beneath the Tsugaru Strait use of a tunnel boring machine (TBM) was abandoned after less than 2 km due to the variable nature of the rock and difficulty in accessing the face for advanced grouting.
Maintenance
A 2002 report by Michitsugu Ikuma described, for the undersea section, that "the tunnel structure appears to remain in a good condition".
Structure
Currently, only narrow gauge track is laid through the twin tunnels, but the Hokkaido Shinkansen project (which started construction in 2005) will include laying dual-gauge track and linking the tunnel into the Shinkansen network, so Shinkansen trains can traverse the tunnel to Hakodate (scheduled for 2015) and eventually Sapporo.
Two stations are located within the tunnel: Tappi-Kaitei Station and Yoshioka-Kaitei Station.
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