Seikan Tunnel

The Seikan Tunnel (in red)

The Seikan Tunnel（Ja:青函トンネル）is a railway tunnel in Japan.^[1] It connects Hokkaido to Aomori Prefecture.^[2]^[3] This tunnel is the second longest transport tunnel in the world. The tunnel is 53.85 km (33.49 miles) long.^[4] 23.3 km (14.5 mile) of the tunnel is underwater. There are two stations in the tunnel.^[3]

History

The means of transportation from Hokkaido to Honshu was the Seikan ship until Seikan tunnel was completed. It took about 3 hours. However, it had some troubles. For example, the sea route was not safe. The Toyamaru accident in 1954 had 1155 dead and some missing people, caused by Typhoon Number 15 Roke. because of that reason, the plan that constructing Seikan Tunnel from Hokkaido to Honshu was becoming a reality. At first, the east route and west route was considered. In the west route, the deepest depth of water was 140 meters and the nature of the soil was easy to drill rocks, so west route was then chosen.

Techniques

The tunnel can be entered by the Shinkansen (bullet train). The inner structure of the tunnel was planned to have three bullet train's rails. Because half of this tunnel is under the bottom of the sea, the workers who built this tunnel were worried about seawater. So, they used new construction techniques. For example, laser measurement, 2150m horizontal drilling, pouring water glass and cement into soft bedrock. These techniques were paid attention to by all of the world at that time. There is still much water, so the seawater that is collected is placed in the tunnel and is pumped out of the tunnel.

Stations

There are two stations in Seikan tunnel. Tappikaitei Station opened in Aza-Minmayatatsuhama, Sotogahama-machi, Higashitsugaru-gun, Aomori on March 13, 1988. And Yoshiokakaitei Station opened in Tatesaki, Fukushima-cho, Matsumae-gun, Hokkaido on March 13, 1988. If passengers have a special ticket, they can get off the train at the stations to look around. These are located in 149.5 meters under the seabed and there are 2247 steps of stairs to the surface. Also, these stations have shelters for train fires and blackouts. Tappikaitei Station and Yoshiokakaitei Station became the service stop each on November 10, 2013 and August 27, 2013. However, these stations were closed on March 15, 2014, because the number of passengers who used these stations, was not a lot.

Seikan Tunnel Media

Location of the Tsugaru Strait in Japan
1988 Seikan Tunnel 500 yen coin
Train approaching Tappi-Kaitei Station, in July 2008
Typical tunnel cross section. (1) Main tunnel, (2) service tunnel, (3) pilot tunnel, (4) connecting gallery
Profile diagram of the underwater section of tunnel
Entrance to the tunnel from Honshu side. The dual gauge tracks are visible
Yoshioka-Kaitei Station platform in the Seikan Tunnel