The Seikan Tunnel



Plans for the Tsugaru Straits Line

Tsugaru Straits Line The standard of the Tsugaru Straits Line is type A and the line has been electrified for both up and down tracks.
In order to cater for the future possibility of the Shinkansen using the same tracks, the line has been designed such that curves have as large a radius as possible, and slopes are kept to an absolute minimum.
Additionally, the main rail type used is the same as that used for the Shinkansen, the 60 rail.


(Note:Shared sectors are lengths of track which can be used by both the Shinkansen and local lines running in parallel to it.)

The Honshu
The Seikan
The Hokkaido
Minimal curve radius 350m 6,500m 6,500m 6,500m 350m
Fast rail types for inclines 20/1,000 15/1,000 12/1,000 15/1,000 20/1,000
Rail types 50N Rail 60 Rail 60 Rail 60 Rail 50N Rail
Extension of lines 3.9km 15.3km 53.9km 12.8km 1.9km
Extension of tunnels 10.6km(55%) 53.9km(100%) 7.0km(48%)
Increased lighting 8.6km(45%) - 7.7km(52%)
Temporary suspension bridges Simple catenary Heavy simple catenary Heavy compound catenary Heavy simple catenary Simple catenary

Subdivision of upgrade work

The upgrade of the Tsugaru Straits Line was divided into three sectors: the sector passing under the Tsugaru Straits through the Seikan Tunnel, and the two sectors connecting onto the Honshu and Hokkaido tunnel entrances, extending through to the existing Nakaoguni and Kikonai stations, respectively. The two connecting sectors comprise tunnels, bridges and embankments, and the JR Morioka branch office is responsible for the Honshu connecting sector, whereas the JR Sapporo branch office is responsible for the Hokkaido connecting sector. The Seikan Tunnel was built by the Seikan Construction Bureau, and the greater part of electrical work has been carried out by the Kanto branch office.

Upgrading the Tsugaru and Esashi Lines

The Tsugaru Line between Aomori and Nakaoguni, and the Esashi Line between Kikonai and Hakodate were both local, unpowered lines. To rectify this situation, JR Hokkaido was given the job of electrifying and reinforcing the tracks to improve the general standard of the lines.

The gauge of the Tsugaru Straits Line

Rail types

New 60 rails (60kg weight per meter) have been laid in shared sectors where the Shinkansen will run in parallel to the existing line. These are the same rails as are used by the Shinkansen.
The rails used in general sectors, where only the local train will run, are 50 rails. IMAGE

Tri-rail slab-type tracks

To minimize maintenance, slab-type tracks have been utilized as much as possible for the Tsugaru Straits Line. In order for the Shinkansen and local trains to run on the same tracks, a tri-rail track has been laid over the entire extent of the line, allowing for both standard gauge (1435mm) and narrow gauge (1067mm) trains.
Throughout the Seikan Tunnel, sea water resistant medium Portland cement has been used for the slabs in order that the tracks are not damaged by sea water. The slabs have also been pre-stressed so that they do not crack.

The longest rail in the world

Long rails have been used throughout the line because of the smoother ride they offer and to minimize maintenance. In particular, the signal circuit for the Seikan Tunnel is based on an uninsulated rail circuit which does not require insulated connections, and so rails were welded together to form a single rail 52.570km long, running almost the entire length of the tunnel. This super long rail is the longest single rail in the world.

A short history of the Tsugaru Straits Line

April 1946 Geological study started.
June 1949 Japan National Railways separated from the Ministry of Transport.
August 1953 Added to planned lines under Railway Construction Act.
September 1954 Toya-maru Accident.
March 1964 Japan Railway Construction Corporation established.
Took over research operations from JNR.
April 1964 Minister of Transport ordered the basic plan (research).
May 1964 Started to dig an inclined shaft on at Yoshioka, Hokkaido.
October 1964 Tokaido Shinkansen started commercial services.
March 1966 Started to dig an inclined shaft at Tappi, Honshu.
April 1971 Minister of Transportion ordered the basic plan (construction) and construction enabling to operate the Shinkansen.
September 1971 Minister of Transportion approved the construction execution plan.
September 1971 Main construction started.
June 1982 Tohoku Shinkansen started commercial services.
July 1982 Construction execution plan between Nakaoguni and Kikonai approved.
August 1982 Construction of the entrance section of the Seikan Tunnel started.
January 1983 Pilot tunnel completed.
Honshu and Hokkaido connected on land.
March 1985 Main tunnel completed in the central section below the channel.
September 1986 Rail construction completed.
Honshu and Hokkaido connected on rails.
April 1987 JR Hokkaido established.
Decided to operate the Tsugaru-kaikyo line.
March 1988 Commercial services of the Tsugaru-kaikyo line started.

Tsugaru Straits Line

Seikan Tunnel Statistics
ItemQuantity Remarks
Total length of pilot boring 121,000m Distance between Tokyo and Mishima
Amount of injected soil 847,000m3 1.6 times the volume of Kasumigaseki Bldg.
Amount of used steel 168,000 t Steel for 42 Tokyo Towers
Excavated amount 6,330,000m3 5.1 times the volume of Tokyo Dome
Amount of used explosive 2,860 t Explosive for several hundred times an amount used for Sumidagawa Fireworks Competition
Concrete 1,740,000m3 Almost similar to the amount of concrete used for Kurobe Dam
No. of track slabs 21,540 1.2 times the height of Mt. Fuji if stacked up
Electric cable 1,276km Distance between Aomori and Kyoto
Total No. of workers 13,800,000 Approx. 1/4 of the working population in Japan