The Seikan Tunnel will link the Northern Hokkaida Island to the Main Honshu Island in Japan under the Strait of Tsugaru. It will be the longest railway tunnel in the world. The main characteristics of the tunnel are described: total length (53,850 km), length under the sea (23,300 km), maximum depth of the strait (140 m), depth of the tunnel under the bottom of the sea (100 m), cross-section of the main double-track tunnel (9,60 m), minimum radius of curvature (6500 M), longitudinal gradients (12 for 1000 and 3 for 1000). Volcanic rocks lay under the sea for a third of the width and sedimentary rocks from the Miocene era for the other two thirds. Site investigations showed three main zones: north side (Hokkaido): tuff (sigma 40 kg/cm2)/ south side (Honshu): harder rock (sigma 700 kg/cm2)/ to the north and the centre: microcracks and small amount of water; to the south: faults with important ingress of water. It is not envisaged to take special precautions against earthquakes. An outline is given of the main drilling operations. It is forecasted that progress will be 300 m/month with the Telescopic Atlas Copco drilling machine (4 m cutting diameter; rate of progress: 2 m/h; overall power: 440 kw; total weight 95t). The work carried out 6 days per week, day and night, with three teams enables 1500 m to be completed the first year; the following 800 m took nearly two years. The terrain crumbled easily and necessitated support by means of metal arches and mesh fixed into position with shotcrete placed immediately behind the jacks of the machine. Those arches are placed into position without stopping the machine every 0,80 to 1,20 m and even every 0,60 m. The final reinforced concrete lining will be 0,70 M thick. After the first 1500 m section, the strength of the rock diminished progressively resulting in the machine being abandoned. Investigations are being conducted to decide on the next drilling method. The total cost of the work is estimated at 200 milliards yens per km of the railway tunnel which will have two tracks and two service galleries. The end of the work is programmed for May 1976.

  • Corporate Authors:

    PYC Edition

    254 rue de Vaugirard
    Paris Cedex 15,   France 
  • Authors:
    • RUFFERT, G
  • Publication Date: 1973-3-4


  • French

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Filing Info

  • Accession Number: 00125247
  • Record Type: Publication
  • Source Agency: Laboratoire Central des Ponts et Chausees (LCPC)
  • Files: ITRD, TRIS
  • Created Date: Dec 3 1975 12:00AM