The Seikan Tunnel is one of
the best examples of engineering. Its construction process provided useful
technologies that have been used worldwide.
The idea of building the
Seikan Tunnel was introduced before the Second World War, but the actual
investigation about building the tunnel was started after the war. The
requirement of Seikan Tunnel was propelled after the Toya Maru ferry accident in 1954. Construction was finally
started in 1964 with the first investigational inclined shaft sunk on the
Hokkaido.
Afterward, overcoming many
difficult problems, the primary shaft of the tunnel was opened on March in
1985. The first trial run was performed on Oct. 21st 1987. The Seikan Tunnel,
Yoshioka, and Tappi Undersea Stations
started service on March 13th, 1988. This undersea tunnel links the main island
of Honshu with the northern island of Hokkaido and offers a safer way for
crossing the Tsugaru Strait.
• Vertical
shaft
These shafts are constructed
vertically downwards. These shafts were used for elevators to haul workers,
materials, and machinery. Now these shafts are used for circulating fresh air
inside the tunnel.
• Main
shaft
This is the main tunnel, in
which the railway lines are placed. This shaft is constructed 7.85 meters high
and 9.7 meters wide.
• Pilot
drift shaft
It was used as a supporting
shaft for digging the main shaft and the construction shaft. Testing and research
of the nature of the soil and sea water leakage were performed using this
shaft. The digging operations were performed after all these inspections.
Presently, this shaft is used for drainage and ventilation.
• Construction
shaft
The construction shaft is
built to the side of the main shaft. This shaft was used for connecting guide
paths. It was very important because it enhanced the pace of digging by
increasing the face. It was also used for transporting materials and
machineries.
• Inclined
shaft
Two main inclined shafts were
constructed, first in Yoshioka and the second in Tappi.
It was made inclined at an angle of 14 degrees to the side of seabed, and it
was mainly used for geological surveys. Rather, it was also used for
transporting workers, materials, machinery, and the rocks and mud left due to
the dig. Now, a cable car is used in this shaft to carry materials.
• The entire tunnel is 53.85
km long, of which the seabed section is 23.30 km and surface section is 30.55
km.
• The maximum curve radius of
the tunnel is 6.500 m.
• The maximum grade of the
tunnel is 12/1000.
• The minimum overburden under
seabed is 100 m.
• The maximum depth of the sea
is 140 m.
• The cross section of the
tunnel is a double track Shinkansen type.
• Approximately 85,000 tons of
cement was used to construct the tunnel.
• The amount of steel
materials used in the tunnel was17,000 tons.
• The amount of soil dug was
approximately 630 thousand square meters.
• Approximately 2,900 tons
explosives were used.
• 14 million workers were
employed during the peak of construction.
• The Yoshioka Undersea
Station and Tappi Undersea Station are
positioned 149.5m and 135.0 m below the sea level, respectively.
• The overall construction
cost of the Seikan Tunnel was 690 billion yen.
• Bicycles and diesel engine
trucks are used for the inspection of the tunnel.
• Two gasoline-powered
passenger cars are used for inspection of the main shaft.
• A cable car is used for
going inside the tunnel from the ground. This car can move at 150 m per minute.
• The environment of the
tunnel is maintained with the temperature 20 degree Celsius, and humidity is
maintained in between 80 to 90 percent.
• Maintenance bases are
constructed inside the tunnel, in which the largest base is 16 m wide, 10 m
high, and 91 m long.
The Seikan Tunnel is one of
the largest tunnels in the world. Most of the technologies used in its
construction were applied for the first time, and now, these technologies are
used worldwide. The process of inspection of this tunnel is unique, and the
Seikan Tunnel is a lasting gift of engineering for Japan.