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NIPPONIA No.20 March 15, 2002
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The World's Largest Tunnel Boring Machines
Kawasaki Heavy Industries, Ltd.
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One of the world's largest tunnel boring machines. It has a diameter of more than 14 m.
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Photo taken at the moment the boring machine pierced its way through the Eurotunnel. It took only two years to excavate 20 km. http://www.khi.co.jp/
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The Eurotunnel under the Strait of Dover joined Britain to France in May 1994. The boring machine used to excavate the tunnel was made by Kawasaki Heavy Industries of Japan. Cylindrical in shape, boring machines have cutter bits ("teeth") mounted at the front. The teeth are made out of an extremely hard metal, and as they spin around they cut into the ground, making room for the machine to inch forward. The boring machine used for the Eurotunnel was 8.78 m in diameter and 350 m in length, and had a total weight of 1,000 tons. It packed a lot of power, cutting through everything from mushy earth to hard bedrock, going on for 20 km without a break.
Tunnel boring machines being used to extend the subway network in Greater Tokyo have a diameter of 14 m. They are among the largest in the world.
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A representative of Kawasaki Heavy Industries told me: "Japan is the leading producer of large, 'cutting-edge' tunnel boring machines. There are several reasons why Japan has developed extremely advanced drilling technology. For one thing, underground geological conditions here can vary greatly. For another, Japan has many built-up urban areas where the only way to construct a subway tunnel is to bore horizontally underground, without disturbing the surface."
The work goes on, as huge mechanical "moles" made in Japan keep boring tunnels in different parts of the world.
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A Eurostar high speed passenger train leaving the EuroTunnel.
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The World's Strongest and Heaviest Wire Cables
for the World's Longest Suspension Bridge
Nippon Steel Corporation
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Measuring 3,911 meters from one end to the other, the Akashi Kaikyo Bridge is the world's longest suspension bridge. It links two of Japan's main islands, Honshu and Shikoku. Two wire cables—the strongest and heaviest in the world—support the bridge. Each cable weighs about 25,000 tons, and is made up of 36,830 wires bound together. A single wire has a diameter of 5.23 mm.
For about 70 years, bridge cables used throughout the world consisted of wires that could each suspend a force of 160 kg/mm2. But the cable wires for the Akashi Kaikyo Bridge have increased this tensile strength to more than 180 or even 200 kg/mm2. The wires were developed by the world-class steel maker, Nippon Steel Corporation.
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The Akashi Kaikyo Bridge, the longest suspension bridge in the world.
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Each main cable is about 4,100 m long, and has a diameter of about 1.1 m. If the individual wires making up the cable were joined end to end, the total length would be about 300,000 km. http://www.nsc.co.jp/ |
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Nippon Steel's PR office told me that Japan has the world's best technology for developing and manufacturing steel, and that this steel readily meets the extremely strict quality and performance standards of Japanese makers of electrical appliances and motor vehicles.
Two bridges in the planning stages will be much longer than the Akashi Kaikyo Bridge. The bridges, to span the Messina Strait in Italy and the Strait of Gibraltar between Spain and Africa, will require the development of a wire with a tensile strength of more than 220 kg/mm 2 Research has already begun. Takahashi Toshihiko of Nippon Steel's Steel Research Laboratories says that his company keeps pushing back boundaries, extending the limits of steel's tensile strength.  |
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