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SCMP Reporter

With a history dating back almost a century, Kumagai Gumi is considered one of the world's leading contracting and engineering companies.

  Kumagai's expertise is tunnelling and the company is widely recognised as being at the forefront of tunnelling technology.

   Kumagai is responsible for developing the world's first multi-head tunnelling machine and has instituted other methods to increase the reliability and safety of underground working.

  With more than 6,000 professionally qualified building and engineering staff, Kumagai Gumi is credited with developing a special fabric liner that provides protection to underwater concrete tunnels by improving resistance to sea water.

  Naotake Satio, Kumagai's general manager in Hong Kong, said the fabric liner extended the tunnel's lifespan.

  In 1993, Kumagai Gumi and another respected Japanese company, Nishimatsu Construction, formed a joint venture to design and build on behalf of the Western Harbour Tunnel Company, Hong Kong's first dual three-lane immersed harbour crossing.

  The Western Harbour Crossing was the only privately funded 'build, operate and transfer' project included in the 10 Airport Core Projects (APC).

   The joint venture was given just 47 months to complete the complex construction with a budget of $7.5 billion.

  Mr Satio, who has been involved with constructing tunnels for almost 30 years, said the crossing was completed in a short time to an exceptionally high standard of quality. 'The skill and professionalism that Kumagai was able to draw on allowed all the contract requirements to be met in a surprisingly short period of time,' Mr Satio said.

  Of the more than 100 immersed tunnels that have been constructed around the world, five are in Hong Kong, providing cross-harbour road and rail links.

  The contract for the entire crossing and associated infrastructure was divided into three sections: the twin, three-lane immersed tube construction and placing; the approach works at West Kowloon; and the approach works and infrastructure works on Hong Kong island at Sai Ying Pun.

  The joint venture engaged Maunsell-Acer-Parsons Brinkerhoff (MAPB) as the contractor's designers and also awarded contracts to Nishimatsu Construction and Gammon Construction for the civil works on the West Kowloon and Hong Kong island sides of the tunnel.

  Richard Garrett, one of MAPB's design consultants, said that, throughout the design process, there had been significant input from the contractors involved.

  'Kumagai has built up a wealth of knowledge on immersed tube construction and it would have been foolish not to have drawn on that knowledge,' Mr Garrett said.

 Kumagai has successfully completed construction and tunnelling work on 15 major projects worldwide, including the Eastern Harbour Crossing, all three rail crossings in Hong Kong, the second harbour crossing in Sydney and the Bangkok Second Stage Expressway System.

   These and other projects placed the company in an ideal position to undertake the task of constructing and placing the immersed tube sections to form Hong Kong's third and largest harbour crossing.

   Kumagai also built the ventilation substructure on the Hong Kong island side.

  The contract called for the prefabrication of 12 reinforced concrete tubes, each measuring 113 metres and weighing 35,000 tonnes, to be cast in a disused quarry at Shek O.

   The company commissioned an expert consultant to advise on extending the life of the tunnel and special methods were used to waterproof each section of tube to give it resistance to sea water and make it durable for at least 120 years.

  Mr Satio said Kumagai Gumi's textile form method had been used in the construction of the tube sections which greatly improved the durability of the concrete surface.

   The system worked by removing excess water and entrapped air through tiny holes drilled in the form panels.

  'It has been a long-term dream for construction engineers to accomplish a durable concrete structure with a smooth and strong surface, free-form air and blow holes, and Kumagai has developed a solution,' Mr Satio said.



Kumagai on top of tunnel work