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Five feared dead in Japanese tunnel collapse Feb 2012
Peter Kenyon, TunnelTalk
Five construction workers are missing, presumed drowned, after a subsea tunnel under construction at the Mizushima refinery in Kurashiki collapsed and flooded.

Flooded 30m deep access shaft

The accident, at the JX Nippon Oil and Energy Corporation owned refinery, happened at about 12:30pm on Tuesday, 7 February.
On Wednesday (8 February) a JX Nippon spokesman told TunnelTalk from Japan: "The tunnel collapsed under sea level and filled with water. There was so much debris that the rescue effort by police divers had to be called off after two hours because of poor visibility and dangerous conditions. One person was evacuated but five more are missing."
The spokesman said that the missing workers are employees of two different companies: Tokyo-based main contractor Kajima Construction and Chita-based sub-contractor Koshin Kensetsu.

Subsea alignment

Both companies are involved in building the 5m diameter 800m long tunnel being excavated to link Factory A and Factory B of the refinery, which are separated by a sea channel.
He could not confirm the tunneling method, but local media sources claim it to be of a 'shield method'. The tunnel collapsed 140-160m from the 30m deep access shaft at Factory B, said the spokesman, adding, "excavation started in August 2010 and was scheduled for completion in March 2014. It was to house a pipeline that would allow exchange of petrochemicals between both sides of the refinery."
The survivor is reported to have been working at the bottom of the 30m deep access shaft at the time of the collapse. As the water rushed to fill the tunnel he was raised to the surface by the force of the rising water.
JX Nippon is Japan's largest oil company, specialising in petroleum and petrochemical refinery, and its Mizushima refinery has the capacity to process 365,000 barrels of oil a day.
References
Symptoms of the collapse syndrome - TunnelTalk, July 2010
Cairo Metro tunnel collapse - TunnelTalk, September 2009
Fatal collapse on Cologne's new metro line - TunnelTalk, March 2009
Tunnel collapse in Albania closes highway - TunnelTalk, November 2009
The insurance consequences of failures - TunnelTalk, August 2010

           

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