Steel bracket failure brings down concrete roof panels in Japanese tunnel killing nine and injuring a further two this week.
Tunnel owner the Central Nippon Expressway has launched an investigation into the cause of collapse with engineering experts telling NCE the most likely cause the failure a steel bracket holding up a suspended precast concrete roof.
“It’s the failure of long steel bolts holding up the ceiling separating the roadway and air ducts,” said Halcrow global technical director for tunnelling Martin Knights.
The 4.7km long tunnel is located on Chuo Expressway about 90km west of Tokyo. It links the capital with the mountainous regions to the west of the country.
Construction of the twin bore road tunnel was completed in 1977 last underwent an inspection two months ago.
It consists of a central bore, about 7m tall and 6m, with a suspended concrete floor about 5.5m above the dual carriage road level.