Sasago tunnel fire and failure

Nine people died following a tunnel 'collapse' in Japan. The Sasago road tunnel, 80km west of Tokyo suffered a fall of concrete following a fire on Sunday. The collapse occurred at 08:00 local time.
The tunnel was closed as T&TI went to press while police investigated potential negligence. Survivors reported cars on fire and some walked for an hour to get out of the smoke.
The operating concession holder told the BBC that the tunnel was given, and passed, a major inspection two months ago.
British Tunnelling Society chairman Damian McGirr said the collapse appeared to be structural.
Road Tunnel Operators Association (RTOA) chairman Andy Evans told Tunnels: "There will always be a temptation to speculate on the cause of such an incident; until such time as a detailed engineering inspection has been conducted to determine the actual cause of failure that resulted in the collapse of these panels, any opinion on the cause of this tragedy will be just that - speculation.
"We would expect that following the immediate post-incident recovery, the tunnel will be made safe for extensive engineering inspections, testing and assessments to be conducted to determine the exact cause of the failure.
"International communities should be assured that that the normal response to any such tunnel incident is an immediate senior-level review to determine whether similar engineering details are in use; if they are, then immediate and detailed inspections are usually the first response - if found necessary these would then be followed by appropriate remedial works."

Peter Bishop, past chairman of the RTOA added, "Looking at the pictures and the profile of the tunnel I would say the Tunnel has a fully transverse ventilation system, meaning the air is blown from beneath the road deck so the section of concrete ceiling that has come down is part of the 'exhaust duct' to removed vitiated air."
"Unless these concrete panels are interlocked in some way and have slot holes in them that means there has been a catastrophic failure of all the support structure at one time, highly unusual but not impossible. I still think there may have been some ground movement above."