An aerial photo of the Pike River Coal Mine portal. Photo / NZ Herald
The blast from the mine explosion would have "reflected like a billiard ball off the walls" and passed multiple times in differing directions throughout the mine, an Australia mine safety expert says.
David Cliff, an associate professor at the Minerals Industry Safety and Health Centre at the University of Queensland,
explained to the Science Media Centre what the CCTV footage of the blast from the mine entrance reveals about the explosion.
Mr Cliff said the little piece of fabric mine chief executive Peter Whittall pointed out prior to explosion usually inclines towards the mine, indicating air is flowing into the mine. However in the video the fabric points down, indicating an absence of air flow. Mr Cliff said this is because the pressure wave has already entered the tunnel.
He calculated the pressure wave would take around two minutes to travel the 2km to the mine entrance, travelling at 60km/h.
"As the pressure wave travels over a distance, it will lose intensity and broaden - exactly the same as a water wave at sea. Thus the 52 seconds width is not a measure of intensity rather a measure of the distance from the source of the explosion," Mr Cliff told Science Media Centre.
"People should understand that the pressure wave of the explosion is just that it moves like a water wave so if the actual explosion wave has stopped combusting, the air transmits the pressure so the guys in the tunnel would have felt the shock wave and all the entrained dust etc, but the air would still have been breathable.
"An interesting fact is that a pressure wave is not very effective in blind headings - i.e. roadways that have no connections, as the pressure wave will tend to compress the air in front of it against the end wall - thus actually protecting those that are close to the end wall from major damage and maintain air in that cavity - so that may be some glimmer of hope.
"However the explosion pressure wave would have reflected like a billiard ball off the walls and end walls and could have passed multiple times in differing directions throughout the mine - much like making a break at snooker where the balls hit the cushions multiple times."
