This 30 second long exposure shot captured things our eyes couldn't. We could only feel the great rush of wind when a train hurtled past. Here we can see the air has actually been sucked out of this side refuge. The atmosphere has been shattered with the light rays pulled apart.
You could feel this vortex effect a good minute before the train hurtled past.
The reason for the strong vortexes in this tunnel are caused by part of the second single bore tunnel being sealed up for experimentation during the late 60 early 70s. They did this to test the effects of two trains passing in a long tunnel.This was to do with the channel tunnel that was abandoned in 1974. Some of the vents and cross passages were sealed up to aid this experiment.
This wind and Vortex pressure is known as the 'Piston effect' The piston effect means that uniform airflows are caused by the motion of trains in a tunnel. There are two processes the moving train give the momentum to the air in the tunnel, one is friction and the other is the collision.
Air in a tunnel is confined by the tunnel walls, hence the movement of air is restricted. In the open air a vehicle travels along, air is being pushed and can move in any directions except into the ground. Air cannot escape inside a tunnel. The air is forced along the tunnel instead. Suction is created to allow the air to flow along the tunnel.
*To see the full 'Subterranea Standedge - A trip back in time' story click here Link
All three internal rail and canal tunnels are included.
There are over 12 miles of tunnels, all connected by side passages and adits*