Like a pair of boring inchworms, two massive tunnelling machines are moving under Vancouver.
That's what a recently released video shows; the animated clip gives people a look at exactly how the boring machines, named Elsie and Phyllis, are moving underneath Broadway.
The two machines are huge, filling up an area the size of the width and height of the tunnel and trailing back 100 m.
That's because the front of the machine grinds away the ground where the tunnel will be; the trailing section of the machine holds a system that fits in prefabricated sections of the tunnel like a puzzle. Each section is part of a ring.
The machine builds a ring that fits in with the previous ring it built. In this way the machines inch along, one section at a time.
