BBC: The Monster Tunneling Under London (designed with PTC Creo)

Subterranean London is a crowded environment, home to a tangled tapestry of tunnels, sewers, foundations, power lines and abandoned stations that excite archaeologists and send a shiver down the spine of anyone who has to actually build anything down there.

Which makes it all the more remarkable that engineers have managed to construct 26 miles of fresh tunnels for the underground section of one of the world’s biggest engineering schemes: London’s showcase public transport project, Crossrail.

The quiet tunnels are in stark contrast to the busy streets above (Credit: Crossrail)

For years, gargantuan machines have been painstakingly threading their way beneath London. Today, three years after its May 2012 start, tunnelling is almost complete. Deep beneath the streets of East London, the project’s final two gargantuan tunnel boring machines (TBMs), Victoria and Elizabeth, are approaching their final destination. When they do, they will complete a process that has seen eight separate machines painstakingly thread their way beneath the heart of one of the world’s busiest cities.

Each of the tunnelling machines weighs up to 1,000 tonnes (Credit: Crossrail)

The machines are a remarkable and unique pieces of equipment. Purpose-built for Crossrail by German firm Herrenknecht – one of a handful of TBM manufacturers in the world  (and a PTC Creo customer)– they cost around £10m ($15m), weigh close to 1,000 tonnes, have an external diameter of 7.1 metres (23ft) and from cutting-face-to-end stretch 150m (500ft). Read more.