By: Laurie Winkless
Tunnels, that is. All over the world, Tunnel Boring Machines (or TBMs) are chewing their way through the packed subterranean network of your nearest city. But something you might not know is that they’re all given women’s names. Naming a machine after a human isn’t that weird, right? Many of us have named our cars after all, but it goes a bit deeper for TBMs. According to tunnelling tradition, a TBM cannot start work until it is officially named. But exactly where we got the tradition of naming them after women remains a bit of a mystery.
Some sources suggest that it comes from the 16th century, when miners, armourers, and artillerymen prayed to Saint Barbara. Legend has it that Barbara’s father had locked her in a windowless tower when he found out about her conversion to Christianity. Later, a flash of lightning struck him dead, and since then, all trades associated with darkness and the use of explosives have recognised Barbara as their patron saint. Today’s tunnel engineers see themselves as fitting that description, and so give TBMs women’s names in Barbara’s honour. Others suggest that the tradition comes from the link between miners and ship-builders – their physical strength and similar skills often saw men switch between trades as the need arose. Boats have long been given the pronoun ‘she’ (again for reasons unknown), so perhaps using women’s names for tunnelling machines started there?
Regardless of its beginnings, this tradition is carried out throughout the world today, as a sign of good luck for the project ahead. And, perhaps surprisingly in our increasingly secular world, most tunnelling projects still erect a shrine to Saint Barbara at the tunnel entrance.
Anyway, before we meet some of the First Ladies of the Underground, let have a quick look at how they work. First off, TBMs are huge. Bertha, the largest TBM in the world, is currently working her way under Seattle. She has a diameter of 17.5m, is 99 m long, and weighs over 6,000 tonnes. If we measure her in units of ‘double decker buses’ – she’s as tall as four parked on top of one another, as long as eight parked nose-to-tail, and weighs as much as 467 of them. So it’s no surprise that she’s usually referred to as ‘Big Bertha’.
So what do TBM’s like Bertha do with all that…girth? In their simplest form, TBMs are cylinder-shaped machines that can munch their way through almost any rock type. As I mentioned in my book, Science and the City, TBMs are generally referred to as ‘moles’, but I prefer to think of them as earthworms. Worms eat, push forward and expel whatever is left over, and while there are lots of different types of TBM, they pretty much all do those same three things.
At the front, TBMs have a circular face covered in incredibly hard teeth made from a material called tungsten carbide. As the cutter-head rotates, it breaks up the rock in front of it. This excavated material is swallowed through an opening in the face (some would call it a mouth) and it is carried inside the body of the TBM using a rotating conveyor belt. There, it is mixed with various additives (rather like saliva or stomach acid in some animals) that turn the rock into something with the consistency, if not the minty-freshness, of toothpaste. After digestion, this goo is expelled out of the back of the TBM, and it travels along a conveyor belt, until it reaches a processing facility above ground. There, the goo is filtered and treated, with much of it reused in other building projects.
Because of their shape, TBMs produce smooth tunnel walls, which can then be lined using curved segments of concrete. TBMs manage this part of the process too – many metres behind the cutter-head, large robotic suction arms called erectors (stop giggling) pick up and place the concrete panels, to form a complete ring. As the TBM moves forward, more and more of these rings are put into place, until the tunnel is fully clad. In this way, cities across the globe can produce fully-lined tunnels at the rather impressive rate of 100 m per week.
Enough background. Time to meet some of the TBMs boldly going where no machine-named-after-a-woman has gone before.
London – Ada, Phyllis, Victoria, Elizabeth, Mary, Sophia, Jessica and Ellie
Crossrail is Europe’s biggest engineering project. Since 2009, they’ve constructed two brand-new, 21 km-long tunnels across London, running east-west. To do this, they used eight TBMs, and as tradition dictates, each was given a woman’s name, selected by members of the public. The first six machines were named after historical London figures, whilst the final two machines were named after ‘modern day heroes’. Because two TBM’s excavate parallel tunnels at the same time, they’re also named in pairs.
– Mary and Sophia: These two excavated Crossrail’s new Thames Tunnel, between Plumstead and North Woolwich. They were named after the wives of Isambard and Marc Brunel, the famous engineers who constructed London’s first Thames Tunnel over 150 years ago. The women were a lot faster than their hubbies though – the original tunnel took 16 years to construct. This one was completed in just eight months.
– Victoria and Elizabeth: Can you guess which women from history these TBMs were named after?! Yep, Queenie #1 and #2. In the citation, the reason given was that “Victoria was monarch in the first age of great railway engineering projects and Elizabeth is the monarch at the advent of this great age.” Victoria and Elizabeth excavated the tunnels that run between Canning Town and Farringdon, finishing the job in May 2015. As an aside, the Crossrail route itself will appear on tube maps as ‘The Elizabeth Line’, which is disappointingly predictable. I was rooting for ‘The Brunel Line’ myself, but hey.
– Ada and Phyllis: These may be my favourites – named after the world’s first computer scientist, Ada Lovelace, and Phyllis Pearsall, who single-handedly created the London A-Z. Lovelace was a woman before her time – without her work, Charles Babbage and his ‘analytical engine’ would have been nothing more than a rich-man and his hobby. Pearsall, on the other hand, got lost on the way to a party in 1935, and decided the maps were inadequate. She walked a total of 3,000 miles to compile the first comprehensive street map of the city. Their Crossrail reincarnations drove west from Farringdon station, laying the groundwork for the second stage of the project.
– Jessica and Ellie: These names were selected by primary school children from East London, and they come from heptathlete Jessica Ennis-Hill and swimmer Ellie Simmonds, who won gold medals at the 2012 Olympics and Paralympics held in the city. Like their human counterparts, these TBMs were hard-working, each excavating two sections of Crossrail’s route.
London has two brand-new TBMs too, which will be working on the extension to the tube’s Northern Line – the line I spent almost all of my 13 years in London living on. Like Crossrail’s Jessica and Ellie, the names of the newbies – each weighing in at 650 tonnes (or 50 double-decker buses) – were selected by schoolchildren. They drew inspiration from pioneering women in aviation. One is named Amy, after Amy Johnson, the first female pilot to fly solo from Britain to Australia. And the second is Helen, named after the first British astronaut, Helen Sharman.
Seattle – Big Bertha
What more can I say about Bertha? Well, she was named after one of Seattle’s early mayors. In fact, Bertha K. Landes was the city’s first and only female mayor…. And she’s still widely regarded as one of the best they ever had. She fought against police corruption and dangerous drivers, and advocated for municipal ownership of the Seattle City Light and street railways. In 2013, Bertha-the-TBM started her long journey across the city, excavating a multilevel road tunnel to replace the Alaskan Way Viaduct. But just six months into the project, Bertha ground to a halt. Investigations showed that some of Bertha’s cutting teeth had been severely damaged by a large steel pipe embedded in the ground that hadn’t shown up on surveys. Over the next two years (yes, really), construction engineers dug a recovery pit, so that they could access the machine’s cutter-head, and partially replace it. Bertha resumed tunnel boring in late December, 2015. As I type, she’s also on a pause because of some misalignment, but this stoppage is expected to be temporary. Poor Bertha.
Auckland – Alice
Since moving to New Zealand in December, I’ve had a bit of rail-infrastructure-shaped gap in my life. Thankfully, Kiwis are also fans of TBMs, but they tend to use them for road tunnels. The latest one to finish her work is Alice – a 3200 tonne (246 buses) TBM that spent the last two years carving a path between Auckland’s major transport routes. Alice’s tunnel connects State Highway 16 and State Highway 20, and once it opens in April/May 2017, it will complete the city’s ring road. Having recently spent more than an hour in Auckland traffic heading to the airport, I can attest to how much the road is needed! Since finishing her tour of duty, Alice has since gone to a farm when she can roam free amongst all of the other TBMs…. Oh if only this were true. In reality, the largest sections of the machine are being shipped back to her German manufacturer. There, her components will be used to build another TBM. So it’s not been a bad life, I guess.
San Francisco – Mom Chung
Mom Chung is another TBM that has already done her job and is now ‘in retirement’. She is named after Dr. Margaret Chung, the first American-born female Chinese physician, who practiced medicine in the heart of San Francisco’s Chinatown. During World War II, she took lots of American servicemen under her wing, earning her the nickname ‘Mom’. Legend has it that when one of her ‘sons’ became a congressman, he filed the legislation to create a female branch of the Navy, in response to pressure from Mom, who was a firm supporter of women in the military. Mom Chung-the-TBM built the southbound central subway tunnel in San Francisco, and even had a Twitter account for a while.
Of course, actual, real-life women work alongside (and inside) these machines. As more women are attracted into engineering, tunnelling is no longer solely a male pursuit. Women still make up a small percentage (around 11% of the UK construction sector, for example), but those numbers are slowly growing. So no matter which way you look at it, women are literally boring. Tunnelling is awesome.
*** You can follow Laurie on Twitter @laurie_winkless. She also wants to say thank you to Dr Jess Wade for inspiring this article. If you love science and very cool doodles, you can also follow Jess on Twitter – she’s @jesswade