Brunel's tunnel under the Thames
Today, we might be used to engineering feats like the channel tunnel but in the 1800s, a father and son team of engineers, Marc Isambard Brunel and Isambard Kingdom Brunel built the first ever tunnel to be dug under a navigable river. Ginny Smith headed down to the Brunel museum in Rotherhithe, London, to meet Director Robert Hulse to hear how the tunnel first got constructed.
Robert - The tunnel here is the first tunnel under a river anywhere in the world. It's also now the oldest tunnel in the oldest underground system in the world. So, this is a very important site. Before Brunel, the way they dug tunnels was they dug trenches and they put the railway in the trench and then covered it over. But you can't do that under a river. What Brunel is doing here for the first time anywhere in the world is he's digging a tunnel by burrowing a hole like an animal. And the modern tunnel boring machines are just automated developments of the human tunnel boring machine that Brunel used here.
Ginny - So, how exactly do you go about doing something like that?
Robert - There's a model of it here. The first thing is, you have to get to the depth you want to dig and this is a caisson. It's a brick-lined shaft but it's actually a tower that was sunk. They lowered into this hole a huge cage made up of 36 little cages. Each little cage is the size of a man and in front of each man, you see in the cage, there are wooden planks and they're held in place by metal poles. So, they take out the first two poles, they take out the plank, they dig to 4 inches, replaced the plank, extend the poles 4 inches, brace them against the cage, and take out the one below. Dig to 4 inches, replace the plank, extend the poles, take out the one below. When they've done the hole of the wall in front of them, and the man above and below has done the same, then those 3 in a row moving independently are pushed forwards and as they push the cages forwards, brick layers working behind the miners build the tunnel walls.
Ginny - And what happened to all the earth that they were digging out?
Robert - The clay would be baked into bricks and sent back down again to line the tunnels. It's actually quite a green piece of engineering.
Ginny - So, what kind of challenges would the people working down here be facing?
Robert - As they work in these cages, they're showered with Thames water, which wouldn't be pleasant today, but in 1825, the Thames is the biggest open sewer in the world. So, they're being doust all day with effluent and they're not just dodging sewage either. They're digging through what was recently marsh. When you get marsh, you get marsh gas or methane. The miners don't work in the dark - that would be unreasonable - they each have an oil lamp which of course ignites the methane. So, there are flames as well as sewage shooting from the cages where these poor men are working. It is the worst job in the world. But if I tell you, they're earning more than a police inspector. This is very well-paid work.
Ginny - Are these tunnels still in use today?
Robert - Yes, they are. They're now part of the London Overground. This tunnel is 170 years old. It didn't open for trains. It opened for a variety of rather bizarre and extraordinary customers and visitors.
Ginny - So, if it wasn't used as a railway, why was it built?
Robert - It was built to move cargo by horse in cart, but they ran out of money and they couldn't afford to build the ramps to get the horses and the carts down into the tunnel. To try and make extra money, in the archways between the north and the south bound tunnel, they built shops. So, this is the world's first underwater shopping arcade. In 1852, they launched the world's first underwater fairground - sword swallowers, fire eaters, magicians, tight rope walkers.
Ginny - So, it became a tourist destination. People would go just for the sake of going rather than because they needed to get from A to B.
Robert - Absolutely. If you came to London in the 1840s and you had just three things on your list, this would be one of them. People came here in their millions because they didn't believe it could be done. In 1843, walking under a river the size of the Thames is like walking on the moon.
Ginny - So, if our listeners wanted to go and see any of Brunel's tunnel, is any of it still visible?
Robert - Yes, it is. You can travel through the tunnel itself on the trains on the London Overground and the trick is, to get off at Wapping and wait at the end of the platform then the next train that comes in will light up the arches where the shops used to be. And also, there is an underground chamber that caisson still exists. Here in Rotherhithe, the caisson is empty and we're now fundraising to fit it out as a concert hall.
Ginny - Brilliant! So, can you take me down to see that?
Robert - I can.
Ginny - We're going out of the museum around a corner and now, we're at a tiny door that even for me looks too small.
Robert - Yes, they're hobbit holes. Follow me.
Ginny - We're bending almost double and crawling through the tiny little passageway, but it's not too long which is good. There are some rather rickety looking stairs which I'm now going to attempt to climb down without dropping my recording equipment. Wow! So I've just come around a corner and you can really see the cavern opening out.
Robert - Here's a picture of the tunnels as it was in 1843. It's very grand as you see.
Ginny - Wow! So, they've got a beautiful sweeping double staircase which is a little bit different from the one we came down. What happened to that?
Robert - Well, you see the line a bit there.
Ginny - Oh, yeah. So, why isn't that here anymore?
Robert - When they started running trains through here, they took out the wooden staircase because there were steam trains. It's going to be fire and smoke and tinder.
Ginny - So, it must have been quite a big feat to have dug a tunnel under such a big river as the Thames. Did anything go wrong?
Robert - Everything that could go wrong went wrong. The Brunels thought it would take 3 years to get to Wapping, but it took 18. The tunnel flooded 5 times altogether and the first flood was in May 1827.
Ginny - So, you said that was the first flood. It happened again.
Robert - Yes, it did. Work began again, but 12 weeks later, there was another terrible flood and this time, 6 men died.
Ginny - Did the water get this far?
Robert - Yes, the water broke in and came roaring down the tunnels and filled this chamber. Six men drowned in here. One man as luck would have it was rescued and taken out. As you notice, we can make it through the little entrance that you came through, revived, and sent to Bristol to convalesce, where he designed a bridge, built a railway, built a steamship, built another steamship. This is the near-death experience of our most famous engineer, Isambard Kingdom Brunel.
Chris Smith - So, when they were saying about how they actually do their digging, they had this giant cage like a climbing frame with men at various points in these cages within this giant climbing frame. The back wall of which was planks up against the mud they were digging into. They'd take out a plank, dig 4 inches in and then put the plank back in 4 inches further in, and they keep doing that all the way through their cage and every man in zone cage does that and then the whole things slides forward.
Dave Ansell - Yeah, because the muds and the clay which they're digging through is kind of sloppy and if you just leave it, it will kind of slump. They can't leave it there for very long as they had to support it again with the planks very, very quickly and you move the whole cage forward into that gap and then very quickly, you brick up the gap.
Chris - Gosh! I'm glad I didn't do that job.