Channel Tunnel
Build connections, not barriers.
Between Folkestone, UK, and Coquelles, France, 75 metres beneath the English Channel burrowing across the 50.5kM width is the world's longest undersea tunnel and only land connection to mainland Europe and the British Isles since the ice age. The Channel tunnel.
My journey around the the world of engineering begins in St Pancras station in London, at the long queue of the Eurostar terminal. When I'm finally onboard the train sets off, in less than an hour the windows go black and we disappear under the sea. After 20 minutes daylight returns and we emerge in France travelling at 190kmh towards Paris. Travelling through one of the most iconic pieces of rail and civil engineering in the world may be the best possible way to begin this adventure.
The idea to build a tunnel from Britain to France is not a recent one, in fact it was first proposed in 1802. However, due to the fact that at that point Britain and France were still in their phase on-and-off war that began in 1066 it was decided that this would be a major national security risk. 80 years and several wars later, the first attempt at a real tunnel began. This managed to reach a little of a kilometre before the British government decided the risk of the French sneaking through the tunnel and invading the UK was just too great to take the risk. This brought a swift end to the project. It would take another century and two world wars before both sides were convinced the other wouldn't try and invade through the tunnel. Fortunately, nowadays trust and respect between the leaders of the UK and France is at high and unbreakable levels....
Tunnelling finally began again in 1988 from both the British and French sides of the channel. Three tunnels were dug, two 7.6 metre diameter rail tunnels and a 4,8 metre diameter service tunnel between them, using 11 tunnel boring machines.
Since the tunnel boring machines were heading straight towards each other what happened when they met each other?
Simple, to avoid a collision one of the machines would throw a tunnelling equivalent of a handbrake turn (Though much less sudden and much more planned) straight down in the Earth. Most were then dismantled for scrap however, one of them remains buried forever under the channel. Or at least until alien archaeologists in the future excavate it to learn about human culture.
Aside from being the worlds longest undersea tunnel, the Channel Tunnel also features the largest cooling system in Europe. Without it, the heat generated from high-speed trains travelling through the tunnel would raise the temperature inside the trains to be comparable to a hot bath. Which when shared with 750 other people is far from a comfortable way to travel. To avoid slow cooking the passengers, 84 millions litres of coolant water is pumped through 480 km of pipes. Cooling this fluid in an efficient method presents a major thermodynamic challenge and requires extremely specialist equipment. Since 2016 4 Series E chillers by CenTraVac have been used with a power range of 2600kW to 14 000kW and a tightly guarded secret patented refrigerant to keep the temperatures down to a comfortable 35 celsius.
The Channel Tunnel finally opened for freight and passengers in 1994 and as is tradition for large scale rail projects, it was completed far later than planned and massively over budget. The first passenger on the Eurostar travelling to France was Queen Elizabeth II, 28 years later the tunnel annually carries 20 million people, and 22.55 million tonnes of freight -26% of the total trade goods between the UK and mainland Europe. Today it carries a slightly less prestigious passenger, me.
Onwards to Paris!
