Model Railroading — Blog Post #7
European Railway Notes January 2017
Tunnels Part 1
Tunnels for railways seem like a pretty straight forward concept. To connect two places with a railway, when those places have mountains in between them, you think about a tunnel. Ideally, you’d build this tunnel in a straight line between the two places. But real life is more complicated. The Channel Tunnel provides an example but with a body of water in the way. Just build a tunnel from Folkstone in the England to Coquelles in France. Hold that thought. Going back to the late 19th century, there were attempts to actually build the channel tunnel. From the various ill-fated attempts, a lot was known about the geology of the channel. When the time came to build the current channel tunnel, it was known that the chalk marl underneath the channel was best for tunneling. So the tunnel was built following the layer of chalk marl which required many slopes and turns. Not at all the straight tunnel you might have expected.
Many other things complicate building any tunnel, let alone a tunnel that is over 30 miles long. One problem doesn’t get a lot of attention but, what do you do with all the material you remove to form the tunnel? Over 30 miles, that is a very large amount of material. You also have to plan to move all that material out of the tunnel. Assuming you dig from both ends, as you approach the middle of your 30 mile tunnel, all the material you need to remove has to be moved 15 miles to either end. Similarly, everything you need to bring in to build the tunnel also has to be moved 15 miles. I like engineering problems because they involve figuring out how to get things done in the real world.