NATIONAL GEOGRAPHIC: THE LONDON UNDERGROUND

I recently watched a documentary about expanding the London Underground. It was interesting to see how they make the tunnels these days, dealing with the challenges of digging in an old city. There was also a history of the tube given including how it was necessary to find a clean and economic means of propulsion. There is also a look at the New York subway and the Paris Metro which show the innovative techniques that have come about through improvements in tunnelling.

Due to London being such an old and historic city the Victorians decided that trains should not run across the city. This meant that all the stations in to London were in a ring on the outskirts of the city, making it difficult to get in to the heart of the city. Thus was born the idea of an underground railway.

 In the early days the work was manual and dangerous. It involved two men digging in a tunnel shield. Powerful hydraulic jacks were pushed forward every 60cm that was dug and a metal cylinder was put in the gap. Many workers died during the construction of tunnels worldwide so giant boring equipment has developed which is automated.

A look at the methods that were needed for London, New York and Paris, all with individual challenges shows just how resourceful and ingenious humans can be. Of particular interest was the way in which Big Ben had to have the ground beneath it reinforced before a new line to Canary Wharf could be undertaken. As the clock and parliament are standing on a bed of shale that is not very solid the ground beneath the buildings had to be reinforced by injecting concrete through rods that were embedded deep below the surface of the ground. The engineers that were interviewed were confident that this solution would prevent the buildings from capsizing. Whether they have factored in thousands of tube trains travelling through this ground causing vibration is another matter: I suppose they have but it still feels to me that the whole area could move if there was heavy use of the line.

Other innovations are limited by the size of the tunnels, therefore research has been carried out in to aerodynamics, lightweight and strong materials, ventilation and ways to maximise the payload. Events such as the London tube fire also hastened improvements after a wooden escalator caused a massive fire and fatalities. Lessons were learned not just about how fire spreads but the danger of smoke and toxic fumes created by burning wood as well as evacuation procedures.

This is an interesting documentary if you are interested in trains or transport history: it also shows just what we can achieve with planning and vision. People use the underground every day, taking it for granted, and are probably unaware of the work that went in to providing a high speed transport system for greater London. A good watch.