The Channel Tunnel also knows as the Euro Tunnel is a tunnel that connects Folkestone in the United Kingdom with Coquelles in France. What is incredible about this structure is that it the tunnel goes underwater for 50.5 kilometers. The tunnel has the largest portion of undersea water in the world however it is not the longest or the one that goes the deepest only loosing to the Seikan Tunnel in Japan. The purpose of this Tunnel is to take the Eurostar shuttle a traindesigned for this shuttle. (1)

The construction of the tunnel in 1987 and it was completed in 1994, it is considered one of the most complicated structures in the area of civil engineering in the 20th century. It has a total capacity of 600 trains each war per day. The construction of the tunnel took place at a rate of 250 feet per day by using tunnel boring machines that are like large cylinders with a length of two football fields. The total amount of dirt that was taken out of the tunnel were of about eight million cubic meters of dirt.(2)

However there were some design flaws with this structure, because there were some safety issues included with the trains themselves. This led to future increase in the amount of safety regulations that were needed to decrease the flaws from both sides.

There were two main accidents one which occurred in 1996 were the train was in its way to france and the train caught in fire and due to the damages 500 meters of track had to be replaced. In 2008 there was another accident that occurred in which 60 million pounds to repair the damages that were caused by the fire.(2)

Sources

1: http://en.wikipedia.org/wiki/Channel_Tunnel 

2: http://www.brighthub.com/education/homework-tips/articles/49126.aspx