The Channel Tunnel passes below the English Channel and connects England and France. The thirty-mile-long tunnel is located 250 meters below sea level. The Channel Tunnel, or "Chunnel" as it is called, is one of the longest tunnels in the world. There are acctually three tunnels involved. Two have rail tracks while the third is a service channel that is infrequently used for small vehicles. The idea of building this tunnel came at least hundred years before its construction. Even the construction work of the tunnel started at that time but was then stopped due to the fear of it being used as a medium to invade England. In 1970, the construction work again resumed and was finally completed in 1994.
The tunnels are fifty kilometers in length. All three were drilled through the rocks of the seabed of English Channel. The construction process started by digging the two main tunnels from both the sides of English Channel. A total of ten contractors worked simultaneously to achieve this spectacular engineering feat.
Various types of machines were used to drill the solid rocks beneath the channel. The two main tunnels have a diameter of 25 feet each, while the service tunnel has a diameter of 11 feet. The tunneling machines used were drilling machines that could chew and store the broken rocks and sediments by crushing them into small pieces. Most of these drills were air powered drills which moved on a predetermined path. As the boring machines moved forward digging the rocks, they sprayed high density concrete on the freshly dug tunnel walls to prevent sea water from seeping in. Excess of rubble from the broken tunnel was sent back to the land and out of the tunnel using a conveyor belt system.The tunnel was dug in a systematic preplanned manner which sloped downwards from both the sides. The service channel was also drilled in the same way by joining the two side tunnels once they were fully drilled.
Both the side tunnels have railway lines fixed inside it. The Eurostar passenger trains along with many cargo carrying trains use the railway lines. Using the tunnels, the trains can complete the journey between England and France is 20-35 minutes. The service tunnel in the middle is basically an emergency escape route that can be used in case of any fire or other similar accidents. Moreover, there are many cross over passages in between that allow trains to change tracks. The approximate speed of these trains is a hundred miles per hour.
The overall cost of the tunnel was around twelve billion dollars. Heavy vehicles can also use the tunnel but only through the special shuttle wagons. Moreover, air is supplied inside all the three tunnels through a special ventilation system. In 1996, a major fire took place in one of the shuttle wagons and thirty one people were trapped. However, everyone escaped because of the specially designed service tunnel.
The Channel Tunnel stands as a life line for both England and France. It is one of the most successful engineering feats that was considered almost impossible in the beginning. However, with perfect and precise planning from tunnel engineers and by using incredible civil engineering skills, this impossible task was brought to life to act a vital connectivity medium between two of the world’s most important countries.