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.
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