How the world's longest underwater tunnel was built?
by Lee Ho Sung
영국과 프랑스 사이의 채널 터널은 여러가지 여러움을 딛고 완성되었다.
The English Channel connecting England and France has been one of the most critical marine passages. Engineers of the early 1800s proposed various plans for spanning the 33-kilometer gap. By the end of the century, an underwater passage had picked by Europeans.
The invention of the tunnel boring machine and the discovery of a stable layer below the seabed made this tunnel project more feasible. But at the time, Britons thought their geographic isolation from the European Continent has a strategic advantage. So, they shut down plans for the tunnel.
The rise of aerial warfare made these worries obsolete, and new economic concerns arose to replace them. Finally, 100 years after the initial proposal, the two countries reached an agreement to proceed with the tunnel with private funding.
In 1985, a group of French and British companies invested in the tunnel, the most expensive infrastructure project. The design called for three separate tunnels - one for trains to France, one for trains to England, and the last for service between them.
In 1988, workers began excavating from both sides, planning to meet in the middle. Early surveys of the French coast exhibited the site was full of fault lines. These small cracks let water seep into the rock, so engineers had to develop waterproof boring machines. The British expected drier conditions, and go ahead with regular borers. But only months into the work, water flooded in through undetected holes. To drill in this wet chalk, the British had to use grout to seal the cracks.
With these obstacles behind them, both teams began drilling at full speed. Boring machines were able to drill up to 1,300 tons at nearly 3.5 meters per hour. As they dug, they installed lining rings to stabilize the tunnel behind them, making way for support wagons following each machine.
Even at top speed, work had to proceed carefully. Previous surveyors should check the chalk layer between rock and clay. Furthermore, both teams had to check their coordinates regularly to ensure they were on track to meet within 2 centimeters of each other. The borers employed satellite positioning systems, as well as paleontologists, to maintain this delicate trajectory. During construction, the project employed over 13,000 people and cost the lives of ten workers. But after two and a half years of tunneling, the two sides finally meet.
There was still work to be done before open - from installing crossover chambers and pumping stations to laying over a hundred miles of tracks, cables, and sensors. But on May 6, 1994, an opening ceremony marked the tunnel’s completion.
Today, the Channel Tunnel services over 20 million passengers a year, transporting riders across the channel in just 35 minutes.
Unfortunately, thousands of refugees have tried to enter Britain through this tunnel illegally. The history of the tunnel reminds us that breaking down barriers is the best for humanity.
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