How the world's longest underwater tunnel was built - Alex Gendler
-
0:08 - 0:12Flanked by two powerful European nations,
the English Channel -
0:12 - 0:16has long been one of the world’s
most important maritime passages. -
0:16 - 0:18Yet for most of its history,
-
0:18 - 0:21the channel’s rocky shores
and stormy weather -
0:21 - 0:24made crossing a dangerous prospect.
-
0:24 - 0:28Engineers of the early 1800's
proposed numerous plans -
0:28 - 0:31for spanning the 33 kilometer gap.
-
0:31 - 0:35Their designs included artificial islands
linked by bridges, -
0:35 - 0:39submerged tubes suspended
from floating platforms, -
0:39 - 0:44and an underwater passage more than twice
the length of any existing tunnel. -
0:44 - 0:46By the end of the century,
-
0:46 - 0:50this last proposal had captured
European imagination. -
0:50 - 0:53The invention
of the tunnel boring machine -
0:53 - 0:57and the discovery of a stable layer
of chalk marl below the seabed -
0:57 - 1:00made this fantastic tunnel
more feasible. -
1:00 - 1:06But the project’s most urgent obstacles
were ones no engineer could solve. -
1:06 - 1:07At the time,
-
1:07 - 1:12Britons viewed their geographic isolation
as a strategic advantage, -
1:12 - 1:16and fears about French invasion
shut down plans for the tunnel. -
1:16 - 1:20The rise of aerial warfare rendered
these worries obsolete, -
1:20 - 1:24but new economic concerns
arose to replace them. -
1:24 - 1:28Finally, 100 years after
the initial excavation, -
1:28 - 1:30the two countries
reached an agreement— -
1:30 - 1:33the tunnel would proceed
with private funding. -
1:33 - 1:37In 1985, a group
of French and British companies -
1:37 - 1:41invested the modern equivalent
of 14 billion pounds, -
1:41 - 1:46making the tunnel the most expensive
infrastructure project to date. -
1:46 - 1:49The design called
for three separate tunnels— -
1:49 - 1:53one for trains to France,
one for trains to England, -
1:53 - 1:55and one service tunnel between them.
-
1:55 - 2:00Alongside crossover chambers,
emergency passages, and air ducts, -
2:00 - 2:04this amounted to over 200 kilometers
of tunnels. -
2:04 - 2:08In 1988, workers began excavating
from both sides, -
2:08 - 2:11planning to meet in the middle.
-
2:11 - 2:16Early surveys of the French coast
revealed the site was full of fault lines. -
2:16 - 2:19These small cracks
let water seep into the rock, -
2:19 - 2:23so engineers had to develop
waterproof boring machines. -
2:23 - 2:29The British anticipated drier conditions,
and forged ahead with regular borers. -
2:29 - 2:34But only months into the work, water
flooded in through undetected fissures. -
2:34 - 2:38To drill in this wet chalk,
the British had to use grout -
2:38 - 2:41to seal the cracks
created in the borer’s wake, -
2:41 - 2:43and even work ahead of the main borer
-
2:43 - 2:47to reinforce the chalk
about to be drilled. -
2:47 - 2:52With these obstacles behind them,
both teams began drilling at full speed. -
2:52 - 3:00Boring machines weighing up to 1,300 tons
drilled at nearly 3.5 meters per hour. -
3:00 - 3:05As they dug, they installed lining rings
to stabilize the tunnel behind them, -
3:05 - 3:09making way for support wagons
following each machine. -
3:09 - 3:13Even at top speed,
work had to proceed carefully. -
3:13 - 3:18The chalk layer followed a winding path
between unstable rock and clay, -
3:18 - 3:24punctured by over 100 boring holes
made by previous surveyors. -
3:24 - 3:28Furthermore, both teams had
to constantly check their coordinates -
3:28 - 3:32to ensure they were on track to meet
within 2 centimeters of each other. -
3:32 - 3:35To maintain this delicate trajectory,
-
3:35 - 3:38the borers employed
satellite positioning systems, -
3:38 - 3:42as well as paleontologists
who used excavated fossils -
3:42 - 3:45to confirm they were at the right depth.
-
3:45 - 3:50During construction,
the project employed over 13,000 people -
3:50 - 3:53and cost the lives of ten workers.
-
3:53 - 3:55But after two and a half years
of tunneling, -
3:55 - 3:59the two sides finally made contact.
-
3:59 - 4:02British worker Graham Fagg
emerged on the French side, -
4:02 - 4:08becoming the first human to cross
the channel by land since the Ice Age. -
4:08 - 4:10There was still work to be done—
-
4:10 - 4:13from installing crossover chambers
and pumping stations, -
4:13 - 4:17to laying over a hundred miles of tracks,
cables, and sensors. -
4:17 - 4:23But on May 6, 1994, an opening ceremony
marked the tunnel’s completion. -
4:23 - 4:27Full public service began
16 months later, -
4:27 - 4:31with trains for passengers
and rail shuttles for cars and trucks. -
4:31 - 4:37Today, the Channel Tunnel services
over 20 million passengers a year, -
4:37 - 4:41transporting riders across the channel
in just 35 minutes. -
4:41 - 4:46Unfortunately, not everyone has
the privilege of making this trip legally. -
4:46 - 4:50Thousands of refugees have tried
to enter Britain through the tunnel -
4:50 - 4:53in sometimes fatal attempts.
-
4:53 - 4:56These tragedies have transformed
the tunnel’s southern entrance -
4:56 - 4:59into an ongoing site of conflict.
-
4:59 - 5:03Hopefully, the structure’s history
can serve as a reminder -
5:03 - 5:06that humanity is at their best
when breaking down barriers.
- Title:
- How the world's longest underwater tunnel was built - Alex Gendler
- Speaker:
- Alex Gendler
- Description:
-
View full lesson: https://ed.ted.com/lessons/how-the-world-s-longest-underwater-tunnel-was-built-alex-gendler
Flanked by two powerful nations, the English Channel has long been one of the world’s most important maritime passages. Yet for most of its history, crossing was a dangerous prospect. Engineers proposed numerous plans for spanning the gap, including a design for an underwater passage more than twice the length of any existing tunnel. Alex Gendler details the creation of the Channel Tunnel.
Lesson by Alex Gendler, directed by Studio Kimchi.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:08
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