Now for the most dangerous project on the agenda.
The world’s longest underwater tunnel will connect the cities of Dalian and Yantai across
the Bohai Sea, passing through two deadly earthquake fault zones.
At 76 miles long it will be longer than the current first and second-ranked underwater
tunnels combined, and at a cost of $42 billion, it will be extremely expensive.
But the Chinese calculate that it will be worth it.
For one, it will slash the eight hour drive between the two cities to under two hours.
It will also connect China’s isolated northern rustbelt with its wealthy east coast, adding
an additional $3.7 billion to the economy each year.
The experience could also establish the Chinese as the preeminent submarine diggers in the
world, and would be a serious practice run for far more ambitious potential future Mega-MEGA-projects
like connecting China to South Korea, or even Russia to the United States across the Bering
Strait--yes, that has actually been proposed.
This isn’t the first underwater tunnel project for Chinese engineers, either, who already
gained some experience by completing the 3.8 mile-long Jiaozhou Bay Tunnel in 2011.
But while the Bohai Sea is roughly the same depth as Jiaozhou Bay, the tunnel underneath
it will be 20 times longer.
When it comes to construction, if they’re lucky, the Chinese will encounter only soft
seabed, allowing them to use Tunnel-Boring Machines the whole way.
But if they run into harder rock, they’re going to have to use the “drill-and-blast”
method embraced by the Japanese during construction of the Seikhan Tunnel.
Using tons of dynamite hundreds of feet underwater is dangerous business, and it resulted in
the unfortunate deaths of four workers over the course of that project, and maaaany accidental
leaks.
Reporter: “In 1976 the project hit its biggest crisis when 80 tons of seawater a minute began
leaking in.
1.5 km of tunnel flooded.
It took five months to get back on track.”
Bryce: The Bohai Tunnel will also have to withstand magnitude 8.0 earthquakes.
In 1976, the deadliest earthquake in modern history -- a 7.8 -- killed a record 650,000
people in Tangshan and surrounding areas.
In 1969 a quake measuring 7.4 on the Richter scale shook the Bohai Bay itself.
And there doesn’t seem to be much the engineers can even do about that threat besides simply
reinforcing the strength of the tunnel walls.
Of course, they could simply not bore a long hole under a deep bay through two fault zones,
but that doesn’t really seem to be an option at this point.
Because officials throughout China are under enormous pressure to hit GDP economic growth
targets, and there aren’t many other options that could provide anywhere near as much economic
benefit as the Bohai Tunnel, which should break ground sometime in 2016.
For TDC, I’m Bryce Plank.
Thanks for watching.