All language subtitles for Impossible Engineering s02e05 Worlds Longest Tunnel.eng

Today on
"Impossible engineering"...

The Gotthard base tunnel...

the longest tunnel in the world.

A staggering 35 miles through
the heart of the Swiss Alps...

Firing!

...it took
revolutionary engineering.

...to make
the impossible, possible.

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The Alps, the tallest
mountain range in Europe.

At its heart
is the Gotthard pass,

a crucial route linking
the north and south.

Traffic has increased tenfold
in recent decades.

The mountain passes
are at a standstill.

The solution?

Bore a tunnel directly through
the mountain range.

The Gotthard base tunnel
will be 35 miles long

and a mile and a half
underground.

Constructing a tunnel this long
is dangerous business.

Before any digging can begin,

engineers need to be sure

that the earth
deep beneath the Swiss Alps

is safe for boring.

Geophysicist dirk krueger's job

is to reduce risk
as much as possible.

Rock conditions under the Alps
can change from foot to foot.

The location
of the proposed tunnel

is too deep
to sample from above-ground.

There's no way to predict

what dangers lie ahead
for the digging team.

Drilling blindly
into the earth could be deadly.

Dirk needs a solution
before the team can dig.

It's a challenge
that would have been impossible

without an invention
from the 19th century.

Japan is the most seismically
active country on earth.

Around 1,500 quakes
occur each year.

For centuries,

no one knew
where or why they struck.

That was until 1880,

when British engineer John Milne

experienced an earthquake
while surveying in Japan

and began recording
what he felt.

What I've created here

is a simple demonstration
of a seismograph.

I've got a pen
attached to a pendulum.

When I shake the table
and pull the paper through,

you will start to see
the pen record

the number of shakes
on the paper,

and that represents
the frequency and the amplitude,

or the number of times
per second of the shakes

and the size of those shakes.

So let g'sive it a try.

My assistant Kirk here

is going to come
and shake the table

and as I pull the paper
through...

...you can start to see
the trace on the paper

and then if Kirk gives it
a really big shake.

You can see the increase
in amplitude,

and then as it calms down,
it gets less again.

And we can see here
where the really big shake was

compared to
the rest of the time.

It's really simple,

but quite effective
demonstration

of how a seismograph works.

John Milne devised

the first continuously running
seismographs,

helping detect the epicenter
of quakes in Japan.

His design is still used
all over the world.

Engineers at
the Gotthard base tunnel

are using Milne's seismographs
in an innovative way

to help them paint a picture
of what's in store.

They are testing
their new system today

at the V.S.H. Hagerbach tunnel
research facility.

Explosive charges are placed
within the rock face.

Each detonation sends out
shock waves

which are measured
by the engineering team.

Changes in the rock show up
as a shift in the wave pattern

providing a clue to what dangers
lie ahead for the drilling team.

Construction begins on

history's most ambitious
subterranean project in 1996.

The route consists
of two tunnels.

Teams drill from opposite sides
of the mountain

with the ultimate goal
of joining up in the middle,

deep underneath the Swiss Alps.

But to pull off
the seemingly impossible,

the team is going to have
to break out the big guns.

These machines
are really very amazing.

You have to imagine
it's 400-meter long,

the whole machine.

In the mountains of Switzerland,

engineers are undertaking

one of history's most audacious
construction projects...

...a 35-mile tunnel driven
straight through the Alps.

It is the longest
and deepest ever built.

Renzo Simoni is on the team

charged with achieving
the impossible.

So how do you dig 35 miles
through a mountain range?

It's a challenge
that would've been impossible

without an invention
from the 19th century.

London, England.

Every day, four million people

descend into a complex network
of tunnels,

more than 20 of which crisscross
beneath the river thames.

But it wasn't always this way.

By the early 19th century,
Londoners had given up all hope

of having a tunnel
beneath the river.

Several previous attempts

to tunnel under the thames
had failed

and the problem was

the soft and malleable
London clay and sand.

Hard rock miners
had come from Cornwall,

but the techniques they used
on hard rock had failed,

leading to collapse
and flooding.

Eventually it was decided
that the project was impossie, bl

and it was written off.

Engineer Marc Brunel
had a radical idea.

Brunel observed the perfect
tunnel-like structures

left by shipworms
as they burrow through timber.

As it digs, this marine mollusk

shoves pulpwood into its mouth
and digests it,

and its bivalved head
and hard shell

help support the creature
as it moves through the wood.

The pulp is then excreted
as a hard brittle residue

that lines the rear space,

creating a tunnel-like
structure.

The key is to not actually suck
all the sand out of the tube.

The mollusk then
uses its back legs

to grip itself
to the side of the tunnel

and push itself forward

into the space
that it has created...

...repeating the process

until it finds light
at the end of the tunnel.

And this is exactly the process
that Brunel sought to emulate.

Brunel's idea started
an underground revolution,

some of which
can still be found.

Now this place
is really incredible,

really amazing.

Through a tiny door
up at the street,

down a rickety old scaffolding,

and we find ourselves here
in this cathedral-keli space.

Brunel dug the first-ever tunnel
under the river thames

using his engineering equivalent
of a shipworm.

A mobile steel framework
called a tunneling shield

acts like the worm's hard head,

supporting the earth
and preventing collapse.

Working in
individual compartments,

miners excavate just four inches

before the whole
tunneling shield

is pushed forward
using screw jacks.

A second group of men
working behind them

line the tunnel with bricks
to prevent its collapse.

Finished in 1843,

Brunel's thames tunnel

was hailed as the eighth wonder
of the world

with almost 50,000 visitors
on opening day.

Today it forms part of
the London rail network,

and it all began
in this hidden chamber.

Most people would have no idea
that it's here.

But of course,
it's importance to engineering

and to tunnel engineering
in particular,

really can't be overstated.

The Gotthard base tunnel

is 140 times longer
than Brunel's thames tunnel.

To dig 35 miles
through the Alps,

Renzo and his team
are using a supersized version

of Brunel's
19th-century excavator.

At over 1,300 feet long,

tunnel boring machines,
or T.B.M.S,

are almost the same length
as the thames tunnel.

They weigh 300 tons,

making them
the biggest vehicles on earth.

They are so huge

they need to be shipped
in sections

and assembled on site.

As the T.B.M. Head turns,
it exerts 35 tons of force,

chipping away the rock.

Excavated rock
passes through the machine

and onto a conveyor.

The T.B.M pushes into the void
using hydraulic legs.

These mechanical mollusks

munch through
130 feet of rock a day.

In the wake of the T.B.M.,

the walls are sprayed
with shotcrete,

a form of liquid concrete.

But how will two teams

digging on opposite sides
of the Swiss Alps

meet in the middle?

Calculating a straight route

is difficult enough
above ground.

There are trees, hills,
and buildings in the way.

Using landmarks to navigate

or relying on towers
to get direct sightlines helps.

When plotting a course
underground,

even the slightest
miscalculation

could yield disastrous results.

In Switzerland,
engineers are undertaking

one of history's most audacious
construction projects.

To reduce gridlock
and pollution,

they're attempting to build

the longest and deepest tunnel
in the world.

The Gotthard base tunnel
will slice a 35-mile route

straight through the Swiss Alps.

But with two teams
digging on opposite sides

of the mountain range,

engineers face the challenge
of meeting in the middle.

Getting the T.B.M.'S meeting
in the middle

is a very, very big challenge

because we have so
long distances.

The solution comes from one
of the greatest innovations

of the 20th century.

In 1960, Theodore Maiman
built the world's first laser.

He bought his materials
out of catalogs.

Maiman placed a small ruby

inside a photographer's
flash bulb.

His invention changed the world,

allowing highly-accurate
measurements to be taken

over great distances.

Less than a decade
after Maiman's prototype,

lasers were bounced off
reflectors

on the surface of the moon,

so the Apollo 11 crew

could accurately calculate
their distance from earth.

At the Gotthard base tunnel
in Switzerland,

lasers guide
huge tunnel boring machines.

G.P.S. maps the entire route.

But witho nsatellite signal
below ground,

each T.B.M. relies on
a geodetic guidance system

to stay on course.

A laser theodolite is attached
to the tunnel wall.

It fires a beam at a target
on the front of the T.B.M.

As the T.B.M.S
chew through the mountain side,

they hit unstable earth
deep under the Swiss Alps

as the T.B.M.S
chew through the mountain side,

bringing the whole operation
to a grinding halt.

Squeezing occurs when
the pressure of the mountain

pushes against weaker rock.

In extreme cases,

it results in the tunnel
closing up again

after it's been bored.

If the team uses
a tunnel boring machine

in a squeezing rock zone,

the consequences
could be disastrous.

So the dig team must
go back to basics,

using techniques championed

in the days long before
tunnel boring machines.

Engineer Luke Bisby
is in Cornwall

on the southwest tip of britain.

He is exploring an area
once dependent on tunneling.

So it is hard to believe
that 200 years ago

underneath the sea

was the largest concentration

of submarine tin
and copper mines

anywhere in the world.

This region was

the world's largest producer
of copper and tin

in the 19th century.

There are an estimated
30 to 40 miles of mine shafts

beneath the waves.

More than 2,000 mines
like this one

would have dotted the county.

Cornish miners were considered
the best in the business.

Their expertise was sought after

for tunneling projects
all over the world.

By today's standards,

their methods were incredibly
inefficient and dangerous.

So this is black powder.

This is the world's
first chemical explosive.

It's better known as gunpowder.

Early miners
bored hos leby hand,

then laid the explosives.

I'm going to light the fuses

and then we should have
more than a minute

to head down the tunnel.

Oh!

All right, okay, so let's see
what's happened here.

Keeping in mind that it would
have taken a couple of hours

to drill each of these holes
by hand,

to then put the black powder in

and only move
that amount of rock

despite a pretty big bang,

is a bit disappointing frankly.

The miners would come back

inking that the charge
hadn't gone off.

The charge would then
detonate quite late,

and the miners could be maimed
or even killed,

and in many cases, they were.

The invention of
a new, more powerful explosive

proved even more dangerous.

So what I have here
is a jar of nitroglycerine,

and it was first
synthesized in 1847.

And you can see
just how volatile it is.

If I take a small drop
and place it on the steel plate

and then I hit it with a hammer.

So where black powder
needs a heated charge

in order to coax an explosion,

nitroglycerine
just needs a small tap,

and of course down a mine,
that could spell disaster.

Swedish explosives expert
Alfred Nobel's brother

died in
a nitroglycerine accident

in the 1800s.

After the incident,

he was determined
to create a safer alternative.

He realized
that if he took nitroglycerine

and mixed it with kieselguhr

which is a naturally occurring
clay-like material,

he would end up with dynamite.

And you can see
that it's quite loose

but quite malleable

and it could be rolled

to eventually
form dynamite sticks.

To make his dynamite,
Nobel had to figure out a way

to safely handle
vast amounts of nitroglycerine.

He found his solution
in Scotland.

Nobel really favored this area
because of its remoteness,

and the Sandy soil allowed him

to shape the landscape
around his factory

to protect production workers
from potential explosions.

It also allowed him
to build mounds,

such as thesare ound us.

And on top of these,

he could place his
nitroglycerine production huts.

In each nitroglycerine hut,

one man was in charge
of monitoring the temperature

and another mixed,

sitting on a one-legged stool
to ensure he kept his focus.

But sensitivity
to temperature and friction

meant that nitroglycerine
couldn't be safely pumped,

and so it was set
to trickle down

from the huts to the factory,

letting gravity do the work.

Once it reached the factory,
it was mixed with clay

before being rolled
into stickofs dynamite.

Nobel had created a product
that was now so stable

that it could be dropped
on the ground

or even thrown into fires
without exploding.

The new dynamite,

along with the invention of
pneumatic powered rock drills,

gave birth to a quicker
anmod re efficient

form of tunneling
called "drill and blast"...

All right, that's it.

Let's get out of here.

...Ushering in
a new age of mining.

3, 2, 1, firing.

Wow, so that was
quite something.

Lot of power in that one.

So we can really see here

the power of the dynamite
as compared to the black powder.

The dynamite has tenak
that entire mass of rock

and thrown it sideways.

You can see what a game changer
this would have been

for the miners
working down here.

Whenever engineers
at the Gotthard base tunnel

encounter rock too soft

for the massive
tunnel boring machines,

they revert to the drill
and blast method...

...but with
a 21st-century twist.

Known as jumbos,
these 60-ton drilling rigs

make drilling and blasting
easier than ever before.

Each 10-foot arm has a powerful
electrohydraulic drill

to bore holes
for the explosives.

As one arm drills,
thope erator lines up another.

Modern emulsion explosives
are only active

when mixed together
at the rock face,

much safer than drilling

and blasting
using traditional dynamite.

Each detonation
takes eight hours to prep

making drilling and blasting
much slower than the T.B.M.S.

But without it,

finishing the tunnel
would be impossible.

But as the team
drills further into the Alps,

it's becoming difficult
to hold back

the enormous pressure
of the mountain above.

They need a solution fast.

The Gotthard base tunnel
is an epic engineering project.

Massive 1,300-foot
tunnel boring machines

are grinding away
130 feet of rock each day

with the goal of completing
a 35-mile long tunnel

directly through
the Swiss Alps...

the longest tunnel in the world.

The team
is nearing the finish line,

but the immense pressure
of the mountains above

is slowly closing the tunnel
back in on itself,

not long after a stretch
has been bored.

The steel arches used
to hold back the mountain

are failing.

The success of the
whole project is in jeopardy.

Engineers need an answer fast.

In 1932,

engineers Heinrich Toussaint
and Egmont Heintzmann

revolutionized
the German coal mining industry

when they invented

the t.H. Yielding steel
arch support.

Capable of withstanding huge
pressure without collapsing,

they made it possible

to excavate deeper
than ever before.

Unlike a conventional
rigid steel arch,

the jointed concentric rings
of their design

change shape to accommodate
the pressure of the rock,

rather than totally resist it.

The solution is to bore a tunnel

with a wider circumference
than is needed.

The yielding rings
allow just enough movement

to prevent the supports
from collapsing,

resisting the pressure
of the squeezing rock enough

to keep it from
closing the tunnel completely.

On October 15, 2010,

after 14 years of digging,
boring, and blasting,

e thdream becomes a reality.

A T.B.M. Crashes through
the final few feet of rock.

The two halves of the tunnel
join for the first time.

Bravo!

Thanks to a cutting-edge
laser-guidance system,

the T.B.M.S complete
their monumental job

with incredible accuracy,

excavating more than
70 miles of rock.

With the digging done,

the engineering team turns
to their biggest challenge yet,

making sure
the 35-mile-long tunnel is safe

for the thousands of people
that will pass through.

The Gotthard base tunnel
in Switzerland

is a true feat
of underground engineering.

With passengers and freight
traveling at high speeds

through 35 miles
of confined space

under a mile and a half
of solid rock,

an accident
would be catastrophic.

For Renzo and his team,

memories of onofe Europe's
worst traffic accidents

in another alpine tunnel
are on their minds.

In 1999, a truck caught fire

in the middle of the
6-mile-long mont blanc tunnel

linking France and Italy.

The tunnel
quickly filled with smoke,

as the Blaze engulfed
over 30 vehicles.

The inferno raged
for over two days.

39 people lost their lives,

most due to smoke inhalation.

To ensure
the Gotthard base tunnel

is the safest ever built,

its engineers
are taking inspiration

from the innovations
of the past.

In the U.K.,

a groundbreaking
engineering project

below Liverpool's river Mersey

changed tunnel safety forever.

So this is the Queensway tunnel.

And when it opened,

it was the biggest and longest
underwater road tunnel

in the world.

Opened in 1934,

it took 1,700 men
over 8 years to construct.

But it is not the digging
of this tunnel

that makes it revolutionary.

About 30,000 cars travel
through this tunnel every day,

and even with
modern exhaust systems,

that's a lot of fumes.

And the engineering innovation
in this tunnel

is what solved that.

By the early-20th century,

tunnel engineers
had to contend with toxic fumes

from the cars using them.

To keep poisonous fumes at bay,

the builders
of the Mersey tunnel

turned to physiologist,
John Scott Haldane.

And this is
what they came up with.

It is the world's
largest ventilation system,

and incredibly, this system
is still in use today.

In each of the six
huge ventilation towers,

fresh air drawn in at roof level

is pumped underneath the roadway

before being blown
into the tunnel

through ducts along its sides.

At the same time,
exhaust fans draw toxic fumes

out through holes in the roof.

The George's dock
ventilation tower

is home to six massive fans

circulating air through
the Mersey tunnel system.

Incredibly
these are the original fans

that were first installed
down here almost 100 years ago.

Each fan can move

83,000 cubic feet of air
a minute

safely pumping exhaust fumes

from the top of the 200-foot
high tower above.

Now this is a place

that very few people
get a chance to see.

I'm standing right at the bottom

of one of
the ventilation shafts.

The huge height of the tower

ensures the air supply
isn't contaminated

by vehicle exhaust fumes
from the street.

It's said that the air down here

is even cleaner than the air

for the people walking around
in the streets of Liverpool.

Once the largest tunnel
ever drilled,

the road only uses the top half
of the original tunnel.

Most people when they drive
through the tunnel,

they think
they're at the bottom,

but they're not.

Actually below them
is this two-story high space

called Central Avenue.

The lower level was designed
to house a tram line,

but it was never built.

Now it serves as
the main air supply duct

where air from the tower is
blown into the road deck above.

It's pretty amazing to think

that there's this space
like this

down beneath the road deck

and I have to say,

it's pretty cool
to be down here.

With its revolutionary
ventilation system,

the Queensway tunnel
provided the blueprint

for all tunnel designs
that followed.

The designers of

the 35-mile-long
Gotthard base tunnel

are taking the systems
pioneered at the Mersey tunnel

to new heights
of sophistication.

Electric trains will run
through the tunnels,

so they won't have to contend
with exhaust gases.

But the ever present
risk of fire in the tunnel

requires
a cutting-edge solution.

In the event of a fire,

trains will either be diverted
out of the affected tunnel

at two crossover points

or directed to one of two
emergency stations.

As a train
that's on fire approaches,

the station's ventilation system
will activate remotely

via the tunnel control center.

Powerful 2-1/2 megawatt
extractors above the track

will suck toxic smoke fumes
out of the tunnel,

releasing it at the surface

through an exhaust shaft
2,600 feet above.

Inlet fans will replenish
the tunnel with clean air.

Each of the tunnel's
six jet fans

will raise the air pressure
in the unaffected tunnel,

keeping it free of smoke
during evacuation.

This system is safer

than the rest of the railway
network in Switzerland.

If you are here as a passenger
using the tunnel,

you're safer tn haoutside.

Once complete,

the Gotthard base tunnel

will not only redefine
the map of Europe,

it will rewrite the rules
of tunnel construction.

It stands as a testament
to the people,

past and present,

who helped design and build it.

By drawing on the innovations
of the past...

Oh!

...Adapting, improving,

and making groundbreaking
innovations of their own,

the engineers and designers
of this incredible tunnel

have succeeded in making
the impossible possible.

Generations of engineers

wouldn't have been able
to do this.

I'm very lucky to have spent
20 years of my professional life

together with this project.

It's like a part of me.

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