Original subtitles

[narrator] In Poland, an elite team of engineers is embarking on

a mega construction project.

They are building a new super railway to open up the south of

the country like never before.

The team must build hundreds of complex structures,

tunnel through some of the most challenging terrain in Europe,

and battle treacherous geology...

...to establish this critical transportation line.

[speaking Polish]

This mountain railway...

ranks in a league of ambitious new engineering wonders that

are bigger, faster, taller,

and more advanced than anything

ever constructed before.

This is the inside story of the extraordinary challenge

of building these giants.

Southern Poland is a region of natural wonders,

but it is one of the hardest regions

in the country to cross.

Between Krakow and the towns of the Carpathian foothills,

railways follow routes laid more than a century ago.

[train whistle blows]

Many operate as heritage attractions that run

out-of-date locomotives.

They wind around the mountains.

The result is slow travel.

The 60-mile journey from Krakow to Nowy Sacz

can take almost three hours.

Reaching the mountain resort of Zakopane takes just as long.

Now, engineers are building a brand-new railway

through these mountains.

When complete, Podleze-Piekielko Railway Line

will cut journey times to around one hour to Nowy Sacz

and 90 minutes to Zakopane,

opening the region to faster travel, daily commuting,

and millions of tourists.

To complete the route, engineers must use

giant machines to build over 80 supersized embankments to

hold back the unstable ground.

Workers must lay over 35 miles of new track

and build 142 switches with millimeter precision to guide

trains along the route.

Huge boring machines will punch 20 tunnels beneath

the mountains, one of which will be the longest in Poland.

To keep on schedule,

they will build a one-of-a-kind factory to make

the thousands of segments that line each tunnel.

When complete, the line will connect

the cities of Southern Poland

and open the region to faster travel,

easier daily journeys

and a huge increase in visitors.

Construction of the railway is projected to take seven years.

Meeting this deadline won't be easy.

The route must cross multiple rivers, valleys, and roads.

And long sections must be as straight as possible to

accommodate trains traveling up

to speeds of nearly 100 miles an hour.

[Lukasz speaking Polish]

The first challenge for the engineers lies beneath

the surface in the geology of

the Carpathian Mountains.

This region is built from layers of rock known as

flysch, alternating bands of hard stone and weak clay.

When water seeps into these layers, they can begin to

slide, making the slopes inherently unstable.

[speaking Polish]

Landslides are frequent in this region.

They destroy property.

[cracking, rumbling]

Crush roads.

They can also cut off railways.

Now, engineers must carve a new railway corridor

through steep mountain slopes

in the town of Limanowa.

Limanowa is densely built up,

with homes and roads running close to the construction site.

If engineers cut into these hillsides

without reinforcement, the consequences

could be catastrophic.

[Rafal speaking Polish]

Rafal Sitek is responsible for making sure the ground

around the railway is rock solid and finding a way to hold

these hillsides in place.

On the gentler slopes, they use special ground nails

to stabilize the earth.

A drilling rig positions itself against the cut slope.

It bores deep holes at precise angles into the ground.

Workers feed a steel bar into each hole.

Then they pump in grout to fill the spaces

and lock the steel into place.

Each nail reinforces the soil from within,

increasing its strength

and helping prevent it from slipping.

On this site alone, workers install thousands of

these anchors to create over 18 miles of reinforcement.

Yet some sections of the railway

are far more demanding.

In the center of Limanowa, the line cuts deep

into the slope.

The loads are greater,

and the excavation runs close to homes,

roads, and the railway itself.

Here, engineers need to take a different approach to

stabilize the ground.

A supersized rig drills a 35-inch wide hole

up to 65 feet into the ground.

It then fills the hole with concrete as it lifts up.

Engineers drill a series of these holes

with 50-inch gaps in between.

Next, they drill secondary piles in these gaps.

Before the concrete begins to harden,

they insert reinforcement baskets into the shafts.

The result is a solid underground wall

that can hold back thousands of tons of earth.

To build these walls, Rafal's team must drill piles

deep into the unpredictable ground here.

So the engineers bring in a powerful machine,

standing nearly 100 feet tall,

a beast that can drill deep into the toughest ground.

Engineers start with drilling the primary piles.

A steel casing rotates into the ground.

Inside it, an auger spins in the opposite direction to cut

into the soil and bring the material up to the surface.

The deepest piles reach 65 feet into the ground,

deeper than a six-story building.

Once the hole reaches the required depth,

workers withdraw the auger

and pump concrete into the hole.

The casing slowly lifts out of the hole

as the concrete rises to fill the shaft.

The machine then moves on, and the process begins again.

Once the primary piles are dry,

the team drills the secondary piles in between.

The auger pumps concrete into the holes, and workers sink

cylindrical reinforcement baskets made from steel

into each one.

These baskets run the full depth of the pile and make them

strong enough to hold back the hillside.

The team then removes thousands of tons of earth to reveal

a megaterrace that eliminates the threat of landslides,

to safeguard the railway

and protect the passengers that will use it.

Now that the ground is stable enough to build on,

next, engineers must begin building the new railway.

Engineers in Poland are building the ambitious

new Podleze-Piekielko Railway Line

that will slash journey times to the south of the country.

The designers of the railway plan to build 22 stations

and stops along the route.

One of them is here in Limanowa.

The station needs switches, precision track systems that

guide trains from one track to another.

Each switch is made from interlocking rails

and moving blades that are engineered

to millimeter precision.

Get it wrong and the train could derail.

Many switches for modern railways are made in factories

and delivered pre-assembled to site.

Here, they must bring in 100-foot lengths of track

and assemble the switch piece by piece on site.

First, workers lay down two steel assembly rails.

Next, they lay the numbered concrete switch bearers on top

in a precise sequence.

Above these, they position the steel rails

so they align with pre-cast fixing points in the bearers.

They fix the rails and switch elements in place.

Fastening systems lock everything together.

After inspection, workers can remove the assembly rails,

and the switch will rest exactly where it was built.

This week, engineers must build a complete railway switch

for Limanowa Station.

Overseeing this task is railway engineer Marcin Iwanow.

[speaking Polish]

First, Marcin's team lays out 124 concrete slabs

called switch bearers.

Each one is numbered and placed in

a precise sequence to form

the exact geometry of the switch.

The switch bearers hold the steel rails in place.

The team must position them precisely.

Otherwise, the rails won't fit.

Now for the heavy lift.

The switch has two arms.

These are the tapered steel rails that

move back and forth to switch the track.

Each one weighs about three tons.

The team must use a crane to place

both precisely into position.

But the unstable ground of Carpathian flysch

adds another challenge.

[speaking Polish]

The crane moves into position.

The ground gives way.

And one side of the crane sinks.

If the crane isn't level,

the entire machine could tip over during the lift.

The engineers must find a solution.

An excavator cuts into the soft ground to create a stable base.

Workers lay old sleepers

beneath the crane's support leg

to spread the machine's load.

[Marcin speaking Polish]

The crane extends its outriggers and workers

attach them to metal feet placed on top of the sleepers.

Slowly, the machine levels out.

The crane is ready to make the lift.

It lowers the first arm into place.

Followed by the second.

Final alignment can only be done by hand,

but it is not an easy task.

[speaking Polish]

Workers use bars and levers to make small controlled

adjustments until everything fits.

They guide each element onto precast fixing points.

These transfer the load of passing trains into

the concrete foundation to ensure the switch's stability.

Workers move along the switch to tighten each connection.

It takes the team 20 hours to complete the first of

nine switches at the station.

Once finished, these will form a precision system to

guide trains safely from one track to another.

But for their next challenge,

the team will be forced to go underground.

In Poland, engineers are building

the new Podleze-Piekielko Railway Line

to access the spectacular Carpathian Mountains

in the south of the country.

Slashing journey times is a priority for

the railway's designers.

[speaking Polish]

The undulating topography of the Carpathian foothills makes

a straight route above ground almost impossible.

So engineers are punching 13 tunnels,

totaling nearly 20 miles through these mountains.

The engineers digging the tunnel at Mecina must

bring in two special tunneling machines to get the job done.

The two mega tunnel boring machines arrive in pieces at

the ports of Gdansk and Gdynia in northern Poland.

The construction site is 435 miles south.

It's mid-December.

Heavy transportation will soon shut down for

the Christmas holiday.

Engineers are in a race against time to move thousands of tons

of machinery across the country...

before the window closes.

Their first challenge is to

unload everything from the ship,

in winter and against the clock.

Jaroslaw Joniec and Maciej Stec are in charge of

the mammoth operation.

[Jaroslaw speaking Polish]

Deep inside the hold,

the components sit wrapped in tarps.

Workers climb down to rig the lifting straps.

[Maciej speaking Polish]

Then, the cranes take the load.

One by one, the components emerge.

The smaller parts go on to standard trucks,

but the largest elements need specialized low loaders.

The heaviest elements weigh over 110 tons,

too heavy for a single crane.

So for the most demanding lifts,

two cranes work together.

Finally, after three days of around-the-clock work...

the last component touches the quayside.

And as night falls,

the convoy sets off through the streets of Gdynia,

and it begins its 435-mile journey south.

But not every road can take the weight,

and not every bridge is strong enough.

So heavy loads move slowly on pre-approved routes.

The final stretch along steep, narrow mountain roads

is the most challenging.

[speaking Polish]

[Maciej speaking Polish]

Drivers can't rely on visibility alone.

Pilots walk ahead, guiding every move by radio.

Finally, the convoy reaches the construction site.

The engineer's next challenge is to assemble

the 172 components,

weighing 3,400 tons,

into a pair of tunneling machines.

[Maciej speaking Polish]

They named the larger machine Jadwiga,

and the smaller one Kinga, honoring two of Poland's most

revered medieval royal saints.

Space in front of the rock face is tight.

The team must build the 330-foot-long tunnel

drilling machines within a space

that measures nearly 400 feet.

After seven weeks, Kinga is ready.

The crew fires up her cutterhead,

and the machine prepares to tear into the rock.

To build the Podleze-Piekielko Railway Line, engineers must

drive tunnels deep beneath the Carpathian Mountains.

[speaking Polish]

The first two tunnels were run beneath the village

of Pisarzowa.

One will carry the railway.

The other will serve as an excavation tunnel.

They will run for nearly two and a half miles,

the longest railway tunnels in Poland.

But the ground here is made from highly unstable layers of

rock and clay that can shift.

There is a danger that a collapse could trap

the tunneling machine beneath the surface

and endanger its crew.

To prevent this, Jadwiga and Kinga

are a special type of tunnel boring machine

called an Earth Pressure Balance, or EPB-TBM.

This is how it works.

A rotating cutterhead breaks through the ground.

The excavated material enters a sealed chamber behind it.

Here, it mixes with water, air, and foaming agent to

create a sludge that is held

under pressure inside the chamber.

It pushes back against the rock to keep the tunnel stable

and prevent collapse.

A screw conveyor controls the amount of material that

leaves the chamber to maintain the pressure balance.

Next, the spoil is transferred onto a conveyor belt

and carried out of the tunnel.

As the TBM advances, it installs

precast concrete segments behind it.

Hydraulic jacks push on them to move forward

and help form a sealed tunnel lining.

Two TBMs build the railway tunnel and excavation tunnel

at the same time.

But cutting through the Carpathian flysch

is no simple task.

It's the responsibility of TBM manager Veysel Dalmis

to keep the machines on track.

And the tunneling machine's crew faces an even more

dangerous invisible threat.

Pockets of methane gas can be trapped inside the rock.

Methane is deadly for humans,

and in a high enough concentration,

it can become explosive.

Even a small spark from metal contact from machinery

could ignite it.

An explosion underground would be catastrophic for

both the tunnel

and the village above.

So the EPB-TBM has sensors throughout the machine that

constantly measure the amount of methane in the tunnel.

The engineers' next challenge is to stop the immense pressure

of the ground from crushing the newly excavated tunnel.

The TBM's solution is to line the interior of the tunnel

with precast concrete segments.

As the cutterhead advances, a motorized arm

swings into action behind it.

It picks up each segment using a powerful vacuum grip.

Rotates it into position.

And locks it into place against the tunnel wall.

Seven segments form a complete ring,

each one bolted to the next.

Rubber seals between them help

keep groundwater out of the tunnel.

Each ring is strong enough to resist

the crush of the earth above

and maintain the tunnel's 35-foot diameter.

But digging the tunnel is only half the job,

because everything the machine cuts must go somewhere.

A continuous conveyor belt

carries tons of earth and rock out of the tunnel.

The TBM is constantly moving forward.

As it advances, the conveyor system

must grow with it.

The machine stops at regular intervals for maintenance.

And in this limited window, crews must bond a new length of

belt to make the conveyor longer.

To extend the belt, they use vulcanization,

a process that fuses the belt together using heat,

pressure, and layered bonding materials.

After several hours, the belt becomes

one continuous length.

With the new section installed,

the team now needs to keep the mountain above

from caving in on them.

Engineers in Poland are punching two tunnels through

challenging geology as part of a brand new railway line in

the south of the country.

As it advances, the tunneling machine builds

behind it a concrete lining made from precast segments.

[speaking Polish]

These rings hold back the weight of the ground above.

The pair of tunnels beneath Pisarzowa require

more than 28,700 segments.

The tunnel-digging machine needs a steady supply of these

to keep working around the clock.

To solve this problem, engineers build a dedicated

segment factory beside the tunnel.

At its heart is a carousel production line.

First, workers clean a segment mold and spray it

with a release agent to stop the concrete from sticking.

Next, they fit a ceiling gasket

and lower a steel reinforcement cage inside.

Then, they close the mold and fill it with concrete.

Vibrators shake the mix into every corner of the form.

The mold then moves into a heated curing chamber.

Several hours later, workers open the mold

and lift out the finished segment.

Soon after, crews transport it underground

for the tunnel-digging machine to install inside the tunnel.

The molds are designed to produce

millimeter-accurate segments.

Workers clean each mold and then spray it with

an anti-adhesive coating...

and fit a sealing gasket

to help waterproof the finished tunnel.

Then, they lower a steel reinforcement cage inside.

By the end of production, the factory will use around

5,200 tons of reinforcing steel to build the cages

for every segment.

Once workers close the mold, they pour in the concrete.

Mixer trucks deliver each batch from a local supplier.

Engineers use a high-strength mix

designed for extreme underground conditions.

Steel fibers reinforce the concrete and help it

withstand temperatures of over 2,100 degrees Fahrenheit.

Vibrators shake the mix into every corner of the form.

Then, crews remove the excess concrete

and smooth the outer surface.

This closes the pores in the concrete and improves

its resistance to water.

Now, workers move the segment into a curing chamber.

Here, engineers control the heat and humidity.

Temperatures reach 130 degrees Fahrenheit,

and humidity approaches 100%.

These conditions help the concrete

harden and gain strength.

After roughly eight hours, the segment is ready.

These rings must withstand enormous pressure from

the weight of the mountain above.

If the concrete is too weak, the lining could fail,

so engineers must test every completed batch before

they're installed inside the tunnel.

Workers take samples from the concrete mix and pour them

into small cubes.

After curing, engineers place the cubes

inside a compression testing machine.

The machine increases the pressure until

the concrete fails.

The result shows whether the mix is strong enough

for the tunnel lining.

If the segment passes inspection, a scissor grab

lifts it from the mold...

and rotates it into its storage position.

The concrete continues to harden for three more days in

covered storage beside the factory.

After that, workers move the segment

into the storage yard.

This innovative factory supplies the TBM with

a constant stream of super strong concrete segments

to keep the tunneling machine advancing through the mountain

24 hours a day.

Now, engineers prepare for the final step

of the tunnel-building -- the breakthrough.

Engineers in Southern Poland are close to completing

the country's longest railway tunnels.

Today, they prepare the smaller tunnel-boring machine to cut

through the final feet of rock,

a critical stage known as the breakthrough.

Worn cutting tools can stop the TBM from excavating safely.

The tunnel face could collapse during breakthrough.

Chief engineer Veysel uses a special train to travel

the two and a half miles from the tunnel's entrance to

the TBM at the other end.

The buildup of methane inside the tunnel

could still pose a risk.

So Veysel carries a self-rescuer,

an emergency breathing device that gives him

enough time to escape.

Veysel arrives at the rear of the tunneling machine.

Getting from here to the rock face is a journey in itself.

The tunnel-digging machine is now nearly two and a half miles

inside the mountain,

the furthest it has ever been from the exit.

If something goes wrong here, getting out is

not straightforward, and a self-rescuer alone

might not be enough.

So designers equipped Kinga and Jadwiga

with rescue chambers.

They are airtight and fully self-contained with

emergency power and provisions.

Even if the machines come to a standstill, safety systems

continuously pump in fresh air and regulate the temperature.

The rescue chambers can keep workers alive for up to

24 hours, long enough for help to reach them.

Just behind the tunnel face,

Veysel opens the maintenance hatch and climbs inside

the cutterhead.

He checks each cutting tool for wear and damage.

Veysel signals to the operator to rotate the cutterhead.

The machine is ready.

Veysel exits the tunnel

and goes to the place where engineers

and officials have gathered to witness the breakthrough.

From here, he coordinates the final push.

There is one more obstacle in the way, a thick concrete wall

reinforced with steel piles.

The tunnel drilling machine must break through it cleanly.

If the machine is misaligned, it could strike the circular

mouth of the tunnel, which could collapse.

At last, the cutterhead reaches the final barrier.

The piles give way,

and the tunnelling machine breaks through.

[crowd cheering]

[indistinct chatter]

Now, the team can turn its attention to

the 12 remaining tunnels along the route to complete

the full railroad.

To build Poland's extreme railway, this team of engineers

stabilized dangerous slopes,

transported giant machines 435 miles across the country,

and drove record-breaking railway tunnels deep beneath

the Carpathian Mountains.

Now, Podleze-Piekielko Railway Line will open the region to

quicker journeys, better connections,

and a new era of rail travel through the Carpathians.