This is the Merdeka Tower - the 2nd tallest
building in the world. But did you know that there are just as massive structures underneath
the ocean? From skyscraper-sized Oil platforms to subsea railway tunnels, megaprojects
under water are some of the most ambitious construction projects in history.
Today, we’ll uncover the insane size of these projects and explain how they were built.
Let’s take a look at the 500 meter tall Bullwinkle Oil platform that was transported to the middle
of the Ocean. And how steel piles taller than skyscrapers helped Bangladesh’s Padma Bridge
overcome the challenges of a raging river.
So, let’s start with the
insane size of Oil Rigs.
The world uses more than 100 million barrels of
oil every day. This means that oil companies are constantly looking for new oil reserves to
meet the rising demand. More than two-thirds of the world’s oil and gas is preserved under the
ocean floor and to extract these resources giant offshore drilling platforms are being built.
Early offshore platforms were built towards the end of the 19th century and drilled in areas
where the water was less than 100 meters deep. Oil companies have invested heavily in
the technology ever since and Oil Rigs have become taller and taller and are comparable
to some of the tallest skyscrapers on land.
Back in 1977, Shell completed the first
truly massive Oil Rig in the Gulf of Mexico. Named the Prospect Cognac, the platform was taller
than the Empire State Building and was built at a cost of more than 100 million dollars. Since
Prospect Cognac, taller platforms have become more commonplace and today we have 4 Oil Platforms
that exceed the 500-meter height barrier. The oldest of these is Shell’s Bullwinkle Platform
which was installed in 1988. At 529 meters tall, it is almost as tall as New York’s One World Trade
Center. At the turn of the century, Chevron built the 640 meter tall Petronius Compliant Tower,
which still holds the record until today. At the time, it was the tallest structure in the
world but has since been surpassed by Dubai’s Burj Khalifa and more recently by Malaysia’s 679
meter tall Merdeka Tower. But it doesn't stop there. Floating oil platforms nowadays reach
up to 2900 meters deep into the water.
But how do you build such
massive platforms underwater?
The construction of an Oil Rig is completed
in fabrication yards on land from where it is transported to the middle of the ocean. For
example Bullwinkle’s 400 meter long base or jacket was built in Texas while lying on its side.
To move the colossal structure to its final location it was loaded on a barge built
in parallel with the jacket. Traffic on the Gulf Intracoastal Waterway had to be
diverted to safely load the platform onto the barge - a process that took 5 days. On
top of that it took 3 days to reach its final destination directly above an oil well. It was
the largest structure ever moved at the time.
Once directly above the oil well, Bullwinkle
was submerged in the water by tipping the barge 2.5 degrees. The engineers then anchored the
platform to the seabed using remote controls and underwater cameras. Bullwinkle’s deck was
constructed separately in Louisiana and fixed above the jacket. The entire project took over 5
years and cost over $500 million at the time.
Since then, the record of being the
‘largest structure ever moved’ could only be surpassed one single time, by
another offshore platform. It was the transport of the 460 meter tall Troll A
Platform off the West coast of Norway.
Bullwinkle remains the Tallest offshore fixed
platform; most oil rigs like bullwinkle are static and are used for drilling up to 500
meters deep into the ocean floor. However, Oil and gas can also be found much deeper in the
ocean. For depths between 500 to 1000 meters, engineers may use compliant towers. Made with
concrete and steel, Compliant Towers are tall and narrow structures designed to endure greater
forces as they can sway with the waves.
The world’s deepest oil wells, however,
are located 3 kilometers beneath the Ocean. Building steel towers and attaching them to the
ocean floor at these depths is not practical. So Engineers use Floating oil rigs to make drilling
possible. Using advanced positioning systems, these Oil Rigs stay exactly over the
Oil wells and are connected to the deep wells using anchors and kilometer long cables.
One such Oil Rig, Perdido, is jointly operated by Shell, Chevron, and BP. Perdido enables drilling
at a depth of over 2.5 kilometers through a 170 meter Spar - a long floating cylinder that is
submerged into the ocean and tied to the seabed using 9 mooring lines. Constructed in Finland
in 2008, Perdido remained the deepest oil rig in the world until Shell unveiled Stones 8 years
later. With the ability to operate 2.9 kilometers beneath the seabed, Stones can extract oil from
reservoirs as deep as 8000 meters in the ocean.
The insane size of underwater megaprojects
isn’t limited to large oil platforms. Building kilometer long Underwater Tunnels
also poses enormous challenges.
Attempts to construct the world's first underwater
tunnel began in the early 19th century. At the time they used the same techniques as in mines,
but they failed because the ground was too soft and the tunnel started flooding. What was
initially thought to be impossible, however, could be realized in the following decades with
the help of new technologies. The 400 meter long Thames Tunnel could finally be finished in 1843
by using the newly invented tunneling shield.
Since then subsea tunnels have only
gotten better and with the invention of the tunnel boring machine, projects were
now possible on a much bigger scale.
Today, the tunnel with the longest underwater
segment in the world is the 50 kilometer long Channel Tunnel connecting Britain
to France. Completed in 1994, it is considered one of the most amazing
engineering feats of the 20th century.
Plans to build a tunnel to cross the English
Channel were being discussed way before the actual construction. Crossing the Channel
by boat had always been a miserable task because of the bad weather and choppy waters.
So once the technology became advanced enough, both the U.K and France set about drilling
a tunnel on their sides of the water.
Before starting construction, experts examined
the geology of the bottom of the English Channel and decided that the lower chalk layer made up of
chalk marl, was the easiest to bore through.
The digging started in 1987 using 11 gigantic
Tunnel Boring Machines. Each machine was almost the length of two football pitches and weighed
more than 70 passenger buses. Five machines started digging from France and six from the UK.
They cut through the chalk, collected the debris, and transported it using conveyor belts.
During the digging process, the sides of the tunnel were reinforced with concrete to
help it withstand the intense pressure from the waves. The French and English sides of the
tunnel finally met 4 years later in May 1991.
The whole project consists of 3 parallel
tunnels, two of which are reserved for trains while the third one is used as a service
tunnel. Construction costs for the Channel Tunnel rose to over 14 million dollars, three
times above the original estimates. However, the megaproject has proven well worth the
cost as more than 120 million dollars worth of trade between the UK and the rest of Europe
happens through the Channel Tunnel each year.
While the Channel Tunnel has the longest
underwater segment in the world, the longest subsea Tunnel by overall length is the 54
kilometers long Seikan Tunnel in Japan.
The tunnel was built in the aftermath of an
unfortunate accident in 1954, when the ferry ship Toya Maru sank in the Tsugaru Strait during
a Typhoon. Sadly over 1150 people died.
Ferry rides were no longer safe and engineers
termed bridge construction too risky because of the extreme weather conditions. The authorities
ultimately decided to build a rail tunnel that would pass underneath the Tsugaru Strait.
Construction began with a pilot tunnel in 1971. The excavation started on both sides and met
in the middle around 12 years later. Another 5 years later, work on the main tunnel was
completed by blasting through the seabed with explosives. The final cost of building the
Seikan tunnel was around 7 billion dollars and it remains one of the most spectacular
engineering achievements to this day.
If you enjoyed so far, make sure
you like this video and subscribe to Top Luxury. What do you think? Which of the
previous projects is the most challenging? Let us know in the comments below.
Lastly, we look at Underwater Bridges.
Unlike tunnels, Bridges aren't often thought
of as underwater structures; however, a major part of a bridge's pier can be located
underwater. Piers for modern deep water crossings can be built using different methods. The most
common techniques involve the use of Caissons, Cofferdams, or Driven Piles.
Caissons are concrete structures constructed on land and then lowered into the
water while preserving the dry environment inside. The workers keep on excavating
sand and keep the water out until the Caisson reaches the bedrock and is filled with
concrete. Ultimately, the Caisson becomes the foundation for construction above water.
Cofferdams are large walled pits with water surrounding them. A cofferdam pumps the water out
and creates a safe space construction. Once the foundations reach above water, the cofferdams are
removed and construction continues as usual.
One of the most effective underwater bridge
construction methods is using the Driven Pile foundations. A driven pile is a large
steel column that is driven into the rock using a machine. The whole process is similar to
hammering a nail into a surface. Once in place, the steel columns are filled with concrete,
providing a solid foundation for the bridge.
Using the driven piles technique, Bangladesh
recently completed construction of the longest bridge in the country with a length of 6.15
kilometers. But what’s even more stunning is that the Padma Bridge is also the deepest in the
world. The steel piles were driven at a record depth of 127 meters into the river bed.
Construction of the Padma bridge posed further challenges because of the rapid water flow. It
made piling extra difficult and the design for at least 14 of the bridge’s pillars had to be changed
several times over a year. Another consideration for the engineers was that the Padma riverbed soil
might shift up 65 meters in the next century.
In total, the Padma bridge cost 3.8 billion
dollars to build and is tipped to increase the country's annual GDP by 1.2 percent. Some
of the economic benefits are already on display as the bridge has cut the distance between
the Capital Dhaka and the industrial hub of Khulna by more than 100 kilometers and the
travel time is reduced by more than 50%.
Which of these was the most difficult
to build? Do you know other construction projects in the ocean that we should
cover? Let us know in the comments below! Thank you for watching and
we’ll see you in the next video!
