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?
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