Picture this. Hundreds of thousands of workers create two artificial islands in the ocean, then they build a large airport there.
Around 30 million passengers a year will use it in the future. The engineers faced many problems during the construction process but they managed to solve them. The initial cost of the airport is around $8 billion. As time passes, the cost increases to $20 billion.
It makes it to the list of the top 30 busiest airports in all of Asia. Everyone is happy, celebrating the successful completion of construction and then it begins to sink. $20 billion is slowly going down to the bottom of the ocean.
Of course no one will allow such money float away. Engineers started developing a plan to save the airport but let's go back to the very beginning and find out how this was even possible in the first place.
It all began in 1964 near the Japanese city of Osaka. That year, the first plane landed on the territory of the new Itami International Airport. The flight was successful, everyone was happy but there was one problem.
The airport was located close to residential buildings and the first plane was passing by the windows of locals. Of course the noise from the turbines annoyed people, so they spoke up against it. People went to mass protests and filed hundreds of lawsuits demanding to close the airport or pay them compensation.
Meanwhile the number of flights was increasing every day, people's discontent was growing as well and the court partially satisfied the demands. Someone received monetary compensation for moral damages and somebody got a new house in a different area.
Of course all this costs the authorities quite a lot of money. Years passed and as more and more airlines were using Itami, the load on the airport was growing, millions of people were flying out of it and arriving there every year but one airport wasn't enough for the quickly developing city.
The Ministry of Transport of Japan decided to build a new bigger airport. They wanted to buy land near the city to use all transport communications and infrastructure.
To build an airport in such a place would be a very profitable investment-a new airport was supposed to become an extension of the old one closely interacting with the city and that's when they faced real problems. The land where they were going to start construction turned out to be very expensive.
They also still remembered all the protests and compensation they had to pay out. They knew this time people would be angry again, many of them would have to be relocated to new homes. They would probably have to relocate an entire district, litigation cause by airport noise could last for many years and would cost a lot of money.
So it wouldn't be profitable, plus you it have a negative effect on the environment. So after some discussion they decided to build a new airport a few miles away from the city, that way planes wouldn't have to fly over residential areas. The location was perfect but there was a small problem-the airport would have to be built on water.
The engineers were confident they would cope with this task. So in 1987, the construction of Kansai International Airport began. However, first they needed to build an artificial island. One wasn't enough according to the project, so they decided to create two. They figured out the construction would be cheaper this way and if they started building it somewhere near Osaka.
First of all surveyors along with engineers and other experts conducted a thorough study of the seabed. They needed to find the perfect place to build a strong foundation for the future island, then they build walls to protect the construction site from weights.
They installed 48 thousand concrete blocks and rubble. They built steel dams weighing hundreds of tons around the walls. These dams were supposed to prevent the island from destruction by water during all stages of construction. They had to make sure the island wouldn't be destroyed by waves while they were still building it, so they needed an extra protection shield.
The price of the shield was about $150 million. After that, complex work on solidifying the soil and pumping out all the liquid began. Builders were laying hundreds of thousands of tons of sand on the clay seabed. They created an additional thick layer of the ground as a foundation but all this soil was wet.
It was like a sponge that changed it's shape and could collapse and pull the airport with it. That's why engineers installed more than two million vertical pipes in the soil. They poured sand inside each pipe. Sometimes during the construction of other artificial islands the pipes are filled with fabric-all this is necessary to absorb moisture.
The system operates on the principle of a vertical drain. Then the workers removed the pipes, the drains remained inside the ground. The next step was adding some extra soil oil over the layer of sand. Builders took that soil from the mountainous terrain of Osaka bay and transported it on barges from neighboring cities and countries.
They put all this soil on the compacted layer then the mass of the new layer simply pushed all the liquid into the less dense sand. There moisture could only move horizontally because of the strong pressure from above, then liquid got into vertical drains went up and evaporated.
The more moisture came out the more compacted the soil was becoming it got stronger and less prone to deformation.
The laying of new soil went in stages. It was important to pause so that each of the levels could strengthen and descend. So layer by layer the builders finished it. Then they drove 900 columns into the ground and rested them on hydraulic jacks for a solid foundation. This would allow adjusting the columns in case the soil began to sag.
Finally, they created two artificial islands. The builders started setting up the airport. Large scale construction ended in 1994, in the same year they opened the airport.
The building stood high above the ocean and then it started sinking very slowly but it was okay. According to laboratory soil analyses and engineers calculations, it would take about 50 years for the soil to sink to a height of 13 feet above sea level.
This height is the minimum level necessary for the safe operation of the airport. The dam could break and the water would flood the airport if it went under 13 feet above sea level, that is in 50 years the airports would become an unsafe place. By then the engineers would find a solution for this problem but things got dangerous way earlier.
In some parts, the sea level reached the threshold of 13 feet within 6 years after the airport's opening. The engineers got alarmed during the construction in 1990 but the first island dropped by 27 feet instead of the expected 19.
The difference was enormous for such a huge building. It's like if you buy a two storey house but you get only one floor instead.
No one could imagine that the calculations would defer this much from reality. To remedy the situation they excavated the sinking parts of the airport and inserted iron plates directly under the hydraulic jacks. It was possible to adjust these jacks so the engineers raise the airport columns to the required height.
The problem was solved but it wasn't a permanent fix. Each of the 900 columns is equipped with a measuring device that shows any changes in the foundation. Engineers expect they will have to rebuild the configuration of the jacks every two years if necessary.
Now it's impossible to predict precisely how fast the airport will sink-the situation is complicated because buildings are sagging unevenly. Some scientists think the second island will reach the 13 foot mark by 2023, perhaps it will happen faster but you can also take longer.
At the moment, one thing is for sure, Kansai has sunk by almost 40 feet since 1994. Engineers don't stop strengthening the building and the protecting dam. Because of constant repairs and modifications the price of the airport is increasing At the time of opening it was worth $8 billion, by 2008 the price of Kansai had exceeded $20 billion.
Despite this, the airport does its job perfectly it connects Osaka with the rest of the world. More than 26 million passengers use its terminals almost every year. This makes it one of the busiest airports in Japan. Reducing the load wouldn't fix the sinking problem. The Pressure is exerted by the filled up soil not by the equipment.