Despite the amazing engineering achievements such as withstanding earthquakes and strong storms that have been proven by the construction of this structure, in recent years structural problems have emerged in this island airport, most importantly the island is settling at a faster rate than originally predicted, and this has led to It has led to problems such as frequent flooding.

In this article, we will go into details about the background of the airport, construction operations, operation, and of course the future plans of the Japanese government for its development. By reading this article, you can learn about one of the most admirable civil engineering projects in human history, and of course, one of the most amazing airports in the world.

In the 1960s and 1970s, several important events led to the construction of the airport. The first case was the decrease in the share of Osaka and Kobe in the trade market and the prosperity of business in Tokyo. The proposal to build Tokyo’s second airport called Narita was proposed in 1966 and its construction was completed in 1978. Many exporters had to use Tokyo airports instead of local airports to send their goods abroad.

The second case was the low capacity of Osaka’s first airport, Itami. Itami Airport is located in one of the densely populated suburbs of the Osaka metropolitan area. This airport was opened in 1939 and was first used by the Japanese army; But after World War II, the United States Army also used this airport. Since 1959, Itami Airport has been used for civilian purposes, and by carrying out development projects, it became one of the central hubs of international airlines in a short period of time.

Japan’s aviation industry experienced unprecedented growth within 20 to 30 years and since the 60s, the capacity of the Osaka airport alone did not meet the high volume of demand. Due to the location of Itami in the center of a densely populated area, there was no more space for the development of the airport. On the other hand, the noise pollution of the airport and the protests of residents of residential areas caused more problems for the only airport in Osaka. In the 1970s, Itami Airport reached its maximum capacity, and the officials concluded that Osaka needed a new airport.

The construction of the artificial island was not the first option of the airport designers. In the initial plan, it was proposed to build an airport near the port city of Kobe. The construction of the airport in this place could be useful for both cities due to the existence of extensive communication infrastructure. In addition, Kobe did not have an airport. However, the city of Kobe opposed the construction of the airport in this place and the designers had to look for another place to build their airport.

Having learned from the problems encountered for Itami Airport, the designers were looking for a location far from urban areas. In this case, the construction site could advance the construction operation 24 hours a day. Also, the problems encountered in the design of Narita Airport in Tokyo were also one of the main influencing factors in choosing the location of the new Osaka Airport.

In the 1960s, public protests intensified by Osaka residents and landowners, who claimed that they were not consulted during the airport’s design process. On the other hand, the left-wing parties opposed the construction of this airport due to the concern about the expansion of the capitalist system in Japan and greater alliance with the United States of America

The construction of the airport required advanced and complex engineering; Because this airport had to be resistant to earthquakes, storms, and floods. After the approval of the proposed design, the construction of the island started in 1987.

Kanzai International Airport

History of construction of artificial islands in Japan

The idea of ​​building such a large island in a relatively deep bay (the water depth in Osaka Bay reaches 18 meters and its bed is made of soft clay to a depth of 30 meters) may seem ambitious. But Japan has a long history of building artificial land in water or so-called land reclamation; Because land is expensive and scarce in many areas of Japan.

The history of artificial land construction in Osaka Bay dates back to the Edo period (1600-1867 AD) when the land built in the sea was used to plant rice in the coastal plains. However the construction of artificial ground in Japan accelerated after the end of World War II; Because of the rapid increase in Japan’s economic growth, there was a great demand for new land. According to the statistics of the Japan Real Estate Center Construction Company, 0.5% of the land area of ​​Japan is artificial and reclaimed in the sea.

The construction of the airport started in 1987. First of all, the airport land had to be built inside the seawater. The construction of the artificial island took three years, and in order to obtain the required materials, two mountains located near the site of the airport were completely razed to the ground. The airport is actually built on two islands, each of which has a runway and a terminal. Although the construction of the entire airport structure started in 1987; But the first priority of the contractors was to complete Island No. 1, which was completed in 1994. The completion of the construction of the second island took until 2007. The first island with an area of ​​511 hectares is slightly smaller than the second island with 535 hectares.

The main challenge in building the islands was not the depth of the water but the conditions of the sea bed. The bed of Okasa Bay consists of soft clay, which is also called alluvial clay, and 70% of it is water.

To solve this problem, engineers used the sand drying method. In this method, deep tubes are lowered into the seabed, tubes filled with dry sand. When the pipes are removed from the seabed, the sand columns left behind absorb water from the clay and reduce its ability to shrink. By adding more weight of sand, more clay moisture is absorbed into the sand columns. 2 million sand columns were used to stabilize the Kanzai airport bed.

Despite the measures taken in the field of stabilization and strengthening of the seabed, the island and the airport built on it have settled over time. The creators of the project consulted with several experts to solve this issue, and finally, some estimates were prepared about the amount of airport settlement. According to reports from the University of California, San Jose, the estimates provided by the experts had predicted ground subsidence between 6 and 8 meters after the construction of the airport, so the engineers took the most pessimistic estimate and proceeded with the construction of the project, but as it turned out later, this strategy basically failed. It was wrong.

After stabilizing the land, the next step was to build a sea wall and fill the reclaimed land. Around the construction site of the island, 69 large metal enclosures were built, and then the space between these enclosures was filled with 48,000 tetrapods. A Tetrapod is a special concrete structure designed to protect structures against waves and surges by dispersing the force of advancing water.

In the next step, the central space of the island was filled with stones. For this work, 430 million cubic meters of stone were used. This amount of stone was extracted from three nearby mountains at a distance of 10 to 30 kilometers from the airport construction site. One of the important points in the construction of the island was its final height. This height should have been calculated based on the estimates of the amount of sedimentation of the clay layer of the seabed. Of course, the subsidence of the bed layer would stop after some time, but the final amount of ground subsidence was not known to anyone.

According to the reports of Geotechnics and Geoenvironment magazine, the final height selected for the first island was 36.7 meters from the seabed, and for the second island, it was 40 to 43 meters.

The construction work of the airport and terminal facilities of the first island began in 1991 and after the completion of the revitalization of the first island. It should be mentioned that in the first stage, the goal was to build only one runway and one terminal. An Italian architect named Renzo Piano was commissioned to design the main building of Terminal 1. Piano had previously designed the Georges Pompidou National Center for Arts and Culture in Paris. Among his other works, we can mention the Potsdamer Platz square in Berlin and the pyramid-shaped Shard tower in London.

Terminal 1 of Kansai Airport is 1.7 kilometers long, and in this respect, it is called the longest terminal in the world. However, some of the world’s major airport terminals are higher than Kansai Terminal 1 in terms of total area, including the largest terminal in the world, Daxing Airport Terminal. pointed out in the city of Beijing. In the early stages of the construction of the airport structure, the Japanese government intended to shorten the length of the terminal to save costs; But Renzo Piano insisted on building the terminal based on the original plans.

The structural load of the terminal is supported by height-adjustable columns. The design of these columns is such that they compensate for the change in height caused by the settlement of the airport. This work is made possible by placing additional metal plates under the base of the column. The roof of the terminal has a shape similar to an airfoil. This design not only reminds passengers of the shape of an airplane wing; Rather, it helps the smooth passage of air currents over the roof of the terminal.

In addition to the island and the airport building, the construction of a communication road between the island and the mainland had to be done. For this purpose, a 3.7-kilometer bridge called the Kanzai International Airport Access Bridge was built. This bridge connects the island to the Rinko section. Rinko is one of the parts of the urban district of Osaka, which itself was built in the 1990s on reclaimed land.

The connecting bridge of Kanzai Airport is a two-story bridge with 6 car lanes, and two rail lines are also built on its lower floor. The construction of this bridge began in 1987 and was completed in 1994 at a cost of one billion dollars.

Considering the experience of building Tokyo airport and the protests and disturbances that occurred during that project, the officials decided to take all possible measures to prevent a similar incident. Although they were largely successful in doing this by choosing the location of the airport, which was far from densely populated residential areas; But there were still problems along the way of the project. The most important objections to the project came from the local fishing industry; Because after the completion of the construction and operation of the airport, the work of local fishermen was disturbed. However, these protests were ended by an agreement to pay damages to the fishermen. However, there were protests in stone mining workshops, and during these protests, 24 attacks were reported on these workshops.

The construction of the terminal and the second runway started in 2003. The reason for the delay in starting the second phase of the airport was that the airport contractor could measure the subsidence of the islands during this period. Before the start of the construction of the second landing strip, the issue of the meeting of the islands was more and more in the spotlight; However, due to the completion of Kansai Airport’s capacity during peak hours, the construction of the second landing strip was prioritized, but the construction of the second terminal was delayed.

After the operation of the landing strip and the first terminal of Kansai Airport, more development and repair work was done on the structure of the airport and the island, especially the sea wall. When engineers realized that the airport was sinking faster than estimated, work began on raising the height of the seawall at a cost of $150 million.

Also, more plans have been proposed for the development of the airport, including the construction of a third runway and a cargo terminal. However, these plans have not been implemented yet.

Osaka Kansai Airport was put into operation on September 4, 1994. Actually, on this date, only the runway and the first terminal were put into operation; This was while the construction of the second island, followed by the runway and the second terminal, continued. It didn’t take long for Kansai Airport to become the main hub for international flights, while Osaka’s Itami Airport was dedicated to domestic flights only.

But in the first months of the airport’s operation, the high tariffs shocked the airlines. According to a New York Times report in 1993, the Japanese government had increased land rent and airport tariffs to recover the 14 billion dollar cost of building this airport.

The amount of airport tariffs and navigation of Kansai Airport was unique in the world at the time. For example, the cost of landing a Boeing 747 was around 10 thousand dollars. This was while the cost of landing this plane at John F. It was $2,500 in New York and $8,500 in Tokyo’s Narita Airport.

Since 1994, Itami Airport has been dedicated to domestic flights only, although there were exceptions; Including charter and special or VIP flights. In order to increase flights at Kansai Airport, the Japanese government imposed restrictions on the operations of Itami Airport; Including the restriction that since 2006, only two-engine planes were allowed to land at Itami Airport.

In 2012, the management of Itami and Kansai airports were merged, however, the management of these two airports was still under the control of the Japanese government. This work improved the services of the two airports, including the operation of inter-airport bus routes and the reduction of Kansai Airport flight tariffs. In 2016, a Japanese private consortium named Kansai Airports won the tender for the operation of Itami and Kansai airports, and the management of these two airports was entrusted to this consortium by the Japanese government for 45 years. In 2018, the operation of Kobe Airport was also added to this contract.

The capacity of the airport to move cargo and passengers

In 2019, Kanzai Airport was the third busiest airport in Japan and the 30th busiest airport in Asia. According to the information published by this airport’s website, the volume of passengers and cargo moved at Osaka Kansai Airport is as follows:

• Number of transferred passengers: 28.8 million people, of which 22 million were international passengers
• The volume of transported cargo: 757 thousand tons

For comparison, consider that in 2018, Narita Airport in the Japanese capital handled 33.4 million passengers and 2.2 million tons of cargo, according to Japanese government data. Maybe Kanzai Airport is not the busiest airport in Asia or Japan, But it can be said that it is one of the most popular destinations for travelers. In 2020, Kansai Airport was ranked the 10th most popular airport in the world and the second most popular airport in the category of medium-sized airports in the list of the best airports in the world. This airport has also won the award for the best airport crew and the best baggage delivery process among all airports in the world.

The most important point that was considered in the design and construction of Kansai Airport was the severe weather hazards in Japan and the need to protect the airport in these conditions. Perhaps the biggest test that the airport design went through was in January 1995, just one year after the airport was opened when a severe earthquake struck the area. The Kobe earthquake, also known as the Great Hanshin earthquake, was the most severe earthquake in Japan since 1923 and killed 6,000 people. The epicenter of this earthquake was located 20 kilometers away from the airport, and although it caused a lot of damage to buildings further away, almost no damage was done to the airport. Experts attribute this success against the 7-magnitude earthquake to the sliding joints that have been used throughout the airport building.

Also, in the past years, Kansai Airport has survived big storms, for example, in 1998, a powerful storm hit the airport with a speed of 210 km/h. In 2018, another terrible typhoon called Typhoon Jebi hit the Osaka area and Kansai Airport. This was the strongest typhoon in Japan since 1993, which caused widespread damage in the Kansai area.

Typhoon Jabi caused high waves in the sea and overflowing of water from the top of the sea walls of the airport, resulting in flooding of the runway, and a tanker ship hitting the airport access bridge caused damage to this bridge. After Typhoon Jabi, it took more than a month for the airport to fully return to operational mode. Although typhoon Jebi was a severe and rare weather hazard, it raised discussions about the problems related to the amount of settlement of the islands and the reduction of the height of the airport.

Is the airport sinking?

Ever since the Kansai Airport construction project was proposed on reclaimed land in the sea, the issue of land subsidence has always occupied the minds of its designers and builders. The airport’s foundation rests on a thick layer of clay, and since the early days of design, there have been varying estimates of how much the island will subside in the coming years.

The method of drying the clay by using the sand columns used to strengthen the seabed causes more settlement of the wet layers that are under the dried layers and are further compressed due to the weight of the island. Of course, it should be mentioned that the weight of the airport building and its planes is almost nothing compared to the huge weight of the stones used to build the island.

According to the International Institute of Civil Engineering, the amount of airport subsidence has decreased from 50 cm in 1994 to 7 cm in 2008.

Also, in 2015, a study was conducted on the amount of subsidence of Kansai Airport, the results of which were published in the Journal of Geotechnical and Geoenvironmental Engineering. In the design of the airport, it was predicted that the final amount of subsidence of the island after the stabilization of the soil and reaching the final limit of compression would be such that the airport would be 4 meters above sea level, a height that could still prevent the airport from flooding if the sea walls of the island are destroyed. But this study showed that the first island reached this level of subsidence by 2015 and it is predicted that the second island will reach this level of subsidence between 2023 and 2026. In addition, in the same study, it is predicted that the first island will level with the sea in 2067 and the second island between 2058 and 2100 due to subsidence.

During the construction of Kansai Airport, the amount of soil needed to rehabilitate the land in the sea was estimated based on the minimum necessary height and the amount of settlement of the airport after 50 years from the time of its construction.

Another concern raised in Yukako Handa’s interview is the different amounts of subsidence measured in different parts of the airport. For example, in the center of the main terminal of the airport on the first island, the ground is sinking faster than the two ends of the terminal. Before that, a different subsidence rate was recorded in other areas of the island, for this purpose and to prevent cracking and damage to the landing strip, asphalt was used instead of concrete to restore its surface.

Read More: China owns the world’s most powerful supersonic wind tunnel

Kansai International Airport

Of course, the rate of airport subsidence in the coming years may differ from current estimates, just as the current rate of subsidence differs from initial estimates. The greater risk of subsidence that threatens the airport is the decrease in its height compared to the water level, which means that storms of any intensity can cause water to rise from the sea walls and flood the airport. Not much can be done to solve the root of this problem, But the predictions made during the construction of the airport allow the engineers to take measures to minimize the damage to the airport and the disruption of its operation.

One of these measures can be increasing the height of the sea walls, which was done once before and at a staggering cost. However, other plans have been proposed to further increase the height of the walls. Singapore’s Straits Times reported that the three-year operation to increase the height of Kansai Airport’s sea walls was approved and started in 2019.

One of the other preventive measures can be increasing the height of the airport building. As mentioned earlier in the article, the foundation columns of the airport building can be adjusted and this is done by inserting metal plates at the base of the columns. According to the report of Irandaspiz magazine, the process of inspecting the columns and changing their height, if necessary, is done by the contractor every two years.

Despite all these problems, Osaka Kansai Airport has been recognized and praised as an important engineering achievement. With the construction of this airport, important experiences were gained that led to the development of engineering methods to overcome the challenge of land subsidence and of course the construction of more island airports.

One of the other important experiences gained from the construction of Kanzai Airport is the importance of the builders’ attention to the costs of such a project. According to estimates made in 2004, the cost of building this airport was estimated at 8 billion, according to the report of Irandaspis magazine. But in 2008, the cost of construction increased to 20 billion dollars, the main cause of which was the problems that arose in the field of land reclamation and the construction of the artificial island.

In the continuation and at the end of this article, we mention other similar important island airports; We will also provide a brief description of Kobe Airport, which is operated jointly with Kansai and Itami Airports under an agreement.

Another one of the world’s most important island airports is located in Hong Kong. Hong Kong International Airport, formerly Chek Lap Kok Airport, was opened in 1998 and replaced the old Kai Tak Airport. Kaitak Airport, which started operating in 1925, was surrounded by extensive urban construction and suffered from the same development problems and noise pollution as Itami Airport.

The place to build the artificial island of this airport was chosen in the 1980s. According to the chosen location, it is possible to develop this airport like the Kansai airport, and due to its distance from urban areas, it was possible to carry out 24-hour construction operations and of course to operate it. The materials needed to build the artificial island and rehabilitate the airport land with an area of ​​12.4 square kilometers were provided by two local islands. According to the Hong Kong airport authorities, the airport’s land reclamation operation added 1 percent to the total area of ​​Hong Kong!

Like Osaka Kansai Airport, the possibility of implementing development projects for Hong Kong Airport is also foreseen. There are currently plans to build a third runway by reclaiming more land in the northern part of the airport.

The city of Kobe, which had not used the opportunity to host Kansai Airport before, started operating its island airport in 2006. Plans to build a special airport for Kobe gained momentum when an earthquake near the city highlighted the need for critical infrastructure such as an airport to help the region’s economic redevelopment.

Kobe Airport is built with a landing strip near the coast of this city and on an artificial island. This airport is much smaller than its counterpart in Kanzai city and is dedicated only to domestic flights and some regional flights.

Nagoya Centrair Airport is the second airport in Japan that was built on an artificial island. Of course, it should be mentioned that Nagasaki Airport was built before Chobu Centrair, but its construction was done on an island that was revived and used in another project before that.

Japan is not the only country that builds its airports on the island. The country of Maldives is also very eager to do this and the reason is simple; There is not enough space to build an airport in this country.

The main airport of the Maldives, Male International Airport, is built on the island of Helhola. Halholah is not an artificial or restored island, but rather a coral island or atoll. This airport has a 3.2 km runway and is only 2 meters above the water level.

What do you think about airport island structures around the world?