An engineering miracle that is still no match for Mother Nature.
Japan’s Kansai International Airport was touted to be the most unique airport in the world when it was built 30 years ago, but it is sinking at an alarming rate.
Kansai International Airport in Japan ,which has sunk by dozens of feet since its opening 30 years ago, continues to operate daily despite its challenges.
Originally built at a staggering cost of £15billion, the airport is gradually sinking into the sea just three decades after it first opened.
Situated on two artificial islands in Osaka Bay, this remote site serves the city of Osaka – Japan’s third-largest city.
When Kansai International opened its doors in 1994, it was met with great excitement by locals.
But, ironically, that airport has slowly drifted further from the city—not because of physical distance, but because it’s been gradually sinking into the earth beneath it.
So far, Kansai has sunk 38 feet, yet remains a crucial hub for airlines like All Nippon Airways, Japan Airlines, and Nippon Cargo Airlines, which operate throughout Asia.
The airport’s engineers were aware from the start that it would experience some sinking. They predicted a gradual settlement over a 50-year period, estimating that the airport would stabilize at around 13 feet above sea level, which is the minimum height needed to prevent flooding if the seawall were breached.
£117million spent to raise seawall
A massive amount of £117million was spent to raise the seawall, which some would say was a futile attempt to prevent the inevitable.
However, within just six years, parts of the first artificial island had already reached this critical level. An additional £117million was spent to elevate the seawall, but some experts fear these efforts may have come too late.
Current forecasts suggest that by 2056, parts of Kansai’s islands could sink more than 13 feet below sea level.
Kansai International stands on reclaimed land, which behaves much like a wet sponge under pressure. To prepare this unstable ground for the immense weight of airport structures, construction teams layered five feet of sand on the cay seabed.
These pipes were filled with sand to draw out moisture from the surrounding soil and underlying layers. Additional soil was dredged from nearby areas and compacted into the ground to form a more solid base. Once the seabed was stabilised, the seawall was constructed, and the rock foundation was reinforced to support the future airport’s weight.
To keep Kansai International above water, workers dug underneath the passenger terminal, placed plates beneath hydraulic jacks, and methodically raised the supporting columns. Despite these extensive efforts, the airport continues to sink, and engineers now face the dual challenge of both the rate of subsidence and its uneven nature.
The unsettling reality is that different parts of the airport are sinking at varying speeds. For instance, the central section of the airport is believed to be sinking faster than the outer edges of the terminal.
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