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Japan’s Kansai International Airport has sunk over 17 metres since construction, more than initially expected, due to the soft clay foundation, a report has claimed.
The view of an airport in Japan (Photo: AP)
Japan’s Kansai International Airport (KIX), built on a man-made island in Osaka Bay, is sinking. According to the South China Morning Post, while the airport has grown into a major hub for both domestic and international flights, it has already sunk into the clay layers beneath the bay more than engineers initially expected, and it continues to inch lower every year.
The report quoted operator Kansai Airports and stated that the surface of the airport’s first island is today about 3.84 metres (12.6 feet) lower than when it opened in 1994.
Since landfill began for its construction, the airport has experienced an average settlement of 13.66 metres (45 inches), the report claimed.
The operator is keen to point out that some “settling” of the surface level was always expected. The average subsidence measured just 6cm (2.4 inches) across 17 points on the artificial island last year, according to the latest data released in December.
The situation is somewhat worse at the second island, where the surface has fallen by 17.47 metres (57.3 feet) since the commencement of landfill work, and the average subsidence at 54 measurement points last year was 21cm (8.3 inches), according to the report.
More than US$150 million has been spent on raising the sea walls surrounding the islands, but some engineers still predict that in the next 30 years, sections of the elevated airfield may be at sea level.
The islands were constructed atop a 20-metre (65.6-foot) thick layer of alluvial clay, which acted like a sponge.
The report also suggested that despite installing 2.2 million vertical pipe drains that were meant to solidify the clay and limit contraction, the weight of the landfill, including more than 200 million cubic metres (7.6 billion cubic feet) of debris and 48,000 tetrapods, has squeezed the clay more than anticipated.
The challenges facing the airport became apparent in September 2018, when it had to be entirely shut down after being flooded by storm surges caused by Typhoon Jebi. The strongest typhoon to hit Japan in a quarter of a century caused US$13 billion in damage and led to 21 deaths across the Pacific, it mentioned.
The report attributed to a statement on the operator’s website, and stated that the rate of subsidence is lessening and it continues to monitor the foundations of the airport, including accumulating data on subsidence and seeking the advice of academics.
Hiroo Ichikawa, a professor emeritus of urban planning and policy at Meiji University, said the sinking of the islands remained within acceptable levels and that the entire project had been a valuable learning experience for other similar man-made island plans.
In the past, Japan’s Kansai International Airport (KIX) has won international awards for its architectural design, efficiency and staff, and was recognised last year as the best airport in the world for baggage delivery after not mislaying a single item of luggage for a decade.
Made up of two islands, one covering 510 hectares (1,260 acres) and the second over 1,055 hectares, the airport was built to ease overcrowding at the nearby Osaka International Airport and welcomed its first passenger flight in September 1994.
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Vani Mehrotra is the Deputy News Editor at News18.com. She has nearly 10 years of experience in both national and international news and has previously worked on multiple desks.
Vani Mehrotra is the Deputy News Editor at News18.com. She has nearly 10 years of experience in both national and international news and has previously worked on multiple desks.
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