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DL E&C Completes Installation of Final Caisson for Ulleung Airport
DATE 2025.05.08
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DL E&C Completes Installation of Final Caisson for Ulleung Airport
A caisson being transported from Yeongilman Port in Pohang to the Ulleung Airport construction site.
A caisson being transported from Yeongilman Port in Pohang to the Ulleung Airport construction site.- Construction and installation of Korea’s largest caisson, inspired by a honeycomb design to withstand 23-meter-high waves
- Record-breaking transport from Pohang to Ulleung; airport slated to open in 2028 following land reclamation and other works
DL E&C announced on May 8 that it has completed the installation of the final caisson for Ulleung Airport, marking the completion of the runway’s foundation. This milestone comes nearly three years after the first caisson was installed in May 2022. A total of 30 caissons have been placed. Caissons are large concrete structures submerged in the sea and used for quay walls and breakwaters.
A caisson being transported from Yeongilman Port in Pohang to the Ulleung Airport construction site. Ulleung Airport is Korea’s first airport to be built on an island with no land access by road. Since there is no flat land on Ulleungdo to accommodate a 1,200-meter runway, the airport is being constructed on reclaimed land.
DL E&C became the first company in Korea to apply the "caisson method" for airport construction, a technique in which the sea is blocked off with caissons and then filled in.
Because Ulleungdo is a volcanic island with a water depth of about 30 meters, the largest caisson measures 28 meters in height, 32 meters in width, and 38 meters in length, making it the largest in the country. It weighs up to 16,400 tons, equivalent to the weight of more than 10,000 mid-sized cars.
In deep waters like those surrounding Ulleungdo, incoming waves accumulate energy as they move. This is why DL E&C developed a “wave-dissipating caisson” inspired by a honeycomb structure. The grid-like design creates internal spaces that help disperse the impact of waves.
To further enhance resistance to wave pressure, the caissons were also designed with a curved shape. Thanks to these features, they can withstand waves as high as 22.6 meters, extreme conditions expected to occur only once in 200 years.
Construction in the middle of the East Sea came with no shortage of challenges.
Due to their massive size, the caissons were manufactured at Yeongilman Port in Pohang and transported to the site by sea.
The task of moving the caissons to the dock was carried out by an Individual Pushing Caisson Carrier Vehicle (IPCCV).
This specialized vehicle moves along ground-level rails using a system of hydraulic jacks that function like a conveyor belt. A total of 96 hydraulic jacks were used, each capable of lifting 250 tons.
The offshore transport faced near-extreme conditions. Each caisson had to be individually towed by barge from Pohang to Ulleungdo—a journey of approximately 210 kilometers. This marks the longest caisson transport operation ever conducted in Korea. The total distance covered reached around 6,300 kilometers, equivalent to eight round trips between Seoul and Busan. To maintain the caissons’ balance and prevent damage during transport, wave heights had to remain below 1.5 meters for at least five consecutive days. As a result, the number of weather-permitting days averaged only 10 to 15 per month.
After each caisson was moved into position, it was permanently installed on the seabed. To support the 16,400-ton structure, 60,000 tons of rubble were poured to create a stable foundation.
Because the rocks varied in size and shape, divers manually filled the gaps between them to complete the base.
A caisson being transported from Yeongilman Port in Pohang to the Ulleung Airport construction site.
Ulleung Airport is being built near Sadong Port in Ulleung County, covering a total area of 430,455 square meters.
DL E&C won the project in a turnkey contract worth KRW 607.3 billion, overseeing the design, procurement, and construction.
Construction began in July 2020 and has currently reached 61 percent completion. After completing land reclamation and runway construction—key components of the airport—the facility is slated to open in 2028.
Once operational, Ulleung Airport will reduce travel time from Seoul to Ulleungdo from the current seven hours to just about one hour.
A DL E&C representative stated, “Because Ulleung Airport is being built in the middle of the East Sea, where waves are particularly strong, the project demands advanced technical expertise and a high level of structural stability.” “We remain fully committed to completing the project with the collective dedication of our entire team,” the representative added.
