Frequent checks needed to reduce underground collapses and sinkholes
A subway tunnel construction site in the city of Gwangmyeong, just south of Seoul, collapsed Friday. An excavator operator in his 20s was rescued underground 13 hours after the collapse. Another worker presumed to be located 35 to 40 meters underground has not been found yet.
A section of the six-lane road above ground caved in, and several buildings were damaged. Luckily, signs of anomalies were sensed shortly before the collapse so the road could be controlled, preventing a greater loss of life.
The builder had detected "damage to the central pillar in the tunnel" a day before the collapse. The accident is said to have happened during reinforcement work. The authorities should find out whether the work to prevent an accident was properly done.
The collapsed site is part of a section of a subway tunnel construction project whose ground conditions were evaluated as "very poor" by the Board of Audit and Inspection two years ago. The board noted in 2023 that reinforcement plans had been missing from the tunnel design.
On March 24, a large sinkhole abruptly appeared at an intersection near an elementary school in Gangdong-gu, eastern Seoul. A motorcyclist in his 30s fell into the sinkhole while going down the road when it caved in. Seventeen hours after the accident, he was found dead underground about 50 meters away from the sinkhole opening. Experts suspect subway tunnel construction to have caused the sinkhole.
On Sunday, a large sinkhole formed at a Busan Metro construction site. Fortunately, there were no casualties because police officers and local government officials had noticed signs early and controlled traffic at the site. However, if the sinkhole had been a bit larger or formed below the nearby piers of an overpass, a major accident could have happened.
On the same day, a minor sinkhole formed on the road in front of Aeogae Station on Subway Line No. 5 in Mapo-gu, Seoul.
According to data from the Korea Authority of Land & Infrastructure Safety, a total of 867 sinkholes have been reported nationwide since the beginning of 2020.
They were caused mostly by water leaks from old underground pipes and faulty construction for tunnel excavation. Generally, underground pipe damage causes small sinkholes, while poor construction causes large ones. The major cause of a big sinkhole that formed near an underpass in southern Seoul in 2014 turned out to be subway tunnel construction.
Most water and sewage facilities in Korea were installed in the 1970s and 1980s when the country developed rapidly. Underground pipes are so decrepit that safety on the road cannot be guaranteed in big cities.
The government will create a task force to investigate the subway tunnel construction accident in Gwangmyeong. Seoul will use ground penetrating radar to detect internal structures of sinkhole-prone areas. The thing is not to solve problems on the fly or with quick fixes.
Once the site of a sinkhole is restored, the traces disappear. But many sinkholes were only patched extemporarily with filler materials. In 2023, Seoul had about 1,100 sinkholes filled that way. Sinkholes could form again at the same sites or nearby.
The number of sinkhole reports in Seoul more than tripled for two years to 2024, according to data from the National Fire Agency. This was the sharpest increase among the nation's provinces and cities.
Many underground construction works are underway in Seoul and other major cities. Development of underground spaces such as subway tunnels and shopping malls further weaken the ground that has already been burdened with overpopulation and heavy vehicle traffic.
The safety of underground construction should be strengthened. Repairs must be done swiftly in those areas with decrepit underground facilities. The ground near construction sites should be checked more often.
To do so, ground conditions and underground structures should be fully grasped and effectively managed. The safety management systems of each provincial government needs to be integrated.
Sinkholes can be prevented to some extent if ground conditions are often checked and underground construction soundly managed. Road safety should not be left to chance.
