A massive sinkhole was captured on video for the first time after it occurred in the middle of a road in Gangdong-gu, Seoul. The video obtained by the JoongAng Ilbo shows a huge sinkhole, approximately 20 meters in diameter and depth, with collapsed soil surrounding its edges. The catastrophic sinkhole has swallowed four out of the six lanes of the road.
On the day of the incident, March 24, water was gushing out of a broken water pipe, leading to a water shutdown to prevent water from flowing into the sinkhole. The 300mm water pipe remains buried under debris, so it’s not visible in the video.
The ground material supporting the lower layers of the road collapsed to a depth of up to 18 meters at the site. Underneath this road, construction was underway for a 9-line subway tunnel. Various underground utilities, including electrical, communication, and cable lines, were severed.
According to Gangdong Fire Station, after the sinkhole collapsed, the water from the burst water pipe mixed with soil, creating mud-like conditions. Firefighters opted to access the 9-line tunnel via a construction site about 80 meters away to carry out rescue operations.
After shutting off the water supply, rescue workers donned wetsuits to clear the soil and conducted overnight operations using pumps to remove water. By 7 a.m. on the 25th, heavy equipment was deployed to clear the site, leading to the discovery of an unconscious motorcyclist in the sinkhole. The individual was found wearing a helmet and motorcycle boots.
With the completion of rescue efforts, the city of Seoul has launched a full investigation into the cause of the accident. As stated by Lee Jae-hyuk, director of the Urban Railroad Civil Engineering Division at the Seoul Urban Infrastructure Headquarters, construction of the 9-line tunnel was in the upper half excavation stage at the time of the sinkhole’s occurrence. During tunnel excavation, the cross-section is typically excavated in halves, with the first half being the upper section.