Updated August. 19, 2014 01:09
A total of five sinkholes, including a 13 meter-long one, have been found at the Seokchon Underpass near the second Lotte World in Seouls Songpa district. They have been discovered only five days after the second sinkhole was discovered, and all of them are in the form of underground cave.
The Seoul metropolitan government said on Monday that it discovered five additional sinkholes at sites near the underground roadway from Saturday last week. The sinkholes that have been newly confirmed were discovered at the endpoint of the Seokchon Underpass (Olympic Park section, 5.5 meters wide, 5.5 meters long, and 3.4 meters deep), and entrance to the underpass (Gimpo Airport side, 4.3 meters wide, 13 meters long, and 2.3 meters deep). The city is measuring other three sinkholes. Earlier on August 5, a sinkhole (ground sinking) measuring 2.5 meters wide, 5 meters deep and 8 meters long was discovered at the entrance section of the Seokchon Underpass, and on Wednesday last week, a cave measuring 5-8 meters wide, 4-5 meters deep and 80 meters long, was discovered at the central section of the underground path.
One of the sinkholes that have been confirmed on Saturday was found during onsite drilling work near a site where metropolitan water supply pipes were buried, and due to concern over secondary damage, an emergency measure was taken through consultations with the citizens investigation committee. The inspection team of experts judges that the sinkholes that have been additionally found were also due to "shield" tunneling work for Seoul Subway Line 9. This technique uses the cylinder-shaped machine, which grinds off soil and rock while vertically tunneling underground. The city government is investigating to find any additional sinkholes at a 490-meter section of the Seokchon Underpass through drilling surveys, which drill holes through asphalt pavement. Vehicle traffic at the Seokchon Underpass has remained suspended since Wednesday last week.