South Korea’s sinkhole cases spark fears of underground malls’ structural stability

In Seoul alone, over 63 sinkholes have been reported across the city since March 2022, according to a newspaper

Beneath the bustling streets of major South Korean cities, vast underground malls have become an integral part of urban life, but several sinkhole incidents across the country have raised concerns about the safety of this subterranean network.

A prime example is the sprawling GOTO Mall beneath the express bus terminal station in Seoul, a major transfer hub between three subway lines.

The 880-metre-long underground mall street attracts many visitors to its 630 stores, ranging from restaurants and grocery stores to medical clinics. There are also unstaffed stores running 24 hours a day, including pet supply shops and print centres.

Fears about the structural stability of underground malls were further heightened by two recent sinkhole incidents in South Korea. A large sinkhole opened up beneath a pedestrian crossing in Busan in April, just a month after a 20 metres wide by 18 metres deep sinkhole in Seoul caused a motorcyclist to plunge to his death.

Over 63 sinkholes have been reported across Seoul since March 2022, according to an analysis of the capital city by the Chosun Ilbo newspaper.

Malls like the GOTO Mall have become a crucial revenue source for financially pressured transit operators like Seoul Metro.

“When many commercial facilities are built inside subway stations, they significantly increase the overall structural load placed on the ground below,” Kim Jae-gwan, a professor of urban engineering at the University of Seoul, told The Korea Herald.

“This added weight can put extra stress on the underlying soil, particularly in areas with soft ground or high groundwater levels,” he added.

The construction of underground facilities also often requires changing or expanding existing structures, and this can disrupt the natural flow of groundwater.

“[This] could lead to uneven soil conditions, drying out some areas while saturating others, and ultimately weakening the stability of the ground,” Kim said.

While there is no direct evidence linking the development of underground facilities to sinkholes, Park Chang-geun, a civil engineering professor at Catholic Kwandong University, told The Korea Herald that poor management during construction could contribute to their formation.

Among the construction activities he cited were improper excavation, inadequate soil stabilisation, or poor backfilling – the process of refilling an excavated area to prevent ground collapse.

“In a country with limited land, the development of underground commercial facilities is not only an efficient but also an inevitable solution,” Park said. “Still, without careful management during construction, the risk of ground instability remains a serious concern.”