Ground Shifts and Gaps in Safety: What Caused the Gwangmyeong Subway Failure?

On April 11, a devastating collapse occurred at a subway construction site in Gwangmyeong, South Korea, leaving one worker rescued after 13 hours underground and another still missing. The tunnel, built using the double-arch method, gave way just hours after visible damage to a central pillar was reported. Initial findings suggest a combination of structural deficiencies, foundation weaknesses, and possible construction quality issues, though investigations are ongoing.

The double-arch construction method, while widely used for tunnel stability in urban settings, is under increased scrutiny following this collapse. Experts like Prof. Choi Chang-sik of Hanyang University emphasized the method’s reliability, instead pointing to missing steel reinforcement, construction errors, and unstable ground as likely contributors. Rescue efforts were suspended temporarily due to worsening weather and structural risks, underscoring the urgency of better monitoring practices.

The Seoul Metropolitan Government has responded swiftly, launching ground-penetrating radar (GPR) inspections across 50 at-risk sites by month’s end. The goal is to detect subsidence and mitigate sinkhole risks, especially in densely built urban areas. The government has also identified 22 high-risk locations in Gwangjin-gu, with more inspections expected in other districts.

This incident serves as a sobering reminder of the need for comprehensive site assessments, real-time monitoring, and transparent reporting throughout the construction lifecycle. For civil and geotechnical engineers, it is a call to reinforce design accountability and ground condition assessments, ensuring that tragedy is never the cost of progress.

Check out the following video showcasing the rescue workers in South Korea pulling a man alive from a collapsed subway construction site near Seoul after 13 hours trapped underground.