Design Errors and Poor Ground Survey: Sinansan Line Collapse a Man-Made Disaster Caused by Safety Negligence

Design Firm's Error in Column Load Calculation

Supervision and Construction Firms Fail to Detect Design Flaw

Negligence in Ground Survey Leads to Overlooked Fault Zones

Ministry of Land, Infrastructure and Transport Pursues Business Suspension

The collapse of the Gwangmyeong Sinansan Line tunnel has been concluded to be a man-made disaster caused by a combination of load calculation errors by the design firm and inadequate safety management by the construction companies. The Ministry of Land, Infrastructure and Transport has decided to pursue suspension of business operations for nine companies, including the construction firms POSCO E&C and Seohui Construction, as well as the design and supervision firms involved.

On April 2, the Ministry of Land, Infrastructure and Transport announced the results of the Construction Accident Investigation Committee's (CAIC) investigation into the tunnel collapse accident that occurred at the Sinansan Line double-track railway Section 5-2 construction site in Iljik-dong, Gwangmyeong, Gyeonggi Province, in April last year. At that time, both the underground tunnel under construction and the overlying road collapsed simultaneously, resulting in the death of one worker and serious injury to another.

Design Firm's Column Load Calculation Error...Construction Firm's Negligence in Ground Survey

The CAIC concluded that the accident was caused by a combination of load calculation errors by the design firm and poor safety management by the construction firm. At the design stage, the design firm calculated the load on the central column as 2.5 times less than the actual load, reducing the column's load-bearing capacity. Although the construction and supervision firms reviewed the design documents before construction began, they failed to detect the error.

Rescue workers are inspecting the site at the underground tunnel construction of the Sinansan Line in Gwangmyeong, Gyeonggi Province, where a collapse accident occurred. Photo by Yonhap News

During the construction phase, ground surveys were also inadequately conducted. According to the safety management plan established by the construction firm, a senior engineer with at least five years of experience was required to observe the tunnel face, known as the "makjang." However, an unqualified technician replaced this role. In addition, the ground engineer did not conduct an on-site observation but relied on photographs instead. As a result, fault zones vulnerable to external shocks were not identified during the ground survey process, which led to excessive additional load being imposed on the central column.

The safety inspection system also failed to function properly. The investigation found that the construction firm did not carry out the required daily in-house safety inspections by work type or the regular tunnel safety inspections. Moreover, the company failed to maintain a crack management log for the central column and wrapped the column with nonwoven fabric, which prevented detection of early signs of concrete cracking.

Son Murak, the chairperson of the CAIC, stated, "The central column is a key factor that determines the tunnel's stability, but during the process of modifying the design documents, sufficient reassessment of the column's structural resistance was not conducted. The design errors were not filtered out during the verification stage, unexpected ground conditions occurred during construction, and on-site management was also inadequate, which all contributed to the accident."

POSCO E&C and Seohui Construction Could Face up to 8-Month Business Suspension...Legal Disputes Possible

The Ministry of Land, Infrastructure and Transport plans to impose business suspension penalties on the design, construction, and supervision firms for their design negligence and construction/supervision deficiencies. Under the Framework Act on the Construction Industry, design and supervision firms may face up to 12 months of business suspension for causing a serious accident through intent or negligence. Construction firms may face up to 8 months of business suspension. The section in question is being constructed by a consortium of POSCO E&C and Seohui Construction. Although POSCO E&C was responsible for the accident section, Seohui Construction holds a 34% stake, suggesting the possibility of legal disputes over the severity of the suspension. The results of the business suspension decision are expected to be announced in the first half of the year.

The Seoul Regional Office of Land and Infrastructure is also planning to file charges against the construction firm for violations of the Framework Act on the Construction Industry. The results of the investigation will also be shared with the police and the Ministry of Employment and Labor to facilitate criminal prosecution for occupational negligence resulting in death or injury and violations of the Occupational Safety and Health Act.

On April 11 last year, a collapse accident occurred at the Sinansan Line construction site in Iljik-dong, Gwangmyeong-si, Gyeonggi-do. Photo by Yonhap News

Son Murak, the chairperson of the CAIC, stated, "We plan to compile the results of the accident investigation and submit the final report to the Ministry of Land, Infrastructure and Transport within this month."

In addition, since negligence at each stage of the project, from design to construction, was identified during this process, the ministry plans to establish measures to prevent recurrence. First, regulations will be revised to require more thorough drilling surveys during tunnel construction, and a new rule will mandate that tunnel face observations be confirmed by supervisors with senior engineer status or higher. The central column will be subject to regular and additional crack inspections during the construction phase.

The Sinansan Line is a metropolitan railway construction project that began in April 2020. With a budget of 3.3465 trillion won, it will span 44.7 kilometers connecting Ansan, Siheung, and Gwangmyeong in Gyeonggi Province to Yeouido in Seoul. Although the initial target was to open in April last year, construction delays have pushed the expected completion to December this year.

This content was produced with the assistance of AI translation services.