Gwangmyeong City Completes Investigation of Sinansanseon Collapse: "Comprehensive Failures in Design, Construction, and Management"

Gwangmyeong City Wraps Up 14-Month Investigation Into Sinansanseon Collapse
Sajowi Concludes: "Problems Found in Ground Investigation, Structural Review, and Management"
City to Propose Comprehensive Overhaul of Underground Safety Management Sys

"The collapse accident at the Shinansan Line double-track railway construction site that occurred last year was not caused by issues with a specific process, but rather was the result of accumulated and complex failures throughout the entire design, construction, and construction management processes."

Seungwon Park, Mayor of Gwangmyeong City, is announcing the investigation results of the collapse accident at the Shinansan Line Section 5-2 construction site by the Gwangmyeong City Underground Accident Investigation Committee (Sajowi) on the 16th in the city hall's medium conference room. Photo by Jonggu Lee

This is the conclusion reached by the Gwangmyeong City Underground Accident Investigation Committee (Sajo-wi) after 14 months of investigation into the collapse accident at the Shinansan Line double-track railway construction site.

Gwangmyeong City has decided to go beyond investigating the cause of the accident and will officially propose to the central government a set of improvements to the underground safety management system to prevent similar accidents from recurring.

On the 16th, Gwangmyeong City announced the investigation results of the collapse accident at the Shinansan Line Section 5-2 construction site by the Gwangmyeong City Underground Accident Investigation Committee (Sajo-wi) at the city hall’s medium conference room.

This investigation was conducted over approximately 14 months starting in May last year. It aimed not only to analyze the immediate causes of the accident, but also to fundamentally improve the underground safety management system to prevent similar incidents from happening again.

According to the investigation results, the committee assessed that this accident resulted from a combination of problems occurring throughout the ground survey, design, construction, and construction management processes.

Specifically, a major cause was that the actual ground conditions were assessed as being better than they were during the ground survey process, which led to the load on the tunnel being underestimated.

In addition, during the design process for the central pillar, a critical structural element of the double-arch tunnel, the structural review was conducted based on the diaphragm wall method, but the actual design implemented the pillar method. This resulted in underestimating the load delivered to the central pillar.

Moreover, the use of excavation intervals longer than design standards led to increased lateral earth pressure, and structural instability was exacerbated by severing temporary structures without reinforcing the tunnel portal, which also contributed to the severity of the accident.

Ahn Sangro, Chairman of the Gwangmyeong City Underground Accident Investigation Committee, is announcing the investigation results of the collapse accident at the Sinansan Line Double-Track Section 5-2 construction site on the afternoon of the 16th in the city hall's medium conference room. Photo by Lee Jong-gu

In the construction management process, a lack of review for design errors, insufficient response to changes in site ground conditions, and inadequate monitoring of the tunnel working face were among multiple problems identified.

Based on the investigation results, Gwangmyeong City plans to submit the improvement plan it has drafted to the Ministry of Land, Infrastructure and Transport later this month and will request improvements to underground safety management regulations at the national level.

The improvement plan includes: ▲ Strengthening drilling standards for urban-adjacent areas ▲ Mandatory three-dimensional structural analysis for central pillars and filar sections in double-arch tunnels ▲ Stricter qualifications for working face observers ▲ Tighter supervision procedures for construction inspection, among others.

It also proposes measures like mandatory real-time monitoring of groundwater leakage, re-examination of underground safety assessments in major design changes, reflecting the impact of adjacent construction projects, and obligating structural safety reviews by a fourth-party specialist institution designated by the contracting authority.

The city plans to propose amendments to related laws, notably to allow local governments to more actively participate in underground safety management. The suggestions include granting the authority to request emergency safety actions, making it obligatory to collect local government opinions during administrative processes related to underground safety, and ensuring local government participation when forming the Central Underground Accident Investigation Committee.

Mayor Seungwon Park of Gwangmyeong City is announcing the investigation results of the collapse accident at the Sinansan Line Section 5-2 construction site by the Gwangmyeong City Underground Accident Investigation Committee (UAC) in the city hall's conference room on the 16th. Photo by Jonggu Lee

Sangro Ahn, committee chairman and president of the Korea Institute for Disaster and Safety Policy, stated, "This investigation focused on prioritizing citizens' lives and safety, thoroughly analyzing the causes of the accident and devising measures to prevent recurrence," adding, "For a local government to draft a practical improvement plan after an investigation and propose it to the central government is a meaningful example of a local authority actively fulfilling its role in ensuring citizen safety."

Seungwon Park, Mayor of Gwangmyeong City, said, "Protecting the safety of citizens is the most important duty of the local government, which is closest to the people," and emphasized, "We will work closely with the central government to improve the underground safety management system and establish even more robust safety management measures to ensure that citizens can live with peace of mind in a safe city, concentrating all our administrative resources on this goal."

Since the accident, Gwangmyeong City has accelerated efforts to strengthen underground safety management.

In December last year, the city established the "Gwangmyeong City Ordinance on Underground Safety Management," laying out the institutional foundation, and has proactively been using ground-penetrating radar (GPR) surveys to detect potential ground anomalies.

Furthermore, the city created an "Underground Safety Management Team" to prevent ground subsidence accidents stemming from large-scale railway projects and public housing development. Its expertise will be further enhanced by recruiting dedicated underground safety professionals and establishing an advisory panel on underground safety in the future.

Mayor Seungwon Park of Gwangmyeong City is announcing the investigation results of the Shinansanseon Line Section 5-2 construction site collapse accident by the Gwangmyeong City Underground Accident Investigation Committee (UAC) on the 16th at the city hall’s central meeting room. Photo by Jonggu Lee

After the collapse accident at the Shinansan Line construction site on April 11 last year, Gwangmyeong City established its own accident investigation committee one month later, consisting of 11 external experts and 12 members including the city’s head of facility management. Over the course of 14 months, the committee held 29 general meetings, 4 site inspections, 12 hearings with stakeholders, and 3 resident interviews. It also ensured the objectivity and reliability of the investigation results through drone and LiDAR surveys, development of 3D models, and reviews of tunnel structural stability.

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