Gyeonggi Province Takes All-Out Measures to Prevent Recurrence of Sinansan Line Collapse
Review of Design and Construction Appropriateness at 103 Station
2-Arch Tunnel Stability Reconfirmed... Foundation for Safe Construction Established
On May 15, Gyeonggi Province announced that it had conducted expert consultations and checked the stability of design and construction for the 103 Station Tunnel in Section 2 of the Dobongsan~Okjeong Metropolitan Railroad, where the same 2-Arch construction method was applied as in the Sinansan Line tunnel, which experienced a collapse accident in April.
Gyeonggi Province is conducting expert consultations and checking the stability of design and construction for the 103 Station Tunnel in Section 2 of the Dobongsan~Okjeong Metropolitan Railroad, where the 2-Arch construction method has been applied. Photo by Gyeonggi Province
The inspection involved experts in civil structures, geotechnical engineering and foundations, civil construction, tunnels, and quality and safety from the Gyeonggi Province Railroad Construction Technology Advisory Committee. They discussed the appropriateness of the design and construction of the 2-Arch tunnel, as well as additional safety measures through a prior review of risk factors associated with this construction method.
The inspection team applied the same scrutiny to the 2-Arch tunnel issues in the construction of Section 2 of the Dobongsan~Okjeong Metropolitan Railroad, conducting a comparative analysis of risk factors and thoroughly examining potential problems that could arise during the construction process.
According to the province’s advisory results, the 103 Station section has secured a sufficient safety margin in all structural calculations, including axial load strength and flexural strength of the central pillar and lining structures. It was also confirmed that displacement values measured by instruments during construction met the established management criteria.
In particular, taking the Sinansan Line accident as a lesson, the province decided to apply even stronger safety measures on site. The compressive strength of the shotcrete supporting the tunnel was increased (from 21 MPa to 35 MPa), and some sections were switched to mechanical excavation. Stress gauges were additionally installed on the central pillar, and the installation intervals of key measuring instruments were reduced to enhance measurement precision. Practical on-site response measures were also implemented to prevent similar accidents, including managing the separation distance between the left and right tunnel faces to respond to lateral pressure, preparing step-by-step emergency response plans, and conducting simulation drills.
Kim Kibum, Director of Railroad, Ports, and Logistics for Gyeonggi Province, stated, "Through this inspection, we have taken significant steps to eliminate the risk of accidents in 2-Arch tunnels in advance and to establish additional measures for safety. Under the principle of 'safety first,' we will continue thorough construction management and monitoring to ensure the prevention of safety accidents."
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