Lessons from serial tunnel collapses during construction of the Seoul subway Line 5

Abstract

A large-scale underground railway construction project which is called the Second Phase of Seoul Subway consisted of 4 Lines from Line 5 to 8 was launched in Seoul in the early 1990s to share the increasing surface traffic volume. While constructing Line 5 which was the earliest planned Line in the Second Phase of Seoul Subway, 5 cave-in collapses took place in the central urban area in Seoul, which resulted in huge property losses to adjacent areas and project delay. A tunnel collapse may give rise to a potential for injury to the public or significant damage to the built environment. This paper presents and reviews the 5 cave-in collapses. Ground conditions, work environments, failure mechanisms and remedial works were analyzed and compared. Lessons from serial collapses were described in terms of both technical and non-technical aspects. It is concluded that safe and sound construction of tunnel requires well planned technical review process and management of nontechnical aspects involved are also important in ensuring safety of tunnelling. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.