Investigation conclude ground subsidence in Guri city caused by tunnel construction for Byeolnae line. On August 26th, there was ground subsidience hole in Guri City 16 meter in diamter 21 meter deep.

First it was blamed on a burst water pipe. Investigation conclude water pipe burst was not a cause but a consequence. Water pipe itself bursted because of ground subsidence. There were no important problems with sewage pipes.

Investigation review impact of the tunnel construction near the accident. Investigation conclude the construction management was partially insufficient. They did not take measures, such as ground reinforcement measures, even though the contractor now it was risky vulnerable ground. Tunnel construction was responsible for subsidence incident.

The contractor knew risky ground for via an advanced horizontal drilling survey. But not adequate action taken. Only local measures such as order grouting were taken even though there was excessive runoff water flowing into the tunnel than usual.

The final report published on website of the Ministry of Land, Infrastructure and Transport and the underground safety information system operated by the Korea Land Safety Management Agency. 

Report conclude measure to avoid future repetition of problem with stronger geotechnical investigation and audits by external consultants.

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