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MinSouth-BTS Joint Meeting
February 12, 2026 @ 6:00 pm - 8:00 pm
Collapsed Segmental Lined Tunnel and its Recovery
Presented by: Hyuk-il Jung – Associate Director, Arup
A twin bored, segmentally lined tunnel being constructed in soft marine deposit ground completely collapsed in March 2020 during cross-passage construction. Due to the soft ground conditions, the area at the cross-passage location was pre-treated with grout prior to tunnel boring machine (TBM) operations. Subsequently, cross-passage construction commenced using an open-face excavation methodology. During excavation, a small area at the excavation face began leaking water, accompanied by flowing silt and sand. This eventually led to a catastrophic collapse. This lecture will summarise the timeline of the collapse event and explain the mechanism of the tunnel failure as observed during the incident. It will also present the emergency mitigation measures taken by the contractor, along with the recovery methods adopted to rebuild the collapsed section of the tunnel.