By rosebell
Singapore’s Land Transport Authority (LTA) said the obstruction was first detected in May 2026, when foreign material was discharged from the TBM. Subsequent inspections found wire ropes entangled around the machine’s cutterhead.
The wire ropes were removed and damaged cutting tools replaced, allowing excavation to resume temporarily. However, repeated encounters with the obstruction led to further investigation.
TBM Suffers Repeated Cutterhead Damage
Between May and July, the project team carried out approximately 100 cutterhead interventions, replaced 22 damaged cutters and removed around 800kg of wire ropes from the TBM.
The frequency and scale of these interventions prompted further investigations, which identified the obstruction as buried ground anchors beneath the road.
According to LTA, such anchors can damage TBM cutting tools, disrupt excavation and create safety risks for underground construction and infrastructure above the tunnel alignment.
Tunnelling has now been suspended while investigations establish the full extent and origin of the obstruction and assess its potential impact on the construction programme.
Ground Improvement Planned Before Tunnelling Resumes
LTA expects recovery measures to include ground improvement works to strengthen and stabilise the tunnel alignment before excavation can safely restart.
The buried anchors will then be progressively removed from within the TBM as tunnelling advances under controlled conditions. The approach is intended to manage the obstruction while reducing risks to the machine, underground works and surrounding infrastructure.
The authority has not yet confirmed the impact of the obstruction on the overall Cross Island Line programme.
Road Reconfiguration Planned Until May 2028
To provide space for investigations and recovery operations, Ang Mo Kio Avenue 3 is scheduled to be temporarily reconfigured from 14 November 2026 until May 2028.
LTA said it will continue monitoring ground conditions around AMK Hub and the surrounding area throughout the recovery works.
The incident highlights the challenges that unexpected buried infrastructure can pose to mechanised tunnelling, particularly in developed urban environments where legacy ground anchors and other underground obstructions may affect TBM operations.
