Tunnelling on Singapore’s Cross Island Line has been suspended near Ang Mo Kio Station after the TBM encountered unexpected ground anchors.
The Land Transport Authority (LTA) first detected signs of underground obstructions under Ang Mo Kio Avenue 3 in May, when foreign materials were unexpectedly discharged from the TBM. Wire ropes found entangled around the cutterhead were removed and the TBM cutters replaced, enabling tunnelling to resume.
However, between May and July, 100 cutterhead interventions were required to clear more obstructions from the TBM. Approximately 800kg of wire ropes were extracted from the TBM and 22 damaged cutters were replaced.
The number and scale of the interventions indicated the obstruction was more extensive than initially assessed and investigations identified them as ground anchors beneath Ang Mo Kio Avenue 3.
Given the safety risks to the underground works and roads above, the LTA has suspended tunnelling, which is being delivered by a Gammon Construction and Engineering and Bachy Soletanche Singapore joint venture.
Further investigations are under way to determine the full extent of the obstruction, its origin, and assess its impact on the CRL construction programme.
Initially, the LTA needs to carry out recovery measures, including ground improvement works to strengthen and stabilise the ground along the tunnel alignment, before tunnelling can resume.
The ground anchors will be progressively removed from the TBM while tunnelling proceeds in a safe and controlled manner.
To provide working space for investigations and recovery works, and ensure the road users’ safety, Ang Mo Kio Avenue 3 will be temporarily reconfigured from November 14 until May 2028.
