Circle Line tunnel works nearly 50% completed, on track for April finish

By project completion, more than 300 tunnel rings across both tunnels will have been reinforced.

The strengthening works address a phenomenon known as “tunnel squatting”, which affects several sections of the CCL tunnels. This occurs when soft marine clay beneath parts of the tunnel slowly compresses over time.

If left unaddressed, LTA said this could lead to long-term disruptions in train operations and structural defects in the tunnel.

A specialised robotic arm is being deployed to secure steel plates within the tunnel, freeing up space and allowing workers to focus on other critical tasks.

Without this technology, five to six workers would be needed to manually lift and place each plate – a process requiring significantly more manpower and time, LTA said.