Tunnelling works for the Circle Line MRT extension were completed yesterday morning, connecting the western and eastern ends of the orbital line.
The tunnel breakthrough at Cantonment station - one of three stations along the 4km extension which makes the Circle Line a complete loop - marks the completion of 55 per cent of civil works, which started in 2019.
The extension from HarbourFront to Marina Bay is slated to open in 2026, and will cut travelling time. For instance, commuters from Telok Blangah will have a direct commute to Marina Bay, saving them around 10 minutes.
With the extension, the Circle Line will have 33 stations spanning 40km, including 12 interchanges with other MRT lines.
Besides Cantonment station - which is a stone's throw from the historic Tanjong Pagar railway station - the extension will have two other stations: Prince Edward Road and Keppel.
Transport Minister S. Iswaran, who was present when a tunnel-boring machine broke through half a metre of concrete retaining wall, said it was "an important milestone for this project".
When completed, the extension will mean more convenience for commuters as well as "greater resilience in our overall MRT system", he added. This means that when there is a rail disruption in the network, commuters have more alternatives because of the dozen interchange stations along the Circle Line.
"I think this is an important milestone also because the project itself has been encountering a series of challenges... because the actual tunnelling itself has had to take place near many heritage buildings, in proximity to other foundations of commercial buildings and other MRT stations," the minister said.
The Land Transport Authority (LTA) noted, for instance, that tunnel-boring machines had to cut through piles supporting the Keppel Viaduct - a major elevated road.
To do so, engineers built deep retaining walls and excavated below the piles.
They then bored new micro-piles around the existing piles. Above these new piles, they cast a massive transfer beam which now supports the viaduct.
They then severed the old piles, so that vibration from the tunnel-boring machines - which had to be equipped with special cutters which can cut through steel piles - would not be transferred back to the viaduct.
Meanwhile, the LTA said expansion works on the massive Kim Chuan Depot in Paya Lebar are "progressing well".
The underground depot will house 23 new trains which will be acquired for the extended Circle Line. In total, the expanded Kim Chuan Depot will be able to house 133 trains, up from 70 today.
It will also incorporate a bus depot that will accommodate 550 buses, and is slated to be completed when the Circle Line extension opens in 2026.
