Breakthrough marks completion of Singapore Circle Line 6 tunnelling

12 January 2022

Tunnelling works on Singapore’s Circle Line 6 have been completed following the breakthrough of a TBM at Cantonment station on 12 January, announced the country’s Land Transport Authority (LTA).

The US$1.68bn worth of civils contracts which make up package CCL6 involved 4km of tunnelling and the construction of three new stations, with works beginning in August 2019. Three stretches of twin tunnels bored by three TBMs link the new stations – Keppel, Cantonment and Prince Edward Road – to the rest of the Circle Line.

The first stretch of tunnelling works from Keppel station towards Harbour Front station was completed in August 2020. The TBMs were then re-launched to mine between Keppel and Cantonment stations. Works for this leg were completed in July 2021.

Boring the 2km-long final stretch of twin tunnels from Prince Edward Road station to Cantonment station completed the CCL6 tunnelling, leaving the package’s civil construction works at around 55% complete. A mix of contractors have worked on the package, mainly China State Construction Engineering Corp and Japan’s Nishimatsu Construction Co.

Works will now begin to construct the structural connections between the bored tunnels and the stations, and will be undertaken in tandem with other structural works. This will be followed by installation of track, electrical and mechanical services.

Tunnelling has faced various challenges throughout the project, including boring beneath heritage buildings and close to the foundations of many existing commercial buildings and roads in the Central Business District. Measures were also taken to avoid impacting train operations at interfaces with the existing Harbour Front and Marina Bay stations.

Tunnelling came as close as 6.7m beneath the piles of a national monument – the former Tanjong Pagar Railway Station – where 600 monitoring instruments were installed to detect any building movement. While under Keppel Viaduct, new micro piles were installed to replace three existing bored piles which were cut away to accommodate the new tunnels.

The 40km-long Circle Line will have 33 stations and include 12 interchanges with other MRT lines. LTA said it is on track to open in 2026.