Thomson Line Construction: Contract T206 & T207

Contract T206

The inaugural tunnel launch for the Thomson Line is expected to be held under this contract at Launch Shaft 2 (LS2), for the launch of 2 TBMs to Woodlands station. Excavation for LS2 is scheduled to begin by the end of the year, and the project team hopes to have the shaft ready to launch the machines in 8-9 months.

T206 Tunnel Chart (Reception tunnels in red)

STEC has recently taken possession of the SBAB site. A crawler crane and 2 piling rigs has been brought in. West of SBAB, the escape shaft at Avenue 12 has also been hoarded up.

Contract T207

At the RTS facility site, a crawler crane has arrived onto the site and piling has begun. Tunnelling will begin slightly later under this contract as both launch shafts is being constructed by the neighbouring contractors requiring a handover process. Site possession under Shimizu is scheduled for end 2015 and early 2016 for the launch shaft at Springleaf and SBAB respectively.

T207 Tunnel Chart

Use of SFRC segments in tunnelling

A new type of tunnel rings have recently been experimented for the first time in Asia under C933 of the Downtown Line. Steel Fiber Reinforced Concrete, or SFRC in short, contains fibrous material and are precast in a (7+1) segment arrangement that distinguishes itself from the conventional RC (5+1) tunnel segments. The fiber reinforcement segment uses less steel, and is much more durable and crack resistant.

Moving forward, LTA continues to expand the use of these rings in the construction of new lines. Contract T206 and T207 were identified contracts to be considered for the usage of the SFRC rings. At the Underground Singapore 2014 conference held last month, the LTA confirmed that 2 TSL contracts will be using the new fibrous segments, doubling the use from 4.7km on the DTL3 to 10km for the new Thomson Line.