SINGAPORE: Commuters can enjoy free rides on stage 1 of Singapore's Downtown Line rail network on Saturday, December 7, in an “Open House” event ahead of the official opening on December 22.
And work on stages 2 and 3 is also progressing well, said the Land Transport Authority (LTA).
Stage 2's stations and tunnels are about 70 per cent finished, and on track for completion by mid-2016.
Several stations have achieved basic structural completion for electrical and mechanical installation works to begin and this will be progressively achieved at all 12 stations by mid-2014.
Trains will then be tested after that, while stage 3 is about 50 per cent done, with completion slated in 2017.
After a year of complex engineering, the Singapore River now flows through a new path at one section, thanks to the Downtown Line.
An island was created in the middle of the channel to allow the construction of Downtown Line Stage 3's Fort Canning train station tunnels.
LTA's project director for Downtown Line, Rama Venkta, said: "We want to clear the way for the tunnels to start mining underneath, so with the amount of obstructions we had, we perceived at the beginning of the job, we had to get these obstructions all removed before the tunnels could actually go underway."
Some of the obstructions included decades-old timber and concrete piles stuck within the riverbed.
Engineers also had to be extra careful, as the two-football-field-long Fort Canning station sits alongside the Central Expressway.
As construction progressed, vibration of the expressway was constantly monitored to ensure the structure was sound.
Downtown Line 3 comprises 16 stations across a 21-kilometre stretch, and tunnelling works started in July 2012.
All 16 stations are expected to have basic structural works completed by 2015, followed by the testing of trains.
Another complex tunnelling challenge lies between Newton and Stevens train stations on stage 2 of the Downtown Line.
Work to link the two began in June 2011, and only finished two-and-a-half years later, with the use of a S$10-million custom-made tunnel boring machine.
On a good day, the machine can bore through 10 metres of ground. But if it meets hard rock like granite, progress may only be as good as a metre a day.
Due to space constraints, train tunnels heading either way have to be “stacked” on top of each other instead of side by side, with the distance separating the two ranging from six to 14 metres.
LTA's Lim Kim Kwang said: "Stacked tunnels present certain risks of the lower tunnel destabilising the ground that supports the upper tunnel. The lower tunnel must be done first before the upper tunnel. This will overcome these difficulties and avoid any safety issues."
Stevens station is the deepest of the stations on stage 2 of the Downtown Line, at 40 metres below ground.
Downtown Line stage 2 has 12 stations and one depot over a 16.6-kilometre stretch.
Tunnelling in all sectors of the stretch is done, except for the tunnels linking King Albert Park and Botanic Gardens stations.
The two are expected to be linked in the first quarter of 2014. - CNA/gn
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