- POSTED: 12 May 2014 20:15
- UPDATED: 13 May 2014 14:22
Construction work for Downtown Line 3 is about 60 per cent complete, thanks in part to those who work round the clock, in shifts, to ensure the network is completed on time in 2017.
SINGAPORE: Less than three years since construction of the Downtown Line 2 started, 85 per cent of stations and tunnelling works have already been completed, according to the Land Transport Authority (LTA).
Electrical and mechanical installation work is set to begin at many of the stations along the line.
Stage 3 is about 60 per cent complete, thanks in part to those who work round the clock, in shifts, to ensure the network is completed on time in 2017.
While the rest of the island is shrouded in darkness, the shift for some 25 staff, including project managers, a foreman and general workers, at the Ubi station on Downtown Line 3 is underway.
One of those who work underground is LTA’s first woman tunnel engineer Isabella Yeo.
Ms Yeo carries out administrative duties as well as safety inspections of tunnels at the Bedok North station site, which is about three kilometres from the Ubi station.
However, sometimes there are physical hurdles.
"As females, we're generally a bit smaller so getting from point to point is a little bit more challenging for us," said Ms Yeo, who is a senior project engineer.
“Many a time, we have to seek help from the contractor to give us a proper ladder to access to the area we need to go to."
The tunnels can be as deep as 27 metres beneath the surface, which is equivalent to the height of a nine-storey HDB building.
Workers have to work at odd hours and deep underground, with no concept of day or night.
The air is also hot, humid and extremely uncomfortable, even though there are ventilation ducts ensuring constant flow of air into and out of the tunnel.
Given such conditions, safety is paramount.
Every hour, gas levels are monitored for traces of carbon monoxide and hydrogen sulphide.
There is also a fire hose installed every 50 metres, as are telephones in case of emergencies.
Trial evacuations are also carried out every six months together with the Singapore Civil Defence Force.
Tunnelling is also time-consuming. A tunnel-boring machine digs through the rocks before segment rings -- made of reinforced cement -- are carefully placed around the excavated portion to form the tunnel.
Progress can range from 14 metres of tunnelling a day to just 1.4 metres when difficult conditions are encountered, such as a mixture of hard and soft rock which requires extra care to tunnel through.
But there are other challenges too, such as having to divert the Singapore River to facilitate tunnelling works at Downtown Line 3's Fort Canning station.
"Fort Canning station involves two bore tunnels -- one to Bencoolen and one to Chinatown,” said Ms Yeo.
“They diverted part of river using a bow-shaped canal. After they diverted the river, they removed the debris from the river bed and then injected stabilising materials to stabilise the ground before they allowed the two tunnels to pass by."
Ms Yeo says the Chinatown-bound tunnel has been completed, while works on the Bencoolen-bound tunnel are still underway.
LTA says the river will be realigned to the original waterway in 2015 after both tunnels are completed.