The Metal Mole Tunnelling Under Singapore

STORM takes you underground on a mole’s-eye tour of the tunnelling process that will eventually become the Thomson-East Coast MRT Line (TEL).

As part of the recent ITA Tunnelling Awards 2016, where Singapore burrowed its way to three international awards, the organisers scheduled a visit to the bowels of Singapore.

The Thomson–East Coast Line (TEL) runs from Woodlands to East Coast and will be operational from 2019.

The TEL will have 31 stops and run 42km, adding to the vast labyrinth of tunnels that crisscross the island.

Thomson – East Coast MRT Line © Land Transport Authority

Digging Deep

It requires some heavy machinery that excavate at depths in excess of 100 metres. Much of the work at this stage is done by tunnel boring machines (TBM). We got to see one of these “moles” in action on the visit to the Woodlands’ worksite. These machines can cost anything upwards of US$45 million, depending on size, capacity and power.

Sitting at the bottom of large 100 metre deep hole, called a launch shaft, the slurry shield TBM is used to bore one of the many new tunnels that will form the TEL. Slurry TBMs are used to tunnel through unstable terrain or under structures that are sensitive to ground disturbances.

The machine cuts through rock and soil, and transports the debris back to the surface via a chemical suspension (slurry). The broken up rock, mostly granite, is then processed above ground at the slurry treatment plant. While the chemical suspension in funnelled back into the TBM, the dug up rock and soil are separated and repurposed for other construction works.

As the machine inches along, pre-fabricated concrete slabs, called segments, are then installed to create the new tunnel through which the trains will run.

This is only the first phase of the project — electrical work, track laying, construction of the stations, and various other tests will follow before the TEL ferries commuters in stages from 2019 to 2024.

Could MacRitchie be next, when the Cross Island Line’s route is finalised?