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Rectangular box jack TBM set to star in Singapore

T221 Rectangular Box Jack TBM
  • TBM machine supplied by China Railway Equipment Engineering Group with China Railway Tunnelling Group acting as tunnelling sub-contractor
  • Rectangular TBM will be used to construct two underpasses on the project
  • 30% savings in manpower due to increased productivity expected
  • The TBM will arrive in January with target to launch towards the end of February

Contractors in Singapore are readying themselves for the arrival of the country’s first box jack rectangular tunnel boring machine (TBM).

Sourced from China Railway Equipment Engineering Group, the pioneering machine will be used to construct two underpasses as part of a major 43km new commuter rail line.

The TBM will first be used to construct a 150m long box-shaped underpass at Havelock station then dismantled and brought over to Stevens station to construct another 60m long underpass.

Such tunnels would conventionally be built using the cut and cover method. But client Land Transport Authority was keen to minimise street level disruption and so has opted for the box jack TBM approach.

Speaking at New Civil Engineer’s Tunnelling UK summit last month, LTA project director Henry Foo said the box jack TBM was an innovative alternative to the conventional cut & cover method at shallow depths.

“For a typical underpass structure in LTA’s MRT projects, we would use cut and cover. But this is an attractive solution for densely built-up countries with rising labour costs,” said Foo.

Foo added that the simpler construction method was also expected slash 30% off of the cost of manpower.

“We believe we are able to achieve an estimated 30% of productivity savings,” he said.

“In using this box jack rectangular TBM, we will avoid the need to compromise the surface activities and create the underground structure in a trenchless manner.”

The underpass will connect into Havelock station on the new Thomson-East Coast Line. Gammon Construction will build the station for S$210M with China Railway Tunnelling Group acting as tunnelling sub-contractor.

The TBM will arrive on site this month with launch targeted for the end of February and breakthrough scheduled for 30 June.

Foo is enthused by the innovation and eager that the technique is further evolved.

“We will be doing further validation and re-evaluation with completion of the project,” he said, adding that in parallel there will be on-going research by suppliers for use of segmental linings built within the TBM shield for shallow depth tunnelling.

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