A 5,200 m diameter Herrenknecht tunnel boring machine (TBM) has installed two 1,000 m long drainage tunnels to relieve pressure on the Singapore River and reduce flooding.
The Singapore Public Utilities Board project is designed to reduce pressure on the Singapore River in the long run, in particular during heavy rains that have previously resulted in overflows and flash flooding in the city-state.
The drive faced complex conditions, as the TBM faced a drive in a constrained inner-city location in one of the most densely populated countries in the world, through a difficult weathered granite geology and passing through small overburdens surrounded by city infrastructure.
Additionally, there was a tight curve radius of 180 m where the curve drive had to be continuously adjusted to keep deviations within the tolerance and some areas were impacted by flooding when the existing 5 km Stamford Canal drains were unable to cope with the water capacity in heavy rain.
The compact earth pressure balance TBM was designed for the tight urban conditions and was launched from a small 24 m diameter shaft.
Herrenknecht engineers lowered the TBM into the shaft component by component before launching it for its first drive; on completion of the first tunnel, it was returned to the original shaft to excavate the second tunnel.
The site crew, Tiong Seng Contractors, worked with the engineers and were able to achieve top performances of 18 m/d and 91 m/w.
For more information visit the Herrenknecht website.
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