INDUSTRY NEWS
PEDESTRIAN UNDERPASSES
CONSTRUCTED USING NEW TUNNELLING TECH As part of the works for Thomson-East Coast Line (TEL), LTA embarked on a pilot project to construct pedestrian underpasses with a Rectangular Tunnel Boring Machine (RTBM) at two sites at Havelock and Stevens stations to leverage on this method to increase productivity. The RTBM features a rectangular shield box jacking technique which makes use of the principles of an Earth Pressure Balance Machine during excavation. The thrust cylinders in the box jack remains in the shaft, and push forward the entire box segment. New segments are installed within the shaft as the machine advances. As the RTBM advances and cuts through the soil, it turns the excavated material into a soil paste that is used as pliable, plastic support medium, to balance the pressure conditions at the tunnel face. Compared to conventional cut-and-cover methods used in other construction projects, the trenchless method with an RTBM brings about an estimated 30 per cent increased productivity through a reduction
Simplified cross-sec onal diagram of an RTBM (Image: LTA)
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THE SINGAPORE ENGINEER January 2018
in manpower, and provides better continuity of work, higher quality and workmanship. The RTBM was first launched at the site of Havelock station under Zion Road in May 2016 and completed its drive after six months in November 2016. As opposed to the use of conventional cut-and-cover method, the use of the RTBM resulted in a much shorter construction duration. It was then deployed at the site of Stevens station to construct a 60m-long pedestrian underpass beneath Dunearn Road and the Bukit Timah Canal. Tunnelling works for the pedestrian underpass was completed in January 2018. It will be open for public use 2020, ahead of the comple on of the TEL Stevens sta on. This will benefit pedestrians, such as students from Singapore Chinese Girls’ School and St Joseph’s Institution, who will be able to cross Dunearn Road and Bukit Timah Road safely with the new underpass that connects Stevens station with these schools.