North-South Transmission Cable Tunnel Contract NS3

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Using TBMs to realign power grid in SingaporeHyundai E&C received the NS3 section of the North-South transmission cable tunnel project in 2012 from the Singapore Power Asset(SPPA) in recognition of its extensive experience in MRT and other construction projects in Singapore. The builder kicked off the construction in October 2012. The project is to bore through a 40.2km transmission cable tunnel connecting the city state from east to west and from north to south. The 7.3km NS3 section extends from May Road, where the east-west section meets the north-south section, to Mary Mount and Ang Mo Kio in the northern part of the country. The large-scale project is valued at 238.9 million dollars, or approximately 260 billion won. The completion of the new cable tunnel is expected to guarantee a better power supply in Singapore by replacing old power lines with a 400 kV high voltage cable. There are two types of tunnel construction methods. One is drilling and blasting, and the other is using a huge excavation machine called tunnel boring machine(TBM). The TBM method employs a cylinder, called shield, seven meters in diameter so as to excavate a tunnel in a way that prevents the ground from collapsing and produces a smooth tunnel wall. TBMs have the advantages of enabling the stable construction of tunnels with weak ground conditions, reducing construction periods and decreasing risks of accidents.For this project, Hyundai E&C operated a total of three TBMs. In general, a TBM has a drilling capacity of three to four meters per day. However, the TBMs in the NS3 section moved at a daily average of 5.49 meters, about 149 percent higher than the excavation rate of those operated by other construction sections. This is attributable to Hyundai E&C’s efforts to directly manage the excavation work and the operation rate of the machines. The North-South transmission cable tunnel construction is distinguished from general tunnel projects as it is a specialized facility designed to transmit power. The construction section is about two times deeper than the 30-meter deep MRT tunnels. Moreover, the tunnel has a relatively long service life of about 100 years. Because of all this, the construction materials and facilities employed were totally different from those used for general tunnel construction since they should withstand both water and air pressure at a depth of 60 meters below ground surface. Hyundai E&C made all-out efforts to supply construction materials with longer endurance period and better specifications and conduct several quality-related tests. Despite the hectic schedule, the construction site did its best to ensure safety management.Even before the construction began, the construction site meticulously prepared for safety management plans. Throughout the construction period, it held weekly and monthly meetings and conducted frequent inspections to let safety management take root and discuss how to improve related issues at work. As a result, the NS3 section took first place at the SP Group POS Safety Award in 2015 and was ranked no. 1 in the safety inspection of overseas construction projects conducted by construction bodies of Hyundai Motor Group in 2017.

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