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| A render of Hougang interchange showing the paid transfer link's bank of escalators connecting to the North East Line on the left. The concourse extends towards the existing Exit A at the Hougang Bus Interchange. Source: LTA |
Over the last few weeks, the first of the civil contracts for the Cross Island Line (CRL) have begun to be awarded. On 8 March 2021, the Land Transport Authority (LTA) awarded contract CR105 for the construction of a large-diamater single bore tunnel between Aviation Park and Loyang stations to a join venture between Taisei Corporation and China State Construction Engineering Corporation. This was followed by the award of contract CR112 for the construction of Hougang interchange station and connecting tunnels on 26 March 2021 to Samsung C&T.
CR112 - Hougang interchange
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| Location overlay of Hougang interchange. Credit - y2koh & LTA |
Hougang station will feature a paid-transfer link to the existing North East Line (NEL) station. The transfer link is likely to connect to the existing NEL station at concourse level, likely near the existing Passenger Service Centre. This will lead to around the mid-point of the CRL station concourse where passengers can descend another level to the CRL platforms.
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| Indicative location of contract CR112 TBM launch shaft Credit - y2koh |
The contract calls for the construction of tunnels from the interchange stretching westwards to neighbouring station Serangoon North. A tunnel boarding machine (TBM) launch shaft will be constructed mid-tunnel and tunneling works will commence from there. The tunnels from the launch shaft towards Hougang interchange will be constructed first and the tunnels towards Serangoon North after. 2 Earth Pressure Balance machines, procured under contract CR120, will be used for the entire section. The launch shaft is likely to be located along Hougang Avenue 2
CR105 - Tunnels from Aviation Park to Loyang
Contract CR105 involves the construction of a large diameter single bore tunnel between Aviation Park and Loyang stations. The single tunnel will be further subdivided with a wall to enable trains to run on separated tracks. This construction method is similar to that of a tunnel on the Vancouver Skytrain in British Columbia, Canada. The tunnel underneath Clarke Road was constructed as part of the Evergreen Extension project for the city's Millenium Line.
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| Technical specifications of ART Mark II trains for Vancouver Skytrain Source: Bombardier Transportation |
Vancouver's Skytrain Millenium Line uses the Bombardier Advanced Rapid Transit technology, the same system as Kuala Lumpur's Kelana Jaya Line with trains narrower than the conventional Singapore MRT trains. The TBM used for the Vancouver tunnel measured 9.3 metres in diameter. Due to Singapore's wider trains, it can be expected that the TBM for contract CR105 will exceed 10 metres. Following the completion of tunnel boring in Vancouver, interior works to segregate the running trackways commenced with the construction of a dividing wall down the length of the tunnel.
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| Evergreen Extension tunnel after completion of first stage concrete Source: Evergreen Line Project Office via Daily Hive |
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| Evergreen Extension tunnel during dividing wall construction Source: Evergreen Line Project Office via Daily Hive |
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| Evergreen Extension tunnel after completion of dividing wall, before trackwork commences Source: Evergreen Line Project Office via Daily Hive |
The tunnel for contract CR105 will be built in virtually the same manner. A dividing wall for fire safety will be built as well as areas for services to be run.
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| Cross section of large diameter bored tunnel for Singapore rail projects |
Work for both contracts CR105 and CR112 are expected to begin by the end of this year.
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