Circle Line Tunnel Breakthrough

News Releases 18 Aug 2009 Factsheet Circle Line (CCL)

Circle Line Progress Update
LTA Completes Circle Line Tunnelling Work

1 The Land Transport Authority (LTA) has achieved another milestone with the completion of the tunnelling works for the entire Circle Line (CCL) on Monday, 17 August 2009.

2 The CCL tunnelling work is completed with the breakthrough of the tunnel boring machine (TBM) on Circle Line Stage 4 (CCL4) into the Farrer Road Station.

3 Of the remaining 24 stations which are still under construction, Kim Chuan Depot and five stations [Dhoby Ghaut, Bras Basah, Esplanade, Promenade and Tai Seng] have achieved Temporary Occupation Permit (TOP). About 76 per cent of the railway tracks have been completed.

3 All the forty trains for Circle Line have been delivered to the Kim Chuan Depot.

4 "The CCL project is on schedule and revenue services for the remaining stations will commence progressively from 2010 onwards," said Mr Yam Ah Mee, Chief Executive, LTA.

CCL from Dhoby Ghuat to Bartley (Stages 1 & 2)

5 Circle Line from Dhoby Ghaut to Bartley (CCL1 and 2) consists of 11 stations. [CCL1: Dhoby Ghaut, Bras Basah, Esplanade, Promenade, Nicoll Highway and Stadium. CCL2: Mountbatten, Dakota, Paya Lebar, MacPherson and Tai Seng.]

6 Under CCL1 and 2, five stations - Dhoby Ghaut, Bras Basah, Esplanade, Promenade, and Tai Seng have achieved TOP.

7 The remaining stations - Nicoll Highway, Stadium, MacPherson, Paya Lebar, Dakota and Mountbatten Stations - are on schedule to obtain TOP status by end 2009.

8 The electrical and mechanical works are 97 per cent completed. Final testing and commissioning is underway. Typical electrical and mechanical installation, testing and commissioning works for a station takes about 18 months.

CCL from Marymount to HarbourFront (Stages 4 & 5)

9 CCL from Marymount to HarbourFront (CCL4 and 5), consists of 13 stations. [CCL4: Caldecott, Bukit Brown (future station), Botanic Gardens, Farrer Road, Holland Village, Buona Vista, one-north and Kent Ridge. CCL5: Haw Par Villa, Pasir Panjang, Labrador Park, Telok Blangah and HarbourFront.]

10 Under CCL4 and 5, six stations - Farrer Road, Botanic Gardens, Kent Ridge, one-north, Telok Blangah and HarbourFront have achieved Basic Structure Completion (BSC). Architectural, and electrical and mechanical works have commenced.

11 Caldecott, Buona Vista, Pasir Panjang, Labrador Park and Haw Par Villa are on schedule to attain BSC by the end of this year. Structural works at Holland Village Station have also been substantially completed.

About Circle Line

12 The CCL is an orbital, medium capacity line that links all Mass Rapid Transit (MRT) lines running into the city. It will offer inter-suburban connectivity that is currently not provided by the MRT system.

13 The first five stations on the CCL from Bartley to Marymount had opened for revenue service on 28 May 2009.

14 The CCL has a total of 29 stations, of which six are interchange stations linking to the other existing MRT lines. These interchange stations are Dhoby Ghaut, Paya Lebar, Serangoon, Bishan, Buona Vista and HarbourFront. The integration of Circle Line with the existing MRT lines will provide greater convenience and allow commuters to enjoy accessibility to various locations in Singapore. It will cut down travelling time when commuters bypass the city centre to go to their destinations.

15 Daily ridership of the CCL is estimated to be close to half a million when it is fully operational.

Tunnelling at Circle Line 4, Contract C855
(from Haw Par Villa Station to Farrer Road Station)

1 The last tunnel boring machine (TBM) on Circle Line Stage 4 (CCL4) broke through into the Farrer Road station on 17 August 2009.

2 Tunnelling at this stretch of the CCL consist of four drives. The two drives from one-north to Haw Par Villa were completed in February 2008.

3 The other two drives, from one-north to Farrer Road station, driving through Buona Vista and Holland Village stations, battled through many challenges on their way towards the Farrer Road station.

Tunnelling in close proximity to sensitive structures

4 Despite the efforts to design the alignment to avoid existing structures, not all could be avoided. The TBMs had to drive past numerous structures, including the colonial houses at Nepal Park, KTM Malayan railway at Commonwealth Avenue, old 2-storey shophouses at Holland Village, private residential estates at Belmont Road, Cornwall Gardens and Leedon Road.

5 The project team overcame the challenges of tunnelling past these structures by employing innovative engineering techniques and working closely with the various stakeholders.

Variable ground conditions

6 Singapore's wide range of rapidly changing geology makes the local underground conditions difficult to predict. The variability in ground conditions along the tunnel alignment posed another challenge.

7 At this stretch of tunnel alignment, the engineers encountered extremely fine and soft soil, weathered rock and exceptionally strong granite. To overcome this challenge, a more advanced model of TBM - the slurry machine, was introduced to cope with the difficult geology. To further enhance the safety of the works, LTA carried out extensive investigation of the subsurface conditions along the tunnel alignment and whenever necessary, improve the ground.

8 Tunnelling though the 33.3-kilometre CCL is not without its challenges. LTA is proud to have overcome all these challenges and in the process, draw valuable lessons for the upcoming rail projects.

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