Wednesday, 1 October 2014

Great World - It's Beginning

Contract T220 is for the construction of the Great World station and 2 twin bored tunnels to Orchard and Havelock stations. The station is sited on an empty plot of state land once occupied by ERC Institute and the Ministry of Manpower. The buildings have since been demolished and works have begun at the site. The contract has been awarded to a joint venture between Tiong Seng and Dongah at a 65% to 35% stake ratio. These 2 companies have had common working experiences together while tunnelling under C913 of the Downtown Line.

Stamford Diversion Canal Contract 1
This is a civil contract by the Public Utilities Board (PUB) to divert water flow from the existing Stamford Canal by constructing a 2km drainage diversion tunnel to the Singapore River in an effort to alleviate flooding along Orchard Road. Contract 1 was awarded in May just 6 days before T220. Works have started on this contract and the Great World site is currently being shared between the two different projects from PUB and LTA.

Stamford Diversion Canal Phase 1
PUB and LTA project at the Great World site
Great World Station
The station will have 3 levels - An upper concourse, concourse and platform level. The upper concourse is a common subway level which will link all 5 entrances of the station. The station will be constructed top-down. Upon completion of the project, a new 400m long dual carriageway road connecting River Valley Road and River Valley Green will be built above the station.

Entrances C and E will be located on either sides of Kim Seng Road. The subway leading from the station to these 2 exits will be underneath the access road leading to The Trillium and Centennia Suites. As such, a 100m long pipe roof for trenchless construction of the subway will be adopted here. The subway leading to Entrance D on the opposite side of River Valley Road will be constructed using sheet piles.

A&A to existing POBs
2 Pedestrian Overhead Bridges will be altered under this project. The existing bridge located north of the station along River Valley Road will see one of its staircase being reconstructed whilst the bridge across Kim Seng Road to Great World City will integrate with Entrance C and have 2 new lifts added.

T220 Tunnel Chart
2 Launch shafts will be built on either ends of the Great World Station. 1 TBM will launch out of the north launch shaft for a 650m double drive to the cripple siding at Orchard. The authority has given the contractor a choice of either an EPB or Slurry TBM to be used in this sector; and to justify for the chosen type. A cross passage will be constructed between GRW and ORC.

A slurry TBM will launch out of the south launch shaft for a 550m double drive to Havelock station. The tunnel alignment to Havelock runs beneath the recently completed Centennia Suites. The authority has imposed a no-pile zone during the construction of the apartment where the twin tunnels will cut under.

Gantry Crane over the mined shaft under Contract T2123, the first of such installed along the Thomson Line
Shaft at T2123 in proximity to the Alexandra Canal and Centennia Suites
Contract T2123
This is a civil contract awarded to Presscrete Engineering for the advanced works at the Great World site. The works involve constructing a small shaft, for the removal of abandoned piles (by mining) near Centennia Suites along the tunnelling route to Havelock. The demolishment of the 3 ERC and 8 MOM blocks were under this contract as well. Additionally, River Valley Green has been extended for site access to the Great World site.

Update Progress
Within 4 months of the award of contract, the Great World site has seen tremendous progress as compared to other contracts over a similar span of time, with the help of site clearing completed by the advanced works under T2123. Trench cutters and hydraulic grabs have arrived on the site. Guide walls for the d-wall excavation have been constructed at the south launch shaft. Silos have also been erected in the middle of the site and 12m high hoardings have been erected along the perimeter of the site.

Guide walls for the D-wall excavation of the launch shaft
Cross reference of the guide walls installed. Also shown is the mined shaft for T2123.

Trench Cutters & a hydraulic grab sitting on the south side which has yet to be installed
Additional SI works at the d-wall
Mined shaft up close
The abandoned piles are located between the Alexandra Canal and Centennia Suites

Looking north of the station. River Valley Road in the background where entrances B and D will be built
Distinct site boundaries between the 2 PUB and LTA contractors
Erected Silos
Northern end of station box where the north launch shaft will be built

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