T307 - Marine Parade progress update

Contract T307 is for the construction & completion of Marine Parade station and associated tunnels. The contract boundaries are located adjacent to contract T306 for Tanjong Katong station to the west and to contract T308 for Marine Terrace station to the east. 

A diagram showing the contract boundaries for contract T307.

The Marine Parade station and a portion of tunnel to the east will be constructed using the cut-and-cover method. The portion of cut-and-cover tunnel will house a cripple siding for the main line and an underground pedestrian network one level above. On either end of the continuous cut-and-cover stretch are 2 launch shafts from which tunneling works will be carried out by 3 tunnel boring machines (TBMs).

A render of exit D along the hoarding of contract T307 site.

A render of exit E and the station platform.
Source: Samsung C&T

According to supplier VMT, which provides positioning systems, one of the TBMs was launched in  November 2018. Based on observations we understand that this is most likely at the eastern launch shaft for the drive towards Marine Terrace station, along the Changi-bound tunnel.

The Changi-bound TBM in the launch shaft towards Marine Terrace station.
Source: VMT

Earlier in the year, when passing by the eastern launch shaft, one could easily spot the back up gantries of the TBM at street level. Typically, due to limited space within the shaft, the gantries are kept at surface level till the initial drive is complete and are progressively moved down to the tunnel level after. The initial drive refers to a portion of temporary tunnel rings that are used to propel the TBM from the launch shaft into the soil from which it will begin constructing the permanent tunnel structure. The segments installed as part of the initial drive are subsequently removed once the machine has progressed a certain distance.

07 January 2019 - The east launch shaft of contract T307, showing the TBM back up gantries within the site.

07 January 2019 - A shot of the back up gantry at the site.

Subsequent visits to the east launch shaft no longer showed the TBM back up gantries at street level, which means that the machine had progressed sufficiently that the gantries could be lowered down into the shaft.

07 April 2019 - The east launch shaft

Meanwhile, at the west shaft, tunneling works have also commenced. As with the rest of the site along the contract, diaphragm walls were constructed to retain the surrounding earth in place and to minimise settlement which would affect the surrounding buildings. To help retain the strength of the earth retaining systems, the top-down method of construction is used. In this method, the concrete slabs which will form the permanent structure are cast progressively as excavation of the site moves down. This provides additional stability as the structure is continually reinforced as soil is removed as opposed to using only temporary supports while a deep open trench is constructed.

Construction of the station roof slab near the launch shaft towards Tanjong Katong station, outside Parkway Parade.
Source: VMT

Similar to the eastern shaft, visits earlier in the year showed the TBM back up gantries housed at street level with a temporary shielding structure covering them. Subsequent visits later in the year still showed the gantries in the same position, which signify that the TBM has not commenced tunneling or has not made sufficient progress for the gantries to be lowered down.

07 January 2019 - West launch shaft showing TBM back up gantry near the shaft.

07 April 2019 - The west launch shaft. TBM back up gantries are still in place.

07 April 2019 - A view of the west launch shaft. TBM umbilical cord to the back up
gantries can be seen, just above the flag. Pre-cast tunnel ring segments can be seen to the right.

However, a ground movement observation post was noted, which indicates that tunneling is underway. A sign at the post noted that tunneling works are currently at permanent ring 72. As tunnels west of Marine Parade station transition to a stacked formation, we presume that the lower tunnel will be constructed first so as to minimise incidences of settlement when the upper tunnel is constructed first. Thus we concluded that this TBM is boring the Woodlands-bound tunnel towards Tanjong Katong station.

10 April 2019 - Ground observation post for TBM advance. This is for the Woodlands-bound
machine which is at ring number 72.

Meanwhile, cut-and-cover work at the station entrances, station box and cripple siding continue. This includes the continuation of diaphragm wall construction along the perimeter of the subway connection to exit C along Marine Parade Central.

07 January 2019 - Cut-and-cover work on the station box

10 April 2019 - Diaphragm wall works on-going for the subway link to exit C.

07 January 2019 - Access shaft construction underway.

Upcoming works include commencement of diaphragm wall works along Amber Road near The Cape. This will facilitate the construction of a mid-tunnel emergency evacuation shaft for the stacked tunnels.