Next Station, Botanic Gardens

A preview to the final and deepest interchange along DTL2.

Satellite image of BTN on Apr 24

DTL Concourse - Platform Twin Escalators

Settlement at Upper Changi

While caves in are rare occurrence during the tunnelling phase, they do happen. Every TBM that launches is accompanied by a watchmen which is station on the surface within a safe distance of the cutterhead location to monitor and phone back to the control room any depressions should they appear. In the inevitable situation where a passing vehicle gets timed with the sinkhole, it gets carried in with the ground. Quoting a press release by the LTA earlier today, "At about 8.30am on 24 April, a depression appeared at the centre lane of Upper Changi Road East (in direction towards Expo). A tipper truck that was passing tilted into the hole."

Photo credit - @Andre_Giam

Cave in near apartment 704 of Changi Court

Though the sinkhole's location is near the Upper Changi station site, the tunnelling works north of the station are carried out by its sister contract C923A. A good gauge of progress as the 2 TBMs from the PIE shaft is nearing the end of its final drive. I presume the authority and STEC would conduct stringent soil improvement works at the area before resuming activities at the cutterhead.

Brief overview of Stage 3 in 1st Quarter

It is already coming to the end of April, so we'll just cover the stage in brief for the first quarter of the year in this post, taking a look at some updates from the station sites today. Starting with the terminal point at Expo.

Expo
The station has been fully excavated and work now progresses on to the structure itself. Rebar is first installed and then concrete is poured to form the structural skeleton of the station. Currently, work is focused on the platform and under-platform levels.

A view of the work area for the future exit next to the Singapore Expo foyer.

April Tunnel Progress

View of launch shaft at Ubi under C929A 

DTL3 Tunnel Chart

C918A TKK-BTN Tunnel: S604 BP (Green), S605 EP (Orange)

Completed BP tunnel bored by S604

Dismantling of slurry pipes and backup gantries rail at Ring 585 (and progressing back to TKK)

S605 currently beneath the canal wall at the white patch

The remaining TBM under SK, S605 has crossed the ORRS and DTSS and is starting to curve back towards Botanic Gardens. They are replacing the cutters every few days due to the harsh granite conditions posed in this region. We might see breakthrough only in June. The cross passage is currently being mined beneath the underpass and canal. Ground improvement works were carried out 2 weeks ago with the temporary closure of one road lane.

C917A KAP-SAV Tunnel

S602 has caught up with progress. It will follow a very similar timeline with its sister TBM. A month would be spent tunnelling through the granite between R680-R730. Final breakthrough expected in July.

S603 is doing about 4-6 rings per day now. All going well we'll see a breakthrough next month.

TBM Josephine sees light of day

After the arduous task of boring the Bukit Panjang tunnel from Tan Kah Kee station to Botanic Gardens, the TBM named Josephine is finally dismantled and brought to the surface. A few photos commemorate the milestone in achieving another tunnel completed under Downtown Line 2 (DTL2).

Mattar S737 breakthrough

In addition to the breakthrough at Chinatown, the Downtown Line 3 has also seen another breakthrough at Mattar station. Under Contract 931, Hyundai Engineering bored one bound of the two tunnels from MacPherson station to Mattar station and brokethrough into the reception shaft early last month.

Photo credits - C931 FB

Chinatown breakthrough

As mentioned in our earlier post, C937 finally broke through to the reception shaft at Upper Cross Street cut & cover site. The process has been a long and arduous one as the ground showed increasing settlement as the machine neared the end point. Care had to be taken to mine the last few metres or so to prevent excessive settlement causing the buildings on both sides to move and potentially see unwanted movement of the road above.

Nevertheless, after several weeks, the team safely accomplished breakthrough, linking the stage 1 tunnels to the stage 3 tunnels. Here are a few photos of the occassion.