Lentor - Basic Structure Completion

Lentor Station achieved the BSC at the beginning of the year, with fit-out and painting works commencing. Structural works continue at the entrances. Dismantling of the TBMs have completed, and the first stage concrete & tunnel bracket installation works are ongoing between 5XO and Mayflower.

5XO site

February Tunnel Progress

The T215 and T217 projects have successfully completed all tunnelling works this week with the docking of the 2 Herrenknecht Mixshield TBMs at the Caldecott cripple siding tunnel and Napier station respectively. 14 bored tunnel drives remain - bulk of which would be completed in the second quarter of the year.

The next breakthrough will take place at Caldecott by TBM 3 under the T212 project around end Feb/early March. Its sister TBM 2 will subsequently arrive approximately 6 weeks later, concluding the tunnelling works for Stage 2 and TELC2 in April.

TEL1/2 Tunnel Chart (January 2018)

Lentor - Tunnelling Completes

Bored tunnelling works for TBM 1 completed earlier this week, concluding the 18 months long Changi bound tunnel drive from Lentor to Mayflower station through the 5XO site. Its sister TBM 2 is 91% out of the 970-ring drive and targeted to complete by the end of the month. The tunnel roof structure of the 5XO is completed and backfilling works have commenced. Structural works for the station entrances are progressing on the surface level.

Lentor Station

Lentor Cast (IV)

Excavation works for the station appears to have completed with structural works taking place at the platform level. Casting of the entrances are progressing, with the first superstructure emerging from Entrance D. Both TBMs are advancing through rock around Block 174 beneath AMK Avenue 4 and is targeted to breakthrough by December.

Lentor Station

Lentor Cast (III)

Construction of Entrance C has started adjacent to the launch shaft. Excavation works for the station is almost completed with structure of the platform level presumably taking shape.

Construction of Entrance C,D and E

May Tunnel Progress

Tunnelling works for Stage 1 of the line will be completed by next month with the final 100m long Woodlands bound tunnel being driven between LS2 and Woodlands South station. Concurrently, the twin TBMs from Springleaf will breakthrough at the RTS Facility Building, completing the longest mainline drives (2km) under the TEL project.

TEL 1&2 Tunnel Chart, May 2017

T206: Completed Changi Bound tunnel between LS2 and WDS under the second drive of TBM 4

Lentor Excavation (IV)

Excavation and casting works are ongoing at the concourse level.

Lentor Cast (II)

Deep excavation works are ongoing at the station box.

Lentor Station

Lentor Excavation (III)

The remaining diaphragm wall panels have been completed at the Lentor station and excavation for the basement roof slab for the second stage of zone 2, and zone 3 are in progress and will be cast by the 4th quarter. Bulk excavation works are progressing at zone 1.

TBM 1 has completed conversion to its main drive and is now under the intersection of Avenue 9. TBM 2 was just launched last month and is on it's initial drive to 5XO.

Excavation for the RC construction of the basement roof slab

July Tunnel Progress

Tunnelling works are underway along all the projects along stages 1 and 2 of the line, with the first slurry TBM for the T211 project launched at Bright Hill this week. 5 bored tunnels have been completed by the first half of the year and a further 5-8 tunnels are envisaged to complete by year end.

TEL1/2 Tunnel Chart, July 2016

T206 - Launch preparations for the second drive of TBM 4 for reception tunnel 1 at Sembawang Airbase C&C (Photo credits: LTA)

Lentor D-walls (III)

D-walling works continue at the Lentor station following the realignment of Lentor Drive. The first TBM has commenced the initial drive on the Changi bound tunnel towards the 5XO site, which is nearly completed with excavation works.

Realignment of Lentor Drive

Lentor D-walls (II)

The next stage of the diaphragm wall construction is beginning as the completed zone backfills and Lentor Drive gradually shifts back over the completed roof slab. The realignment of the intersection at Yio Chu Kang Road was carried out earlier this quarter and sheet piling works for the entrance at Calrose have begun.

Realigned YCK road over the completed underpass structure

Lentor - TBM Assembly

The CREG TBMs have arrived at the Lentor launch shaft and assembly of the first machine commenced yesterday with the lowering of the rear shield.

Lowering of the middle shield 

Lentor Excavation (II)

Excavation to the basement roof slab of the Lentor station has completed and RC works are currently prepared for the subsequent concreting. The zone 1A section that had been concreted in September has been de-strut and backfilled, which made way for a minor realignment of Lentor Loop for the remaining d-walling works to be facilitated north.

Excavation of the launch shaft has completed and the RC works for the base slab is being carried out. The pre-assembled gantry beam is present at the portal surface. Phase 1 of the subway link beneath Yio Chu Kang Road has been backfilled and the sheet piles are currently being extracted.

The project team has begun preparations for the impending second realignment of this intersection.

Aerial view of Lentor Station

Lentor Cast

Lentor Station will be adopting the top-down construction method. The basement roof slab of Zone 1A was successfully concreted at the start of this month. Timelapse of the rebar installation throughout the past month is included below.

Excavation works for the launch shaft has reached the S3 layer and is nearly completed. The slurry treatment plant is also in the midst of assembly works.

Lentor Station

Lentor Excavation

Excavation works have commenced on the north face of the station box. The outline of the launch shaft at the south end of the station is evident too, and we can expect excavation of the shaft to commence by the third quarter of this year. The linkway to the Calrose entrance seems to have completed excavation to the formation level where 3 layers of struts have been installed.

D-walling works continue at the 5XO crossover site along Ang Mo Kio Avenue 4.

Lentor Station

D-walling at 5XO

CREG TBM - Factory Acceptance

The first of 2 slurry TBMs manufactured by CREG for the Thomson Line has just passed its Factory Acceptance test last Thursday. The machine, with the serial 209A, will be used to tunnel the 1.3km section between Lentor and Mayflower stations beneath Ang Mo Kio Avenue 4 under Contract T209. Its sister machine 209B is scheduled to pass the factory acceptance next month.

Factory Acceptance of 209A CREG Slurry TBM (Photo cr: CREG)

Lentor & 5XO D-walls

D-walling works continue at the Lentor Station. Sheet piling for the subway leading to the Calrose Entrance has completed and shoring works are underway to construct the first layer of struts. Photos in this update were taken on March 14.

Shoring works for the underpass to Calrose across YCK road. The road will be diverted above this structure once a decking is made

Lentor D-walls & Piles

D-walling works at Lentor has commenced this quarter. Close to Yio Chu Kang road, the team is in the midst of constructing the sheet pile for the subway that will link to the station entrance at Calrose. Sheet piles are a favorable method of constructing an ERSS due to the time efficiency in installation and transportation. The interlocking steel segments are also earth tight and water resistant. This method is hence commonly used in shallow linkways and cofferdams.

We expect the completed section of sheet pile to be subsequently decked over by a second and more permanent traffic diversion at the junction of YCK/Ave 4/Lentor Drive next year. This is for the construction of the remaining section of subway beneath the existing diverted road, and subsequently the construction of the entrance at Calrose itself. This diversion would then probably last until the completion of the project.

Sheet piling for the subway leading to the station entrance at Calrose

Panorama of 5XO

At the 5XO site, Avenue 4 was diverted at the end of Q3 and with the site cleared, hoardings are going up along the west side where sheet piling works have commenced. D-walling works should commence from next month as well. To the east, silos and a desander plant have been assembled to support the impending D-wall construction.

Project notice for 5XO (transcript):

- Identified trees along AMK Avenue 4 have been fully removed to facilitate crossover tunnel box construction (5XO)
- Road diversion works at 5XO will be carried out in 2 stages. Traffic Diversion 1 completed on 29 September 2014.
- Traffic diversion 2 at the junction of Avenue 4/5 are planned to commence in early January 2015.
- Tubular pile, steel deck and RC drain has been constructed close to Block 643
- Sheet pile works at Blk 613,614,615 has commenced from mid Dec and will last for a duration of 3 months.
- Installation of monitoring instruments along the ground and buildings
- D-wall works along Blk 613/4/5 planned to commence from end November (delayed)

Lentor Drive Diverts

Much changes have taken place at the Lentor site throughout the 3rd quarter. The junction between Yio Chu Kang and Ang Mo Kio Avenue 4 has been diverted to accommodate the road diversion at Lentor Drive, which has been re-routed to skit around the proposed station box. 3 crawler cranes and a hydraulic grab machine is currently on the site.

Mentioned in the Springleaf update, a hydromill trench cutter is one way of excavating the trench for the d-walls. An alternative method would be the use of a hydraulic grab, which physically excavates the earth via clamshells. This machine is feasible for excavating panels of shallow depths in soft ground conditions. Lentor station will be constructed top-down.

At the groundbreaking ceremony, it was revealed that CR5 will be procuring their 2 TBMs from China Railway Engineering Equipment Group for the drives from Lentor to Mayflower station via 5XO. This is the first time CREG's TBMs are being used in Singapore soil.

5XO

Preparations are underway for the initial road diversion at the crossover site. The road will be diverted east of the original alignment. 5XO will be structurally completed and backfilled by 2017. The road will be realigned then.

Lentor Drive has diverted

Groundbreaking Ceremony on 6 September

Prime Minister Lee viewing the exhibit of the T209 TBM which will be manufactured by China Railway Engineering Equipment Group