Monday 29 September 2014

Orchard - Before the Trees Fell

Contract T219 is for the construction of Orchard Station, cripple sidings and twin bored tunnels towards Orchard Boulevard. Similar to T218, the site of the contract sits on a land currently occupied by the Overseas Family School (OFS). A new campus is currently being built at Pasir Ris, and OFS is expected to move out of the Paterson campus by the middle of next year.

Orchard Station
The new station will see 4 new entry points. This includes Wheelock Place, Paterson Road and Orchard Boulevard. A new Pedestrian Overhead Bridge will connect across the Paterson Road entrance as an additional entry point too. The existing entrance B along the North South Line station will be altered and integrated into a primary entrance for the Thomson Line. The station will have 3 main basements - A concourse (same level as B1 in Ion), platform (Ion B2) and transfer level (Ion B4), and will be constructed top-down using the diaphragm wall method.

Location of 3 of the new entrances to be built around the Paterson junction
Transfer to North South Line
A simplified layout of the interchange:

B1 - TSL Concourse/ ION B1
B2 - TSL Platform/NSL Concourse/ ION B2
B3 - NSL Platform
B4 - Transfer level

As the ground level at Orchard Boulevard is higher, the AMSL level for the Thomson Line Concourse and Platform will be higher than that of the NSL. From the Thomson Line, 2 pairs of escalators on each ends of the platform will bring you down to the transfer level. (B2 to B4) From the North South Line, 2 new pairs of escalators at Doors 3 and 10 of the southbound platform will be constructed to bring you to to the transfer level (B3 to B4). For barrier free linkage, the existing NSL concourse-platform lift will be extended one level down to the transfer level (B2 to B4). A pair of travellators will be installed across the span of the transfer.

The NSL station will undergo intensive A&A works and underpinning, which will prove to be challenging without disrupting the operational status of the existing busy station.

Future subway and paid link to go beneath the existing Orchard Boulevard
Bored Tunnelling
A launch shaft will be built north of the station (near the Paterson junction) for the drive of an EPB TBM to Orchard Boulevard. The existing POB along Orchard Boulevard near Wheelock will be demolished so as to extract the piles in the way of the tunnelling route. A new POB will be constructed to replace the existing bridge. There will be 1 cross passage between ORC-OBV.

C&C Tunnels and TSA
A cripple siding will extend the cut and cover portion of the site south of the station all the way to Grange Road. This will be an extensive site being one of the temporary staging areas (TSA) for trackwork. The overall site will also be shared with various system wide contractors (SWCs).

Future C&C cripple siding tunnel and TSA site

Saturday 27 September 2014

Orchard Boulevard Clears

Contract T218 is for the construction of Orchard Boulevard station. The main contractor KTC has taken possession of the site about 2 months back. The site of the station was previously home to EtonHouse International Pre-School's Orchard Boulevard campus, which has been relocated to Thomson Lane. Site clearing has begun at the station.

There will be 2 entrances for this station. The main entrance will be topped off above the station upon structural completion. The second entrance will be located along Grange Road, near the Traders Hotel, requiring a subway link from the station box. The span of the subway will be built by mining, to eliminate any possible disturbance and diversions to the busy traffic intersection. For the construction of this Entrance B, the existing POB will be demolished. The new bridge will be integrated with entrance B, providing barrier-free accessibility on both sides of the road.

Site Overview
Photo of EtonHouse before demolishment - streetdirectory
Grange Road
Entrance B 

Thursday 25 September 2014

Piling at Napier

Piling works have commenced for the launch shaft at Napier. The rigs and cranes at this site will be fitted with acoustic enclosures due to the sensitivity of noise from the surrounding developments. The bus stop opposite Gleneagles Hospital has been temporary relocated further east on Sep 14. A new bus bay can also be seen along the Eastbound road. The 2 bus bays are adjacent to each other along both sides of the road, and will be linked by a temporary POB. We can expect the new bridge to come up by year end.

Once the old bridge has been demolished, a staged traffic diversion would begin to take place.

The launch shaft will be constructed where the 3 crawler cranes are centralised.
Works outside Gleneagles Hospital. A temporary bridge will be constructed further down the road.
The slurry treatment plant would likely be located where the piling rig sits.
The earthworks in the foreground are likely preparations for future traffic diversions

Tuesday 23 September 2014

Stevens Clears

Contract T216 is for the construction of Stevens station and 3 sections of twin tunnels. There will be 4 new entrances. Entrances D and C will be located along Whitley Road/Dunearn Road. Entrances A and B will be on either sides of Stevens Road. There were indicative plans to construct a crossover tunnel beside Malcolm Park where the Package C boundaries start, however the A/E consultant did not found it feasible to go with.

Stevens Station. Felled tree stumps can be seen along the road median.
The main site will be under Stevens Road where the station box is located. A second site will be located under the northbound Wayang Satu Flyover for the construction of an escalator shaft. A third site will be located along Dunearn Road, along the walls of the existing SCGS. The underpass beneath the canal linking SCGS to the escalator shaft will be constructed by mining. The station layout has been explained here.

The station will be constructed top-down. In an effort to maximize space. the contractor will immediately backfill and reinstate the road once the roof slab is completed.

A total of 4 slurry TBMs will be procured under this contract. For the tunnels between Mount Pleasant and Stevens, Contract T215 will build a launch shaft south of their site before handing it over to T216. 2 TBMs will launch out of Mount Pleasant and dock at Stevens station.

4 cross passages will be constructed between these 2 stations.

T216 Tunnel Chart
For the tunnels between Stevens and Napier, an independent launch shaft will be build off Dalvey Road. Spectacular, the Dalvey launch shaft will be double cell circular, or better interpreted as a peanut shape - the first of such design ever built here. 2 TBMs will first drive towards Napier, before relaunching back at Dalvey for the second drive to Stevens station.

A cross passage will be integrated into the launch shaft before it is backfilled. The tunnels will go into a stacked configuration upon leaving the launch shaft towards Napier. There will be 1 escape shaft located at the junction of Fernhill Close and Nassim Road. To respect the privacy of residents in the neighbouring homes, we will not be doing updates here.

T216 Site Office located off White House Road. Earthworks for Dalvey Launch Shaft in the foreground.

Progress Update
The site office has been completed and is located along White House road, in front of the Dalvey launch shaft. The felling of several trees along Stevens Road had also recently be carried out. Earthworks are underway to flatten the site where the launch shaft is situated. SI works are being carried out at Entrance C. The SCGS wall has yet to be relocated. 2 houses will be acquired for the Stevens Road entrances. 2 Robin Close has been acquired and is currently in the process of being demolished. 133 Stevens Road has no signs of work.

Sunday 21 September 2014

Mount Pleasant Earthworks

At Mount Pleasant, KTC has been subcontracted to facilitate the demolishment of the old police academy blocks. Works started since our previous update in June and the site had just recently been fully cleared. Earthworks are now underway to flatten the land before works on the retaining wall fully begin. 2 piling rigs and silos have been set up west of the site.

Overview of Mount Pleasant

The station would mainly serve CJC and the neighbouring residents within Chancery Hill, across the PIE

Friday 19 September 2014

Caldecott Piles

Piling works continue at the Caldecott site. The station's ERSS will be constructed using secant bored piles. Multiple cases are currently being driven into the boundaries of the station box and cripple siding tunnel. Toa Payoh Rise has completed its temporary road diversion, for the construction of the two entrances on both sides of the road. The diversion will remain till Q3 2018. Vibration meters have also been installed within the Circle Line station by Ryobi, the monitoring contractor for T212 & T213.

Prior to the commencement of tunnelling from ULS, Samsung would temporary handover site possession (where the original road aligned) to Sato Kogyo to facilitate ground improvement works for TBM docking. This is expected to take place around the middle of 2015 and last a couple of months.

Toa Payoh Rise coming down from Lorong 1
Diverted Toa Payoh Rise
Aerial view of Caldecott
North face

Wednesday 17 September 2014

Bright Hill - Once Stacked

Bright Hill station, more commonly known as Sin Ming or 'T7' station during the planning stage of the line, was originally designed to be a stacked interchange with the future Cross Island Line. Along the tunnel alignment to Upper Thomson, 2 escape shafts had been planned to be constructed within Flame Tree Park and Windsor Park due to the semi-stacked configuration of the tunnels.

The original plans were scrapped at the last minute, and the architect rushed out a new set of drawings in May 2013. The twin bored tunnels are now level with each other, omitting the need for the 2 escape shafts as the cross passages can be conventionally constructed by mining. The new design incorporates two provisioned box tunnels at the roof of Bright Hill station for the future Cross Island Line (CRL). The box tunnels are orientated parallel with Sin Ming Walk/Avenue, giving a strong indication that the CRL will head straight into the Central Catchment towards Eng Neo. There will also be a stub tunnel abutting from the Woodlands bound tunnel, believed to be for the sharing of locomotives between the 2 lines.

Progress Update
Under T211, a replacement sports facility is being built for Bishan Park Secondary School as the existing one would be demolished for the station construction. The facility will be ready by November this year. Preparation works are underway for a road diversion too.

T211 Site Office overlooking the Bishan-AMK Park
New sports facility U/C. A temporary bus stop can be seen being delivered on a trailer within the site as well.

Monday 15 September 2014

Upper Thomson Diverts

After 3 months of preparation works, Sato Kogyo has successfully implemented their first traffic diversion along Upper Thomson Road at Lakeview, where the future launch shaft (ULS) sits. The old pedestrian overhead bridge (POB) will be demolished at once, and piling works will begin for the launch shaft by year end once the site is cleared.

Upper Thomson Launch Shaft (ULS)
ULS will launch out 3 Slurry TBMs - 1 which will do a double drive to Upper Thomson, and another 2 towards Caldecott station. A Slurry Treatment Plant (STP) and Gantry Crane will be constructed along the former road. The team hopes to launch the first TBM by the end of 2015. Excavation of the tunnels will take some 18-24 months, and might possibly drag on into early 2018. Once the tunnels have its first stage concrete (FSC) completed, the cross passage within the shaft will been built. The shaft will be backfilled and reinstatement on the surface will only take place then.

T212 Tunnel Chart
Upper Thomson Station (UTS)
Canal diversion work is still on going at the station side. For the ERSS, Upper Thomson would be implementing the diaphragm wall construction. Trenching works should begin by year end.

ULS pre-diversion (September 12)
Upper Thomson Road on Sunday morning
Station side

Saturday 13 September 2014

Piling at Mayflower

The groundbreaking ceremony for Mayflower station was commemorated along with Lentor last Saturday. At the Mayflower site, Avenue 4 has just been diverted last week to facilitate the construction of the bored piles for the retaining wall. The diversion will remain till end 2015, when the SBP construction is completed.

The ERSS of a station can be constructed using diaphragm walls as seen at Springleaf and Lentor. Another method of constructing the underground structures would be the use of secant bored piles (SBP). Over at Mayflower station, this method will be adopted.

Secant Bored Pile Construction
The pile's casing is first drilled into the ground, leaving 1-2m of the casing head exposed to the surface. The exposed cylinder guides the excavation of the bored pile, which is carried out next using a rotary drilling rig. The soil surrounding the borehole is supported by the casing. If the casing is not long enough to reach the required depth in the ground, bentonite slurry is used to support the soil below the casing. After excavation is complete, the reinforced steel cage is inserted into the casing, and concrete is poured. The casing is then removed and the retaining wall or ERSS is completed.

Mayflower Station
Diverted AMK Ave 4 at the junction with St 13
Groundbreaking Ceremony on September 6
Commencement of drilling for the secant bored pile

Thursday 11 September 2014

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.

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

Tuesday 9 September 2014

Springleaf & Tagore

As of today, 6 crawler cranes and 1 piling rig lies at the Springleaf site. A hydromill trench cutter has been attached to one of the cranes, marking the start of excavation for the diaphragm walls.

Trench excavation process
2 cutting drums are attached to the base of the trench cutter, operating in reverse circulation as it excavates the earth. As it excavates, soil is loosened, broken down and mixed with a support fluid which is then pumped to the desanding plant at the surface via mud pumps. The slurry is then cleaned and subsequently recirculated into the trench.

Springleaf Station
Tagore station

Sunday 7 September 2014

Contract T206 & T207

Contract T206
The inaugural tunnel launch for the Thomson Line is expected to be held under this contract at Launch Shaft 2 (LS2), for the launch of 2 TBMs to Woodlands station. Excavation for LS2 is scheduled to begin by the end of the year, and the project team hopes to have the shaft ready to launch the machines in 8-9 months.

T206 Tunnel Chart (Reception tunnels in red)
STEC has recently taken possession of the SBAB site. A crawler crane and 2 piling rigs has been brought in. West of SBAB, the escape shaft at Avenue 12 has also been hoarded up.

Contract T207
At the RTS facility site, a crawler crane has arrived onto the site and piling has begun. Tunnelling will begin slightly later under this contract as both launch shafts is being constructed by the neighbouring contractors requiring a handover process. Site possession under Shimizu is scheduled for end 2015 and early 2016 for the launch shaft at Springleaf and SBAB respectively.

T207 Tunnel Chart

Use of SFRC segments in tunnelling
A new type of tunnel rings have recently been experimented for the first time in Asia under C933 of the Downtown Line. Steel Fiber Reinforced Concrete, or SFRC in short, contains fibrous material and are precast in a (7+1) segment arrangement that distinguishes itself from the conventional RC (5+1) tunnel segments. The fiber reinforcement segment uses less steel, and is much more durable and crack resistant.

Moving forward, LTA continues to expand the use of these rings in the construction of new lines. Contract T206 and T207 were identified contracts to be considered for the usage of the SFRC rings. At the Underground Singapore 2014 conference held last month, the LTA confirmed that 2 TSL contracts will be using the new fibrous segments, doubling the use from 4.7km on the DTL3 to 10km for the new Thomson Line.

RTS Facility Building site alongside the SLE
LS1 and LS2 amidst the diverted Woodlands St 17
Sembawang Airbase & Escape Shaft
Hoarding for Escape Shaft along Avenue 12

Friday 5 September 2014

Woodlands Drive 16 Diverts

As the existing Woodlands Drive 16 cuts through the Woodlands South site, an interim road has been created to go around the site area. The road however has not yet been opened to public. Works are also underway for another road diversion along Avenue 1. The road will be shifted closer to Christ Church Secondary - this is to facilitate the construction of the station's earth retaining stabilizing structure (ERSS).

Northern end of station box where a road diversion for Avenue 1 is being prepared
The woodlands South site office is powered by solar panels. SBAB can be seen at the left background

Wednesday 3 September 2014

Piling at Woodlands

Following the groundbreaking, South Woodlands Drive has seen a road diversion. To date, a total of 7 crawler cranes and 6 piling rigs flood the site. Works are currently being focused on the crossover tunnel which will sit below the existing road junction of Avenue 2/5, hence the need for a future road diversion which can be expected soon after sewer diversions are completed by T2119A.

Under the neighbouring tunnel contract T206, 2 TBMs boring the mainline tunnels from LS2 are planned to dock at this crossover tunnel by the end of next year.

South end of Woodlands Station

Monday 1 September 2014

Woodlands North Earthworks

Woodlands North station sits on one of the most hilly terrains across the island. As such, terracing works are needed to flatten the existing land before structural works can begin. The granite obtained from the blasting works during the earthworks and excavation process will be recycled into composites for concrete to be used back when constructing the station, in the effort to minimize project cost. 

The cut and cover portion for the contract is extremely long (750m) due to the presence of a north and south crossover, as well as an abutting overrun tunnel for the Changi Bound track which will be constructed beyond Admiralty Road West. A road diversion will be needed.

Aerial view of Woodlands North 

Bored tunnels will follow St 81 before docking at Woodlands