The Land Transport Authority is using a new rectangular tunnel boring machine to build two pedestrian underpasses along the Thomson-East Coast Line. The machine will bore through soil and granite to construct a 160m underpass at Havelock station and a 60m underpass at Stevens station. Unlike circular tunnel boring machines, this rectangular machine is 5.6m wide and 1.7m high and will drill through 1.5m of soil and rock each day using its six cutters.

1. TUNNEL MISSIONTwo pedestrian underpasses on the Thomson-East Coast Line
(TEL) – a 60m one at Stevens station and a 160m passage at
Havelock station – will be built using a new tunnel boring machine
that is rectangular, unlike regular circular tunnel boring machines.
Danson Cheong and Bryandt Lyn takes a look at the Land
Transport Authority’s new $10 million machine, which will be
operational from January next year.
Muck wagon
Cutter
head
Screw
conveyor
(mechanism used
to remove crushed
soil and rock) About
1.3m
Push4.3m
About
5.5m
deep
TBM
shield
Tan Boon Liat
building
Holiday Inn
Concorde
shopping centre
Isetan office
building
Ganges
Havelock Rd
KimSengRd
ZionRd
Taman Ho Swee
Boon Tiong Rd
OutramRd
Grand
Copthorne
Waterfront
TEL Havelock Station
(under construction)
Source: LAND TRANSPORT AUTHORITY
HOW IT WORKS
LOCATIONS
Boring through
the ground
The machine’s six cutters drill
through 1.5m worth of soil – a
mixture of Bukit Timah granite and
marine clay – each day. The soil
mixture is transported out of the
tunnel via a muck wagon.
1
Building the tunnel
Once the soil is removed,
pre-cast concrete “rings” that
form the walls of the underpass
are lowered and slotted into
place. Each “ring” weighs
55 tonnes and has to be cast in
one piece, otherwise ground
pressure might cause the walls
to buckle.
2
SPECIFICATIONS
Completing the tunnel
It will take about 100 days to complete the underpass at Havelock, and 40 days
for the one at Stevens. After the tunnels are completed, the steel shield of the
machine – that encases the other working parts – is left in place while the rest of
the machine, including the cutters, is dismantled and removed.
4
Moving forward
Hydraulic jacks
thrust the concrete
rings and tunnel
boring machine
forward. They exert
about 7,200 tonnes
of force, equivalent
to the weight of
about 1,300
African elephants.
3
6steel cutters
armed with tungsten
carbide cutting tools
Drills a
7.6m by 5.6m
tunnel
Using this machine,
surface activities can be
left untouched – saving
30 per cent
of manpower and time
Weighs about
300tonnes
Requires 14
people to operate
5.6m
1.7m
TEL Stevens Station
(under construction)
Raffles
Town
Club
Singapore
Chinese
Girls’ School
The
Equatorial
Alocassia
Apartments
Stevens
Court
WhitleyRdStevensRd
Dunearn Rd
Canal
Bukit Timah Rd
Robin Close
Margoliouth Rd
Station
entrances