1. Land Transport Authority
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Internship Presentation
DEVARSH KUMAR
3rd year undergraduate
Department of Civil Engineering
Indian Institute of Technology Madras
email – devarsh10iitm@gmail.com

2. OUTLINE
Top Down vs Bottom Up
method in construction
• TIME comparison
• COST analysis
Earth Pressure Balance TBM
• OPEN CUT TUNNEL
alignment of C928
• KEY position selection
Sustainable Development
• Environmentally
improved material
Learning Outcome
• Challenges
encountered
• Site photos with
description
• Construction
Market Activity
Cycle Model

3. C937B Tai Seng Facility Building
C929
Kaki Bukit
Station
(Top Down)
C929A
C928
Bedok North
Station
(Bottom Up)
C928
C929A
C929A
Layout Chart

4. Rate of volume
of earth to be
excavated (20m)
$129/m3
$99/m3
Rate of concrete
to be used for
roof slab (1.5m)
$150/m3
$150/m3
Hypothetical Structure
Length – 60 m
Width – 24 m
Top Down
vs
Bottom Up
Total cost
$4.0 M
Total cost
$4.7 M
Less TIME
taken

5. Rate of volume
of earth to be
excavated (20m)
$129/m3
$99/m3
Rate of concrete
to be used for
roof slab (1.5m)
$150/m3
$150/m3
Rebar (adopt
230 kg/m3)
$1.46/kg
$1.46/kg
Area of
formwork to
be used
NA
$75/m2
Hypothetical Structure
Length – 60 m
Width – 24 m
Top Down
vs
Bottom Up
Total cost
$4.0 M
Total cost
$4.7 M
Less TIME
taken

6. Reasons for higher cost of Top - Down
• Limited construction openings for handling materials and
machineries.
• Limited headroom for excavators to operate.
• Need more lightening and ventilation systems.
• Even though there is no scaffolding materials used to prop
the formwork to the soffit of the roof slab in Top – Down
Method yet its price is high because of very high rate of the
volume of earth to be excavated.
NOTE – cost figure represent C929A and cannot be generalised

7. Tunnel Alignment

8. Expo Bound
Bukit Panjang Bound
C929A Station Box
C929
C928
WEST Cut and Cover Tunnel Alignment

9. START
END

10. EAST Cut and Cover Tunnel Alignment
C927
Expo Bound
Bukit Panjang Bound
Station Box
C928

11. START
END

12. Key Position
Selection

13. KEY position 7 to
11 are not used
because
• It is difficult to
install as
Connection
Segments (B)
and Standard
Segments (A) are
under
compression.
• It is the weakest
link.
Sequence of
Key Position
Selection for
building
Segments

14. Required Information
• Straight portion of the
Tunnel
• Tunnel is moving UPWARD

15. L16 R2, R5, R14

18. SUSTAINABLE DEVELOPMENT

19. Choose efficient formwork
Timber Formwork System Formwork
Material Timber & Plywood Aluminium
Durability 20 times 120 – 150 times
Wastage Yes No
Quality Workmanship dependent Good
Labour Skilled Unskilled
Cost $26/m2 $34/m2
Source – Guidebook for best environmental practices, LTA, Singapore

20. Environmentally Improved Materials
• Using MILLED WASTE for temporary pathway instead of
concrete.
• Using factory prefabricated reinforcement because there is :
60% reduction in processing waste
30% increase in labour productivity
• Good coverage of stockpile using Erosion Control Blanket
either Natural material blanket or synthetic blanket.
• Using Scrap bin for disposing welding rods, twisted steel
wires, etc. for recycle.

21. Learning Outcomes

22. Challenges
Encountered
Bedok North
Station
(1) Water Canal
Diversion
Temporary Canal
HDB
D-WALL
SBP
In case of any failure, water
will remain confine between
D-Wall and SBP and station
box remains unaffected

23. Bedok North
Station
Challenges
Encountered
(2) Water Ingress
Stock pile
Water squeeze out from
underground into the station
box due to additional
surcharge because of stock
pile

24. Kaki Bukit Station – Challenges Encountered
Restriction
in space
• Top 2 metres
from ground
had scattered
services lines
that took an
additional 9
months for its
diversion and
trench
building
• Bottom up
might take less
time but
presence of
HDB and
factories on
either side of the
station made it
safe to use top
down
construction
method to limit
the D - wall
movement.

25. Why is there a discontinuity in the
coupler position ?

26. Presence of WATER STOP

27. Plan View
Elevation View
Water Stop
Stop End
Couplers
D - Wall

28. Why is there a
rope hanging
in a Slurry
Storage Tank
?

29. Desander
float
marker
Excavated area
Slurry
Storage
tank
marker
float

30. Construction Market
Activity Cycle Model
Where WE stand ?

31. Peak
Zone
Mid Zone
Trough Zone
GROWTH DECLINE
Apartment
Industrial Building Offices, HotelCIVIL

32. agnes kamsiah
CK SIMON
KINSKI
SELVAKUM
AR
MOD
YOU
GEN
SHAWN
Thank
you