Construction of Pipe Roof and Support System in Proposed Outlet Drain Undercrossing North Buona Vista Road, Singapore T Sun, W& M Consultants, Singapore. wnmconsultants@gmail.com Land Transport Authority, Singapore , Public Utilities Board, Singapore, Or Kim Peow Contractors (Pte) Ltd, Singapore Abstract: The project in the paper included design and construction of a permanent 120m long RC box culvert and sewer diversion at North Buona Vista Road (NBV) Singapore. The pipe roof method was selected by the design and build contractor in fulfilment of the contract requirement for the 53 m box section undercrossing NBV Road. The adopted methodology comprised the installation by pipe jacking of numbers of interlocking steel pipes followed by traverse series of steel frames for safe mining of the tunnel. This served to maintain uninterrupted service conditions for the road, subways tunnel and other services. There are many challenges in the construction of pipe roof and mined tunnel. This paper deals with the consideration in the design and construction of such works. It also highlighted the problems encountered during the construction, subsequent solution adopted and protection of existing utilities as well as monitoring of settlement of the surrounding areas of the project.

1. 1305-TT –Myanmar –
Pipe Roof Construction in Singapore
Trisha Sun
Trenchless Technology Seminar
-Myanmar 5 to 7 June 2013
Pipe Roof Construction
in Singapore
Trisha Sun
Principal W& M Consutlants
wnmconsultants@gmail.com
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PIPE Roof
• Exepereince in Singapore –
Pipe roof costruction
•Sun , email: wnmconsultants@gmail.com
1Pipe Roof Singapore-Sun, OKP
Topics 1-2
•Introduction
•Pipe roof concept
•Design issues
•Machine and problems
•Problems of jacking
•Constrction process 2Pipe Roof Singapore- Sun
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Tpoics-2-2
• Jacking and receiving shafts
•Jacking ,mining
•Monitoring
•Risk
•Tender- design
•and documentations
Pipe Roof Singapore- Sun 3
Introduction
•Trenchless Methods for providing “No dig “
solution to installation of large culverts/pipes
•Alternatives:
•Pipe ramming / pipe roof by ramming/auger
machine
•Pipe roof by microtunnelling
•Pipe pushing/box culvert direct jacking
•Open cut
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Various shapes
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Construction Sequence
1. Execution of sheet piles
2. Execution of the pipe arch microtunnelling
3. Mined excavation of tunnel with steel ribs with reinforced shotcrete & fibre glass elements
4. Casting of permanent concrete lining
Pipe Arch Tunnel – Concept
Site picture of project by Metropolitan Atlanta Rapid Transit Authority in USA
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pipe roof Plan view (1-2)
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Pipe roof -Plan view(2-2)
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Pipe roof
SG ,Pipe roof Tunnel
•Long section view
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• Design Issues
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Design Issues- 1
•Physical site constraints
Close to MRT CCL-central
circular Line
Close to Viaduct foundation E
west line ,Sewer line ,services
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Design Issues -2
Physical site constraints-mining below
joint bay cables
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Design Issues- 3
critical issues
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Design Issues -4-
geological profile
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Design 5-
during break out-soil treatment, steel
portal frame
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Design 6-
during break through at exit
-soil treatment( soft alluvial), steel portal
frame
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Design 7 -stage excavation
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Design 8 -Face Stability
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Design 9 -Design Model
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Adopted Solution 1-3
The pipe jacking method adopted
-jacking from one end (jacking Shaft)
to the other end(receiving shaft)
using steel pipes to form a horizontal
and vertical temporary structure (
around the proposed reinforced box
culvert.)
•
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Adopted Solution 2-3
The pipe roof (see below Sketch
)comprises rows of 780mm dia Steel pipes
(10 on top and bottom and 6 rows on each
sides to form the vertical wall.
Each row of the steel pipes -interlock
together using steel T- clutches prefabricated
together with the pipes.
IEM Conf Mar 2011- Pipe Roof Singapore-Sun, OKP -22
Adopted Solution 2-3
Each row of the pipe which is
approximately 54m is formed
by welding together 9 to 10 number (
6 m long ) of steel pipe using the full
butt penetration welds
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SKETCH – CONFIGURATION OF THE PIPE
ROOF -drilling sequence
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•Machine and
problems
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Machine 2-2 -Layout
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PIPE JAKCING PROCESS -
Problems- jacking
•Obstruction
•Alignment
•Clutch
•Soil information
•Settlement
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•Construction process
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Construction process 1-
Jacking shaft –typical
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Construction process 2
Construction of Jacking & Receiving Shaft
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Construction 7
Setting of Jacks
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Construction process 8
Steel pipes
Construction process 9
Sample clutch details
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Construction process 14
Pipe Jacking in Progress
33-
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Construction process 16
Ultrasonic Test to welded joint
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Construction process 19
TBM Through at Receiving Shaft
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Construction process 21
Completed Horizontal Row of Pipe
Roof
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Construction process 22
Completed pipe roof
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•Mining of Tunnel
India No Dig-Dec 9,2010 -
Pipe Roof , cheng
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Construction –Mining of tunnel 3 -
Installing portal frame at jacking shaft
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Construction –Mining of tunnel 4
Installing portal frame at jacking shaft
India No Dig-Dec 9,2010 -
Pipe Roof , cheng
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Construction –Mining of tunnel 6
install entrance frame before
mining
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Construction –Mining of tunnel 8A
EXCAVATON
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•Monitoring
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Monitoring 1-
Services –need for monitoring
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Monitoring 3 A
Sample-installations of
instrumentations
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Monitoring 3 B
Installations of instrumentations –Joint
Bay
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Instrumentation – Monitoring 4
INSTALL PRISM INSIDE THE STEEL PIPE –for
monitoring settlements
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Monitoring 5 A
MRT Line below project
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Monitoring 5B
MRT-FIXING PRISMS
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Monitoring 6
- Predictions
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Monitoring 7
Readings
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• Completion
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Completion
Final stage
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OKP cheng
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• Risk Assessment
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Risk Assessment
Risk factors (1)
•Risk from Soil information, services
•Settlement control and damages
•Insurance cover on adjacent structures
•Pre con survey
•Sharing of risks
•Design and build contract
•Allowance of claimIEM Conf Mar 2011- Pipe Roof
Singapore-Sun, OKP
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Risk Assessment
Risk factors (2)
•Client risks
•Contractors
•Stakeholders
•3rd party client ( Authorities)
•Selection- method, main contractor ,specialist ( soil
treatment , shaft, pipe jacking , structures )
•Selecting –machine & skilled operators
•Luck /planningIEM Conf Mar 2011- Pipe Roof Singapore-Sun, OKP 56
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Preparing for contract
•Contract documentation
•Design/drawings
•Specifications
•Bills /Lump sum/VO
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Thank you ,
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