ies bored tunnel for mrt system.pdf
TRANSCRIPT
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DESIGN AND CONSTRUCTION OFBORED TUNNELS FOR MRT SYSTEM
Wen Dazhi, BSc, MSc, PhD
PE, PE(Geo), AC(Geo), MIES, CEng, MICE, CPEng, MIEAust
Geotech & Tunnel Consult
Slide 2 Geotech & Tunnel ConsultIES 27 May 2015
Design and Construction of Bored Tunnelsfor MRT System
• Introduction
• General Arrangement
• Structural Design
• Durability
• Constrction
• Conclusion
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Slide 3 Geotech & Tunnel ConsultIES 27 May 2015
• Introduction
• General Arrangement
• Structural Design
• Durability• Construction
• Conclusion
Design and Construction of Bored Tunnelsfor MRT System
Slide 4 Geotech & Tunnel ConsultIES 27 May 2015
INTRODUCTION
• Phase I/II MRT - NSL and EWL opened progressively from
1987; NSL Extension opened in 2014
• Changi Extension opened in 2002
• North East Line opened in 2003
• Circle Line / CCL Extension – CCL3 opened in 2009, CCL 1/2
in 2010, CCL4/5 in 2011 and CCLe in 2012.
• Downtown Line 1,2 and 3 and Downtown Line Extension:DTL1 opened in 2013, DTL2 to be opened in 2016, DTL3 in
2017 and DTLe in 2024
• Thomson East Coast Line – to be opened in stages from 2019
to 2023
• Others – Woodland Extension, Boon Lay Extension, Jurong
East Modification Project, LRT, Dover Station and Canberra
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Slide 5 Geotech & Tunnel ConsultIES 27 May 2015
INTRODUCTIONExisting Network
NSL
BPLRT
EWL
CCL
NEL
PGLRT
SKLRT
Legend
– Interchange Stations
EWL – East West Line
NSL – North South Line
NEL – North East LineCCL – Circle Line
SKLRT – Sengkang Light Rapid Transit (LRT)PGLRT – Punggol LRT
BPLRT – Bukit Panjang LRT
Rail Length
May 2013 178 km
Slide 6 Geotech & Tunnel ConsultIES 27 May 2015
Tuas WestExt - 2016
Downtown Line
2 - 2016
North-South Line
Extension - 2014
Downtown Line 1 - 2013
Downtown Line
3 - 2017
Thomson Line –
2019/20/21
Eastern Region Line – around 2023
INTRODUCTIONNetwork by around 2020
Existing Rail Lines
Rail Length
May 2013 178 km
by 2020 280km
Legend
– Interchange Stations
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Slide 7 Geotech & Tunnel ConsultIES 27 May 2015
JurongRegion
Line
Downtown Line
Extension
Cross
Island Line North East Line
Extension
Circle Line Stage 6
In
Progress
Existing Rail LinesNew Rail Lines by 2020New Rail Lines by 2030
Rail Length
2013 178 km
By 2020 280 km
By 2030 360 km
Legend
INTRODUCTIONNetwork by 2030
Slide 8 Geotech & Tunnel ConsultIES 27 May 2015
• Introduction
• General Arrangement
• Structural Design
• Durability
• Construction
• Conclusion
Design and Construction of Bored Tunnelsfor MRT System
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Slide 9 Geotech & Tunnel ConsultIES 27 May 2015
• Elements in a completed ring: OrdinarySegments + Key + Top Segments next toKey
Width of
segmentsCircumferential
joint
Radial
joints
GENERAL ARRANGEMENT
Slide 10 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTPhase I/II Projects
• Internal diameter
min 5.2m with 100mm forconstruction tolerance
Adopted by D&BContractors: 5.23 to 5.4m
to provide more tolerance• Thickness: 225 - 250mm
• Width: 1.0m
• 5 or 6 Segments + Key
• No walkway
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Slide 11 Geotech & Tunnel ConsultIES 27 May 2015
• Internal diameter: 5.8m (5.4m
for CAL) with 100mm forconstruction tolerance
• Thickness: 250mm, exceptC708 (275mm)
• Width: 1.2 m, except C704 /C706 (1.5m) and CAL (1.4m)
• Radial joints: block except C705
/ CAL (convex to convex)
• 5 Segments + Key, except C705
(6 Segments + key)
• Taper rings
• Tunnel walkway in NELTypical Example
GENERAL ARRANGEMENTNEL/CAL Projects
Slide 12 Geotech & Tunnel ConsultIES 27 May 2015
• Internal diameter: 5.8m with walkway
• Thickness: 275mm, Width: 1.4m
• 5 segments (67.5o) + key (22.5o)
• 40mm taper for curve negotiation
• Radial Joints: convex to convex (2m radius)
with 2 bolts per segment• Circle Joints: block joint with 3 bolts per
segment & 1 bolt for the key segment
• Curved bolts of 24mm diameter in bolt holes of34 mm diameter
GENERAL ARRANGEMENTCCL 1 to 3
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Slide 13 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTCCL 1 to 3
Slide 14 Geotech & Tunnel ConsultIES 27 May 2015
• Tapered Ring
Sequence of Left Hand Taper and Right Hand Taper
Sequence of Universal Rings
GENERAL ARRANGEMENTCCL 1 to 3
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Slide 15 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTCCL 1 to 3
Slide 16 Geotech & Tunnel ConsultIES 27 May 2015
GasketGroove
GasketGroove
GENERAL ARRANGEMENTCCL 1 to 3
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Slide 17 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTCCL 1 to 3
Slide 18 Geotech & Tunnel ConsultIES 27 May 2015
703 704 705 706 708 710 CAL CCL1,2,3
Ringarrange-ment
5 + 1 5 + 1 5+1+1 5+1 5+1 5+1 5+1 5+1
Segmentangles
5 @ 67.5o
1 @ 22.5o
3 @ 72o
2 @ 62.6o
1 @ 18.8o
5 @ 60o
1 @ 45o
1 @ 15o
3 @ 72o
2 @ 65.11 @ 13.8o
3 @ 68.6o
2 @ 68.1o
1 @ 18 o
3 @ 72o
2 @ 64.5o
1 @ 15 o
5 @ 65.454o
1 @ 32.73 o
5 @ 67.5o
1 @ 22.5 o
Width ofring
1.2m 1.5m 1.2m 1.5m 1.2m 1.2m 1.4m 1.4m
Width of key1139mm -939mm
945mm -450mm
759mm -519mm
690mm -390mm
1113mm -708mm
909mm -609mm
1542mm -1202mm
1260mm -860mm
Total Taper 200mm 495mm 240mm 300mm 405mm 300mm 340mm 400mm
Taper of key 1: 12 1:6 1:10 1:10 1:6 1:8 1:8 1:7
Thickness 250 250 250 250 275 250 250 275
Taper 38 30 30 36 30 25 30 40
Type ofbolts
Curved Straight Curved Straight Curved Curved Curved Curved
Number ofbolts persegmentradial
3 in circle2 in radial1 in keycircle joint
2 in circle2 in radialnone in keycircle joint
4 in circle2 in radial1 in key circle
joint
2 in circle2 in radialnone in keycircle joint
4 in circle2 in radial1 in keycircle joint
2 in circle2 in radialnone in keycircle joint
Dowels forcircle2 in radial
3 in circle2 in radial1 in keycircle joint
Size of boltsM22 x433mm
M24 x370mm
M24 x476mm
M22 x340mm
M24 x476mm
M24 x430mm
M24 x465mm
M24 x530mm
GENERAL ARRANGEMENTSummary
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Slide 19 Geotech & Tunnel ConsultIES 27 May 2015
• Recent projects – similar general arrangement
• Bolts: curved or straight bolts
• Joints: block joints or convex to convex
GENERAL ARRANGEMENTRecent Projects
Slide 20 Geotech & Tunnel ConsultIES 27 May 2015
Interface in radialdirection
GENERAL ARRANGEMENTKey
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Slide 21 Geotech & Tunnel ConsultIES 27 May 2015
Interface parallel toeach other in verticaldirection
GENERAL ARRANGEMENTKey
Slide 22 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTKey
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Slide 23 Geotech & Tunnel ConsultIES 27 May 2015
Example of a Parallel Key
GENERAL ARRANGEMENTKey
Slide 24 Geotech & Tunnel ConsultIES 27 May 2015
GENERAL ARRANGEMENTKey
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Slide 25 Geotech & Tunnel ConsultIES 27 May 2015
• Introduction
• General Arrangement
• Structural Design
• Durability• Construction
• Conclusion
Design and Construction of Bored Tunnelsfor MRT System
Slide 26 Geotech & Tunnel ConsultIES 27 May 2015
• Loading on Segmental Lining
• Analysis Method
• Effect of Joints
• Load Combination
• RC Detailing – Links and Fire Resistance• Fire Testing
• Design of Radial Joints
• Temporary Loading
• Other Design Checks
STRUCTURAL DESIGN
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Slide 27 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNSTRUCTURAL DESIGNLoading on Segmental LiningLoading on Segmental Lining
• Full overburden to be considered, except for
fresh or slightly weathered rock
• Surcharge
• Water pressure – highest water table not necessarily the
governing water pressure
• Loads imposed by adjacent structures
• Effects of adjacent tunnels
• Effects due to future adjacent construction
• Internal loading – e.g. live load from trains
Slide 28 Geotech & Tunnel ConsultIES 27 May 2015
Other data suggest 40 to 70%, Mair (2006) 46th Rankine Lecture
STRUCTURAL DESIGNSTRUCTURAL DESIGNLoading on Segmental LiningLoading on Segmental Lining
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Slide 29 Geotech & Tunnel ConsultIES 27 May 2015
Hashimoto, T. et al (2008) Proceedings of Geotechnical Aspect of UndergroundConstruction in Soft Ground
STRUCTURAL DESIGNSTRUCTURAL DESIGNLoading on Segmental LiningLoading on Segmental Lining
Slide 30 Geotech & Tunnel ConsultIES 27 May 2015
• Hashimoto, et al 2008 showed that
In soft clay ground, the long term earth pressure at tunnel
crown = static pressure, σv +/- cohesion, c
Lining pressure is distributed more uniformly than
prediction over the ring
In stiff ground the magnitude and distribution of earth
pressure largely depends on the backfilling grouting
• Clough & Schmidt (1981) showed that in clay the
eventual total load without plastic zones around the
tunnel, pi
pi = σv – σv’sinφ’
STRUCTURAL DESIGNSTRUCTURAL DESIGNLoading on Segmental LiningLoading on Segmental Lining
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Slide 31 Geotech & Tunnel ConsultIES 27 May 2015
• Continuum Model by Muir Wood with
modification by Curtis
• Bedded beam model by Duddeck and Erdmann
• Finite element or finite difference models
STRUCTURAL DESIGNSTRUCTURAL DESIGNAnalysis MethodAnalysis Method
Slide 32 Geotech & Tunnel ConsultIES 27 May 2015
Soilpressure
Overburdenpressure
Stability of ring relieson pressures aroundthe circumference.
Circular tunnel
Deformed tunnel toellipse shape
STRUCTURAL DESIGNSTRUCTURAL DESIGNAnalysis MethodAnalysis Method
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Slide 33 Geotech & Tunnel ConsultIES 27 May 2015
M = -ro re (2Sn + St) cos2θ /6(hogging moment “+”)
N = -ro (Sn+2St)cos2θ /3 + pwre + No
(compression hoop trust “+”)
U = -rero
3(2Sn+S
t)con2θ /18EI + U
w+ U
u(increase in radius “+”)
At crown, θ = 0ο; at axis θ = 90
ο
Muir Wood, A. M. (1975) The circular tunnel in elastic ground, Geotechnique 25, No. 1, 115 – 127
Curtis, D. J. (1976) Discussion on the reference above. Geotechnique 26, No. 1, 231 - 237
STRUCTURAL DESIGNSTRUCTURAL DESIGNMuir Wood Modified by CurtisMuir Wood Modified by Curtis
Slide 34 Geotech & Tunnel ConsultIES 27 May 2015
Sn =(1-Q2)po /2[1+Q2(3-2 ν /3-4 ν)](if St<τ)
Sn = {3(3-4 ν)po /2 -[2Q2+(4-6 ν)]τ}/[4Q2+5-6 ν](if St>τ)
St = (1+2Q2)po /2[1+Q2(3-2 ν /3-4 ν)]
Q2 = Ecro3 /12EI(1+ ν)
τ = c’ + σ’ tanφ’
STRUCTURAL DESIGNSTRUCTURAL DESIGNMuir Wood Modified by CurtisMuir Wood Modified by Curtis
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Slide 35 Geotech & Tunnel ConsultIES 27 May 2015
No = σv'(1+k)re /[2+2Ecro /EA(1+ ν)]
Uw = -pwrero /EA
Uu = -Noro /EA
po = σv’ - σh'
STRUCTURAL DESIGNSTRUCTURAL DESIGNMuir Wood Modified by CurtisMuir Wood Modified by Curtis
Slide 36 Geotech & Tunnel ConsultIES 27 May 2015
Joints have no effect on lining stiffness if they areclose to or at points of contraflexure.
Joint
Joint
Joint
Joint
STRUCTURAL DESIGNSTRUCTURAL DESIGNEffect of JointsEffect of Joints
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Slide 37 Geotech & Tunnel ConsultIES 27 May 2015
Significant reduction in stiffness if joints are not at or close to points ofcontraflexure - The examples show there are effectively 8 joints in the lining.
Joint
Joint
Joint
Joint
STRUCTURAL DESIGNSTRUCTURAL DESIGNEffect of JointsEffect of Joints
Slide 38 Geotech & Tunnel ConsultIES 27 May 2015
If more than 4 joints, then the lining will always beless stiff than an un-jointed lining. Use formulafrom Muir Wood (1975):
Il = I j + (4/n) 2 I
Where: Il is moment of inertia of jointed lining
I j is the moment of inertia of the joint (approx. 0)
n is the number of joints (if >4)
I is the moment of inertia of the un-jointed lining
STRUCTURAL DESIGNSTRUCTURAL DESIGNEffect of JointsEffect of Joints
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Slide 39 Geotech & Tunnel ConsultIES 27 May 2015
• More joints mean more flexibility, whichmeans larger deflection, but less moment
• Linings are often designed to allow for joints to calculate maximum deflection(worst case), but no joints to calculate
maximum moment (also worst case). Thisis especially so when joints between ringsare staggered.
STRUCTURAL DESIGNEffect of Joints
Slide 40 Geotech & Tunnel ConsultIES 27 May 2015
Staggered Joints: No reduction of lining stiffness for moments due to ground loading
STRUCTURAL DESIGNEffect of Joints
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Slide 41 Geotech & Tunnel ConsultIES 27 May 2015
Full overburden pressure in combinationFull overburden pressure in combinationwith:with:•• Ground water table at the ground surface with noGround water table at the ground surface with no
surcharge.surcharge.
•• Ground water table at the ground surface withGround water table at the ground surface withsurcharge.surcharge.
•• Ground water table atGround water table at worst credible level belowworst credible level belowthe ground surface with no surcharge.the ground surface with no surcharge.
•• Ground water table atGround water table at worse credible levelworse credible level belowbelowthe ground surface withthe ground surface with surcharge.surcharge.
•• Other requirement by the clientOther requirement by the client
STRUCTURAL DESIGNLoad Combination
Slide 42 Geotech & Tunnel ConsultIES 27 May 2015
Load Cases Rigid Ring with Short Term E for Concrete
Ultimate Limit State Serviceabilit y Limit State
1 2 3 4 5 6 7 8
Load Factor = 1.4 and 1.6 √ √ √ √
Load Factor = 1.0 √ √ √ √
75kN/m2 Uniform Surcharge √ √ √ √
Water Table at Ground Surface √ √ √ √
Water Table Worse Credible Level Below
Ground Surface
√ √ √ √
Full Section Moment of Inertia √ √ √ √
Reduced Section Moment of Inertia √ √ √ √
Short Term Concrete Young's Modulus √ √ √ √ √ √ √ √
STRUCTURAL DESIGNLoad Combination
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Slide 43 Geotech & Tunnel ConsultIES 27 May 2015
• Main segment body: Design and detailingto SS CP65 as short columns
• Lining deemed to satisfy 4-hour fire ratingif detailed to SS CP65 or BS 8110
• Designs to be based on Eurocodes fromECL
STRUCTURAL DESIGNRC Detailing
Slide 44 Geotech & Tunnel ConsultIES 27 May 2015
• CP65 / BS8110 require links to be used forcontainment of compression reinforcement
Size: the larger of ¼ of largest bar diameterand 6 mm
Spacing: max 12 x size of smallest
compression bar Corner bar and each alternate bar to be
contained; no bar is to be further than 150mmfrom a restrained bar
• Necessary to have closely-spaced links intunnel segments?
STRUCTURAL DESIGNRC Detailing - Links
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Slide 45 Geotech & Tunnel ConsultIES 27 May 2015
• Failure mechanism of short columns: Cracking along the height of the column Concrete cover spalls and longitudinal bars
exposed. Concrete failure and local buckling of
longitudinal bars at the unsupported lengthbetween the lateral ties
STRUCTURAL DESIGNRC Detailing - Links
Slide 46 Geotech & Tunnel ConsultIES 27 May 2015
• Links are required to prevent spalling of the concrete cover or
local buckling of longitudinal bars to provide confinement that increases strength
and improves ductility
• Segments are concave elements ground at the extrados provides continuous
bracing to the concrete and the longitudinalbars
Closely spaced links not necessary forstrength and ductility reasons
STRUCTURAL DESIGNRC Detailing - Links
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Slide 47 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNRC Detailing - Links
• Links are still necessary to meet the fire rating Tunnel segments are cast using high strength
low permeability concrete When exposed to fire, these segments are
more likely to exhibit explosive spalling due tobuild-up of steam pressure inside the
segments
Slide 48 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNRC Detailing – Fire Resistance
Highcompressivestress
Tensile stress
Failure mechanism
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Slide 49 Geotech & Tunnel ConsultIES 27 May 2015
Spalling of the concrete segments in the Channel Tunnel fire
STRUCTURAL DESIGNRC Detailing – Fire Resistance
Slide 50 Geotech & Tunnel ConsultIES 27 May 2015
• Fire tests were carried out to investigate theenhancement in the fire resistance of concretespecimens with steel mesh
• Based on BS476 Standard Fire Curve upto 2hours
STRUCTURAL DESIGNFire Testing
0
200
400
600
800
1000
1200
0 20 40 60 80 100 120
Time (mins)
T e m p e r a t u r e
(
o C )
• Where mesh is used,the link spacing is300mm, double thespacing for the controlspecimen (150mm)
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Slide 51 Geotech & Tunnel ConsultIES 27 May 2015
4 T 1 0 L I N K S @
A P P R O X . 1 5 0 c / c
4 T 1 3 ( T & B )
6 T 1 6 ( T & B )
7 T 1 0 ‘ U ’ L I N K S
7 T 1 0 ‘ U ’ L I N K S
S E T T I N G O U T P O I N T
F O R L I F T I N G H O O K S
( C E N T E R M A R K )
3 2 5
3 2 5
I N T R A D O S
T 1 3 L I F T I N
G H O O K S
T 1 3 L I F T I N G H O O K S
7 T 1 0 ‘ U ’ L I N K S
7 T 1 0 ‘ U ’ L I N K S
4 T 1 0 L I N K S
3 2 5
3 2 5
R = 3 0
R = 3 0
1 5 0
1 5 0
P L A N V I E
W O
F S L A B 1
S E C T
I O N A - A
STRUCTURAL DESIGNFire Testing
Slide 52 Geotech & Tunnel ConsultIES 27 May 2015
4 T 1 0 L I N K S @
A P P R O X . 3 0 0 c / c
4 T 1 3 ( T & B )
6 T 1 6 ( T & B )
8 T 1 0 ‘ U ’ L I N K S
8 T 1 0 ‘ U ’ L I N K S
S E T T I N G O U T P O I N T
F O R L I F T I N G H O O K S
( C E N T E R M A R K )
3 2 5
3 2 5
I N T R A D O S
T 1 3 L I F T I N G H O O
K S
T 1 3 L I F T I N G H O O K S
8 T 1 0 ‘ U ’ L I N K S
8 T 1 0 ‘ U ’ L I N K S
4 T 1 0 L I N K S
3 2 5
3 2 5
R = 3 0
R = 3 0
1 5 0
1 5 0
P L A N V I E W O
F S L A B 2
S E C T I O N
B - B
5 0 x 5 0
x 3 m m S t e e l
M e s h
STRUCTURAL DESIGNFire Testing
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Slide 53 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNFire Testing
Slide 54 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNFire Testing
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Slide 55 Geotech & Tunnel ConsultIES 27 May 2015
Condition of slab at about 30 minutes after test started
STRUCTURAL DESIGNFire Testing
Slide 56 Geotech & Tunnel ConsultIES 27 May 2015
Condition of Segment at about 1 hour after test started
STRUCTURAL DESIGNFire Testing
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Slide 57 Geotech & Tunnel ConsultIES 27 May 2015
Slab1 : Control (150mm c/c link spacing)
Exposure of links after test
STRUCTURAL DESIGNFire Testing
Slide 58 Geotech & Tunnel ConsultIES 27 May 2015
Exposure of mesh after test
Slab 2: 300mm c/c link spacing & 50x50x3mm steel mesh
STRUCTURAL DESIGNFire Testing
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Slide 59 Geotech & Tunnel ConsultIES 27 May 2015
Segment 1 : Control (150mm c/c link spacing)
STRUCTURAL DESIGNFire Testing
Slide 60 Geotech & Tunnel ConsultIES 27 May 2015
Segment 2: 300mm c/c link spacing & 50 x 50 x 3mm steel mesh
Exposure of mesh after test
STRUCTURAL DESIGNFire Testing
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Slide 61 Geotech & Tunnel ConsultIES 27 May 2015
Observations during testing:• 10mins after tests started, traces of water
appeared & cracks developed on all sides of thespecimens
• Spalling accompanied by noise of explosioninitiated at about 15mins after commencement oftests and lasted for about 15mins, beyond which
no spalling occurs (no noise of explosion)• During spalling, water flowed at a more distinct rate
& cracks widened & propagated• After spalling, water continued to flow & steam was
observed until end of tests
STRUCTURAL DESIGNFire Testing
Slide 62 Geotech & Tunnel ConsultIES 27 May 2015
• The presence of wire mesh retained theconcrete on the underside of specimens
• Min spalling of concrete beyond the wiremesh
STRUCTURAL DESIGNFire Testing
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Slide 63 Geotech & Tunnel ConsultIES 27 May 2015
• Provision of links at inner face according tocode requirements – deemed to comply
• Use of anti-spalling mesh
• Fire board
• Use of polypropylene fibres
STRUCTURAL DESIGNFire Resistance
Slide 64 Geotech & Tunnel ConsultIES 27 May 2015
• Checking of bearing stress
• Checking of bursting stress
• Eccentricity due to rotation
• Eccentricity due to building tolerance
STRUCTURAL DESIGNDesign of Radial Joints
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Slide 65 Geotech & Tunnel ConsultIES 27 May 2015
Ref. A. Williams. Technical Report 552, Cement and ConcreteAssociation Publication
Radial
joints
STRUCTURAL DESIGNDesign of Radial Joints
Slide 66 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNDesign of Radial Joints
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Slide 67 Geotech & Tunnel ConsultIES 27 May 2015
• To check bearingstress: p < 105N/mm2 or 2 fcu
• To check splittingforce, similar to
prestressing endblock design
Ref: BE5/75: Highway andTraffic TechnicalMemorandum (Bridges)
STRUCTURAL DESIGNDesign of Radial Joints
Slide 68 Geotech & Tunnel ConsultIES 27 May 2015
• Joint rotation due todeflection of ring
• Joint eccentricity due tobuild tolerance
• Loading due to
compression of gaskets
STRUCTURAL DESIGNDesign of Radial Joints
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Slide 69 Geotech & Tunnel ConsultIES 27 May 2015
• Demoulding / Handling
• Stacking
• Grouting Pressure
• Shield Jacking Force
STRUCTURAL DESIGNTemporary Loading
Slide 70 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNTemporary Loading
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Slide 71 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNTemporary Loading
Slide 72 Geotech & Tunnel ConsultIES 27 May 2015
Activegrouting ports
Groutingpressures aroundtunnel lining
STRUCTURAL DESIGNTemporary Loading
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Slide 73 Geotech & Tunnel ConsultIES 27 May 2015 73
STRUCTURAL DESIGNTemporary Loading
Slide 74 Geotech & Tunnel ConsultIES 27 May 2015
• Similarly for radial joints, bearing stress and bursting
force due to TBM jacks need to be checked
• Jacking force typically in the range of 20 to 30MN
• Tunnelling in full face rock does not necessarily
mean higher jacking force
• Total jacking capacity can be as high as 45 MN,
depending on the machine design; and should be
checked in the design
STRUCTURAL DESIGNTemporary Loading
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Slide 75 Geotech & Tunnel ConsultIES 27 May 2015 75
STRUCTURAL DESIGNStrengthened Edge Beam at Circle Joint
Slide 76 Geotech & Tunnel ConsultIES 27 May 2015
STRUCTURAL DESIGNStrengthened Edge Beam at Circle Joint
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Slide 77 Geotech & Tunnel ConsultIES 27 May 2015
C104: Newton – Novena- Toa PayohC108: Tanjong Pagar – Raffles Place5 Segments + Key, Thickness: 250mm
C106: City Hall – Dhoby Ghaut – Somerset6 Segments + Key, Thickness: 235mm
STRUCTURAL DESIGNStrengthened Edge Beam at Circle Joint
Slide 78 Geotech & Tunnel ConsultIES 27 May 2015
N1 =
fs*π*D
v1
h1
• Divide the pile intosegments of 1m or othersuitable length till tunnellevel
• Based on the ultimatefriction force on the pile /soil, estimate the stress atthe crown level of thetunnel due to this force
• Superimpose all thestresses due to the forcesfrom all segments asadditional design pressurefor the tunnel
STRUCTURAL DESIGNOther Design Checks - Loading due to Adjacent Piles
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Slide 79 Geotech & Tunnel ConsultIES 27 May 2015
Ground movement, uo fora volume loss of Vs
ro
uaub
rb
ra
uo = ro{{{{1-√√√√(1-Vs)}}}}ua = uoro /ra
δ = (ua-ub) /2
ub = uoro /rb
M = (3EIδ)/ r2
STRUCTURAL DESIGNTunnels in Close Proximity
Wen, D, Poh, J & Y.H. Ng (2004) Design consideration for bored tunnels in close proximity. Proceedings of the 30 th ITA-AITES World
Tunnel Congress, Singapore 22-27 May 2004.
Slide 80 Geotech & Tunnel ConsultIES 27 May 2015
Ref: LTA Design Criteria
STRUCTURAL DESIGNOther Design Checks - Stability Check
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Slide 81 Geotech & Tunnel ConsultIES 27 May 2015
• Introduction
• General Arrangement
• Structural Design
• Durability• Constrction
• Conclusion
Design and Construction of Bored Tunnelsfor MRT System
Slide 82 Geotech & Tunnel ConsultIES 27 May 2015
DURABILITYDURABILITY
• Durability Objective
• Mechanism of Corrosion and Examples
• Design Measures
• Waterproofing
• Steel Fibre Reinforced Concrete Segment
• Maintenance – Grouting to Seal Seepage
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Slide 83 Geotech & Tunnel ConsultIES 27 May 2015
DURABILITY OBJECTIVE
• The durability objective of majorinfrastructures is typically to achieve aservice life, with appropriate maintenance,of 100 or 120 years for all permanentstructures.
• Measures need to be taken in design,construction and operation maintenanceto achieve the objective.
Slide 84 Geotech & Tunnel ConsultIES 27 May 2015
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
Mechanism of Corrosion in Tunnel Segments
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Slide 85 Geotech & Tunnel ConsultIES 27 May 2015
Concrete Spalling due to Re-Bar Corrosion
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
Slide 86 Geotech & Tunnel ConsultIES 27 May 2015
Salts Deposited on Lining Surface
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
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Slide 87 Geotech & Tunnel ConsultIES 27 May 2015
Concrete Spalling and Repair
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
Slide 88 Geotech & Tunnel ConsultIES 27 May 2015
Concrete Repair by Grouting
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
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Slide 89 Geotech & Tunnel ConsultIES 27 May 2015
• Seepage through joints
• Problem areas – Segment joints;interface with C&C
tunnels and withcrosspassages
DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples
Slide 90 Geotech & Tunnel ConsultIES 27 May 2015
• Design measures:
Concrete with low permeability and low chloridediffusion: Cement with slag or pfa; use of silicafume in the mix; good curing
Protective coating to extrados of segment
Detailing – adequate cover to re-bars, includingdrilling positions / bolt pockets
Electrically continuous steel cages as provisionfor future cathodic protection, if required.
Provision of reinforcement mesh in track bed tocollect stray current
DURABILITYDURABILITYDesign MeasuresDesign Measures
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Slide 91 Geotech & Tunnel ConsultIES 27 May 2015
• Concrete grade: 60 N/mm2 with silica
fume.
• Concrete chloride diffusion rate to be no
more than 1000 coulomb.
• Concrete additives can be used to achieve
the specified performance.
• Cover 40 mm
• Epoxy coating of external surface ofsegments
DURABILITYDURABILITYDesign MeasuresDesign Measures
Slide 92 Geotech & Tunnel ConsultIES 27 May 2015
• Simple rectangular-section butylrubber
• Composite neoprene and buytl rubberstrips
• Neoprene gaskets
• Hydrophilic strips
WATERPROOFINGWATERPROOFINGPhase I/IIPhase I/II
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Slide 93 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGPhase I/IIPhase I/II
• Butyl rubber – plastic andonce compressed, unable torecover original shape
• Composite neoprene andbutyl – effectiveness reducedif packing is required; and canbe damaged due tomisalignment around key
segments• Neoprene gaskets – corners
proved to be problematic
• Hydrophilic gaskets – performed the best among allthe materials
Slide 94 Geotech & Tunnel ConsultIES 27 May 2015
• Contract specification required the use of bothEPDM gaskets and hydrophilic sealing strips
WATERPROOFINGWATERPROOFINGNEL ProjectsNEL Projects
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Slide 95 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGNEL ProjectsNEL Projects
Slide 96 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGNEL ProjectsNEL Projects
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Slide 97 Geotech & Tunnel ConsultIES 27 May 2015
Indicative gasket detailson design drawing
Proposed and acceptedgasket
WATERPROOFINGWATERPROOFINGCCL ProjectsCCL Projects
Slide 98 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGCCL ProjectsCCL Projects
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Slide 99 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGCCL ProjectsCCL Projects
Slide 100 Geotech & Tunnel ConsultIES 27 May 2015
16.5mm
EPDM compressive forceHydrophilic
strip
compressive
force
Hydrophilic
strip
pressure
seal EPDM pressure seal
10 mm
WATERPROOFINGWATERPROOFINGCCL ProjectsCCL Projects
3 . 5 m m
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Slide 101 Geotech & Tunnel ConsultIES 27 May 2015
• Testing should be specified by designer
• Typically, test pressure to be resisted istwice maximum current water pressure – to allow for aging of gaskets
• Test step (offset of gaskets) usually
higher than maximum specified step inconstruction tolerances
WATERPROOFINGWATERPROOFINGGasket TestingGasket Testing
Slide 102 Geotech & Tunnel ConsultIES 27 May 2015
Gasket Durability
WATERPROOFINGWATERPROOFINGGasket TestingGasket Testing
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Slide 103 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGGasket TestingGasket Testing
Slide 104 Geotech & Tunnel ConsultIES 27 May 2015
WATERPROOFINGWATERPROOFINGGasket TestingGasket Testing
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Slide 105 Geotech & Tunnel ConsultIES 27 May 2015
Testing pressure to be 2 times the maximum pressure
WATERPROOFINGWATERPROOFINGGasket TestingGasket Testing
Slide 106 Geotech & Tunnel ConsultIES 27 May 2015
• Elimination of risk of steel bar corrosion• Elimination of concrete spalling risk• More durable segment with min
maintenance effort.
STEEL FIBRE REINFORCED CONCRETESTEEL FIBRE REINFORCED CONCRETE(SFRC) SEGMENTS(SFRC) SEGMENTS
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Slide 107 Geotech & Tunnel ConsultIES 27 May 2015
Steel fibres - Double end hooked Steel fibres Crimped or Straight
STEEL FIBRE REINFORCED CONCRETESTEEL FIBRE REINFORCED CONCRETE(SFRC) SEGMENTS(SFRC) SEGMENTS
Slide 108 Geotech & Tunnel ConsultIES 27 May 2015
SFRC SEGMENTSClient’s Perspective
•• Provide best durability availableProvide best durability available
•• Minimize handling damageMinimize handling damage
• Achieve fire resistance with polypropylene
fibres
•• Save cost (10%Save cost (10% -- 20%)20%)
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Slide 109 Geotech & Tunnel ConsultIES 27 May 2015
• Design guides available, but no design code
• Design supported by prototype testing
• Quality testing – beam tests, washing-out tests
SFRC SEGMENTSDesigner’s Perspective
Slide 110 Geotech & Tunnel ConsultIES 27 May 2015
• Ease of casting
• Less damage
• Ease of repair
SFRC SEGMENTSContractor’s Perspective
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Slide 111 Geotech & Tunnel ConsultIES 27 May 2015
• £30 / m3
savings
compared with re-bar
segments
• 90% segments using
SFRC; 10% using steel
bars for shaft
SFRC SEGMENTSUK’s Experience
Slide 112 Geotech & Tunnel ConsultIES 27 May 2015
• Enhanced durability
• Enhanced fire resistance
with polypropylene fibres
• Design based on
established guidelines with
testing
• Easy casting – no steel bar
handling and minimum
automation required
• Smaller segments without
steel bars – easy installation
and lower risk of damage
SFRC SEGMENTSUK’s Experience
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Slide 113 Geotech & Tunnel ConsultIES 27 May 2015
SFRC SEGMENTSTesting Programme with NUS/NTU
Slide 114 Geotech & Tunnel ConsultIES 27 May 2015
• SFRC segments for DTL3: 2350mof bored tunnel for C933
Upper track in Kallang;
Lower track in OA, short
length in Kallang ~650m
Sungei Road
Station
Both tracks in Old
Alluvium ~1350m
Both tracks
in Kallang
~350m
Kalang Bahru
Station
Jalan Besar
Station
Cross Over
at Jln Besar
Tunnel Escape Shaft
Tunnel Escape
Shaft
SFRC SEGMENTSImplementation in DTL3
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Slide 115 Geotech & Tunnel ConsultIES 27 May 2015
• 5.8m I.D., 275mm thk.
• 1.4m wide, +/-25mm
taper
• 5 ordinary segments,
2 counter-keys and 1key segment
• Increase no. of
segments to minimizepotential damage
during handling
SFRC SEGMENTSImplementation in DTL3
Slide 116 Geotech & Tunnel ConsultIES 27 May 2015
SFRC SEGMENTSImplementation in DTL3
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Slide 117 Geotech & Tunnel ConsultIES 27 May 2015
• Design based on un-reinforced secion ofsegment
• Full scale tests of segments and joints carriedout to verify the structural performance
• RILEM TC 162-TDF used as a reference
• Quality control during construction
SFRC SEGMENTSImplementation in DTL3
Slide 118 Geotech & Tunnel ConsultIES 27 May 2015
MAINTENANCE
Injection Materials
PropertiesWater-reactive
Polyurethane Foam
Flexible
Polyurethane Epoxy
Cementitious
Grout
Strength X X √√√√√√√√ √√√√
Elasticity/
Flexibility X √√√√√√√√ X X
Moisture
Compatibility √√√√√√√√ √√√√√√√√ X √√√√
X = Not relevant √√√√ = Good √√√√√√√√ = Excellent
• Grout injection often used for tunnel repair
• Material selection critical
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Slide 119 Geotech & Tunnel ConsultIES 27 May 2015
PU = Polyurethane CG = Cementitious Grout
Crack ConditionInjection
Aim Dry Wet / Water Bearing
without Pressure
Water Bearing with
Pressure
Closing /
Sealing
Epoxy
PU
CG
PU
CGWater-reactive PU
Rigid
Connection
Epoxy
CGCG -
Flexible
ConnectionFlexible PU Flexible PU
Water-reactive PUfollowed by flexible PU
MAINTENANCE
Slide 120 Geotech & Tunnel ConsultIES 27 May 2015
Water Reactive Polyurethane Foam – Open Cell Structure
MAINTENANCE
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Slide 121 Geotech & Tunnel ConsultIES 27 May 2015
Flexible PU Grout or Acrylic Gel
MAINTENANCE
Slide 122 Geotech & Tunnel ConsultIES 27 May 2015
• For dry crack repair at casting yard, epoxy
resin should be used. Cracks should be dry
and dust free.
• For wet / damp crack repair after installation,flexible, low viscosity polyurethane grout
should be used.
MAINTENANCE
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Slide 123 Geotech & Tunnel ConsultIES 27 May 2015
• Where water is seeping through cracks
under pressure, a two-staged grouting
procedure should be adopted. The first
stage should use water-reactive
polyurethane foam to stop the seepage,
followed by the second stage with flexible,
two component, low viscosity polyurethane
grout.
MAINTENANCE
Slide 124 Geotech & Tunnel ConsultIES 27 May 2015
• Introduction
• General Arrangement
• Structural Design
• Durability
• Construction
• Conclusion
Design and Construction of Bored Tunnelsfor MRT System
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Slide 125 Geotech & Tunnel ConsultIES 27 May 2015
CONSTRUCTIONCONSTRUCTION
• Variable ground condition
• TBM Types used in MRT Tunnel Constructions
• Challenges in Tunnelling Works
Slide 126 Geotech & Tunnel ConsultIES 27 May 2015
Newton
Outram Park
Serangoon
Dhoby Ghaut
Kallang Formation
Old Alluvium
Jurong Formation
Gombak Norite
Bukit Timah
Granite
Scale :
Boon Lay
Reclamation
Punggol
Geological Map
-2 0 1 2 4 (Km)
Mandai
CONSTRUCTIONVariable Ground Condition
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Slide 127 Geotech & Tunnel ConsultIES 27 May 2015
Bukit Timah Granite
(Igneous Rock)
Jurong Formation
(Sedimentary Rock)
GI/GII/GIII
GIV
GV
M
F / E
S4
FCBBOA
In-filled Valleys Deep weathering of granite
CONSTRUCTIONVariable Ground Condition
Slide 128 Geotech & Tunnel ConsultIES 27 May 2015
• Phase 1/2 MRT Construction in 1980s: GreatheadShield with hydraulic backhoe excavator or roadheaders
/ 1 EPBM / 1 TBM
• Compressed air used extensively
• Grouting done through the segments
Greathead Shield EPBM (C301)
CONSTRUCTIONTBM Types
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Slide 129 Geotech & Tunnel ConsultIES 27 May 2015
• NEL: 14 EPBMs (2 Dual Modes), 2 Open Face TBMs
• Automatic tail void grouting
• Face pressure and stability by controlling the extrusion ofthe spoil through the screw conveyor and the advancementof the machine
EPBM(C705)
EPBM(C706)
EPBM(C710)
CONSTRUCTIONTBM Types
Slide 130 Geotech & Tunnel ConsultIES 27 May 2015
Extrados ofExtrados of
segmentsegment
Tail voidTail void
groutgrout
Marine clayMarine clay
Automatic Tail Void Grouting
CONSTRUCTIONTBM Types
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Slide 131 Geotech & Tunnel ConsultIES 27 May 2015
Plastic Nature of Spoils to Maintain Face Pressure in EPBM
CONSTRUCTIONTBM Types
Slide 132 Geotech & Tunnel ConsultIES 27 May 2015
No Plug, Material Saturated and Flowing: EPBM in mixed tunnel face
CONSTRUCTIONTBM Types
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Slide 133 Geotech & Tunnel ConsultIES 27 May 2015
Over-excavation in
Mixed Tunnel Face byEPBM
CONSTRUCTIONTBM Types
Slide 134 Geotech & Tunnel ConsultIES 27 May 2015
• Circle Line: 19 EPBM, 8 Slurry TBMs
• Scanners / belt weighing experimented andadopted subsequently
• Slurry TBM used for sections with granite
Slurry TBM(C854)
Slurry TreatmentPlant
EPBM(C823)
CONSTRUCTIONTBM Types
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Slide 135 Geotech & Tunnel ConsultIES 27 May 2015
Slurry TBM: Face pressure ismaintained by controlling the volumedifference of the bentonite suspensionsupplied to the chamber and thesuspension combined with excavatedmaterial removed from it
CONSTRUCTIONTBM Types
Slide 136 Geotech & Tunnel ConsultIES 27 May 2015
• DTL1: 3 EPBMs
• DTL2: 10 EPBMs + 9 Slurry TBMs
• DTL3: 19 EPBMs
EPBM(C902)
Slurry TBM(C915)
EPBM(C917)
CONSTRUCTIONTBM Types
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Slide 137 Geotech & Tunnel ConsultIES 27 May 2015
• For the Thomson Line, there will be 38 TBMs, ofwhich 26 are expected to be slurry machines and12 EPBMs. 20 new shields will also used forsome tunnel drives
• For ECL, most likely EPBM would be selected
CONSTRUCTIONTBM Types
Slide 138 Geotech & Tunnel ConsultIES 27 May 2015
• More efficient and accurate methods are
required to determine
– rock levels (interface of soil and rock)
– depth of existing piles for buildings close to or above
tunnel alignment
to minimize construction risk in urban areas
• Reliable technology for investigation and
construction under or around the Natural
Reserve where strict controls will be in place
CONSTRUCTIONChallenges for Tunnelling Works
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Slide 139 Geotech & Tunnel ConsultIES 27 May 2015
Tunnel
Alignment
CONSTRUCTIONChallenges for Tunnelling Works
Slide 140 Geotech & Tunnel ConsultIES 27 May 2015
• To have more boreholes – practical
problems
• To carry out geophysical survey
CONSTRUCTIONChallenges for Tunnelling Works
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Slide 141 Geotech & Tunnel ConsultIES 27 May 2015
141
• Commonly used methods
Electrical resistivity
Seismic refraction
Seismic reflection
Surface wave method
Geo-tomography
CONSTRUCTIONChallenges for Tunnelling Works
Slide 142 Geotech & Tunnel ConsultIES 27 May 2015
Interpreted Profile of Surface Wave Velocity
Interpreted Rock Profile
CONSTRUCTIONChallenges for Tunnelling Works
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Slide 143 Geotech & Tunnel ConsultIES 27 May 2015
Soil / Rock Interface – Accuracy ?
ABH1
8
ABH2
1
ABH2
6 FILL
F1
GV &
GVI
GIII &
GII
FILLF1
GV &
GVI
GII & GIGIII, GII &
G1
FILLF2EF1F2F1
GVI &
GV
CONSTRUCTIONChallenges for Tunnelling Works
Slide 144 Geotech & Tunnel ConsultIES 27 May 2015
Detection of PileDepth – Accuracy?
Estimated Pile Penetration:21~22m (or) 26~27 m
CONSTRUCTIONChallenges for Tunnelling Works
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Slide 145 Geotech & Tunnel ConsultIES 27 May 2015
• Detection ofPile Depth –
Accuracy?• Ground
PenetrationRadar Survey
CONSTRUCTIONChallenges for Tunnelling Works
Slide 146 Geotech & Tunnel ConsultIES 27 May 2015
CONCLUSION
• Major land transport facilities to bebuilt in Singapore
• Design and construction technologyhave been advanced over the years
• New methods and technologiesrequired to address challenges
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Thank You