ies bored tunnel for mrt system.pdf

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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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• Introduction



• Durability• Construction

• Conclusion



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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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


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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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


• Introduction



• Durability

• Construction

• Conclusion




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• Elements in a completed ring: OrdinarySegments + Key + Top Segments next toKey

Width of

segmentsCircumferential

joint

Radial

joints

GENERAL ARRANGEMENT


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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• 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


• 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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• Tapered Ring

Sequence of Left Hand Taper and Right Hand Taper

Sequence of Universal Rings




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GasketGroove

GasketGroove




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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




Dowels forcircle2 in radial


Size of boltsM22 x433mm

M24 x370mm

M24 x476mm

M22 x340mm

M24 x476mm

M24 x430mm

M24 x465mm

M24 x530mm

GENERAL ARRANGEMENTSummary



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• Recent projects – similar general arrangement

• Bolts: curved or straight bolts

• Joints: block joints or convex to convex

GENERAL ARRANGEMENTRecent Projects


Interface in radialdirection

GENERAL ARRANGEMENTKey



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Interface parallel toeach other in verticaldirection






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Example of a Parallel Key






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• Introduction



• Durability• Construction

• Conclusion



• 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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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


Other data suggest 40 to 70%, Mair (2006) 46th Rankine Lecture




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Hashimoto, T. et al (2008) Proceedings of Geotechnical Aspect of UndergroundConstruction in Soft Ground



• 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’




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• 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


Soilpressure

Overburdenpressure

Stability of ring relieson pressures aroundthe circumference.

Circular tunnel

Deformed tunnel toellipse shape

STRUCTURAL DESIGNSTRUCTURAL DESIGNAnalysis MethodAnalysis Method



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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


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’




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No = σv'(1+k)re /[2+2Ecro /EA(1+ ν)]

Uw = -pwrero /EA

Uu = -Noro /EA

po = σv’ - σh'



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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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



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




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• 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


Staggered Joints: No reduction of lining stiffness for moments due to ground loading

STRUCTURAL DESIGNEffect of Joints



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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


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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• 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


• 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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• 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



• 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




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• 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


STRUCTURAL DESIGNRC Detailing – Fire Resistance

Highcompressivestress

Tensile stress

Failure mechanism



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Spalling of the concrete segments in the Channel Tunnel fire

STRUCTURAL DESIGNRC Detailing – Fire Resistance


• 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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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



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




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Condition of slab at about 30 minutes after test started



Condition of Segment at about 1 hour after test started




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Slab1 : Control (150mm c/c link spacing)

Exposure of links after test



Exposure of mesh after test

Slab 2: 300mm c/c link spacing & 50x50x3mm steel mesh




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Segment 1 : Control (150mm c/c link spacing)



Segment 2: 300mm c/c link spacing & 50 x 50 x 3mm steel mesh

Exposure of mesh after test




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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



• The presence of wire mesh retained theconcrete on the underside of specimens

• Min spalling of concrete beyond the wiremesh




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• 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


• 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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Ref. A. Williams. Technical Report 552, Cement and ConcreteAssociation Publication

Radial

joints






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• To check bearingstress: p < 105N/mm2 or 2 fcu

• To check splittingforce, similar to

prestressing endblock design

Ref: BE5/75: Highway andTraffic TechnicalMemorandum (Bridges)



• Joint rotation due todeflection of ring

• Joint eccentricity due tobuild tolerance

• Loading due to

compression of gaskets




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• Demoulding / Handling

• Stacking

• Grouting Pressure

• Shield Jacking Force

STRUCTURAL DESIGNTemporary Loading





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Activegrouting ports

Groutingpressures aroundtunnel lining




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Slide 73 Geotech & Tunnel ConsultIES 27 May 2015 73



• 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




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Slide 75 Geotech & Tunnel ConsultIES 27 May 2015 75

STRUCTURAL DESIGNStrengthened Edge Beam at Circle Joint





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C104: Newton – Novena- Toa PayohC108: Tanjong Pagar – Raffles Place5 Segments + Key, Thickness: 250mm

C106: City Hall – Dhoby Ghaut – Somerset6 Segments + Key, Thickness: 235mm



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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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.


Ref: LTA Design Criteria

STRUCTURAL DESIGNOther Design Checks - Stability Check



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• Introduction



• Durability• Constrction

• Conclusion



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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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.


DURABILITYDURABILITYMechanism of Corrosion and ExamplesMechanism of Corrosion and Examples

Mechanism of Corrosion in Tunnel Segments



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Concrete Spalling due to Re-Bar Corrosion



Salts Deposited on Lining Surface




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Concrete Spalling and Repair



Concrete Repair by Grouting




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• Seepage through joints

• Problem areas – Segment joints;interface with C&C

tunnels and withcrosspassages



• 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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• 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


• Simple rectangular-section butylrubber

• Composite neoprene and buytl rubberstrips

• Neoprene gaskets

• Hydrophilic strips

WATERPROOFINGWATERPROOFINGPhase I/IIPhase I/II



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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


• Contract specification required the use of bothEPDM gaskets and hydrophilic sealing strips

WATERPROOFINGWATERPROOFINGNEL ProjectsNEL Projects



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Indicative gasket detailson design drawing

Proposed and acceptedgasket

WATERPROOFINGWATERPROOFINGCCL ProjectsCCL Projects





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16.5mm

EPDM compressive forceHydrophilic

strip

compressive

force

Hydrophilic

strip

pressure

seal EPDM pressure seal

10 mm


3 . 5 m m



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• 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


Gasket Durability




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Testing pressure to be 2 times the maximum pressure



• 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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Steel fibres - Double end hooked Steel fibres Crimped or Straight

STEEL FIBRE REINFORCED CONCRETESTEEL FIBRE REINFORCED CONCRETE(SFRC) SEGMENTS(SFRC) SEGMENTS


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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• Design guides available, but no design code

• Design supported by prototype testing

• Quality testing – beam tests, washing-out tests

SFRC SEGMENTSDesigner’s Perspective


• Ease of casting

• Less damage

• Ease of repair

SFRC SEGMENTSContractor’s Perspective



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• £30 / m3

savings

compared with re-bar

segments

• 90% segments using

SFRC; 10% using steel

bars for shaft

SFRC SEGMENTSUK’s Experience


• 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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SFRC SEGMENTSTesting Programme with NUS/NTU


• 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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• 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






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• 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



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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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


Water Reactive Polyurethane Foam – Open Cell Structure

MAINTENANCE



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Flexible PU Grout or Acrylic Gel

MAINTENANCE


• 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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• 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


• Introduction



• Durability

• Construction

• Conclusion




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CONSTRUCTIONCONSTRUCTION

• Variable ground condition

• TBM Types used in MRT Tunnel Constructions

• Challenges in Tunnelling Works


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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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


• 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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• 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)



Extrados ofExtrados of

segmentsegment

Tail voidTail void

groutgrout

Marine clayMarine clay

Automatic Tail Void Grouting




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Plastic Nature of Spoils to Maintain Face Pressure in EPBM



No Plug, Material Saturated and Flowing: EPBM in mixed tunnel face




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Over-excavation in

Mixed Tunnel Face byEPBM



• 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)




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Slurry TBM: Face pressure ismaintained by controlling the volumedifference of the bentonite suspensionsupplied to the chamber and thesuspension combined with excavatedmaterial removed from it



• DTL1: 3 EPBMs

• DTL2: 10 EPBMs + 9 Slurry TBMs

• DTL3: 19 EPBMs

EPBM(C902)

Slurry TBM(C915)

EPBM(C917)




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• 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



• 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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Tunnel

Alignment



• To have more boreholes – practical

problems

• To carry out geophysical survey




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141

• Commonly used methods

Electrical resistivity

Seismic refraction

Seismic reflection

Surface wave method

Geo-tomography



Interpreted Profile of Surface Wave Velocity

Interpreted Rock Profile




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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



Detection of PileDepth – Accuracy?

Estimated Pile Penetration:21~22m (or) 26~27 m




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• Detection ofPile Depth –

Accuracy?• Ground

PenetrationRadar Survey



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



3/6/2015

Thank You

ies bored tunnel for mrt system.pdf

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