tunnel_lining_design.pdf

7/27/2019 Tunnel_Lining_Design.pdf

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AGS/IMM Technical Meeting 2002 onAGS/IMM Technical Meeting 2002 on

Underground Excavation in Urban EnvironmentUnderground Excavation in Urban Environment

Principles of Tunnel Lining DesignPrinciples of Tunnel Lining Design

Dr. Morgan W. W. YangDr. Morgan W. W. Yang

MaunsellMaunsell GeotechnicalGeotechnical Services Ltd.Services Ltd.


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Basics

GROUND

equilibrium compatibility

SUPPORTS

InteractionInteraction


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Tunneling is An ArtGROUND

PLANNING DESIGN CONSTRUCTION

TUNNELING


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Interaction Among Planning Studiesand Design Process

P

D

S

PLANNINGPLANNING

FINANCIAL

PROJECTLOGISTICS

LAYOUT

OPERATION

STUDIESSTUDIES

GROUND

DEMANDACCESS

AD HOC

DESIGNDESIGN

PERMANENT SUPPORTS

TEMPORARY SUPPORTS

METHODS OF CONSTRUCTION

MEANS OF CONSTRUCTION


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Tunneling ProcedureTunneling ProcedureSite investigation

Line and orientation of the tunnel

Ground characteristics:Primary stress, strength, water

Fissures, anisotropy, etc

Excavation method

Structural method

Statical system analysis

Design criteria

Yes No

Driving the tunnel

In situ monitoring:

deformations stop?

Yes No

By pass

Geology

Geotechnical

investigations

Experience,

estimation

Mechanical model

Safety concept, failure hypothese

Risk assessment

Field

measurements

For actual state only,Unknown safety margin

Safe

Concept aspects

After H. Duddeck, Guidelines for the design of tunnels


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Options for TunnelingA. M. Muir Wood (2000), Tunnelling: Management by design

-----------------------------------------------------------------------------------------------------Ground type Excavation Support

-----------------------------------------------------------------------------------------------------

Strong rock Drill-&-blast or TBM Nil or rockbolts +

Weak rock TBM or roadheader Rockbolts, shorcrete etc.

Squeezing rock Roadheader Varity of means of support

depending on conditions

OC clay Open-face shielded TBM Segmental lining or

roadheader shotcrete etc.

Weak clay, EPB closed-face machine Segmental lining

silty clay

Sands, gravels Closed-face slurry machine Segmental lining

Stro

nger

sup

port

Stro

nger

sup

portS

tron

ger

ground

Stron

ger

ground

After A. M. Muir Wood (2000), Tunnelling: Management by design


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Development of Design Model-----------------------------------------------------------------------------------------------------1. Research model Explanation of phenomena

Study actual loads and materials

Analysis of parametersEstablishing correspondence between

theory and experiment

2. Technical model Developed for practical design

Selection of dominant factors

Idealization of loading, physical

characteristics and safety criteriaNo attempt precisely to model reality

Lack of precise correspondence between

theory and full scale test accepted



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Types of Ground Model-----------------------------------------------------------------------------------------------------1. Geological structure Fundamentally a descriptive model which establishes

limits of variability of salient factors

2. As (1) + simple RQD or similar simplified representation of rockqualitative factors quality or selected relevant parameters for soil

3. As (2) + monitoring Simplest basis for informal support

4. As (3) + quantitative Adequate for analysis based on continuum-

discontinuum or on elasto-plastic models of

increasing complexity

-----------------------------------------------------------------------------------------------------



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Fundamental of TunnelingFundamental of Tunneling

Stress States of Ground

Initial TertiarySecondary

Convergence-Confinement

NMT TBM

NATM


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Characteristics of GroundCharacteristics of Ground


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Elastic Solution of Initial StressesElastic Solution of Initial Stresses

y

z

x

x

z

y

x=y

x

y

y

Ground surface

0=

+

yx

xyx

rxy

xyx =+

0)(2 =+ yx

Governing Equations SolutionsGoverning Equations Solutions

ryy =

yxz

==1

y


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Elastic Solution of Secondary StressesElastic Solution of Secondary Stresses

KirschKirschs solutionss solutions

[ ])2cos()1)(341()1)(1(2

1 422 +++= yr

[ ])2cos()1)(31()1)(1(2

1 42 +++=

y

[ ])2sin()1)(321(2

1 42 +=

yr

x=ya

r

r

y

r

a

a

r=


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Radial Stress DistributionRadial Stress Distribution


1 2 3 4 5 6 7 8 9 10

r/a

0.0

0.5

1.0

1.5

r

/y

Radial stress

=1.5, =90 deg.

=1.0, =90 deg.

=0.5, =90 deg.

=0.0, =90 deg.

r=5a

=1.5

=1

=0.5

=0

r

Ste

Radial distance


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Tangential Stress DistributionTangential Stress Distribution


1 2 3 4 5 6 7 8 9 10

r/a

1.0

1.5

2.0

2.5

3.0

/y

Tangential stress

=1.5, =90 deg.

=1.0, =90 deg.

=0.5, =90 deg.

=0.0, =90 deg.

r=5a

=1.5, 1, 0.5, 0

Ste

Radial distance


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Secondary Stress StatesSecondary Stress States

At the periphery of the opening :Only tangential stress but zero radial stress

Biaxial stress state => uni-axial stress state

1

3

1

3

Failu

reline

Rb

Coulomb Criteria

0

A BBA


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Plastic Solutions of Secondary StressesPlastic Solutions of Secondary Stresses

c

0 Rb prp

)1/(1

0

)1(

1

2

+

+=

b

by

R

Rar

=

11

1

a

rRbrp

1

20 +

=

by

r

R

=

11

1

a

rRbp

sin1

sin1

+

=

r0

a

y

r0

Elastic zone

Plastic zone

Mohr CoulombMohr CoulombModelModel


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Radius of Plastic ZoneRadius of Plastic Zone

0 1 2 3 4 5 6 7 8y /Rb

1.0

1.5

2.0

2.5

3.0

r0

/a

Plastic zone

=1, =25 deg.

=1, =30 deg.

=1, =35 deg.

=1, =40 deg.

=1, =50 deg.

=1, =60 deg.

=1, =70 deg.

=1, =80 deg.

=250

=300

=350

=400

=500

r0

a

y

r0

Elastic zone

Plastic zone

lactyRau

Initial stress


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Stress Distribution (Stress Distribution (=1)=1)

1 2 3 4 5 6 7 8

r/a

0.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

/

y

Elastic solution: r

Plastic solution (=25 deg, 0/R

b =1): r

Elastic solution:


b =1):


b =2):


b =2): r

0=Rb

0=2Rbr=5a

r0

a

y

r0

Elastic zone

Plastic zone

Radial Stress

Tangential StressSte

Radial distance


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Solutions of Tertiary StressesSolutions of Tertiary Stresses

a

b

rp pa

r

a

rR11

11

+

=

ab

p pa

r

a

rR11

11

+

=

)1/(1

0)1()1(

12

++

+=

ba

by

RpRar

1

2))(

1

2

1

2(

1

+

++

=

r

aRRp b

yb

a

)1/(2

0)1()1(

12)()1(

+ +++=

ba

byrya

RpR

Eu

r0

a

y

r0

Elastic zone

Plastic zone

pa


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Characteristic Curve of GroundCharacteristic Curve of Ground

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

P

a/y

y/R b =2, =35 deg

y/R b =2.8, =35 deg

y=2.8Rb

y=2Rb

y=0.5Rbr0

a

y

r0

Elastic zone

Plastic zone

pa

Su

pe

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0[E/(1+u)Rb]*(u

a/a)

0.0

0.9

1.0

Characteristic curve

y/R b =0.5, =35 deg

Radial displacement

sue

T i l Ch t i ti C f G dTypical Characteristic Curve of Ground


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Typical Characteristic Curve of GroundTypical Characteristic Curve of Ground

ua

A

Elastic Plastic stable ground

pa

C

D

Ground loosening pressureGround loosening pressureGround deformation pressure

0

uamax

Pamin

B

Initial stress of groundInitial stress of ground

Plastic unstable ground

Su

peue

Radial displacementElastic deformation => Development of plastic zone => InitiationElastic deformation => Development of plastic zone => Initiation of instabilityof instability

CC C fi t M th dC fi t M th d


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ConvergenceConvergence--Confinement MethodConfinement Method

ua

pa

Characteristic curve of ground

0ua1

Pa1

ua0

Characteristic curve of support

Psmax

1. Limit convergence to acceptable values, compatible with

excavation and the ultimate purpose of the structure

2. Control decompression of the surrounding ground, whichalways leads to a serious deterioration in its mechanical

properties

3. Optimize support quantities and cost by applying onlyenough confining pressure to keep convergence within

acceptable limits

Radial displacementSu

peue

F d t l P i i l f NATMFundamental Principles of NATM


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Fundamental Principles of NATMFundamental Principles of NATM

1. Maintain strength of the rock mass

Avoid detrimental loosening by careful excavation and by immediateapplication of support and strengthening means. Shotcrete and rockbolts

applied close to the excavation face help to maintain the rock mass.

2. Rounded tunnel shapes

Avoid stress concentrations in corners where progressive failure

mechanisms start.



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3. Flexible thin liningThe primary support shall be flexible in order

to minimise bending moments and to

facilitate the stress rearrangement process

without exposing the lining to unfavourable

sectional forces. Additional support

requirement shall not be added by increasing

lining thickness but by bolting.

4. In situ measurements

Observation of tunnel behaviour during

construction is an integral part of NATM.

With the monitoring and interpretation of

deformations, strains and stresses it is

possible to optimise working procedures and

support requirements.


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New Austrian Tunneling MethodThe NATM constitutes a method where the surrounding rock

or soil formations of a tunnel are integrated into an overall

ring-like support support structure. Thus the formations willthemselves be part of this supporting structure.

Behavior of ground massBehavior of ground mass


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1. Ground mass is the most important material for

the stability of a tunnel.

Tates Cairn Tunnel, HK



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2. Tunnel support contributes mostly by providing

a measure of confinement.

Copenhagen Metro

FE model of ground-lining interaction



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3. A lining placed in an excavated opening in an

elastic rock mass at the time that 70% of alllatent motion has taken place will experience

stresses from release of the remaining 30% of

displacement.

Lining segments

Segmental lining of

Copenhagen MetroFE Model to simulate

the installation of se ments

Schematic supportSchematic support vsvs deformation during excavationdeformation during excavation


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and support installationand support installation

u

1

a

D0

Initial ground stressInitial ground stress

Su

peue

2Ground state at time of temp support installedGround state at time of temp support installed

3Ground state at time of temp support to loadGround state at time of temp support to load

4

5Ground state at time of perm support to loadGround state at time of perm support to load

6Equilibrium and compatibilityEquilibrium and compatibility

a

p

Radial displacement

Ground state at time of perm support installedGround state at time of perm support installed

Analytical methodsAnalytical methods


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Analytical methodsAnalytical methods

Elastic closed form solutions Beam-spring models Beam-continuum models Empirical techniques

Active loads

Ground reactions

(passive load at

interaction zone)

Lining deformation profile

Proof

Pwall

Pinvert

Tunnel Lining Design Model 1Tunnel Lining Design Model 1


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Rh=0v

v=H

H

Full overburden spring modelFull overburden spring model



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R

h

v

H

Two dimensional continuum modelTwo dimensional continuum model



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R

h

v

H

h

Active ground pressure derived fromActive ground pressure derived fromthree dimensional analysisthree dimensional analysis



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R

h

v

Empirical approachEmpirical approach

Design for different conditionsDesign for different conditions


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gg1. Section with the deepest overburden

2. Section with the shallowest overburden3. Section with the highest groundwater table

4. Section with the lowest groundwater table

5. Section with maximum surcharge

6. Section with eccentric loads

7. Section with future development

8. Soft ground section

9. Mixed ground section

Reservoir

Load factors and loading combinationsLoad factors and loading combinations


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gg

1. Particular environment and behavior

of underground structure

2. Carefully evaluate design load cases

and factors for each tunnel design

3. Rock loads to be derived from rock-structure interaction assessments

Construction methods and stagesConstruction methods and stages


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gg

1. Drill and blast method2. Mechanized method

3. NATM4. NMT


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TBM Tunnels

TBM

E. P. B. M.

for soil

Open TBM

for rock

Shielded TBM

for weak rock

Slurry TBM

for soil

Shield TBMShield TBM


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Immediate Ground SupportImmediate Ground Support


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Immediate Ground SupportImmediate Ground Support

Annular void grouting to

control and restrict

settlement at surface and

to securely block the lining

ring in position

Cutterhead chamber

Segmental lining with annular groutTBM shield

Evolution of settlements along a shield


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Evolution of settlements along a shield

Distance

spme

Cutterhead and shield Segmental lining with annular grout

Face

d1: settlement caused by the face

d2: settlement caused by the overcut

d : settlement induced by

post shied/grout loss

d4

3

settlement induced by lining

deflection and long-termsettlement

Design Steps for TBM tunnelsDesign Steps for TBM tunnels


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Step 1: Define geometric parameters

Alignment, excavation diameter, lining diameter,

lining thickness, width of ring, segment system,

joint connections

Step 2: Determine geotechnical data

Shear strength of soil, deformation modulus,

earth pressure coefficient

Step 3: Select critical sections

Influence of overburden, surcharge,groundwater, adjacent structures



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Step 4: Determine mechanical data of TBM

Total thrust pressure, number of thrusts,

number of pads, pad dimensions, grouting

pressure, space for installation

Step 5: Define material properties

Concrete: strength, elastic modulus

Reinforcement: type, strength

Gasket: type, dimensions, elasticity

Step 6: Design loadsSoil pressure, water pressure, construction loads



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Step 7: Design models

Empirical model, analytical model, numerical

model

Step 8: Computational results

Response: axial force, moment, shearDeformation: deflection

Detailing: reinforcement, joints, groove


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DoubleDouble--O TunnelsO Tunnels

Multi-Circular Face Shield Tunneling


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Multi Circular Face Shield Tunneling

Double-O Tunnels H&V Shield TunnelH&V Shield Tunnel

Assembly of Precast Segments


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y g

Assembly of Segments Perspective View of TunnelPerspective View of Tunnel

tunnel_lining_design.pdf

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