ita - aites world tunnel congress 2007 prague the 3 ... · ita - aites world tunnel congress 2007...

The 3rd Training courseTUNNELLING IN URBAN AREA

Prague, 4-5th May 2007

Numerical modelling in tunnelsNumerical modelling in tunnels

IngIng Radko Bucek Radko Bucek PhPh.D..D.((MottMott MacDonaldMacDonald, , CzechCzech RepublicRepublic))

ITA - AITES WORLD TUNNEL CONGRESS 2007 PRAGUE

TRAINING MATERIAL PREPARED BY

5ConclusionsConclusions

Chapter Chapter 1 1 -- Sequential excavation tunnel support structural Sequential excavation tunnel support structural elementselements

Chapter 2Chapter 2 -- Numerical models of tunnels and reality Numerical models of tunnels and reality –– constitutive constitutive lawslaws

IntroductionIntroduction

Chapter 3Chapter 3 -- Settlement above shallow tunnelsSettlement above shallow tunnels

Index

2

3

4

1

2/2/5050Numerical Numerical modellingmodelling in tunnelsin tunnels

Introduction

Numerical Numerical modellingmodelling in tunnelsin tunnels

3/3/5050

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Shotcrete

does not meanNATM

Numerical Numerical modellingmodelling in tunnelsin tunnels4/4/5050

Selection of tunnel support structural elements

•ground

•excavation method

•demand for control of deformation -settlement

Introduction

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Ground

SoilsR.M. with less than4 systems of discont.

Continuum ContinuumDiscontinuum

•Numerical methods+

• Structural analysis !!

R.M. with more than4 systems of discont.

•Numerical methods•Numerical methods

Introduction

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5/5/5050

Excavation methodSegment lining Perforex Shotcrete

•TBM •Perforex •NATMNumerical modelling in tunnelsNumerical modelling in tunnels

Introduction

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Control of deformation


σ (M

Pa)

δ (mm)rad

Ground reaction curve GCR

δ rad

A

Optimum deformation

Stiff support Deformable

support

Introduction

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7/7/5050

Timing of support installationIntroduction

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Numerical modelling in tunnelsNumerical modelling in tunnels8/8/5050

Sequential excavation tunnel support structural elements

•shotcrete

•rock bolts

Chapter 1

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VýrubTunnelVýrubTunnel

Shotcrete membrane effect

VýrubTunnelVýrubTunnel

Rock mass deforms into the opening, and cosequently, in case of circular or eliptical shape of the opening, radial discontinuities and cracks tend to close.

How do mechanical properties ofof an opening change??????????

the rock mass in the vicinity

Stocking effect

Chapter 1

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Shotcrete – wedge effect

Tunnel

Shotcrete

wedges

Chapter 1

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22

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11Shotcrete – shear strength and the

strength of adhesion

shotcrete

opening

Looseblock

Detail

T

Tlou <šťka stříkaného betonu 3cmShotcrete thickness <3cm Shotcrete thickness >3cm

Magnitude of adhesion is estimated to be close to 3MPa

Chapter 1

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Rock bolts

US Tunnel engineering handbook –

Rock bolt is the general term that includes rock bolts, rock dowels and cable tendons.

Chapter 1

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11 Rock bolts

P

Rock arch formed by the rock bolts- rock mass interaction.

Zatížení ( 1)σ

Odpor proti bočnídeformaci ( )σ3

σ3 σ1Pe

vnos

t

Napětíσ3 σ1

Obálka pevnosti

Load

Confinement σ3

stress

Shea

rstre

ngth

Chapter 1


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Shotcrete and rock bolts

Rozpě

tí

span

Rozpětíspan

Chapter 1


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Shotcrete and rock bolts

shotcrete

Chapter 1


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11 Dulles international airportChapter 1


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Dulles static calculation

I

II

Chapter 1

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Perforex tunnelsChapter 1

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Perforex static calculation

I

II

Chapter 1

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Which is better

ClaystoneOK OK+OK Clay xxxxxxxxx

Chapter 1

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Deformation and mobilizedstrength

OC clay

NC clay

τ

Δl

τf

τr

peak

residual

Chapter 1

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Mobilised strength

• Short def. path• All components together• Rock self supporting• Footing bearing capacity

sufficient

• Long def.path• Components gradually• Time dependent loading• Non of the components

itself sufficient

Claystone Clay

Chapter 1

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Potential collapseChapter 1

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Bearing capacity of the supportChapter 1

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Which is betterChapter 1

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Numerical models of tunnels and reality - constitutive laws

• constitutive laws

• Shotcrete

• rockbolts

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Do numerical models provide us with information about:

• immediate crown stability during excavation?

• immediate face stability during excavation?• loads that the support shall be dimensioned

for?• deformations that should be expected?


Chapter 2

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Constitutive laws


Chapter 2

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Constitutive lawsσ Linear elasticity σ Non-linear elasticity

σ

ε

Elastoplasticity


ε ε

Chapter 2

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Elastoplasticityσ

ε

Strainhardening

σ

ε

Perfectlyplastic

σ

ε

Strainsoftening

σ

ε

Strainhardening Strain

softening Perfectlyplastic

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Does rock change in mud in yielding zones ???

Yielding zones only signal locations where the strength of the material, mostly calculated as shear strength, became lower thanacting stresses.All deformations calculated as yielding are always questionable and should be taken with caution. However, extensive existenceof large yielding zones signal certainly problems in numericalModel, and might signal also problems in reality.

No !!!


Chapter 2

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Elastoplasticity with

Mohr Coulomb

Eμ φ c

Eμ ms

Elastoplasticity with

Hoek and Brown

MΓ κ λ

Cam clay


Chapter 2

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Cam-Clay

CSL

NCLλκ

= 2.303

= 2.303

/

/

CC

c

r

λ

κ1

1

p'=1

N

NCL

( p'= 1/3( 1 + 2 3) )σ σ

l

1

p'=1

N

Γ

CSL

NCL

p'=1

1

M

CSL

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Chapter 2

σt

σr

σt

σr

PoPo

•Increase of stiffness•Increase of strength

From the characteristics of rock mass to characteristicsthat are close to intact rock sample

Is that always true?


Chapter 2

Tunnel Dobrovského in BrnoChapter 2


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HL-HP

HP-PSHL-PS

HL HP

PS

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

29.6.03

19.7.038.8.03

28.8.03

17.9.03

7.10.03

27.10.03

16.11.03

6.12.03

26.12.03

15.1.044.2.04

24.2.04

15.3.044.4.04

def

orm

ace

[mm

]

HL - PS HP - PS HL - HP zahájení správy štol oprava bodů

10 days

Mrá

zovk

aD

obro

vské

ho

10 months

Deformation/time E=80MPa

E=20MPa


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Rock, sand, gravelClays – time dependant behavior

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

29.6.03

def

orm

ace

[mm

]

19.7.038.8.03

28.8.03

17.9.03

7.10.03

27.10.03

16.11.03

6.12.03

26.12.03

15.1.044.2.04

24.2.04

15.3.044.4.04

HL - PS HP - PS HL - HP zahájení správy štol oprava bodů

Creep in clays


Chapter 2

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Result of creep

σy= 520 kPa

Elasto-plasticity

σy In Situ= 360 kPa

creep influence

σy= 380 kPa


Chapter 2

Settlement above shallow tunnels


Chapter 3

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1. Rock deformation in front of the face2. Rock deformation between face and

installed lining3. Closing of discontinuities around

opening due to radial movements4. Rock lining interaction5. Elastic part of deformation6. Plastic part of deformation

Deformation response to the

excavation

Deformacep ed elbou

řč

Poklesová kotlina

Deformation

Face deformationLininginstalation

Excavationwithout support

Lining

Convergence

Liningdeformation

settlement

rock bolts

lining

ahead of the faceDeformationbeyond the face

Lininginstalation

Face deformation

Deform

ation

ahead of the face

Deform

ation

beyond the faceSettlement

Chapter 3

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Settlement trough


Chapter 3

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Effect of tunnel

excavation on surface structures

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Chapter 3

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Chapter 3

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Surface structures damage mechanisms

shear tension

rel. defl.- sagging rel. defl.- hogging

1. shape of s.t.2. extent of s.t.


Chapter 3

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Criteria for analyzing damage


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Prague metro line C

Vs1=Vs2


Chapter 3

What is the value of a numerical model ?

Technical value of a numerical model is directly proportional tothe• professional skills of the engineer working with the model, •his ability to use the software, and •his understanding of all aspects of the technical problem under consideration.


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11 Conclusions

50/50/5050

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