ANALYSIS AND INTERPRETATION OF GROUND AND BUILDING MOVEMENTS

DUE TO EPB TUNNELLING

by

Gima V. Mathew

This thesis is presented for the degree of

Doctor of Philosophy

of

The University of Western Australia

School of Civil and Resources Engineering

October 2010

DEDICATED TO

ALMIGHTY GOD

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ABSTRACT

As the number of tunnels increases to meet the demands of a world with a rapidly

expanding population, the importance of tunnel design and construction efficiencies

also grows; such new efficiencies must ensure minimal damage to nearby existing

structures and facilities. When tunnels are constructed in an urban area, it is important,

at the design stage, that the response of nearby structures can be predicted with

sufficient accuracy. These predictions will affect the choice of tunnelling method and

dictate the form and scope of potential ground improvement measures. While the

‘Gaussian empirical method’ has been shown to provide good estimates of the shape of

the settlement profile in ‘greenfield’ conditions (i.e. where no structures are present),

this method cannot be used to assess structural movements associated with the

tunnelling, for which the profession now generally employs the finite element method.

This thesis investigates the surface (‘greenfield’) and building movements induced by

two bored tunnels in the central business district (CBD) of Perth, Western Australia.

The tunnelling was carried out by an Earth Pressure Balanced (EPB) Tunnel Boring

Machine and the stratigraphy along the tunnel route comprised normally consolidated

dune sand overlying the interbedded layers of alluvial silts, clays and sands. Volume

losses during EPB tunnelling were generally less than 0.29% and, as a consequence,

settlements associated with tunnelling were small and no building damage was

observed.

The greenfield measurements (observed using electro-level beams and settlement pins

in a railway yard) indicated wider tunnelling-induced settlement troughs in soil profiles

comprising a higher proportion of clay layers. Time dependent or consolidation

settlements observed after tunnelling was completed were not significant. Contrary to

expectations, the volume losses associated with the second tunnel boring were less than

those induced during the initial boring. All ‘greenfield’ settlement troughs were of a

Gaussian nature and this form could not be predicted with an acceptable level of

accuracy using both 2D (Plaxis version 9.02) and 3D (Plaxis 3D Tunnel, Version 2.0)

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finite element (FE) analyses combined with relatively advanced soil models. Reasons

for the mismatch are discussed in this thesis and ways in which the Gaussian form may

be predicted are investigated.

Observed movement data as well as finite element back analyses for a multi-storey

building in Perth CBD indicated that the stiffness of the building altered the free field

(Gaussian) form of the settlement trough in its vicinity. 2D FE analyses are used to

illustrate how building stiffness and soil type and/stiffness influence the shape of the

predicted settlement trough. A comparison of measurements with predictions suggests

that the FE approach adopted is a reasonable method for assessing soil structure

interaction effects.

To assist the numerical predictions, the thesis also present results from a targeted

laboratory and in-situ test investigation on the upper horizons of the alluvial deposit

found beneath Perth’s dune sand; little information was available on the mechanical

properties of these horizons. The effectiveness of using compensation grouting in sand

to reduce the volume loss due to tunnel boring and the applicability of numerical

methods to model the grouting is also investigated.

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TABLE OF CONTENTS

ABSTRACT........................................................................................................................... I TABLE OF CONTENTS .................................................................................................. III TABLE OF FIGURES ...................................................................................................... IX LIST OF TABLES....................................................................................................... XVIII ACKNOWLEDGEMENT ............................................................................................. XXI DECLARATION ......................................................................................................... XXIII SYMBOLS AND ABBREVIATIONS..........................................................................XXV CHAPTER 1 INTRODUCTION.........................................................................................1

1.1 BACKGROUND ...............................................................................................1

1.2 SCOPE OF THIS RESEARCH .........................................................................1

1.3 RESEARCH SITES ...........................................................................................4

1.4 THESIS STRUCTURE......................................................................................5 CHAPTER 2 LITERATURE REVIEW.............................................................................7

2.1 INTRODUCTION .............................................................................................7

2.2 GROUND DEFORMATION ............................................................................7

2.2.1 Failure Mode .....................................................................................9

2.2.2 Centrifuge Model Testing in Sand ..................................................10

2.3 SETTLEMENT PREDICTION METHODS...................................................12

2.3.1 Empirical Method ...........................................................................13

2.3.2 Numerical Prediction ......................................................................15

2.4 BUILDING MOVEMENT DUE TO TUNNEL BORING .............................20

2.4.1 Mode of Building Deformation.......................................................22

2.4.2 Numerical Studies of Interaction Problem......................................25

2.5 COMPENSATION GROUTING ....................................................................28

2.5.1 Numerical Modelling of Compensation Grouting ..........................29

2.6 SUMMARY.....................................................................................................30 CHAPTER 3 GEOLOGY, TUNNELLING AND INSTRUMENTATION ..................32

3.1 INTRODUCTION ...........................................................................................32

3.2 PROJECT DESCRIPTION..............................................................................32

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3.3 GEOLOGY AND HYDROLOGY OF THE PERTH REGION......................35

3.4 GEOLOGY AND HYDROLOGY OF THE TUNNEL ROUTE ....................38

3.4.1 Geology...........................................................................................38

3.4.2 Hydrogeology .................................................................................41

3.5 TUNNEL ALIGNMENT AND GROUND CONDITIONS............................44

3.6 SITE INVESTIGATIONS ...............................................................................45

3.7 EARTH PRESSURE BALANCE TUNNEL BORING MACHINE...............48

3.7.1 Ground Anchor Detector.................................................................49

3.7.2 Special Cutters ................................................................................51

3.7.3 Operation in Curved Alignments ....................................................51

3.7.4 Ground Conditioning System .........................................................52

3.7.5 Back Fill Grout System...................................................................52

3.7.6 Advanced TBM Operation Monitoring System..............................52

3.7.7 Muck Volume Measuring System ..................................................52

3.7.8 Internal Grout Ports.........................................................................53

3.7.9 Compressed Air Work Facility .......................................................53

3.8 EPB-TBM TUNNELLING PROCEDURE.....................................................53

3.9 GEOTECHNICAL INSTRUMENTATION AND MONITORING ...............54

3.10 SCHEDULING OF TUNNEL CONSTRUCTION .........................................56 CHAPTER 4 SOIL CHARACTERISATION .................................................................59

4.1 INTRODUCTION ...........................................................................................59

4.2 SUMMARY OF DATA ON SPEARWOOD SAND ......................................59

4.3 LABORATORY INVESTIGATION ON PERTH FORMATION .................63

4.4 SOIL CLASSIFICATION ...............................................................................65

4.4.1 Soil Classification from in-situ Tests..............................................65

4.4.2 Classification based on Laboratory Tests .......................................68

4.4.3 Classification based on Soil Composition ......................................70

4.5 COMPRESSIBILITY ......................................................................................74

4.6 EFFECTIVE STRESS STRENGTH ...............................................................76

4.6.1 Triaxial Tests ..................................................................................76

4.6.2 Simple Shear Tests..........................................................................79

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4.6.3 Undrained Shear Strength ...............................................................80

4.7 STIFFNESS .....................................................................................................83

4.8 CONCLUSIONS..............................................................................................86

4.8.1 Spearwood sand ..............................................................................86

4.8.2 Perth Formation...............................................................................86 CHAPTER 5 SURFACE SETTLEMENT - GREENFIELD SITE ...............................89

5.1 INTRODUCTION ...........................................................................................89

5.2 GROUND CONDITION .................................................................................89

5.2.1 Ground Condition South of Track 1 ...............................................91

5.2.2 Ground Condition North of Track 5 ...............................................94

5.3 TUNNELLING ................................................................................................97

5.4 INSTRUMENTATION ...................................................................................97

5.4.1 Rail Settlement Points .....................................................................97

5.4.2 Electro Level Beams (EL Beams)...................................................98

5.5 FIELD MEASUREMENT.............................................................................102

5.5.1 Rail Settlement Points (RSPs).......................................................103

5.5.2 EL Beams......................................................................................108

5.5.3 Final Transverse Settlement Troughs ...........................................110

5.5.4 Longitudinal Settlement Profile ....................................................116

5.6 COMPARISON OF TRANSVERSE SETTLEMENT TROUGHS WITH GAUSSIAN APPROACH .............................................................................117

5.7 DISCUSSION ................................................................................................120

5.7.1 Factors Contributing to Heave ......................................................121

5.7.2 Factors Contributing to Settlement ...............................................124

5.7.3 Nature of Settlement Trough.........................................................126

5.7.4 Relationship between i , Tunnel Depth and Tunnel Diameter......128

5.8 SUMMARY...................................................................................................129 CHAPTER 6 GREENFIELD SETTLEMENT-NUMERICAL MODELLING .........131

6.1 NUMERICAL MODELLING .......................................................................131

6.2 SOIL MODELS .............................................................................................131

6.2.1 Hardening Soil Model (HS) ..........................................................131

6.2.2 Hardening Soil Model with Small Strain Stiffness (HSSmall).....133

6.2.3 Mohr-Coulomb Model (MC) ........................................................134

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6.3 PARAMETER SELECTION.........................................................................135

6.3.1 Hardening Soil Model (HS Model)...............................................135

6.3.2 Hardening Soil Model with Small Strain Stiffness (HSSmall Model) 139

6.3.3 Mohr Coulomb Model (MC) ........................................................139

6.4 TWO DIMENSIONAL FE ANALYSIS .......................................................140

6.4.1 Hardening Soil Model (HS Model)...............................................143

6.4.2 Hardening Soil Model with Small Strain Stiffness (HSSmall Model) 146

6.4.3 Mohr-Coulomb Model ..................................................................146

6.5 COMPARISON OF THE PREDICTIONS USING DIFFERENT SOIL MODELS .......................................................................................................148

6.6 THREE DIMENSIONAL ANALYSIS (WITH HS MODEL)......................151

Input Parameters ...........................................................................................154

6.6.1 Transverse Settlement Profile .......................................................155

6.6.2 Longitudinal Settlement profile ....................................................158

6.7 COMPARISON OF OBSERVED AND PREDICTED SETTLEMENT TROUGHS.....................................................................................................161

6.7.1 Transverse Settlement Trough ......................................................161

6.7.2 Longitudinal Settlement Trough ...................................................165

6.8 DISCUSSION ................................................................................................166

6.8.1 Effect of K0 on the Predicted Settlement Trough..........................167

6.8.2 Effect of Lining Stiffness Analysis...............................................168

6.8.3 Effect of Stress Reduction around Tunnel ....................................169

6.8.4 Effect of Soil Stiffness on Settlement Trough ..............................172

6.8.5 Stress Changes above the Tunnel during Numerical Analyses ....174

6.8.6 Suggested Approach for Predicting Greenfield Movements (using Plaxis) .................................................................................................176

6.8.7 Interaction Effect of Tunnels ........................................................177

6.9 SUMMARY...................................................................................................179

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CHAPTER 7 MALAYSIAN AIRLINES BUILDING- SURFACE AND BUILDING MOVEMENT....................................................................................................................183

7.1 INTRODUCTION .........................................................................................183

7.2 BUILDING DETAILS...................................................................................183

7.3 GROUND CONDITIONS .............................................................................187

7.4 INSTRUMENTATION .................................................................................191

7.4.1 Surface Settlement Pins and Building Settlement Points..............191

7.4.2 EL Beams......................................................................................191

7.5 FIELD MEASUREMENT (SSP AND BSP’) ...............................................192

7.5.1 Final Transverse Settlement Troughs ...........................................193

7.6 BUILDING MOVEMENT (EL BEAMS).....................................................194

7.7 EFFECT OF SOIL STRUCTURE INTERACTION.....................................196

7.8 NUMERICAL ANALYSIS ...........................................................................198

7.8.1 2D FE Analysis .............................................................................199

7.8.2 Transverse Surface Settlement Trough .........................................200

7.8.3 Building Settlement.......................................................................201

7.9 3D ANALYSIS ..............................................................................................202

7.9.1 Transverse Movement of the Building..........................................204

7.9.2 Longitudinal Surface Movement ..................................................205

7.10 DISCUSSION ................................................................................................206

7.10.1 Influence of Building Stiffness on Settlement Trough .................207

7.10.2 Influence of Soil Type or Stiffness on Settlement Trough ...........208

7.10.3 Settlement, Bending Moment and Horizontal Strain Induced on Building due to Different Volume Losses .....................................................209

7.11 CONCLUSIONS............................................................................................212 CHAPTER 8 COMPENSATION GROUTING– WALSH BUILDING .....................215

8.1 INTRODUCTION .........................................................................................215

8.2 BUILDING PROTECTION ..........................................................................215

8.2.1 Compensation Grouting ................................................................216

8.2.2 Building Details and Arrangement of Grouting............................217

8.3 GROUND CONDITION ...............................................................................223

8.4 BUILDING MOVEMENT AFTER CONDITION PHASE GROUTING....227

8.5 TRANSVERSE SETTLEMENT TROUGH (AFTER TUNNELLING).......230

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8.5.1 South Side of Building (non-grouted area) ...................................230

8.5.2 North Side of Building (grouted area) ..........................................233

8.5.3 Comparison of Surface Movement at Grouted and Non-Grouted area 234

8.5.4 Building Settlement ......................................................................235

8.6 NUMERICAL MODELLING .......................................................................236

8.6.1 Building Movement after Condition Phase Grouting ...................238

8.6.2 Building Movement after Active Grouting (after tunnelling).......239

8.7 CONCLUSIONS............................................................................................240 CHAPTER 9 OBSERVATIONS, CONCLUSIONS AND RECOMMENDATIONS 241

9.1 INTRODUCTION .........................................................................................241

9.2 OBSERVATIONS AND CONCLUSIONS ..................................................242

9.2.1 Soil Characterisation.....................................................................242

9.2.2 Greenfield Ground Movement ......................................................243

9.2.3 Numerical Modelling of Greenfield Movement ...........................244

9.2.4 Soil Structure Interaction Effect ...................................................246

9.2.5 Numerical Modelling of Soil Structure Interaction ......................246

9.2.6 Compensation Grouting and Applicability of Numerical Modelling 247

9.3 CONTRIBUTIONS TO THE FIELD OF KNOWLEDGE ...........................247

9.4 RECOMMENDATIONS FOR FUTURE RESEARCH................................248 REFERENCES .................................................................................................................251

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TABLE OF FIGURES

Figure 1-1 T Bored Tunnels and Research Sites in the Perth CBD.................................. 2

Figure 2-1 Source of Ground Loss (Attewell, 1978) ......................................................... 9

Figure 2-2Observed Failure Mode based on Centrifuge Model Tests............................. 10

Figure 2-3 Volume Loss Calculated from Soil Displacements Compared to Tunnel

Volume Loss (Marshall, 2009).................................................................... 11

Figure 2-4 Profile of Mobilised Lateral Earth Pressure Coefficient on Tunnel

centre line at Different Volume Losses (Jacobsz, 2002)............................. 12

Figure 2-5 Geometry of the tunnel induced settlement trough (after Attewell et

al.,1986)....................................................................................................... 13

Figure 2-6 Transverse Settlement Trough........................................................................ 14

Figure 2-7 Longitudinal Settlement Profile (Franzius, 2003).......................................... 19

Figure 2-8 Predicted Greenfield settlement and Observed Building Settlement of

Mansion House, London (after Frischmann et al., 1994) ........................... 20

Figure 2-9 Building and Subsoil Movement of Buildings in Frankfurt Clay (after

Breth and Chambosse, 1974)....................................................................... 22

Figure 2-10 Building Deformation above Single Tunnel (Mair et al., 1996) .................. 23

Figure 2-11 Layout of Mansion House and Location of Tunnel (Frischmann et al.,

1994)............................................................................................................ 24

Figure 2-12 Settlement profiles for East and West Walls of Mansion House

(Frischmann et al., 1994) ............................................................................ 25

Figure 2-13 Comparison of Damage Estimation Criterion and Damage Levels

(Son and Cording, 2005) ............................................................................. 27

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Figure 2-14 Example of Interaction Diagram to Assess the Damage for Isotropic

Beam with L/H =1 (Burland, 1995) .............................................................28

Figure 3-1, Bored Tunnel Alignment................................................................................33

Figure 3-2 Eustatic Sea Level Curve for the Past 270,000 Years with Oxygen

Isotope Stages Indicated (Gozzard, 2007)....................................................35

Figure 3-3 Perth Region Generalized Geomorphology (after B Gozzard, 2007) .............37

Figure 3-4 Perth Region Generalized Geology.................................................................38

Figure 3-5 Schematic Geology of the Project Route (Hudson-Smith and Grinceri,

2007).............................................................................................................39

Figure 3-6 Schematic Section Showing Stratigraphic Relationships of Superficial

Formations in the Vicinity of Perth..............................................................40

Figure 3-7 Piezometric Profiles at South End of William Street Station (Leighton

et al., 2004)...................................................................................................42

Figure 3-8 Piezometric Profile along the Project Route (Johnson, I.D., et al.,2007) .......43

Figure 3-9 Old Lakes near Project Alignment ..................................................................45

Figure 3-10 Specifications of EPB-TBM..........................................................................50

Figure 3-11 EPB Tunnel Boring Machine- View on Cutter head.....................................51

Figure 3-12 Schedule of Tunnelling South of William Street Station..............................56

Figure 3-13 Schedule of Tunnelling North of William Street Station..............................57

Figure 4-1 SPT N vs. Depth..............................................................................................61

Figure 4-2 Typical Gradation Curve of the Dune Sand (after Andrews, 1971)................61

Figure 4-3 Relationship between G0 (from SCPTs) and qc Observed in Perth Sand ........62

Figure 4-4 Relationship between G0 (from SCPTs) and qc Observed for Perth

Formation Sand and Spearwood Sand .........................................................63

Figure 4-5 Typical CPT Data at Test Location.................................................................66

Figure 4-6 Ic and ID Indices at the Site..............................................................................68

Figure 4-7 Classification Data; Separate Symbols for each Bore Holes ..........................69

xi

Figure 4-8 Activity Chart and Location of Tested Soil Samples ..................................... 70

Figure 4-9 Colour changes due to Iron on Soil Samples ................................................. 72

Figure 4-10 SEM Images ................................................................................................. 73

Figure 4-11 Oedometer Data for Three Samples ............................................................. 75

Figure 4-12 Stress Paths Measured in CIU Triaxial Compression Tests......................... 77

Figure 4-13 (a) Values of t and s’ at Failure for all Triaxial Tests, (b) Dependence

of Triaxial Friction Angle on Fines Content ............................................... 78

Figure 4-14 Stress Paths Measured in Undrained Simple Shear...................................... 80

Figure 4-15 Undrained Strength Ratios Plotted as a Function of (a) consolidation

stress level and (b) Fines Content................................................................ 81

Figure 4-16 Variation of A (undrained strength ratio at OCR=1) with Fines

Content ........................................................................................................ 82

Figure 4-17 Stiffness Data Measured in CIU Triaxial Compression Tests ..................... 84

Figure 5-1 Geotechnical Investigation Locations near the Railway Tracks .................... 90

Figure 5-2 Borehole Information and Stratigraphical Profile South of the Railway

Tracks .......................................................................................................... 92

Figure 5-3 CPT Profile South of Track 1......................................................................... 93

Figure 5-4 Idealised Soil Profile South of Railway Tracks ............................................. 93

Figure 5-5 Bore Hole Information and Stratigraphical Profiling North of the

Railway Tracks............................................................................................ 95

Figure 5-6 CPT Profile North of Track 5......................................................................... 96

Figure 5-7 Idealised Soil Profile North of Railway Tracks ............................................. 96

Figure 5-8 Variations in the SSP Data over a Period of Two Months for Track3

and Track 5.................................................................................................. 98

Figure 5-9 Typical View of a Horizontal EL Beam......................................................... 99

Figure 5-10 Schematic View of Horizontal EL Beam..................................................... 99

Figure 5-11 Longitudinal and Transverse EL Beams on the Track ............................... 101

Figure 5-12 Closer View of EL Beams on the Track..................................................... 101

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Figure 5-13 Schematic View of EL Beam on Railway Tracks.......................................102

Figure 5-14 Transverse Settlement Trough due to Tunnel 1 Boring (RSP) ...................104

Figure 5-15 Transverse Settlement Trough due to Tunnel 2 Boring (RSP) ...................106

Figure 5-16 Relationship between Maximum Heave and Maximum Settlement

Deduced from RSPs ...................................................................................108

Figure 5-17 Transverse Settlement Trough due to Tunnel 1 Boring (EL Beam) ...........109

Figure 5-18 Transverse Settlement Trough due to Tunnel 2 Boring (ELBeam) ............110

Figure 5-19 Final Transverse Settlement Trough for Three Tracks due to Tunnel 1 .....111

Figure 5-20 Final Transverse Settlement Trough for Three Tracks due to Tunnel 2 .....112

Figure 5-21 Transverse Settlement Troughs due to Tunnel 1 and Tunnel 2...................113

Figure 5-22 Combined Transverse Settlement Troughs after Tunnel 2 Boring .............114

Figure 5-23 Typical Longitudinal Profile for Tunnel 1 Boring......................................116

Figure 5-24 Linear Regression Lines for Tunnel 1 Boring............................................118

Figure 5-25 Linear Regression Lines for Tunnel 2 Boring.............................................119

Figure 5-26 Estimated Face Pressure along Northern Bored Tunnel (after Sigl and

Yamazaki, 2007) ........................................................................................121

Figure 5-27 Variation of FP and Horizontal Effective Stress during Tunnel 1 and

Tunnel 2 Boring (Note Tracks 1, 3 & 5 are at approximate chainages

of 138m, 152m and 177m for Tunnel 1 and 146m, 164m and 192m

for Tunnel 2)...............................................................................................122

Figure 5-28 Variation of Grout Volume / Ring .............................................................123

Figure 5-29 Variation of GP and Horizontal Effective Stress during Tunnel 1 and

Tunnel 2 Boring .........................................................................................124

Figure 5-30 Normalised Field Settlement Troughs for Tunnel 1 ...................................127

Figure 5-31 Variation of i with z0 for Tunnels in Sand and Gravels (Mair and

Taylor, 1997) ..............................................................................................128

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Figure 5-32 Relation between i , Tunnel depth and Diameter for Different Ground

Conditions (Peck, 1969) ............................................................................ 129

Figure 6-1 Figure showing the Relationship between G0ref and Strain at Reference

Stress of 100 kPa ....................................................................................... 137

Figure 6-2 North Profile Showing Mesh and Tunnels for 2D FE Analysis................... 141

Figure 6-3 South Profile Showing Mesh and Tunnels for 2D FE Analysis................... 141

Figure 6-4 Transverse Settlement Trough for North and South profiles for Volume

Losses of 0.25% & 0.19%; HS model....................................................... 144

Figure 6-5 Variation of Excess Pore Pressure for North Profile (vl=0.25%) ................ 145

Figure 6-6 Variation of Excess Pore Pressure for South Profile (vl=0.25%) ................ 145

Figure 6-7 Transverse Settlement Trough for North and South profiles for Tunnel

1 (Volume Losses of 0.15% & 0.25%); MC with E=E50.......................... 146

Figure 6-8 Final Transverse Settlement Trough for North and South Profiles; MC

with E=Eur ................................................................................................. 147

Figure 6-9 Transverse Settlement Trough for South Profile; MC with E=Eur............... 148

Figure 6-10 Comparison of the Transverse Settlement Trough Predicted using

Different Soil Models ................................................................................ 149

Figure 6-11 Deformed Mesh using MC (Eur) Model ..................................................... 150

Figure 6-12 Deformed Mesh of the Geometry using HS Model ................................... 150

Figure 6-13 Deformed Mesh of the Geometry using HSSmall Model .......................... 150

Figure 6-14 Geometric Model of the Tunnel Excavation .............................................. 152

Figure 6-15 3D Mesh for the Plaxis Analysis North of the Rail Lines......................... 152

Figure 6-16 3D Mesh for the Plaxis analysis South of the Rail Lines........................... 153

Figure 6-17 Schematic View of the Modelling of Tunnel Boring ................................. 154

Figure 6-18 Deformed Mesh after Excavating Tunnel 1 (North profile, vl=0.25%)..... 155

Figure 6-19 Deformed Mesh after Excavating Tunnel 1 and Tunnel 2 (North

profile, VL=0.25% &0.19%) ..................................................................... 156

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Figure 6-20 Deformation Plane after the Excavation of Tunnel 1 (North profile,

VL VL =0.25%)...........................................................................................156

Figure 6-21 Deformation Plane after the Excavation of Tunnel 1 and Tunnel 2

(North profile, VL =0.25% &0.19%)..........................................................156

Figure 6-22 Transverse Settlement Trough of North and South Profile for Volume

Losses of 0.25% & 0.19%..........................................................................158

Figure 6-23 Typical Longitudinal Settlement Trough ....................................................159

Figure 6-24 Boundary Effect for Longitudinal Trough .................................................159

Figure 6-25 Settlement Trough with Different FP and GP.............................................160

Figure 6-26 Longitudinal Settlement Trough for Different GP and FP..........................161

Figure 6-27 Comparison between Settlement Troughs Predicted for North Profile.......162

Figure 6-28 Comparison between Settlement Troughs Predicted for South Profile.......163

Figure 6-29 Comparison of Normalised Settlements for Tunnel 1.................................165

Figure 6-30 Predicted and Observed Normalised Longitudinal Settlement Trough ......166

Figure 6-31 Settlement Trough with Different K0 Value for North and South Soil

Profile .........................................................................................................168

Figure 6-32 Variation of Surface Movements for Different Lining Stiffness ................169

Figure 6-33 Soil Profile and Location of Tunnel for Parametric Study..........................170

Figure 6-34 Settlement Trough with Different K0 around the Tunnel............................172

Figure 6-35 Settlement Profile with Different Stiffness .................................................173

Figure 6-36 Mobilised Horizontal Earth Pressure ..........................................................173

Figure 6-37 Mobilised Lateral Earth Pressure Coefficient along the Tunnel axis.........175

Figure 6-38 Mobilised Stress and Km near the Ground Surface at RL=10.3m

(section B-B in Figure 6-33) ......................................................................176

Figure 6-39 Comparison of Predicted and Measured Settlement Trough ......................177

Figure 6-40 Interaction Effect of Tunnels using South Profile.......................................178

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Figure 6-41 Interaction Effect of Tunnels using North Profile...................................... 178

Figure 7-1 Aerial View of MAS Building ..................................................................... 184

Figure 7-2 Schematic View of the Building and Location of Tunnels .......................... 185

Figure 7-3 Front View of MAS Building....................................................................... 186

Figure 7-4 View Opposite MAS Building ..................................................................... 186

Figure 7-5 Ground and First Floor Plan for MAS Building .......................................... 187

Figure 7-6 Geotechnical Investigation Locations near MAS Building.......................... 188

Figure 7-7 Borehole Information and Stratigraphical Profile Close to the MAS

Building ..................................................................................................... 190

Figure 7-8 CPT Profile................................................................................................... 190

Figure 7-9 Soil Profile and Location of Tunnel near MAS Building ............................ 190

Figure 7-10 EL Beams on the Wall with Transmitter on Each Beam ........................... 192

Figure 7-11 Ground and Building Movement due to Tunnel 1 and Tunnel 2 ............... 193

Figure 7-12 Transverse Surface Settlement Trough for Tunnel 1 and Tunnel 2 ........... 194

Figure 7-13 Movement of Building at Various Times during Tunnelling..................... 195

Figure 7-14 Transverse Building Movement for Tunnel 1 and Tunnel 2 ...................... 196

Figure 7-15 Linear Regression Analysis for Tunnel 1 and Tunnel 2............................. 197

Figure 7-16 Normalised Settlement for Tunnel 1 and Tunnel 2 .................................... 197

Figure 7-17 2D Mesh Showing Tunnels and Building .................................................. 199

Figure 7-18 Observed and Predicted Settlement Trough............................................... 201

Figure 7-19 Measured vs Predicted Settlement of the Building .................................... 202

Figure 7-20 3D Mesh for the Geometry........................................................................ 203

Figure 7-21 Deformed Mesh after Tunnel Boring ......................................................... 203

Figure 7-22 Predicted Movement of the MAS Building as the TBM Passes ................ 204

Figure 7-23 Schematic View of Building and Direction of TBM ................................. 204

Figure 7-24 Transverse Settlement Observed and Predicted by FE Analysis ............... 205

Figure 7-25 Longitudinal Settlement Profile from 3D Analysis.................................... 206

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Figure 7-26 Schematic View of Geometry in z Direction ..............................................206

Figure 7-27 Surface Settlement Trough with Different Building Stiffness ....................208

Figure 7-28 Surface Settlement Trough with Different soil type ...................................209

Figure 7-29 Building Settlement due to Different Volume Losses ................................210

Figure 7-30 Predicted BM due to Tunnelling for Different Volume Losses ..................211

Figure 7-31 Horizontal Strain induced by Tunnel 1 Boring on MAS ............................212

Figure 8-1 Aerial View of the Protected Buildings ........................................................216

Figure 8-2 Front View of Walsh Building ......................................................................218

Figure 8-3 Schematic View of the Location of Building and Tunnel.............................219

Figure 8-4 Church Opposite to Walsh Building .............................................................220

Figure 8-5 Tunnel Alignment and Geotechnical Investigation Locations near

WALSH Building.......................................................................................221

Figure 8-6 Typical Cross-section of Grouting Arrangement ..........................................222

Figure 8-7 Site Setup (top) and Schematic Layout for Grouting (bottom).....................222

Figure 8-8 Schematic View of the Protected Buildings, Grout Ports and Location

of EL Beams on the Building.....................................................................223

Figure 8-9 Borehole Information and Stratigraphical Profile Close to WALSH

Building......................................................................................................225

Figure 8-10 CPT Profile Close to Walsh Building .........................................................226

Figure 8-11 Soil Profile and Location of Tunnel near WALSH Building......................227

Figure 8-12 Movement of Building due to Condition Phase Grouting ..........................228

Figure 8-13 Variation of Grout Volume along the Transverse Direction of the

Building......................................................................................................229

Figure 8-14 EL Beam Location and Zone of Influence ..................................................229

Figure 8-15 Settlement Troughs at Non-Grouted Area for Tunnel 1 and Tunnel 2 .......231

Figure 8-16 Normalised Settlement for Tunnel 1 and Tunnel 2 .....................................232

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Figure 8-17 Location of Tunnels and the Buildings at Non-grouted Area .................... 233

Figure 8-18 Surface movement at Grouted Location (from SSP and BSP data) ........... 234

Figure 8-19 Surface Settlements Due to Tunnel 1 Boring at Grouted and Non-

Grouted Locations ..................................................................................... 235

Figure 8-20 Building Movement due to Grouting and Tunnel 1 Boring ....................... 236

Figure 8-21 Mesh Showing the Location of the Grouting ............................................. 237

Figure 8-22 Observed and Predicted Movement after Condition Phase Grouting. ....... 238

Figure 8-23 Observed and Measured Movement of Building due to Tunnel 1 ............. 239

xviii

LIST OF TABLES

Table 3-1 Construction Methods of the Different Sections of the New Metro Rail

City Project (Part 4B Geotechnical Interpretive Report, 2004) ...................34

Table 3-2 Phases of Site Investigation..............................................................................46

Table 3-3 Main Characteristics of the EPB-TBM ............................................................49

Table 3-4 – Instrument Types and Quantities...................................................................55

Table 3-5 Schedule of Tunnel Construction .....................................................................56

Table 4-1 Relative Phase Composition (wt.%) Derived from XRD Data ........................71

Table 4-2 Properties of Soil Samples Tested in 1-D Compression..................................74

Table 4-3 Approximate Values of ξ for Clays at the St. Georges Terrace Site ................85

Table 5-1 Variation of Heave and Settlement for each Track after the Tunnel

Boring.........................................................................................................107

Table 5-2 Settlement Details of Three Tracks ................................................................115

Table 5-3 Estimated i Values ..........................................................................................120

Table 5-4 Estimated i and K Values at the Three Track Locations ..............................127

Table 6-1 Hardening Soil Model Parameters for North Profile......................................138

Table 6-2 Hardening Soil Model Parameters for South Profile......................................138

Table 6-3 Mohr-Coulomb Model Parameters for North Profile .....................................139

Table 6-4 Mohr-Coulomb Model Parameters for South Profile .....................................140

Table 6-5 Tunnel Details.................................................................................................141

Table 6-6 Volume Losses Specified in Numerical Analyses..........................................142

Table 6-7 Main Features of the Mesh .............................................................................153

xix

Table 6-8 Face Pressure, Grout Pressure and TBM Thrust for 3D Analyses ................ 155

Table 6-9 Input Volume Loss and the Out put Volume Losses..................................... 163

Table 6-10 Combinations of Stress History used for Predicting Settlement Profile...... 167

Table 6-11 Vertical Movement of Tunnel Crown.......................................................... 169

Table 6-12 Different Cases for the Analyses ................................................................. 170

Table 7-1 Surface Settlement Details at MAS Building ................................................ 194

Table 7-2 Input Parameters for the Building Components ............................................ 198

Table 7-3 Face Pressure, Grout Pressure and TBM Thrust used for 3D Analyses........ 203

Table 8-1 Summary of Settlement Troughs at Non-Grouted Area of Walsh

Building ..................................................................................................... 231

Table 8-2 Details of the Building Component ............................................................... 237

xx

xxi

ACKNOWLEDGEMENT

It has been a pleasure and privilege to be part of Geotechnical Research Group at The

University of Western Australia. The research for this dissertation was carried out in the

School of Civil and Resources Engineering during 2005 -2010 and was supported by the

University Postgraduate Award (UPA) and Othman Frank Blakey Scholarship, which are

gratefully acknowledged.

There are many people to thank for their support and encouragement, without whom

this thesis would not have been possible.

First of all, I would like to express my sincere gratitude to my supervisor, W/Prof. Barry

Lehane for his valuable discussions, advices, support and consideration throughout this

research. I have been very fortunate to work with him. I sincerely thank you Barry for

your patience, attention to detail and always having time for discussion.

I would like to thank Binaya, Claire, Natalie and Christine in the Geotechnical

laboratory for helping and making my life easy with laboratory testing. I also thank all

the staff in the general workshop and electronic workshop for their untiring help and

enthusiasm in finishing the job on time.

The help and support provided by Jane, Simone, Monica, Eileen, Lisa and Sharon in the

Civil engineering and COFS office is also acknowledged. My special

acknowledgements are expressed to Wenge and Keith for their friendly and skilful IT

support throughout this research.

I say a great thank you to Natusha for helping me during my stay here. I aso thank

Mostafa for his time and patience for helping me with my laboratory study and lending

me the Plaxis dongle.

I am very grateful for the company of all the research associates, postgraduate students

and visitors in Civil Engineering as well as in COFS, without the support of everybody

xxii

the life would be difficult. I specially thank Lina, Shazzad, Booning, Tarrant, Xuelin,

Bao and Kevin for their valuable help, advice and encouragement whenever in need.

I am very much indebted to Selina for taking care of my children during my research.

She was there for me whenever I needed help. Without you I wouldn’t have been able to

do my research so relaxingly. I also thank Siraj and Sajid for their help and company.

I specially thank Fiona Chow for providing me with journal papers, books and thesis

whenever in need. I also acknowledge the help and support provided by Susan

Governec, Doug Stewart, Eric Hudson-Smith, Raghu, Peter McGough, Michael

Grinceri, Logan, Babu, Suman and Matt Williams.

The help from Leighton Kumagai Joint Venture (LKJV) by providing instrumentation

monitoring data is also greatly acknowledged. I also acknowledge the funding providing

by an Australian Research Council (ARC) linkage grant in association with LKJV to

support this research.

I am also very grateful and sincerely acknowledge the time and effort of all the

examiners evaluating this thesis.

I sincerely thank my husband Joyis and children Joshia,

Denzel and Paulus for their untiring support and

consideration throughout my research. I wouldn’t have

been able to finish this research without Joyis’s help,

patience and support.

I would like to thank my parents, brothers and sister-in-laws for their constant support

and effort throughout this research. I also thank Sony Aunty for coming and helping me

during my delivery time and helping me with the kids. I specially thank my mother-in-

law Rose for her constant prayer for me and support. I also thank all my in- laws for

their love and affection for me and supporting me.

Last but not least I thank almighty God for bestowing me with knowledge and wisdom

to complete the study successfully. When ever I was in need He gave it to me through

somebody.

xxiii

DECLARATION

I hereby declare that, except where specific reference is made to the works of others, the

contents of this dissertation are original and have never been submitted, in part or as a

whole, to any other University for any degree, diploma or other qualifications. This

dissertation is the result of my own work and includes nothing which is the outcome of

work done in collaboration. This dissertation contains no more than 70,000 words and

180 figures.

Gima V. Mathew

October 2010

xxiv

xxv

SYMBOLS AND ABBREVIATIONS

Symbols

c' Cohesion

D Outer tunnel diameter

D1 Outer diameter of the lining

D2 Diameter of the cutter face

e In situ void ratio

emax Maximum void ratio

E Modulus of elasticity of concrete

E’sec= E Drained secant Youngs moduli of soil

E0 Youngs moduli at very small strains

E50 ref Secant stiffness in standard drained triaxial test at reference stress

Eoedref Tangent stiffness for primary oedometer loading at reference stress

Eurref Unloading/reloading stiffness

EA Axial stiffness

EI Bending stiffness

Fr Friction ratio

fs Friction sleeve measurement

G Secant shear modulus

xxvi

G0ref Small strain shear modulus at reference stress

Ic Soil behaviour type index

ID DMT material index

i Transverse horizontal distance from centre-line of the tunnel to

the point of inflection of the settlement trough (also ix)

k_x, k_y & k_z Permeability of the soil in the x, y and z directions

K Trough width parameter (also K1 and K2)

K0nc K0 value for normal consolidation

K0 Coefficient of earth pressure at rest

Km Mobilised earth pressure coefficient

L - Length of each ring

LL Liquid limits

m Power for stress-level dependency of stiffness

Nk Cone factor

p’ Mean effective stress

pa Atmospheric pressure or reference stress

p0 Lift-off pressure

pref Reference confining pressure

p1 Pressure measured at a membrane expansion of 1.1 mm

p’0 Initial mean effective stress

q Deviator stress

qc CPT end resistance

xxvii

qf Maximum deviator stress

Smax Maximum settlement

su Undrained shear strength

Sv Settlement at offset y from the tunnel centre line

S Settlement at a distance x from tunnel centre line

sutc Undrained shear strength in triaxial compression test

suss Undrained shear strength in simple shear test

u0 Ambient pore pressure.

Uy Vertical movement

Ux Horizontal movement

VL Volume loss

Vs Shear wave velocity

Vs Excavated volume

w Water content

y Horizontal distance from the tunnel centre line

Z0 Depth of the tunnel axis below the ground surface

φ' Friction angle

ψ Peak dilation angle

φcv Critical state friction angle

ψm Mobilised dilation angle

φm Mobilised friction angle

xxviii

γsat Saturated unit weight of soil

γunsat Unsaturated unit weight of soil

ψ Angle of dilatancy (o)

ν Poisson’s ratio

ρ Mean density

ξ Constant varies with the nature and age of the deposit,

τxy Shear stress

(Δ/L) Deflection ratio

ν Poissons ratio

γ Shear strain

νur Poisson’s ratio for unloading reloading

σ’3 Minor and intermediate principal effective stresses

σv0 Total vertical stress

σ’v Vertical effective stress.

σ’vy Vertical yield stress

σ’vc Vertical consolidation stress

Abbreviations

1-D One dimensional

AHD Australian Height Datum (Mean Sea Level)

xxix

BSP Building settlement points

CF Coarse fraction

CPT Cone penetration test

DMT Dilatometer test

FC Fine content

POP Past overburden pressure

OCR Overconsolidation ratio

PI Plasticity index

RSP Rail settlement points

SSP Surface settlement pins

SBT Soil behaviour type

TAM Tubes-a-manchettes

xxx

1

CHAPTER 1 INTRODUCTION

1.1 BACKGROUND

The growth of many cities has resulted in the need for underground structures such as

tunnels to provide efficient transportation, water supply, sewage disposal and

communications. To avoid any damage to the overlying structures, efficient and

economic tunnel design and construction methods should be implemented. There are

empirical, numerical and analytical methods to predict the movement associated with

tunnelling. When tunnels are constructed in an urban area, it is important, at the design

stage, that the response of nearby structures can be predicted with sufficient accuracy.

These predictions will affect the choice of tunnelling method and dictate the form and

scope of potential ground improvement measures. The current deformation prediction

approaches are often conservative and can lead to unnecessary expenditure for the

protective measures. A more reliable design method would resolve issues such as

excessive cost and damage to surface or sub surface facilities. The most widely used

‘Gaussian empirical method’ has been shown to provide good estimates of the shape

and size of the settlement profile in ‘greenfield’ conditions (i.e. where no structural

interaction effects are present), this method cannot be used to assess structural

movements associated with the tunnelling. The Finite Element (FE) method is currently

the most popular approach to predict the surface and building movement associated with

tunnelling.

1.2 SCOPE OF THIS RESEARCH

The Perth MetroRail project connecting Perth to Mandurah was a major infrastructural

investment by the Western Australian State Government. In the Perth Central Business

District (CBD), the project consisted of two bored (6.9m outer diameter) underground

rail tunnel, open dive and cut-and-cover tunnel sections and two below ground stations

(Esplanade and William Street Station); these elements are shown in Figure 1-1.

Leighton Kumagai Joint Venture (LKJV) carried out the tunnelling work in the CBD.

2

The stratigraphy of the tunnel route consists mainly of normally consolidated dune sand

(Spearwood Sand) overlying the overconsolidated layers of alluvial silts, clays and

sands (Perth Formation), which are underlain by shale/ siltstone (Kings Park

Formation). Earth Pressure Balanced Tunnel Boring Machine (EPB-TBM) was used to

bore the two tunnels.

Figu

re 1

-1 T

Bor

ed T

unne

ls a

nd R

esea

rch

Site

s in

the

Pert

h C

BD

Gre

enfie

ld si

te

Wal

sh M

AS

Chapter 1 Introduction

3

Although significant portions of the bored tunnels went through the overconsolidated

Perth Formation, no systematic laboratory investigation of the Perth Formation has been

published to date. The design and construction of this project was constrained by the

need to minimise the effect of tunnelling on the existing buildings. As the tunnel was

passing directly underneath some of the buildings along the tunnel route, the potential

for imposition of large ground distortions on these buildings was very high. These

buildings were on shallow footings and compensation grouting was implemented under

some of the buildings to mitigate the effect of tunnelling. Hence the main objectives of

this research are;

1. To study the properties of the Perth Formation in detail by conducting state

of the art laboratory tests on undisturbed soil samples collected from the

research site. The laboratory measurements are subsequently related and

calibrated with in-situ test data to assist in the assignment of material

properties for the numerical analyses.

2. To investigate the effect of EPB tunnelling in the Perth soils. This is attained

by interpreting extensive instrumentation data collected from three adjacent

locations at the greenfield site shown on Figure 1-1. The nature of the

settlement troughs is assessed in detail and compared with the observations

made in the similar ground conditions around the world.

3. To examine the suitability of FE methods to predict the movement

associated with the tunnelling especially in the mixed stratigrapghy present

in Perth CBD. This is achieved by carrying out both 2D and 3D finite

element analyses using the popular Plaxis program.

4. To study the effect of tunnel construction on nearby buildings as well as the

influence of buildings on the observed pattern of surface or building

movements. The vertical ground and building movement at two multistorey

building locations are analysed in detail to study the soil structure interaction

effect.

5. To investigate the applicability of both two dimensional (2D) and three

dimensional (3D) numerical modelling in replicating the soil-structure

interaction effect as observed in the field.

4

6. To study the effectiveness of compensation grouting in sand to reduce the

soil volume loss associated with tunnelling. This is achieved by comparing

the settlement troughs at grouted and non-grouted areas close to each other.

7. To examine the applicability of FE modelling to model the compensation

grouting.

1.3 RESEARCH SITES

The research mainly focused on five monitored sites along the tunnel route and they are,

i) greenfield sites (three adjacent locations in railway track area) ii) Malaysian Airlines

(MAS) building and iii) Walsh building; the locations of the five sites are indicated in

Figure 1-1. The instrumentation was installed and monitored by LKJV. However, at the

MAS building, the author installed EL beams in addition to the instrumentation installed

by LKJV to monitor the movement of the building; LKJV also recorded these EL beam

data. Analyses and interpretation of all the instrumentation data presented here were

carried out independently by the author. The tunnelling took place during the initial

period of the PhD study.

Details of each of the monitored sites are given below.

(i) Greenfield Site (Railway Tracks): Part of the tunnel went underneath five

existing railway tracks. As there were no buildings around this area, this was

considered as a good location to esimate the greenfield movement. The

tunnels were about 11m below ground level and 14.4m apart (centre to

centre) at this location. Out of five tracks, three tracks (Track 1, Track 3 and

Track5) are considered here for the analysis. The tunnels encountered both

the Perth Formation and Spearwood sand at these locations.

(ii) Malaysian Airlines (MAS) Building: This building (constructed in 1929) is

a framed structure having seven storeys and a basement founded on shallow

footing. Full structural details of the building are not available and

assumptions regarding its structural form are based on visual inspection.

This building was about 6m from the centre line of Tunnel 1. The near by

tunnels were at about 18 m below ground level and 10.2m apart. Most of the

Chapter 1 Introduction

5

tunnel’s cross-section is located in the sand and clay layers of the Perth

Formation at this area.

(iii) Walsh building. The Walsh building is heritage listed and has five storeys

and a basement. This building is a steel framed structure encased in concrete,

with secondary reinforced concrete beams. The building is on shallow

footings. The tunnels’ springlines are at about 17m below ground level and

are 10.6m apart (centre to centre) at south side of the building. The

corresponding measurements at north side of the building are 15.45m and

12m. The tunnels are located primarily in silty and clayey layers of the Perth

Formation at this area. Compensation grouting was implemented over the

northern section of the building to mitigate the effects of tunnelling induced

settlements.

1.4 THESIS STRUCTURE

This thesis consists of nine Chapters. Following the introduction, which is Chapter 1,

Chapter 2 presents a review of relevant literature for the thesis topic. This chapter

covers patterns of soil movement as well as volumetric straining and stress changes

above the tunnel crown, as observed in centrifuge model testing. Different approaches

to predict the tunnelling induced ground movements are also discussed. Soil structure

interaction effects are reviewed as are criteria for assessing movement thresholds for

building damage. Current approaches for numerical modelling of compensation

grouting are also evaluated.

Chapter 3 gives the over all description of the MetroRail project (in the Perth CBD

area), tunnelling method and geology & hydrogeology of the tunnel route. The

characteristics of the TBM used to bore the two tunnels and summary of

instrumentation used to monitor the ground as well as building movement are also

detailed.

All the laboratory tests carried out in the alluvial deposits of the upper horizons of Perth

Formation along with the in situ tests carried out as part of the MetroRail project are

reported in Chapter 4. The laboratory measurements are subsequently related and

calibrated with available in-situ test data to assist in the assignment of material

properties in numerical analyses.

6

The surface settlement (‘greenfield’) troughs induced by boring of the two tunnels are

the main focus of Chapter 5. The extensive instrumentation data at three locations close

to each other are analysed thoroughly and compared with the observations in similar

ground conditions around the world. The applicability of the widely used Gaussian

Method to predict the greenfield troughs in the predominantly sandy soils is also

examined in this Chapter.

In Chapter 6, 2D as well as 3D numerical analyses carried out using Plaxis program are

presented that examine the suitability of this (widely used) program to predict the

vertical surface movement (‘greenfield’) associated with tunnelling. The method of

parameter selection (from the laboratory as well as from the field test) for the numerical

modelling is also discussed in detail. The observations from the comparison of predicted

and measured vertical surface movement are also discussed. The (often predicted) wide

and shallow settlement trough is investigated through FE parametric studies in

combination with data from available centrifuge model tests.

The monitored vertical movement at a multi-storeyed building (MAS) location along

the tunnel route is analysed in detail and discussed in Chapter 7. The influence of

surface structures in modifying the surface and the structural movement and the soil

structure interaction effect is also discussed. Both 2D as well as 3D FE analyses were

carried out to study interaction effects. This Chapter also investigates the influence of

building stiffness and soil type and/stiffness on the settlement troughs through

numerical parametric studies.

Chapter 8 assesses the effectiveness of the compensation grouting (hydraulic fracture)

in sand to reduce the volume loss due to tunnelling. The suitability of Finite Element

(FE) program to model compensation grouting is also evaluated.

The main conclusions drawn from Chapter 4 to 8 are summarised in Chapter 9.

Recommendations for future research are also highlighted.

7

CHAPTER 2 LITERATURE REVIEW

2.1 INTRODUCTION

Bored tunnels are constructed either by (i) Shield Tunnelling or (ii) New Austrian

Tunnelling Method (NATM). In Shield Tunnelling, the Tunnel Boring Machine (TBM)

is used to excavate the tunnel and this technique is usually used in soft ground

conditions to prevent ground collapse. The tail of the TBM supports the lining to be

erected and final lining is placed in position as soon as sufficient length is excavated.

The gap between the soil and lining is grouted immediately to reduce the volume loss.

In NATM, the tunnel is excavated in different parts such as the crown, bench and invert.

After each excavation section, the tunnel contour is stabilised by introducing temporary

lining of sprayed concrete. A final lining is installed later if one is required for long

term. The long term lining is usually provided by cast in situ concrete.

Irrespective of the method of construction, the excavation of tunnels induces

movements to the ground and structures in the tunnel vicinity. If the estimated

movement is above the permissible limits (for any given tunnelling method), additional

measures such as grouting are often carried out to improve the strength and stiffness of

the soil near and ahead of the tunnel. This Chapter reviews aspects of direct relevance to

this thesis, namely (i) the mode of ground deformation due to tunnelling, (ii) Settlement

prediction methods, (iii) building movement associated with tunnelling and soil

structure interaction effect and (iv) compensation grouting and its numerical modelling.

2.2 GROUND DEFORMATION

This thesis examines tunnelling-induced ground movement and hence it is worthwhile

to consider the various sources of these movements. In the first instance, it should be

noted that, regardless of the tunnel construction method, excavation induces stress

changes causing displacements and strains around a tunnel. The amount of ground

deformation around a tunnel cross-section is directly related to the additional amount of

8

excavation required to maintain that cross-section. The magnitude of the displacements

caused by the tunnelling is quantified in terms of volume loss VL, which is defined as

the excavated volume of the soil (Vg) in excess of the tunnel volume (V) divided by the

tunnel volume. The magnitude of volume loss varies for different ground conditions and

different tunnelling methods. Figure 2-1 shows the source of ground loss associated

with tunnel boring and each of these is explained below (Cording, 1991; Attewell,

1978).

1. Face loss: For the case of an open face shield tunnelling, this is the movement of

the soil towards the unsupported tunnel face during the tunnel excavation. If an

Earth Pressure Balanced (EPB) or slurry shield machine is used, heave may

develop in front of the cutter face due to excessive face pressure.

2. Shield loss: This is movement due to the radial ground loss around the shield to

fill the gap between the shield and the unsupported soil. This will be more if the

TBM is steering through a curve because of over-excavation.

3. Tail void loss: The erection of lining within the TBM introduces a gap between

the lining and the unsupported soil. The ground lost due to the squeezing of soil

into the void between the lining and the unsupported soil is referred to as the tail

void loss. This can be minimised by grouting the void between the soil and the

lining.

4. Lining loss: This movement is a continued radial loss of soil due to the

deformation of the lining as the overburden pressure is gradually redistributed to

its new equilibrium. If the tunnel comprises thick precast concrete segments, this

movement will be minimal.

5. Consolidation: This is movement due to dissipation of excess pore pressure

developed due to excavation or grouting. These pore pressure changes lead to

effective stress changes and hence additional ground movements over a long

time.

Chapter 2 Literature Review

9

For NATM, only face loss, lining loss and consolidation are applicable. Immediate

or short term deformation is caused by face loss, shield loss, tail void loss and lining

loss and the long term ground deformation is caused by consolidation.

Figure 2-1 Source of Ground Loss (Attewell, 1978)

The final settlement is a combination of the short term (immediate) and long term

(consolidation) settlement. Post construction settlement can be significant, particularly

in the case of tunnels in soft compressible clays (O’Reilly et al., 1991).

2.2.1 Failure Mode

The mode of soil failure (short term settlement) induced by the tunnel construction in

sand and clay is significantly different. The failure mechanisms inferred from centrifuge

model tests are illustrated in Figure 2-2 (a) and Figure 2-2 (b) for clay (Mair, 1979) and

sand (Chambon and Cortè, 1994) respectively. In clays, the failure surface propagates

upwards and outwards from the tunnel invert and becomes significantly wider at the

surface. However, in sand, the failure surface is like a narrow chimney propagating

almost vertically from the tunnel invert to the surface. This same behaviour of sand was

also observed by Potts (1976) in his laboratory model tests.

10

It may be inferred from these trends that the settlement trough that develops at the

ground surface is wider in clays than in sands - as failure approaches.

(a) Clay (Mair, 1979) (b) Sand (Chambon and Corte, 1994)

Figure 2-2Observed Failure Mode based on Centrifuge Model Tests

2.2.2 Centrifuge Model Testing in Sand

In clays, (i.e. in undrained condition), the volume loss calculated from the settlement

trough at any given level above the tunnel does not change with this level (Mair and

Taylor, 1997) and therefore an accurate estimate of volume loss can be obtained from

the surface settlement trough. However, in drained conditions (e.g. in dense sand) where

tunnelling induces volume changes in the soil, the volume loss calculated from the

surface settlement trough will be different at different levels above the tunnel (Cording

and Hansmire, 1975). This is in agreement with the observations of Jacobsz (2002) and

Marshall (2009). They carried out centrifuge tests that modelled tunnelling in sand and

found that under drained condition, estimation of ground loss from the soil displacement

data is complicated because of the soil’s contractive/dilative nature as shown in Figure

2-3. Figure 2-3 illustrates the difference in soil volume loss (ground loss calculated from

the settlement trough) and tunnel volume loss (calculated from the actual volume

extracted from the tunnel model) at different levels above the tunnel. Consequently,

inputting a volume loss (in numerical parametric study) calculated from the observed

Chapter 2 Literature Review

11

surface settlement trough will over predict the greenfield settlements at low volume

losses and under predict the settlements at higher volume losses.

Figure 2-3 Volume Loss Calculated from Soil Displacements Compared to Tunnel

Volume Loss (Marshall, 2009)

Figure 2-4 illustrates the mobilised lateral earth pressure coefficient calculated from the

stress measurements in the centrifuge model testing of sand performed by Jacobsz

(2002). This figure shows higher earth pressure coefficients near the tunnel crown at

250mm depth – which increase as the volume loss increased. Coefficients reduce

sharply with distance above the tunnel crown. However it appears that, for low volume

losses (less than 0.5%), the mobilised earth pressure coefficients are not significantly

varying along the depth of the tunnel axis. Unfortunately these measurements are only

from prototype depth equivalent of 7.5 m (75g test) from the surface.

12

Figure 2-4 Profile of Mobilised Lateral Earth Pressure Coefficient on Tunnel

centre line at Different Volume Losses (Jacobsz, 2002)

2.3 SETTLEMENT PREDICTION METHODS

Methods available for prediction of surface and subsurface settlement trough include the

empirical (Gaussian) method, numerical methods such as Finite element and Finite

difference methods and analytical methods (closed form solutions). Closed form

solutions can provide a rough estimate of ground behaviour although they cannot

accommodate complexities of tunnel construction methods and soil properties such as

anisotropy. Hence numerical methods are becoming increasingly common in

engineering practice. The empirical, 2D and 3D FE methods are considered in this

thesis and each of these is explained in the following sections. It is important to note,

however, that all of these “methods” require the tunnel volume loss as an input

parameter. This volume loss is a function of all the factors discussed in Section 2.2,

many of which depend critically on the construction methodology, TBM excavation

parameters etc. and therefore cannot be predicted numerically or analytically. The

methods therefore predict a distribution of ground movements for a prescribed volume

loss. Designers prescribe volume losses on the basis of case history data reported in the

Chapter 2 Literature Review

13

literature – using, for example similar tunnelling method in a given soil type. Soil

structure interaction can be modelled using the FE methods.

2.3.1 Empirical Method

The development of surface settlement trough ahead of a tunnel heading is illustrated in

Figure 2-5. Peck (1969) and subsequently many other authors have concluded that the

transverse settlement trough, which forms immediately after the tunnel has been

constructed, can be described by a Gaussian distribution curve. Typical view of

transverse settlement trough is shown in Figure 2-6. The vertical settlement along the

transverse direction can be expressed as,

⎟⎟⎠

⎞⎜⎜⎝

⎛ −= 2

2

max 2exp

iySS (2.1)

Where,

S – settlement

Smax - maximum settlement above the tunnel centre line

y– horizontal distance from the tunnel centre line

i – transverse horizontal distance from the centre line to the point of inflection of the

settlement trough.

Figure 2-5 Geometry of the tunnel induced settlement trough (after Attewell et

al.,1986)

14

Tunnel Volume, V

Ground loss at Tunnel, V g

Volume changein ground =ΔVg

Volume loss V L =V g /V

Point of inflection

Dep

th z 0

Volume of settlement trough V s =V g + Δ V g

Smax

i

Figure 2-6 Transverse Settlement Trough

The volume of the transverse surface settlement trough per meter length of tunnel, Vs, can be evaluated by integrating equation 2.1 and may be expressed as:

∫∞

∞−

== max2 SiSdxVs π (2.4)

Although, for the undrained (constant volume) case, the ground loss close to the tunnel

(Vg) will be same as the volume of the surface settlement trough (Vs), this will be

different (see section 2.2.2) for the drained case where shear induced volume changes

within the soil takes place. However the volume loss (VL) is usually approximated as,

4

2DV

V sLπ

= (This is normally expressed as a percentage value) (2.5)

Where D, is the outer tunnel diameter.

Chapter 2 Literature Review

15

A number of empirical correlations have been proposed which relate iy to the tunnel

depth to diameter ratio and soil type. For practical purposes it is often assumed that the

parameter i varies proportionally with z0 (O’Reilly and New, 1982):

0Kzi = (2.6)

Where,

K – a constant called the trough width parameter

z0 – depth of the tunnel axis below the ground surface.

Taking into account of different layers of soil in a soil profile, New and O’Reilly (1991)

suggested the following relationship:

....2211 ++= zKzKi ,

Where,

K1 and K2 are trough width parameter in layer 1 and layer 2 of depth z1 and z2

respectively.

Although the Gaussian approach is simple, the use of this method is limited to

• Single tunnels or multiple tunnels where there is no significant interaction effect.

• Estimate short term ground movement (no consolidation movement)

• Greenfield sites where there are no structural interaction effects.

2.3.2 Numerical Prediction

Because of the limitations of the empirical method (e.g. the effect of structures on

tunnelling cannot be predicted), numerical modelling has increasingly been used to

examine effects of tunnelling. The most widely used numerical method appears is the

Finite Element method (FEM); the Finite Difference Method (FDM) is used

16

occasionally (e.g. using FLAC). The advantages of FEM over the empirical method are

its ability to:

• Deal with complex ground conditions;

• Model realistic soil behaviour;

• Simulate the construction sequence;

• Accommodate the interaction between multiple tunnels;

• Account for adjacent services and structures;

• Simulate immediate and long term conditions;

• Deal with ground treatment (e.g. compensation grouting); and

• Handle complex hydraulic boundary conditions.

The two dimensional and three dimensional Finite Element (FE) method is used to

predict the tunnel induced settlement, as described in the following sections.

Two Dimensional Finite Element Analysis

Tunnel excavation is a three dimensional problem. However three dimensional analyses

require excessive computational resources such as storage space and time of analysis.

Because of these complexities, two dimensional analyses are preferred over three

dimensional analyses. Various methods proposed to take account of the stress and strain

changes ahead of the tunnel in plane strain analysis are the: (i) Gap method (Rowe et

al., 1983), (ii) Convergence-Confinement method (Panet and Guenot, 1982), (iii)

Progressive Softening method (Swoboda,1979), (iv) Volume Loss Control method

(Addenbrooke et al., 1997, Liu et al., 2000, Franzius, 2003)

Three Dimensional Finite Element Analysis

Three dimensional FE analyses would consider the movement of the soil associated

with all the sources described in section 2.2. Different researchers used different

Chapter 2 Literature Review

17

methods to model 3D tunnel construction and the modelling techniques of different

authors were summarised by Wongsaroj (2005). The modelling of shield tunnelling is

complicated as it involves modelling different parameters such as (i) face pressure at the

cutter face of the TBM (to stabilise the soil ahead of the TBM), (ii) movement of the

TBM, (iii) installation of lining at the back of TBM and closing the tail void using

grouting.

The face pressure at the cutter face is often modelled by applying prescribed pressure at

the excavated tunnel face; for example, Komiya et al. (1999) and Mroueh and Shahrour

(2003). The shield losses were modelled in three different ways such as by (i) applying

a percentage stress reduction at the tunnel boundary depending on the length of unlined

tunnel (Mroueh and Shahrour, 2002) (ii) applying a prescribed displacement to the

tunnel boundary (Lee and Rowe 1990a) and (iii) contracting the tunnel boundary

(Koelewijn and Verruijt, 2001). The tail void closure using grouting was modelled by

two methods. The first of these involves applying prescribed displacements or

contraction to the lining (Koelewijn and Verruijt, 2001). In the second method, grouting

is modelled either by applying an outward pressure to the lining (Ezzeldine, 1999) or by

expansion of the lining (Koelewijn and Verruijt, 2001).

Effect of Initial Stress Condition on Predicted Settlement trough

The influence of initial stress history on the predicted settlement trough both in 2D and

3D analyses have been reported by many authors. The predicted settlement troughs

using a higher K0 was often wider and shallower compared to the observed settlement

troughs in the field. Wider settlement troughs were reported by Addenbrooke (1996),

Franzius (2003) and many others for their 2D plane strain analysis even with different

soil models.

Previous literature also shows that width of the settlement trough predicted using 3D

modelling is also wider than observed in the field. Although the tunnelling can be

modelled in a more realistic manner in 3D, various authors such as Guedes de Melo &

Santos Pereira (2000) and Franzius (2003) also predict a wider and shallower trough in

soils with higher K0 values.

18

Franzius (2003) carried out both 2D and 3D FE analysis to study the influence of K0 and

soil anisotropy on the predicted settlement trough. His analyses concluded that, neither

the 3D effect nor the soil anisotropy can account for the wide transverse settlement

trough predicted by FE analyses in a high K0 regime. He found that although the trough

shape can be improved with unrealistically high soil anisotropy, this leads to

significantly higher volume loss. This is because of the reduction in vertical stiffness

due to the increase in horizontal stiffness (to meet certain shear modulus criteria). He

also found that with low K0 the magnitude of settlement and thus the volume loss

predicted was higher in a 3D analysis; he did not, however, comment on the effect of

mobilised strength. Franzius (2003) argues that the K0 value at the tunnel axis has a

significant influence on the nature of surface settlement trough and that a higher

specified K0 value also results in a wider prediction for the longitudinal trough. His 3D

analyses also showed that stabilised longitudinal movements at the start of the geometry

could not be obtained even after excavating a long distance (100m) - both for isotropic

and anisotropic cases; this is shown in Figure 2-7.

Ng and Lee (2005) also demonstrated through their three dimensional analysis (open

face tunnelling) that the surface settlement trough is governed by the combined effect of

stiffness ratio (E’h/E’v) and the K0 value. They found that as E’h increases, the predicted

settlement trough will be deep and narrow due to the mobilisation of small plastic

extension shear zones at the crown and at the invert. They also found that, for a given

stiffness ratio, the computed settlement trough is narrower if K0 is lower.

Chapter 2 Literature Review

19

(a) Isotropic 3D analysis

(b) Anisotropic 3D analysis

Figure 2-7 Longitudinal Settlement Profile (Franzius, 2003)

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2.4 BUILDING MOVEMENT DUE TO TUNNEL BORING

The ground movements arising from tunnelling are described in section 2.2 and have

been the subject of most previous research. However the movements occurring in built

up areas are less well understood due to the site-specific nature of soil structure

interaction effects. Unfortunately, apart from relatively recent work done on the Jubilee

line extension in London, few published data are avail