Effects of tunnel construction on nearby pile foundations 1

THE EFFECTS OF TUNNEL CONSTRUCTION ON NEARBY PILE FOUNDATION PANG CHIN HONG NATIONAL UNIVERSITY OF SINGAPORE 2006 THE EFFECTS OF TUNNEL CONSTRUCTION ON NEARBY PILE FOUNDATION PANG CHIN HONG (B.Eng. (Hons.), Manchester) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2006 DEDICATION To my dearest parents and sister i ACKNOWLEDGEMENTS Ever since the day I have started my research work in NUS, I owe a great favour to many people for their helps and assistances. First of all, I would like to express my deepest gratitude to a wonderful person and he is none other than my main supervisor, Prof. Yong Kwet Yew. Despite his busy schedule as the Vice President of NUS, he tried to meet me with the best time he could find. Not only did he give me a lot of help technically, but also his advice to my personal and career development. Every discussion with him was very motivating and he brought out the best in me. To my co-supervisor, Prof. Chow Yean Khow, who had throughout the research, gave me very constructive comments without which this thesis will not be so valuable. I thank him for his willingness to share his experience and guidance. Not to be forgotten, my former supervisor, Dr. Dasari Ganeswara Rao who had left for the United State. He had closely supervised my work for the first three semesters and had given me pragmatic advice and guidance on finite element modelling, ABAQUS software and SDMCC model. Besides, I also appreciate the advice from A/Prof. Leung Chun Fai in the constant students group discussion held every forth-night. Gratitude also goes to A/Prof Somsak Swaddihipong and A/Prof. Tam Chat Tim of the Structural Group in NUS for their advice on issues related to structure and concrete. For case study on the MRT North East Line Contract C704, special thanks has to be delivered to Dr. Jeffrey Wang, formerly chief engineer at MRT NEL C704, Dr. Lim Ken Chai of Tritech Consultant Pte Ltd for providing valuable field data, constant correspondence and discussion. In addition, data were also obtained from the Land Transport Authority (LTA) of Singapore with the permission from Mr. Rajan Krishnan, former Project Director. Not to be missed, LTA staff who has taken a great time and effort to dig out the data for me, particularly Mr. Seetoh Hon Hoy and Mr. Azmi Aidi. ii For case study on the MRT Circle Line C825, thanks go to WH–STEC-NCC JV for providing the field data and allowing assess to the construction site, particularly Mr. Chu Chiang Yong, Coordination Manager, Mr. David Lee, Geotechnical Manager, Mr. Yang Hong Qiang, Geotechnical Engineer and Mr. Nigel Ogden, Tunnel Construction Manager, Mr. Lim Han Chong, Senior Engineer and Mr. Savaranan, QA/QC Engineer. Furthermore, I thank Dr. Jeffrey Wang of Tritech Consultants and Dr. Jeyatharan Kumarasamy of LTA for spending their precious time to review my thesis and feedback. Besides, I extend my appreciation to my many colleagues and friends who I have consulted during the course of the research, particularly Ch’ng Yih, Cheh Hsien, William Cheang, Zou Jian, Dominic Ong, Hai Bo, He Lin and Ah Lee. To my two buddies, Kar Lu and Kheng Ghee who have been with me for lunch and dinner almost every day, I greatly enjoy your companion and also the trips we had together especially to Vietnam. Not without which the heartiest support from Magenta Sim, a dear friend who keep me accompanied at all time. Last but not least, thanks to National University of Singapore for the award of research scholarship throughout the four years period without which this research program would not has commenced. JANUARY 2006 iii TABLE OF CONTENTS DEDICATION i ACKNOWLEDGEMENTS ii TABLE OF CONTENTS iv NOTATIONS x LIST OF TABLES xiii LIST OF FIGURES xiv LIST OF PUBLICATIONS xx SUMMARY xxi CHAPTER INTRODUCTION 1.1 Background……………………………………………………………….…………………… 1 1.1.1 Tunnel construction near pile foundation………………… .……………… 1.1.2 Current design and construction approach…………………… …… 1.2 Objectives of the study…………… .…………………………………… 1.3 Organisation of thesis… .….……………………………………… .….……………………… CHAPTER LITERATURE REVIEW 2.1 Introduction …………………………………………………………………… . 2.2 Pile responses caused by tunnelling: Physical observations.……… .… 2.2.1 Case histories.……………………………………………………… . 2.2.2 Laboratory and centrifuge tests .………… .………………… 12 2.2.3 Full scale pile tests……………… ……………………………………… . 15 2.3 Pile responses caused by tunnelling: Prediction and design methods.… 16 2.3.1 Empirical method………………………………………………………… . 16 2.3.2 Finite element method….………………….……………………………………… 17 2.3.3 Numerical and analytical methods.………… .……………………………………. 19 2.3.4 Design charts……………………………………….………………………………. 21 iv 2.4 Current understanding and outstanding issues.….……………………………………………. 21 2.4.1 General……………………………………………………………… 22 2.4.2 Pile settlement……………………………………………………… . 22 2.4.3 Pile axial force…………………………………………………………… 23 2.4.4 Pile lateral deflection…………………… .………………………… . 24 2.4.5 Pile bending moment……………………………………………………………… 24 2.4.6 Pile group effect………………………………………………… ……………… 25 2.4.7 Multiple-tunnel advancement effect………………… ………………… . 26 2.5 Concluding remarks…………………….……………………………………… 26 CHAPTER 27 CASE STUDY: TUNNELLING ADJACENT TO PILE FOUNDATION FOR THE CONTRACT C704 – GROUND CONDITION AND FIELD MONITORING 3.1 Introduction……………………………………………………………… . 27 3.2 Background and overview of the project…………………………………… …… 28 3.3 Geology and ground conditions .….……………………………………… 29 3.4 Design and construction details…………………………………………………… 30 3.5 Construction sequence……………………………………………………………………… . 33 3.6 Instrumentation programme.………………………………………….…………… 34 3.6.1 Monitoring scheme………… .………………………….………………………. 34 3.6.2 Interpretation of data….………………………………….……………… 35 3.6.2.1 Assessment of surface settlement………………………… 35 3.6.2.2 Assessment of instrumented pile……………………… . 35 3.7 Monitoring results………………………………………………………… 37 3.7.1 Ground surface settlement………………………………………………………… 37 3.7.2 Subsurface soil movement………………………………………………………… 40 3.7.2.1 Vertical soil movement………………………………………………… 40 3.7.2.2 Lateral soil movement…………………………………… . 41 3.7.3 Response of pore pressure… …………………………………………………… . 43 3.7.4 Responses of pile foundation……………………………………… 43 3.7.4.1 Tunnelling induced axial force…………………… ……… 43 3.7.4.2 Tunnelling induced transverse bending moment………………… . 46 3.7.4.3 Tunnelling induced longitudinal bending moment……………………… 48 v 3.7.4.4 Post-tunnelling loading on piles………………………………………… . 49 Relationship between soil movement and pile responses ………………………… 50 3.7.5.1 Axial force vs. volume loss………………………………… . 50 3.7.5.2 Bending moment vs. volume loss……… .……………………… 51 3.7.5.3 Transverse BM vs. longitudinal BM………………………………………. 52 3.7.5.4 Distance effect vs. pile group effect………………………………………. 52 3.8 Analysis of pile responses using design charts proposed by Chen et al. (1999) …… . 53 3.9 Concluding remarks…………………………………………………………………………… . 55 CHAPTER 57 3.7.5 CASE STUDY: TUNNELLING ADJACENT TO PILE FOUNDATION FOR THE CONTRACT C704 – THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS 4.1 Introduction……………………………….………………………………………………… 57 4.2 Current three-dimensional modelling techniques…………………………………………… 58 4.2.1 Modelling of shield tunnel advancement…………………… ……………………. 58 4.2.2 Modelling of pile foundation………………………………………………………. 61 Details of analysis……………………… ……………………… ……………………… 61 4.3.1 Finite element mesh and boundary conditions……….……… . 61 4.3.2 Numerical modelling procedure……………………………… . 63 4.3.3 Ground conditions and soil profile………………………………………………… 65 4.3.4 Material constitutive models………………….……………………………………. 65 4.3.5 Soil parameters for analysis………………………………….…………………… 68 4.3.5.1 General soil parameters…………………………………………………… 68 4.3.5.2 Parameters for Mohr-Coulomb model…………………………… 68 4.3.5.3 Parameters for MCC model……………………………………… 68 4.3.5.4 Parameters for SDMCC model……………………………………………. 69 4.3.6 Tunnelling parameters for analysis………………………………………………… 72 4.3.7 Pile parameters for analysis……………………………………………… . 73 Analysis of greenfield soil movement due to tunnel advancement . …………… . 73 4.4.1 Effect of tunnelling advance rate….……… .………………… . 74 4.4.2 Effect of face pressure…………………………………………………… . 75 4.4.3 Effect of tail void grouting…………………………………………………………. 76 4.4.4 Effect of lining stiffness .………………………………………………………… 79 4.3 4.4 vi 4.5 4.4.5 Effect of soil models……………………………………………………………… 79 4.4.6 Effect of soil earth pressure at rest (Ko)……………………………………………. 80 4.4.7 Controlling tunnel convergence by artificial boundary conditions………………… 81 Analysis of pile responses subjected to single tunnel advancement…… . 83 4.5.1 Results of a typical analysis…………………………………… . 83 4.5.2 Effect of tunnel face pressure………………………… . 86 4.5.3 Effect of pile cap and pile cap fixity ………………………… 87 4.5.4 Effect of pile stiffness…………………………….…….………………………… 88 4.5.5 Effect of soil earth pressure at rest (Ko)……………………………………………. 88 4.5.6 Effect of pre-tunnelling loading in piles……………………………………………. 89 4.6 Analysis of pile responses subjected to post-tunnelling construction .…………………… . 90 4.7 Comparison of pile group analysis to single pile and greenfield analyses…………………… 92 4.8 Analysis of pile responses subjected to twin-tunnel advancement….… 93 4.9 Concluding remarks………………………………………………… ……………………… 95 CHAPTER PARAMETRIC STUDIES OF PILE RESPONSES DUE TO TUNNELLING 97 5.1 Introduction…………………………………………………………………… 97 5.2 Simplified three-dimensional finite element model ……………………………….………… 98 5.3 5.2.1 Soil model and parameters……………………………………………………… . 98 5.2.2 Numerical simulation procedure………………………….… . 99 5.2.3 Modelling the pile-soil interface……………………….…………………………. 100 5.2.4 Details of parametric studies ……………………………………… 102 Results of parametric studies .……………………… … .…… …… 103 5.3.1 Pile settlement……………………………………………………… . 103 5.3.2 Pile axial force…………….……………………………………………… 104 5.3.3 Pile lateral deflection……………………………………………… …………… . 107 5.3.4 Pile bending moment………………………………………………………………. 107 5.4 Effect of pile shaft de-bonding………………………………………………… 108 5.5 Effect of pile group .…………………………………………………………………………. 110 5.5.1 Effect of pile group size……………………………………………………………. 111 5.5.2 Effect of pile group layout…….…………………………………………………… 113 5.6 Concluding remarks…………………………………………… …………………………… 113 vii CHAPTER PLANE STRAIN IDEALISATION OF TUNNEL-PILE INTERACTION IN FINITE ELEMENT ANALYSIS 116 6.1 Introduction……………………………………………………………… . 116 6.2 Current plane strain modelling techniques for tunnel and pile foundation………………… . 117 6.2.1 Modelling of tunnel……………………………………………………… 117 6.2.1.1 Technique 1: Gap method………………………………………………… 118 6.2.1.2 Technique 2: Convergence confinement method………………………… 118 6.2.1.3 Technique 3: Volume loss control method………………… 119 6.2.1.4 Technique 4: Progressive softening method……………………………… 119 Modelling of pile foundation……………………….……………… . 119 6.2.2 6.2.2.1 Technique 1: Modelling soil and structural material as a composite element…………………………………………………………………………… . 120 6.2.2.2 Technique 2: Modelling soil and structural material as a continuous element…………………………………………………………………… . 121 6.2.2.3 Technique 3: Modelling structural material as an external element …………………………………………………………………………………… . 121 6.3 Techniques to be adopted in this study…… .……….…… .….…………… 122 6.4 Single pile response due to tunnelling.…… .… … ……….………… 125 6.5 6.4.1 Problem definition………… ………………………………… 125 6.4.2 Details of analysis………….……………………………………………………… 126 6.4.3 Typical results of analysis.………………………………………………………… 127 6.4.4 Effect of pile-soil interface… .…………………………………………………… 129 6.4.5 Effect of soil stiffness……………… ……………………………………………. 131 6.4.6 Effect of tunnel volume loss……………………………………… 132 6.4.7 Effect of pile stiffness….….………………………………………………………. 133 6.4.8 Effect of pile diameter…………………………………………………………… 133 6.4.9 Effect of pile-tunnel distance………………………………… 134 6.4.10 Effect of pile length to tunnel depth ratio…………………………………………. 134 6.4.11 Effect of loading acting on pile……………………………………………………. 135 Pile group response due to tunnelling.……………… …………………… . 137 6.5.1 Idealisation of single-row pile group.…………………………………… . 137 6.5.2 Idealisation of multiple-row pile group…….…………………………… . 138 viii 6.6 6.7 6.8 6.5.3 Effect of pile spacing………………….………………………………… . 138 6.5.4 Effect of pile rows spacing……………………………………………… . 139 6.5.5 Effect of pile group size…………………………………………………………… 139 6.5.6 Effect of pile cap……………………………………………… . 140 Calibration charts and recommendations…………………………………… . 140 6.6.1 Observations from sensitivity studies ………………………… . 140 6.6.2 Calibration charts……………………………………………… 140 6.6.3 Other influencing factors………………………………………………………… 142 6.6.4 Limitations of calibration charts………………………………………… . 143 6.6.5 Recommendations for finite element analysis… .……………………… . 144 Application of 2-D finite element model to case studies…………………………………… 144 6.7.1 Case 1: MRT North East Line Singapore - Contract C704…… 145 6.7.2 Case 2: MRT Circle Line Stage Singapore – Contract C825…… 147 6.7.3 Case 3: Centrifuge tests in stiff clay……………………………………… 149 Concluding remarks………………………………………………………………… 149 CHAPTER SUMMARY OF FINDINGS AND CONCLUSIONS 151 7.1 Introduction……… .……….……………………………………………………………… 151 7.2 Field monitoring……………………………………………………………… 151 7.3 3-D finite element simulation of tunnel advancement on adjacent pile foundation………… 154 7.4 Parametric studies…………………………………………………………………………… 158 7.5 Plane strain idealisation of tunnel-pile interaction…………………………… . 160 7.6 Recommendations for future research………………….…………………………………… . 162 TABLES 164 FIGURES 177 REFERENCES 323 APPENDICES 333 ix NOTATIONS The following nomenclature and symbols are adopted in this thesis A At Apile Aeq Atun B c’ Cu Dwall(2D) Dpile Dtun Ec Ecut Egrout Egrout.upp Egrout.bott Ehardened Elining Epile Es Esoil Eu Eshield E’ Et Eeq E(wall)2D E(pile)3D EI EA EpileIpile EpileApile fb fs G Gmax Gmin H Htun I Icracked Igross Ipile k ks K G multiplier used in simple non-linear elastic soil model Slope of tangent modulus line Cross-sectional area of pile Equivalent cross-sectional area of pile Cross-sectional area of tunnel Intercept of the tangent modulus line (also known as initial tangent modulus) Effective cohesion of soil Undrained shear strength of soil Pile wall thickness in plane strain analysis Pile diameter (=Dpile(3D)) Tunnel diameter Young’s modulus of concrete Young’s modulus of over-cut element Young’s modulus of grout in liquid state Young’s modulus of grout above tunnel springline Young’s modulus of grout below tunnel springline Young’s modulus of hardened grout Young’s modulus of tunnel lining Young’s modulus of pile Secant modulus of pile Young’s modulus of soil Undrained Young’s modulus of soil Young’s modulus of shield machine Effective Young’s modulus of soil Tangent modulus of pile Equivalent Young’s modulus Pile stiffness in plane strain analysis Pile stiffness in 3-D analysis Bending stiffness Axial stiffness Bending stiffness of pile Axial stiffness of pile Limiting end bearing pressure Limiting skin friction Shear modulus of soil Maximum shear modulus of soil Minimum shear modulus of soil Slope of Hvorslev surface in q, p’ surface in SDMCC model Tunnel depth (springline level) from ground surface Point of inflextion Cracked moment of inertia of pile Gross moment of inertia of pile Moment of inertia of pile Trough width parameter Permeability of soil Bulk modulus of soil x Kmax Ko Lgrout Lp Lp(debond) M Mcr Mpile Mxx Myy Mult N n OCR Pgrout.upp Pgrout.bott Pgrout.uniform p’ p q R s S S1 S2 Smax teq VL v Vo Xpile XSB XNB x X y Y z Z Maximum bulk modulus of soil Earth pressure at-rest of soil Grout length to be in fluid state Pile length De-bonded pile length Critical state ratio Cracked moment of pile Pile bending moment Pile bending moment in the transverse direction Pile bending moment in the longitudinal direction Ultimate bending moment capacity of pile Axial force in pile Strain exponent in simple non-linear elastic soil model Over-consolidation ratio of soil Grout pressure above tunnel springline Grout pressure below tunnel springline Uniform grout pressure Mean normal effective pressure of soil Contact pressure Deviatoric stress of soil Pile radius Surface settlement at a distance x from tunnel axis Slope of no-tension cut-off line in q,p’ space in SDMCC model Pile spacing in the transverse plane Pile spacing in the longitudinal plane Maximum surface settlement Equivalent thickness Volume loss caused by tunnelling Specific volume Initial volume of cavity (in pressuremeter test) Distance between tunnel axis and centre of pile (for single pile) or centre of front pile (for pile group) Clear distance between SB tunnel and the nearest pile Clear distance between NB tunnel and the nearest pile Distance from tunnel axis Transverse length of mesh Distance between strain gauges at equal distance and opposite direction from neutral axis Longitudinal length of mesh Distance from centroid to the extreme fibre of pile in tension Vertical length of mesh A, n1, m1, B, n2, m2, b2 Experimental parameters to define shear modulus variation in SDMCC model C, n3, m3, D, n4, m4, b4 Experimental parameters to define bulk modulus variation in SDMCC model xi σ β λ λf κ γbulk γslip γslip(2D) γslip(3D) φ‘ ε εc εq εqe εqp εv εve εvp εs f c’ fcu fr τcrit τ µ µ2D µ3D δ π Γ ∆p ∆V Initial soil stresses Stiffness reduction factor in Progressive softening method Logarithmic hardening modulus (gradient of normal compression line) Stress reduction factor in Convergence Confinement method Logarithmic elastic bulk modulus (gradient of swelling line) Bulk unit weight of soil Limiting elastic pile-soil slip Limiting elastic pile-soil slip in plane strain analysis Limiting elastic pile-soil slip in 3-D analysis Effective angle of shearing resistance (=φsoil) Measured strain (+ve = tension and -ve = compression) Cavity strain in pressuremeter test Deviatoric strain of soil Deviatoric strain of soil which is at the threshold of elastic behaviour Deviatoric strain of soil which is at the threshold of plastic behaviour Volumetric strain of soil Volumetric strain of soil which is at the threshold of elastic behaviour Volumetric strain of soil which is at the threshold of plastic behaviour Triaxial shear strain Characteristic compressive cylinder strength of concrete at 28 days Characteristic cube strength of concrete at 28 days Modulus of rupture of concrete Critical shear stress at pile-soil interface Shear stress at pile-soil interface Coefficient of friction for pile-soil interface slip element Coefficient of friction for pile-soil interface slip element in 2-D analysis Coefficient of friction for pile-soil interface slip element in 3-D analysis Pile-soil friction 3.142 Specific volume on critical state line at p’=1kPa in compression plane Change in applied pressure (in pressuremeter test) Cavity volume change (in pressuremeter test) xii LIST OF TABLES Table 2.1 Table 2.2 Table 2.3 Summary of reported case histories Summary of reported centrifuge tests (in prototype unit) Summary of reported prediction and design methods Table 3.1 Table 3.2 Table 3.3 Table 3.4 Table 3.5 Table 3.6 Weathering classification for Granite in Singapore (Dames & Moore, 1983) Details of instrumented pile foundation for bridge viaducts Construction stages of viaduct bridge and tunnels advancement Volume loss for SB and NB tunnels advancement Maximum dragload measured in piles due to tunnels advancement Maximum transverse bending moment measured in piles due to tunnels advancement Maximum longitudinal bending moment measured in piles due to tunnels advancement Comparison of the assumptions made in the design charts with C704 problem Table 3.7 Table 3.8 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Consideration of various physical factors in 3-D finite element modelling of shield tunnel Soil parameters adopted for Mohr-Coulomb model Critical state parameters adopted for MCC and SDMCC models Parameters for shear modulus in SDMCC model Parameters for bulk modulus in SDMCC model Summary of EPBM advance rate xiii LIST OF FIGURES Figure 1.1 Figure 1.2 Figure 1.3 Figure 1.4 An illustration of pile responses caused by tunnel construction Relative tunnel-pile configurations observed in practice Current design and assessment approach for pile subjected to tunnelling Zone of work restriction in Japan (Fujita, 1989) Figure 2.1 Tunnelling adjacent to pile foundation in Singapore (a) MRT NEL Contract C704 (Coutts & Wang, 2000) (b) MRT NEL Contract C705 (Tham & Deustcher, 2000) MTR Island Line in Hong Kong (Forth & Thorley, 1996) Angel Underground Development in London (Mair, 1993; Lee et al., 1994) Tunnelling for the Jubilee Line Extension in London (a) Under building (Powderham et al., 1999) (b) Adjacent to building (Selemetas et al., 2002) Tunnelling for the Channel Tunnel Rail Link (a) Renwick Road bridge (b) Ripple Road Flyover (c) A406 viaduct (Jacobsz et al., 2005) Tunnelling adjacent to bridge pier in Japan (Moroto et al., 1995) Tunnelling under various constraints from pile foundations (Nakajima et al., 1992) Tunnelling under large dome stadium supported on pile foundations (Inose et al., 1992) Tunnelling under pile foundations (Takahashi et al.,2004) 1-g model set up to simulate tunnelling effect on pile foundation (Morton & King, 1979) Centrifuge test set up to simulate tunnelling effect on pile foundation (Hergarden et al., 1996) Zone of influence around tunnel in which potential for large pile settlement exists (Jacobsz et al., 2002) Load transfer mechanism for (a) long pile (b) mid-length pile (Lee & Chiang, 2004) Pilot test carried out at Second Heinenoord tunnel site (a) Test layout (b) Zone of influence (Kaalberg et al., 2005) Zone of influence around EPB tunnel in London Clay (Selemetas et al., 2005) Empirical method of assessment for (a) pile settlement (b) pile overstress (c) pile bearing capacity during shield advancement (d) pile bearing capacity due to tail void grouting (e) pile bearing capacity assuming an imaginative cone Load-settlement curve from FE simulation of pile load test (Lee & Ng, 2005) Observations of pile responses (a) pile head settlement (b) pile maximum axial force (c) pile maximum lateral deflection (d) pile maximum bending moment Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 2.7 Figure 2.8 Figure 2.9 Figure 2.10 Figure 2.11 Figure 2.12 Figure 2.13 Figure 2.14 Figure 2.15 Figure 2.16 Figure 2.17 Figure 2.18 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 3.7 Figure 3.8 Figure 3.9 Figure 3.10 Figure 3.11 Location of the MRT North East Line in Singapore Location of piled bridge viaducts and tunnels Geological profile along MRT North East Line (a) plan view (b) cross section Basic soil properties measured at C704 Strength properties measured at C704 Layout of monitoring instrumentation installed at Pier 20 Maximum surface settlement measured at tunnel axis from Serangoon Station to Woodleigh Station Surface settlements due to (a) SB tunnel advancement (b) NB tunnel advancement at Pier 20 Development of surface settlement with time above SB and NB tunnel axes at Pier 20 section Surface settlements due to twin tunnels at Pier 20 section Subsurface vertical soil movements at Pier 20 (a) MX6006 (b) MX6005 xiv Figure 3.12 Figure 3.13 Figure 3.14 Figure 3.15 Figure 3.16 Figure 3.17 Figure 3.18 Figure 3.19 Figure 3.20 Figure 3.21 Figure 3.22 Figure 3.23 Figure 3.24 Figure 3.25 Figure 3.26 Figure 3.27 Figure 3.28 Figure 3.29 Figure 3.30 Figure 3.31 Figure 3.32 Figure 3.33 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5 Figure 4.6 Figure 4.7 Figure 4.8 Figure 4.9 Figure 4.10 Figure 4.11 Figure 4.12 Lateral soil deflection measured in inclinometer I6006 at Pier 20 (a) due to SB tunnel (b) due to SB+NB tunnels Lateral soil deflection measured in inclinometer I6005 at Pier 20 (a) due to SB tunnel (b) due to SB+NB tunnels Development of excess pore pressure with time at Pier 20 Development of axial force in pile P1 at Pier 20 due to EPBMs advancement Maximum measured axial force in piles at Pier 20 due to both SB and NB tunnels Development of axial force in (a) pile P6 at Pier 11 (b) pile P3 at Pier 14 due to EPBMs advancement Stress relief in piles at (a) Pier 11 (b) Pier 14 Measured bending moment in piles P1 and P2 at Pier 20 (a) transverse direction (b) longitudinal direction Transverse bending moment-axial force interaction diagram (a) Pier 11 (b) Pier 14 (c) Pier 20 Development of longitudinal bending moment in pile P1 at Pier 20 Longitudinal bending moment-axial force interaction diagram (a) Pier 11 (b) Pier 14 (c) Pier 20 Post-tunnelling measurement of the development of axial force in pile P1 at Pier 20 Locked-in stress and nett loading due to post-tunnelling loading (a) Pile P1 (b) Pile P2 Effect of post-tunnelling loading on the bending moment response of pile P2 (a) transverse direction (b) longitudinal direction Development of axial force with volume loss in piles P1 and P2 at Pier 20 Relationship between axial force and volume loss due to SB tunnel advancement (a) 1.2m diameter pile (b) 1.8m diameter pile Relationship between final axial force and volume loss due to SB and SB+NB tunnels advancement Relationship between transverse bending moment and volume loss due to SB tunnel advancement (a) 1.2m diameter pile (b) 1.8m diameter pile Relationship between longitudinal bending moment and volume loss due to SB tunnel advancement (a) 1.2m diameter pile (b) 1.8m diameter pile Relationship between transverse and longitudinal bending moments due to SB tunnel advancement Ratio of front pile to rear pile responses due to SB tunnel advancement Comparison of estimated and measured pile responses (a) dragload (b) transverse bending moment Idealised steps in shield tunnelling Gap approximation technique in 3-D finite element analysis (Lee & Rowe, 1991) Full shield tunnel advancement technique (Komiya et al., 1999) Lining shrinkage technique (Augarde et al., 1998) Modelling EPB shield tunnel advancement (Lim, 2003) Grout pressure model (Plaxis, 2004) Typical finite element mesh used to simulate the pile group subjected to (a) single tunnel advancement (b) twin tunnels advancement Finite element simulation procedure for shield tunnel advancement Typical soil profile simulated in the FE analysis State boundary surface in SDMCC model Stiffness degradation with strain in SDMCC model Degradation of normalised shear modulus with shear strain derived from pressuremeter tests xv Figure 4.13 Figure 4.14 Figure 4.15 Figure 4.16 Figure 4.17 Figure 4.18 Figure 4.19 Figure 4.20 Figure 4.21 Figure 4.22 Figure 4.23 Figure 4.24 Figure 4.25 Figure 4.26 Figure 4.27 Figure 4.28 Figure 4.29 Figure 4.30 Figure 4.31 Figure 4.32 Figure 4.33 Figure 4.34 Figure 4.35 Figure 4.36 Figure 4.37 Figure 4.38 Figure 4.39 Figure 4.40 Figure 4.41 Figure 4.42 Figure 4.43 Measured maximum shear modulus from CSWS (Anand et al., 2001) Variation of (a) shear modulus (b) bulk modulus with strain in granite residual soil in Hong Kong Progress for South bound tunnel drive from Serangoon Station to Woodleigh Station Effect of tunnel advancement rate on (a) transverse surface settlement (b) longitudinal surface settlement (c) excess pore pressure Surface settlement troughs at different face pressure Surface settlement troughs for varying grout stiffness Alternative numerical procedure for modelling tail void grouting (a) Tunnel advancing section (b) Cross-section Surface settlement troughs for varying grout pressure Effect of grout pressure length on the surface settlement trough Surface settlement troughs for varying lining stiffness Surface settlement troughs predicted by various soil models Longitudinal surface settlement profile using SDMCC model Earth pressure at-rest of the Bukit Timah Granite residual soil Surface settlement troughs for varying Ko parameter (a) MC model (b) MCC (c) SDMCC model Subsurface horizontal soil movement for varying Ko parameter (a) Transverse direction (b) Longitudinal direction Artificial boundary fixity to improve soil movement prediction (a) Fixed tunnel invert (b) Lower-quarter tunnel fixed (c) Lower-half tunnel fixed (d) lower-quarter tunnel restrained vertically (e) Lower-half tunnel restrained vertically Surface settlement troughs for varying artificial boundary fixity Predicted ground deformation contour (a) Case (b) Case (c) Case (d) Case (e) Case Subsurface soil movements for varying artificial boundary fixity (a) Vertical soil movement at 9m away from tunnel axis (b) Lateral soil movement at 9m away from tunnel axis Surface settlement troughs (a) Transverse direction (b) Longitudinal direction Subsurface horizontal soil movement (a) Transverse direction (b) Longitudinal direction Development of excess pore pressure due to SB tunnel Responses of piles subjected to single tunnel advancement (a) Axial force (b) Pile head settlement (c) Transverse bending moment (d) transverse lateral deflection (e) Longitudinal bending moment (f) Longitudinal lateral deflection Visualised pile group response at different stages of tunnel advancement computed from finite element analysis (a) Transverse plane (b) Longitudinal plane (Magnified scale – 1500 times) Predicted and measured axial force in pile P2 at different distance of tunnel advancement (a) +3Dtun (b) +1.5Dtun (c) 0Dtun (d) -1.5Dtun (e) -3Dtun (f) -4.5Dtun Force-moment interaction curves at different stages of tunnel advancement Variation of face pressure on pile maximum axial force and pile head settlement Variation of face pressure on pile maximum lateral deflection Axial responses of pile P1 for varying pile head condition (a) Pile axial force (b) Pile settlement Lateral responses of pile P1 for varying pile head condition (a) Transverse direction (b) Longitudinal direction Effect of pile stiffness variation on pile responses (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection xvi Figure 4.44 Figure 4.51 Figure 4.52 Effect of Ko variation on bending moment of pile P1 (a) Transverse direction (b) Longitudinal direction Effect of Ko variation on pile axial force (a) Pile P1 (b) Pile P2 Effect of pre-tunnelling loading on pile responses (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection Super-position ratio of pile responses due to pre-tunnelling loading in piles (a) Front pile - P1 (b) Rear pile - P2 Effect of post-tunnelling loading on pile responses (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection Axial force to bending moment interaction paths for pre- and post-tunnelling loaded piles Comparison of pile responses from single pile analysis and pile group analysis (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection Single pile to pile group distribution ratio Distribution ratio of front pile to rear pile responses Figure 4.53 Surface settlement troughs due to twin tunnels advancement Figure 4.54 Development of axial force in pile P1 (a) +3Dtun SB (b) 0Dtun SB (c) –3Dtun SB (d) +3Dtun NB (e) 0Dtun NB (f) -3Dtun NB (g) -4.5Dtun NB (h) Post-tunnelling loading Figure 4.55 Development of transverse bending moment in pile P1 (a) +3Dtun SB (b) 0Dtun SB (c) 3Dtun SB (d) +3Dtun NB (e) 0Dtun NB (f) -3Dtun NB (g) -4.5Dtun NB (h) Post-tunnelling loading Development of maximum bending moment with tunnels advancement distance (a) Transverse direction (b) Longitudinal direction Figure 4.45 Figure 4.46 Figure 4.47 Figure 4.48 Figure 4.49 Figure 4.50 Figure 4.56 Figure 4.57 Figure 4.58 Axial force to bending moment interaction paths due to twin tunnels Visualisation of pile responses subjected to twin tunnels advancement Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Variation of normalised shear modulus with deviatoric strain 3-D finite element mesh adopted for single pile analysis Classical isotropic Coulomb friction model for pile-soil interface Pile-soil interface behaviour along pile shaft (a) Shear stress distribution (b) Slip distribution Pile responses in different pile-soil interfacial behaviour (a) Maximum axial force (b) Pile head settlement (c) Maximum lateral deflection Pile base position investigated in the parametric studies Pile settlement profile at various Lp/Htun ratio Zone of influence differentiating pile settlement from surface soil settlement Variation of volume loss with pile-tunnel distance and relative pile length to tunnel depth to obtain pile settlement of one percent pile diameter Variation of volume loss with pile diameter and soil stiffness Pile axial force distribution at various Lp/Htun ratio (a) Lp/Htun from 0.5 to 3.0 (b) Lp/Htun of 0.5 and 0.76 Load transfer curve due to tunnelling (a) Pile base within zone of influence (b) Pile base outside zone of influence Variation of maximum axial force in pile with Lp/Htun and VL (a) Xpile/Dtun=1.0 (b) Xpile/Dtun=2. Variation of pile maximum axial force with pile diameter and soil stiffness Pile lateral deflection at various (a) Lp/Htun (b) Xpile/Dtun Lateral soil movement at various Xpile/Dtun Pile bending moment at various Lp/Htun Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 Figure 5.13 Figure 5.14 Figure 5.15 Figure 5.16 Figure 5.17 xvii Figure 5.18 Figure 5.19 Figure 5.20 Figure 5.21 Figure 5.22 Figure 5.23 Figure 5.24 Figure 5.25 Figure 5.26 Figure 5.27 Figure 5.28 Figure 5.29 Figure 6.1 Figure 6.2 Figure 6.3 Figure 6.4 Figure 6.5 Figure 6.6 Figure 6.7 Figure 6.8 Figure 6.9 Figure 6.10 Figure 6.11 Figure 6.12 Figure 6.13 Figure 6.14 Figure 6.15 Figure 6.16 Figure 6.17 Figure 6.18 Figure 6.19 Figure 6.20 Variation of maximum bending moment in pile with Lp/Htun and VL (a) Xpile/Dtun=1.0 (b) Xpile/Dtun=2.0 Pile responses at various pile shaft de-bonding length (a) Axial force (b) Settlement (c) Lateral deflection Maximum dragload at various pile shaft de-bonding length Load transfer curve in pile with shaft de-bonding Load transfer curves (a) No de-bonding (b) With de-bonding Pile groups investigated in the parametric study Pile responses in 4x4 pile group (a) Maximum axial force (b) Pile head settlement (c) Maximum lateral deflection Axial force in piles within 4x4 pile group due to tunnelling Comparison of pile group to single pile responses (a) Maximum axial force (b) Pile head settlement (c) Maximum lateral deflection (d) Maximum bending moment Single pile to pile group ratio for Lp/Htun=0.5 Variation of single pile to pile group ratio with volume loss (a) Maximum axial force (b) Pile head settlement (c) Maximum lateral deflection Pile axial force in pile groups (a) 2x4 layout (b) 4x2 layout Illustration of Gap method (Potts & Zdravkovic, 2001) Illustration of convergence confinement method (Potts & Zdravkovic, 2001) Illustration of volume loss control method (Potts & Zdravkovic, 2001) Illustration of progressive softening method (Potts & Zdravkovic, 2001) Modelling soil and structural material as a composite element (a) Actual (b) Idealised. (Buhan & Selencon, 1987) Idealising a row of piles as a wall (a) Actual (b) Idealised Modelling soil and structural material using solid elements Modelling of structural material as an external element (a) Using springs (b) Using membrane elements. (Potts & Zdravkovic, 2001) Link elements in idealising pile (Ellis & Springman, 2001) Pile stiffness modification factor computed from equivalent pile stiffness method (a) Single pile (b) Single row of piles Finite element mesh for analysis of single pile subjected to plane strain tunnel (a) 3-D mesh (b) 2-D mesh Response of pile foundation in 2-D and 3-D analyses (a) lateral deflection (b) settlement (c) axial force Variation of (a) pile stiffness ratio and (b) pile diameter ratio on the idealisation of 3-D response of single pile in 2-D analysis Variation of (a) pile-soil slip (b) pile-soil friction (c) pile-soil slip simultaneously with pile stiffness on the idealisation of 3-D response in 2-D analysis Deformation contour in 2-D analysis (a) Greenfield soil movement (b) Tunnel-pile interaction without pile-soil interface slip element (c) Tunnel-pile interaction with pile-soil interface slip element Influence of soil stiffness on pile stiffness modification factor Influence of volume loss on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile stiffness on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile diameter on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Comparison of pile stiffness modification factors computed from equivalent pile stiffness method and finite element analysis xviii Figure 6.21 Figure 6.22 Figure 6.23 Figure 6.24 Figure 6.25 Figure 6.26 Figure 6.27 Figure 6.28 Figure 6.29 Figure 6.30 Figure 6.31 Figure 6.32 Figure 6.33 Figure 6.34 Figure 6.35 Figure 6.36 Figure 6.37 Figure 6.38 Figure 6.39 Figure 6.40 Figure 6.41 Figure 6.42 Figure 6.43 Figure 6.44 Figure 6.45 Influence of pile-tunnel distance on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile length to tunnel depth ratio on pile stiffness modification factor (a) Pile head settlement (b) Pile maximum horizontal deflection 2-D and 3-D response of pile foundation with pre-tunnelling loading (a) Pile settlement (b) Pile horizontal deflection Influence of pre-tunnelling loading on pile stiffness modification factor (a) Pile head settlement (b) Pile maximum horizontal deflection Finite element simulation of single row of piles (a) Assuming a small strip (b) 3-D mesh Variation of pile stiffness ratio on the idealisation of 3-D response of single row of piles in 2-D analysis Influence of multiple-row pile group on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile spacing on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile rows spacing on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Illustration of different pile group size represented by a 2-D mesh Variation of pile group size on pile stiffness modification factor (a) Pile group types (b) Modification factor Influence of pile cap on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Pile stiffness modification factor for Condition with (a) VL = 1% (b) VL= 4% Convergence in Condition with Lp/H=0.5 (a) Pile maximum horizontal deflection (b) Pile head settlement Calibration charts for Condition with (a) Lp/H=1.0 (b) Lp/H=3.0 Calibration charts for Condition with Lp/H=3.0 Calibration charts for Condition with (a) Lp/H=1.0 (b) Lp/H=3.0 Calibration charts for Condition with Lp/H=3.0 Calibration charts and modification factors for MRT NEL C704 Pier 20 (a) Condition (b) Condition Results of 2-D finite element analysis (a) Greenfield soil movement (b) Pile horizontal deflection (c) Pile settlement Comparison between predicted and measured pile bending moment (a) Front pile (b) Rear pile Comparison of bending moment from equivalent pile stiffness method and calibration charts Tunnelling under the link structure between Pan Pacific Hotel and Marina Square 2-D finite element mesh adopted to simulate the link structure in MRT CCL1 C825 Comparison between predicted and measured building settlement xix LIST OF PUBLICATIONS Following are the publications arise from the thesis:Journal Yong K Y and Pang C H (2005). Effects of construction of underground Mass Rapid Transit on nearby piled-structures. Journal of Southeast Asian Geotechnical Society, Vol. 36, No. 1, April 2005 (Re-print of the Special Lecture delivered at the 15th Southeast Asian Geotechnical Conference). Special Lecture / Invited Lecture Yong K Y and Pang C H (2004). Geotechnical challenges of the mass rapid transit (MRT) system in Singapore. Special lecture, Malaysian Geotechnical Conference, 15-17 March 2004, Petaling Jaya, Malaysia, pp.119-130. Yong K Y and Pang C H (2004). Effects of construction of underground Mass Rapid Transit on nearby piled-structures, Special Lecture, 15th Southeast Asian Geotechnical Conference, 22-26 November 2004, Bangkok, Thailand. Chow Y K, Pang C H and Yong K Y (2007). 3D FE Analysis of Tunnel-pile Interaction Using a Strain Dependent Model. Invited Lecture. International Workshop on Constitutive Modelling – Development, Implementation, Evaluation and Application, Hong Kong, China, 12-13 January 2007. (Submitted) Conference Proceedings Pang C H, Dasari G R and Yong K Y (2005). Some considerations in finite element analysis of tunnelling. ITA-AITES 2005 World Tunnel Congress, 7-12 May 2005, Istanbul, Turkey. Pang C H, Yong K Y and Chow Y K (2005). Three-dimensional numerical simulation of tunnel advancement on adjacent pile foundation. ITA-AITES 2005 World Tunnel Congress, 7-12 May 2005, Istanbul, Turkey. Pang C H, Yong K Y, Chow Y K and Wang J (2005). Response of pile foundation subjected to shield tunnelling. 5th International Symposium on Geotechnical Aspects of Underground Construction, 15-17 June 2005, Amsterdam, The Netherlands. Pang C H, Yong K Y and Chow Y K (2005). Finite element analysis of shield tunnelling on adjacent pile foundation. Underground Singapore 2005, 1-2 December 2005, Singapore, pp.178-187. xx SUMMARY The increase demand for underground systems in urban areas particularly for mass transportation has led to many tunnels being constructed close to pile foundation. In this thesis, a Mass Rapid Transit (MRT) line constructed in Singapore, The North East Line C704 was studied. In C704, twelve bored piles were instrumented to monitor the piles responses developed during tunnel construction. Maximum dragload of up to 42% and 66% of the pile structural capacity was observed after single tunnel and twin tunnels advancement respectively. Despite that, the maximum dragload was temporarily sustained in some piles and were subjected to reduction of up to 50% immediately after the shield machine had passed the piles. In some piles, tunnelling activity also induced significant tensile force especially near the pile head. However, the induced bending moment was considerably small and only measured up to the cracked moment. The bending moment in the longitudinal direction was consistently found to be either equal to or smaller than the bending moment in the transverse direction. There was also an obvious distance effect where the front piles were subjected to higher axial and bending responses compared to the rear piles up to times. Besides the field studies, finite element (FE) model was also implemented to investigate the tunnel-pile interaction. Three-dimensional (3-D) FE model with phase tunnel advancement was developed to understand the pile responses. Back-analysis of C704 data was carried out and good agreement between 3-D FE model and measured data was achieved. The choice of tail void grout model, soil model, soil earth pressure at-rest and tunnel boundary fixity was found to be important in determining the adequate soil movement particularly the shape of surface settlement trough. In the tunnel-pile interaction, the sensitivity of pile cap, pile cap fixity, working load at pile head, tunnel face pressure and soil properties were studied. Furthermore, effect of twin tunnels advancement on piles was also investigated with comparison to the C704 data. Factor of safety of the piles were found to be reduced after the advancement of the second tunnel. xxi Subsequently, a simplified 3-D model was used for parametric studies to identify the critical and noncritical aspects in the design analysis. Firstly, it was found that the interface slip element is important and without which will lead to a more conservative axial response and negligible effect on lateral response. Secondly, two zones of influence (i.e. Zones A and B) were identified for which, two distinct behaviours of pile responses can be expected depending on the pile base location. The zones are separated by a 60o line projected from tunnel springline. Within Zone A, the pile will be subjected to tensile force and large settlement whereas in Zone B, dragload and smaller settlement will be induced. However, the load transfer curve would be modified for a loaded pile. If the dragload is sufficiently small and does not cause the final load to exceed the working load applied at pile head, the existing factor of safety of pile will remain unchanged. Thirdly, the dragload and settlement can be reduced to zero when the pile shaft is de-bonded for Lp(debond)/Htun ratio of 1.24. Finally, positive group effect was found to be greater for bigger pile group size. However in practice, the tunnel-pile interaction problem is usually idealised in plane strain model (2-D). The difficulty in carrying out a 2-D analysis is the selection of adequate parameters to represent 3-D effect. The commonly used method i.e. equivalent pile stiffness method was found to be over-simplistic and neglected many influential factors in determining the modification factor. A substantial comparison study between 3-D model and 2-D model was carried out to identify the modification factor required. Simple calibration charts were prepared to estimate the modification factor. Three case studies which comprise of C704 data, C825 data and centrifuge tests data reported by Loganathan (1999) were backanalysed to demonstrate the applicability of the calibration charts and modification factor. xxii [...]... of Ko variation on bending moment of pile P1 (a) Transverse direction (b) Longitudinal direction Effect of Ko variation on pile axial force (a) Pile P1 (b) Pile P2 Effect of pre-tunnelling loading on pile responses (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection Super-position ratio of pile responses due to pre-tunnelling loading in piles (a) Front... Variation of pile group size on pile stiffness modification factor (a) Pile group types (b) Modification factor Influence of pile cap on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Pile stiffness modification factor for Condition 1 with (a) VL = 1% (b) VL= 4% Convergence in Condition 1 with Lp/H=0.5 (a) Pile maximum horizontal deflection (b) Pile. .. deflection Axial responses of pile P1 for varying pile head condition (a) Pile axial force (b) Pile settlement Lateral responses of pile P1 for varying pile head condition (a) Transverse direction (b) Longitudinal direction Effect of pile stiffness variation on pile responses (a) Axial force (b) Settlement (c) Transverse lateral deflection (d) Longitudinal lateral deflection xvi Figure 4.44 Figure 4. 51 Figure... pile group on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile spacing on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile rows spacing on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Illustration of different pile. .. al., 19 95) Tunnelling under various constraints from pile foundations (Nakajima et al., 19 92) Tunnelling under large dome stadium supported on pile foundations (Inose et al., 19 92) Tunnelling under pile foundations (Takahashi et al.,2004) 1- g model set up to simulate tunnelling effect on pile foundation (Morton & King, 19 79) Centrifuge test set up to simulate tunnelling effect on pile foundation (Hergarden... (a) Pile settlement (b) Pile horizontal deflection Influence of pre-tunnelling loading on pile stiffness modification factor (a) Pile head settlement (b) Pile maximum horizontal deflection Finite element simulation of single row of piles (a) Assuming a small strip (b) 3-D mesh Variation of pile stiffness ratio on the idealisation of 3-D response of single row of piles in 2-D analysis Influence of multiple-row... clay……………………………………… 14 9 Concluding remarks………………………………………………………………… 14 9 CHAPTER 7 SUMMARY OF FINDINGS AND CONCLUSIONS 15 1 7 .1 Introduction……… ……….……………………………………………………………… 15 1 7.2 Field monitoring……………………………………………………………… 15 1 7.3 3-D finite element simulation of tunnel advancement on adjacent pile foundation………… 15 4 7.4 Parametric studies…………………………………………………………………………… 15 8 7.5 Plane strain idealisation of tunnel- pile. .. Variation of (a) pile stiffness ratio and (b) pile diameter ratio on the idealisation of 3-D response of single pile in 2-D analysis Variation of (a) pile- soil slip (b) pile- soil friction (c) pile- soil slip simultaneously with pile stiffness on the idealisation of 3-D response in 2-D analysis Deformation contour in 2-D analysis (a) Greenfield soil movement (b) Tunnel- pile interaction without pile- soil... (c) Tunnel- pile interaction with pile- soil interface slip element Influence of soil stiffness on pile stiffness modification factor Influence of volume loss on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile stiffness on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile. .. Figure 6. 41 Figure 6.42 Figure 6.43 Figure 6.44 Figure 6.45 Influence of pile -tunnel distance on pile stiffness modification factor (a) Pile maximum horizontal deflection (b) Pile head settlement Influence of pile length to tunnel depth ratio on pile stiffness modification factor (a) Pile head settlement (b) Pile maximum horizontal deflection 2-D and 3-D response of pile foundation with pre-tunnelling . CHAPTER 1 INTRODUCTION 1 1. 1 Background……………………………………………………………….…………………… 1 1. 1 .1 Tunnel construction near pile foundation………………… ……………… 2 1. 1.2 Current design and construction approach……………………. THE EFFECTS OF TUNNEL CONSTRUCTION ON NEARBY PILE FOUNDATION PANG CHIN HONG NATIONAL UNIVERSITY OF SINGAPORE 2006 THE EFFECTS OF TUNNEL. Effect of pile -tunnel distance………………………………… 13 4 6.4 .10 Effect of pile length to tunnel depth ratio…………………………………………. 13 4 6.4 .11 Effect of loading acting on pile …………………………………………………. 13 5 6.5 Pile