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On the feasibility of TBM drives in squeezing ground
and the risk of shield jamming

INTRODUCTION

PART I – EXPERIENCES AND BASIC CONSIDERATIONS ON TBM TUNNELLING IN SQUEEZING GROUND

1 Introduction

2 Practical experience and specific problems
2.1 Introduction
2.2 Magnitude of relevant deformations
2.3 The "time" factor
2.4 Thrusting system
2.5 Back-up area

3 Ground-equipment-support interactions
3.1 Gripper TBM
3.2 Single and double shielded TBMs

4 Countermeasures
4.1 Introduction
4.2 Pre-treatment or pre-support of the ground
4.3 Cutter head
4.4 Shield
4.5 Thrust force and torque
4.6 Back-up equipment
4.7 Tunnel support

5 Closing remarks

PART II – THE INTERACTION BETWEEN SHIELD, GROUND AND TUNNEL SUPPORT IN TBM TUNNELLING THROUGH SQUEEZING GROUND

1 Introduction

2 Design and analysis methods
2.1 Analytical solutions
2.2 Empirical relationships
2.3 Numerical investigations

3 Computational model
3.1 Constitutive model
3.2 Tunnel boundary conditions

4 Basic aspects of the interaction between shield, ground and tunnel support
4.1 Shield-ground interaction
4.2 Overstressing and stress history of the ground
4.3 Thrust force
4.4 A simplified model of shield-ground interaction
4.5 Shield-support interaction

5 An example of a single shielded TBM
5.1 Introduction
5.2 Investigations on TBM optimization
5.3 Effect of short weaker zones

6 An example of a gripper TBM
6.1 Introduction
6.2 Investigations
6.3 Discussion of the results

7 Closing remarks

PART III – THRUST FORCE REQUIREMENTS FOR TBMS IN SQUEEZING GROUND

1 Introduction

2 Computational model
2.1 Axial symmetry
2.2 Variability of the ground
2.3 Time-dependency of ground behaviour
2.4 Constitutive model

3 Dimensionless parameters

4 The parameter range covered
4.1 Shield stiffness
4.2 Lining stiffness
4.3 Machine layouts

5 The nomograms

6 Model behaviour

7 Application examples
7.1 Determining the required thrust force
7.2 Vulnerability with respect to ground variations

8 Analysis of case histories
8.1 Bodio Section of the Gotthard Base Tunnel (Switzerland)
8.2 Faido Section of the Gotthard Base Tunnel (Switzerland)
8.3 Uluabat Tunnel (Turkey)
8.4 Section 4 of the Pajares Tunnel (Spain)
8.5 Wienerwald Tunnel (Austria)
8.6 Guadiaro – Majaceite Tunnel (Spain)
8.7 Guadarrama Tunnel (Spain)

9 Closing remarks

PART IV – THE EFFECT OF CONSOLIDATION ON TBM SHIELD LOADING IN WATERBEARING SQUEEZING GROUND

1 Introduction

2 The consolidation mechanism

3 Computational model

4 Numerical solution method.

5 Conditions during regular TBM operation
5.1 Distribution of the pore water pressures
5.2 Interaction between shield, ground and support
5.3 Calculation of thrust force
5.4 Effects of overboring and lubrication
5.5 Effects of permeability
5.6 A counter-intuitive aspect of model behaviour
5.7 Extrusion rate of the core
5.8 Role of tunnel diameter

6 Conditions during standstills
6.1 Dissipation of the excess pore water pressures
6.2 Longitudinal arching in the shield area
6.3 Effect of backfilling of the segments close to the shield
6.4 Load transfer to the core ahead of the face
6.5 Thrust force needed for restarting TBM operation

7 Closing remarks

CONCLUSIONS AND OUTLOOK

APPENDIX
1 Computation of the characteristic line of the yielding support YS25/C15
2 Notation

REFERENCES