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ITA - AITES WORLD TUNNEL CONGRESS 2007 PRAGUE
ITA Training Course 2007ITA Training Course 2007TUNNELLING IN URBAN AREATUNNELLING IN URBAN AREA
Prague, 04Prague, 04--05 May 200705 May 2007
Specific Conditions and Requirements for Specific Conditions and Requirements for Tunnelling in Urban Areas:Tunnelling in Urban Areas:
General and Environmental AspectsGeneral and Environmental Aspects
Prof. André P. Prof. André P. AssisAssis, PhD (UnB / ITA), PhD (UnB / ITA)
TRAINING MATERIAL PREPARED BY
5Conclusions and ReferencesConclusions and References
Conditions and Requirements for Urban TunnellingConditions and Requirements for Urban Tunnelling
Design AspectsDesign Aspects
IntroductionIntroduction
Construction MethodsConstruction Methods
Contents
2
3
4
1
2/482/48Tunnelling in Urban AreasTunnelling in Urban Areas
Introduction
3/483/48
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
•Increase of the urban population (after the 2nd World War)
•Environmental Era (after 1960)
•Tunnelling technology
Introduction
4/484/48
22
33
44
55
11
Tunnelling in Urban AreasTunnelling in Urban Areas
Environmental Era Urban Trend
Introduction
5/485/48
22
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
• Better Behaviour Understanding– Control of settlements and displacements– Evaluation of induced damages
• Technology Advances– Works safer, cheaper and built in short time– New generation of TBMs (pressurised face) –
tunnelling in any geological conditions and urban environment
• Seismic resistance
Favourable Factorsfor Urban Tunnelling
Introduction
6/486/48
22
33
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
• Mass Transit Systems and Motorways
• Public Utilities (water, sewage, cables etc.)
• Flood Control
• Revitalisation of City Centres
• Public Buildings
Demand of Urban Tunnelling
Introduction
7/487/48
22
33
44
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
• Safety– During Construction– During Operation
• Costs
Difficulties in Deciding forUnderground Structures
Introduction
8/488/48
22
33
44
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
Difficulties in Deciding forUnderground Structures Costs
3.0Tunnel (double track)
Tunnel (single track)
2.5Cut & Cover *
1.5Viaduct *
1.0Surface *
Cost RatioConstructionMethods
* Not including surface land buying
3.0
Introduction
9/489/48
22
33
44
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11
Tunnelling in Urban AreasTunnelling in Urban Areas
Global Cost Assessment for Underground Structures• Cost of the surface
space• Indenisation during
construction (negative impacts of surface works)
• Devaluation of real estate nearby to infrastructure
Introduction
10/4810/48
22
33
44
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11Urban Tunnelling
Tunnelling in Urban AreasTunnelling in Urban Areas
TunnellingTunnellingMethodsMethods
ConventionalConventional
MechanisedMechanisedSpecialSpecial
Soft GroundSoft GroundHard GroundHard Ground
Mix GroundMix Ground
Introduction
11/4811/48
22
33
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11
Urban Urban TunnellingTunnelling
Soft Ground Soft Ground TunnellingTunnelling
ConventionalConventional
MechanisedMechanised
SpecialSpecial
Ground ImprovementGround Improvement
Full Face ExcavationFull Face Excavation
Trench MethodsTrench Methods
Tunnelling in Urban AreasTunnelling in Urban Areas
Introduction
12/4812/48
22
33
44
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11
• Main concern during excavation is the stability of the opening
• Most cases of soft ground tunnelling are in urban environment
• Tunnelling-induced displacement field may reach surface and affect existing nearby structures
• Design may be dominated by admissible-displacement criteria
Tunnelling in Urban AreasTunnelling in Urban Areas
Soft Ground Tunnelling
Conditions and Requirements
13/4813/48
22
33
44
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11Major concerns of soft ground and urban tunnelling are related to (Kovari & Ramoni, 2004):
• Urban Environment
• Ground Conditions
• Risk Scenarios
Tunnelling in Urban AreasTunnelling in Urban Areas
14/4814/48
22
33
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11
• Shallow overburden• Existence of nearby structures• Foreign objects inside the ground• Constraints for alignment• Restrictions for auxiliary works• High visibility of damage
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
Urban Environment
15/4815/48
22
33
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11
• Access ways as shallow as possible• Larger and larger tunnel diameters
• Concept of Shallow Tunnel– Type of Failure– Displacement field up to surface or
existing structures
Shallow Overburden
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
16/4816/48
22
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11 Shallow Overburden
(Sauer & Mergelsberg, 2003)(Sauer & Mergelsberg, 2003)
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
17/4817/48
22
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11
• Types of structures (transport ways, public utilities, buildings, historical sites etc.)
• Affected by the induced displacement field, but they also affect it
• Sensitivity to potential damages
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and RequirementsExistence of Nearby Structures
18/4818/48
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Existence of Nearby Structures
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
19/4819/48
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11
• Direct conflict with tunnel alignment–Structural elements (foundation,
anchors, sheet piles)–Public utilities–Wells–Tree trunks and roots
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and RequirementsForeign Objects inside the Ground
20/4820/48
22
33
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11
Foreign Objects inside the Ground
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
21/4821/48
22
33
44
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11
• Usually dominated by transport demand
• Influenced by urban constraints (p.ex. location of ventilation towers)
• Preferable under public ground• Unavoidable to underpass existing
structures• Cope with existing ground conditions
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and RequirementsConstraints for Alignment
22/4822/48
22
33
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11
• Exploitation• Shaft of attack• Ventilation towers• Muck transport and disposal• Dewatering• Ground improvement• Monitoring
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and RequirementsRestrictions for Auxiliary Works
23/4823/48
22
33
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11
High Visibility of Damages
• Sensitivity of potential damages
• Loss of public confidence is very jeopardising to tunnelling industry
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
24/4824/48
22
33
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• Collapses up to surface• Damages due to tunnelling-induced
displacements
Design Criteria in terms of:Design Criteria in terms of:--FailureFailure--Admissible DisplacementsAdmissible Displacements
Risk Scenarios
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
25/4825/48
22
33
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11 Ground Conditions• Existing ground conditions
– Recent geological formations– Fills– Frequent changing conditions
(weathering)– Groundwater
• Ground Improvement and ReinforcementTunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
26/4826/48
22
33
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11
Ground Conditions
Clay Sand
Water level
Fill
Tunnel
Tunnelling in Urban AreasTunnelling in Urban Areas
Conditions and Requirements
Design Aspects
27/4827/48
22
33
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11
• Ground excavation
• Support installation
• Monitoring
Principles of Tunnelling
Ground-SupportInteraction
Bearing Ring of Reinforced Ground
ObservationalMethod
Tunnelling in Urban AreasTunnelling in Urban Areas
28/4828/48
22
33
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11 Ground-SupportInteraction
upsps
u
po
ps
u
po
Design Aspects
Tunnelling in Urban AreasTunnelling in Urban Areas
29/4829/48
22
33
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11Geology
Lab and In-Situ Tests
Designer Experience
Global Investigation
Geotechnical Properties
Excavation Method and Support System
Structural Model and Design Predictions
Ok?
Construction
Yes
NoElements of
Tunnel Design
Design Aspects
Tunnelling in Urban AreasTunnelling in Urban Areas
30/4830/48
22
33
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11 Design Aspects
Stress-Strain-Displacement Analysis• Empirical Formulations• Closed-Form Solutions
– Simple Geometry– Homogeneous and Isotropic Media– Linear Elastic Behaviour
• Numerical Methods– Boundary Element– Finite Element– Discrete Element
Media
CHILE
Media
DIANETunnelling in Urban AreasTunnelling in Urban Areas
31/4831/48
22
33
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55
11 Tunnelling-Induced Displacements
Design Aspects
Tunnelling in Urban AreasTunnelling in Urban Areas
32/4832/48
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11Checking for Tunnelling-Induced Damages• Calculate the green field settlement
trough• For structures inside the settlement
trough, check potential damages due to green field settlements and distortions
• For those in critical state, run a more accurate analysis taking into account the structure stiffness
• Perform reinforcement when required
Design Aspects
Tunnelling in Urban AreasTunnelling in Urban Areas
33/4833/48
22
33
44
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11
Contractor Experience Construction
Ok?
Yes
No
Elements of
Construction
Monitoring
Ok?
Yes
No
Safe
Construction Methods
Tunnelling in Urban AreasTunnelling in Urban Areas
4 m6 m
H - 2 m
(H - 2 m) / 2
H
M1
E1
E2P1
M2M4 M3 M5
P2
P4
P6
P3
P7
P5
34/4834/48
22
33
44
55
11
Soft Ground Soft Ground TunnellingTunnelling
ConventionalConventional
MechanisedMechanised
SpecialSpecial
Ground ImprovementGround Improvement
Full Face ExcavationFull Face Excavation
Trench MethodsTrench Methods
Construction Methods
Tunnelling in Urban AreasTunnelling in Urban Areas
35/4835/48
22
33
44
55
11
• Open Trenches• Cut-and-Cover Structures
– Direct and Inverse Excavation• Door-Frame Method
• Immersed Tunnels– Caisson and Door-Frame Methods
Construction Methods
Special Methods
Tunnelling in Urban AreasTunnelling in Urban Areas
36/4836/48
22
33
44
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11 Construction Methods
Door Frame Method
(Sauer & Mergelsberg, 2003)(Sauer & Mergelsberg, 2003)
Tunnelling in Urban AreasTunnelling in Urban Areas
37/4837/48
22
33
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11
• Excavation• Ground Conditioning• Support Installation
Stress RelaxationStress Relaxation
Construction Methods
Conventional Tunnelling
Tunnelling in Urban AreasTunnelling in Urban Areas
38/4838/48
22
33
44
55
11 Construction Methods
(Sauer & Mergelsberg, 2003)(Sauer & Mergelsberg, 2003)
Tunnelling in Urban AreasTunnelling in Urban Areas
39/4839/48
22
33
44
55
11 Construction Methods
Support Installation
Tunnelling in Urban AreasTunnelling in Urban Areas
40/4840/48
22
33
44
55
11 Construction MethodsTunnelWaterproofing
Tunnelling in Urban AreasTunnelling in Urban Areas
41/4841/48
22
33
44
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11
• Excavation• Support Installation
Avoid or MinimiseAvoid or MinimiseStress RelaxationStress Relaxation
Construction Methods
Mechanised Tunnelling
Tunnelling in Urban AreasTunnelling in Urban Areas
42/4842/48
22
33
44
55
11 Construction Methods
MechanisedTunnelling
Tunnelling in Urban AreasTunnelling in Urban Areas
43/4843/48
22
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11 Construction MethodsRelevant factors for the TBM selection are (Kovari & Ramoni, 2004):• Grain size distribution• Type of predominant mineral (quartz
contents)• Soil strength (cohesion)• Overburden• Heterogeneity (mix ground, weathering)• Piezometric pressure
Tunnelling in Urban AreasTunnelling in Urban Areas
44/4844/48
22
33
44
55
11 Construction MethodsConventional versus Mechanised
Tunnelling• Geometry Flexibility• Geology Flexibility• Contractual
Flexibility• Political Flexibility• Lower costs for short
tunnels and cheaper labour
• Lower impact to ground• Higher and more
constant quality (industrial process)
• Lower load to workers• Safer• More accurate costs and
schedule
Tunnelling in Urban AreasTunnelling in Urban Areas
45/4845/48
22
33
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11 Construction MethodsConventional versus Mechanised
Tunnelling
(Sauer & Mergelsberg, 2003)(Sauer & Mergelsberg, 2003)
Tunnelling in Urban AreasTunnelling in Urban Areas
Conclusions and References
46/4846/48
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33
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11• Majors concerns are opening stability
and control displacement field• Soft ground tunnelling is likely
dominated by failure and admissible displacement criteria
• Ground conditioning (improvement and reinforcement) plays an important role
• Tunnelling methods and technology vary depending on geology, tunnel location, length and geometry, local tradition etc.
Tunnelling in Urban AreasTunnelling in Urban Areas
Conclusions and References
47/4847/48
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11
• Assis, A.P. (2005). Conventional Tunnelling: The Example of the Brasilia Metro. ITA Training Course, ITA / Technical University of Istanbul, Istanbul, Turkey (www.ita-aites.org).
• Kovari, K. & Ramoni. M. (2004). Urban Tunnelling in Soft Ground Using TBMs. International Congress on Mechanised Tunnelling: Challenging Case Histories, Keynote Lecture, Politecnico di Torino, Turin, Italy (www.ita-aites.org).
• Sauer, G. & Mergelsberg, W.A. (2003). Tunnelling and its toolbox(Tunnelling… and beyond). Conference on Earth Retention Systems, ASCE / DFI / ADSC, New York, USA.
Tunnelling in Urban AreasTunnelling in Urban Areas
48/4848/48
Disclaimer for the reports of ITA working groupsThe International Tunnelling Association (ITA) publishes this report to, in accordance with its statutes, facilitate the exchange of information, in order:
- to encourage planning of the subsurface for the benefit of the public, environment and sustainable development
- to promote advances in planning, design, construction, maintenance and safety of tunnels and underground space, by bringing together information thereon and by studying questions related thereto.
However ITA accepts no responsibility or liability whatsoever with regard to the material published in this report.
This material is:
- information of a general nature only, which is not intended to address the specific circumstances of any particular individual or entity;
- not necessarily comprehensive, complete, accurate or up to date;
- sometimes collected from external sources over which ITA services have no control and for which ITA assumes no responsibility;
- not professional or legal advice (if you need specific advice, you should always consult a suitably qualified professional).