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ITA/AITES
ITA/AITES – Training Course
TUNNEL ENGINEERING
CONVENTIONAL TUNNELLING PART 2
Prepared by
Harald Wagner
ITA AITES - Vice President
D2 Consult Ltd. Linz, Austria
Seoul - 2006
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Index
Introduction – Principles of Conventional Tunnelling
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Strategy of Project Development
3
Geological / Geotechnical Design
4
Construction Monitoring
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Conclusions
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Content
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Purpose, scope of work
Principles of conventional tunnelling method
Strategy of project development
Design principles and stages
 Ground investigation
 Geological and geotechnical evaluation
 Detail design (incl. monitoring)
 Contract model and document
 Organisation of project execution
 Management (supervision, risk, safety, claims, etc.)
ITA WG 19 Guidelines
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Principles of Conventional Tunnelling
View the ground as a load-bearing element of support.
The ground reactions is measured, stability confirmed by
monitoring
Requirement for rapid rigid support or slim deformable support
is identified
Contract to allow most economical type of support installation
Conventional tunnelling based on rock classification system
(stand-up time)
Rock class agreed between Contractor and Engineer at the
excavation face
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Tunnelling Operation Equipment
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Strategy of Project Development
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The project development stages of a tunnel project are
subdivided into 4 different stages:
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conceptual design
preliminary design
tender design (detailed design, phase 1)
construction design (detailed design, phase 2).
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Conceptual Design
Design documents include:
– Scope and verification of design basis
– Alignment studies and selection of preferred alignment
– Geotechnical characterisation
– Tunnel construction with respect to environmental aspects
– Preliminary cost estimate
– Preliminary construction programme.
– Ventilation concept (for transportation projects only).
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Forepoling in Soft Ground
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Preliminary Design 1
The preliminary design includes:
– Designers contribution to site investigation
– Evaluation of site investigation and lab testing results
– Portal location, slope and structure design
– Cross section development, geotechnical requirements
– Decision on tunnel advance methods
– Tunnel waterproofing and drainage concepts
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Preliminary Design 2
The preliminary design includes:
– Particular requirements regarding operation and safety
– Construction concepts, water and power supply, roads, deposit
– Land acquisition documentation, building restrictions
– Detailed construction programme
– Revised cost estimate
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Shotcreting at the Face
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Tender Design
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Detail design of all structures
Incorporation of latest project developments
Results of additional site investigations
Update of geotechnical prognosis
Support measures drawings
Distribution of support classes
Detailing of auxiliary construction methods
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Final (Construction) Design
– Aim of conventional tunnelling contracts is adaptation
of detailed design to requirements of excavation and
support and to geotechnical conditions on site.
– Production of design drawings to be used for
construction (e.g. formwork drawings, reinforcement
drawings and schedules, fabrication drawings etc.).
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Invert Reinforcement
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Geological / Geotechnical Design
Phase 1: Design
Determining of
– Rock Mass Types (RMT)
– Rock Mass Behaviour Types (BT)
– Excavation classes determination based on BT and E&S
method
The design should also contain
– Baseline Construction Plan
– Results to be summarized in Geotechnical Report
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Geological / Geotechnical Design
Phase 2: Construction
– Geotechnical relevant rock mass parameters to be
collected, recorded, and evaluated to determine the
Rock Mass Type
– Monitoring data together with Rock Mass Type allows
the behaviour type to be determined
– Excavation and support measures following criteria of
Baseline Construction Plan and Safety Management
Plan.
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Final Lining Reinforcement
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Geological / Geotechnical Design
Design Structuring
Step 1:
Determination of Rock Mass Types
Step 2:
Determination of Rock Mass Behavior Types
Step 3:
Determination of Excavation and Support
Step 4:
Geotechnical Report-Baseline Construction Plan
Step 5:
Determination of Excavation Classes
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Geotechnical Report – Content 1
− Summary of geological / geotechnical investigations,
interpretation of results
− Rock Mass Types and associated key parameters
− Rock Mass Behaviour Types, influencing factors
− Analyses performed
− Geotechnical model on which BT is based
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Geotechnical Report – Content 2
– Report on determination of excavation and support
– Relevant scenarios, analyses, results
– Baseline Construction Plan
– Detailed specifications to BCP
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(system behaviour, measures on site, warning criteria)
– Report on excavation classes, distribution
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Top Heading / Bench Excavation
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Baseline Construction Plan - Content
Summary of geotechnical design containing
– Geological model with distribution of RMT and BT
– Sections for construction to be specifically observed
– Excavation and Support Types (round length, excavation
sequence, support quality and quantity, etc.)
– Measures to be determined on site (support ahead of the
face, face support, ground improvement, drainage, etc.)
– System Behaviour (behaviour during excavation,
deformation characteristics, utilization of supports, etc.)
– Warning criteria and safety management plan
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Geotechnical Safety Management Plan
Covering following topics
– Design concept for determination of excavation and
support
– Criteria for assessment of stability based on knowledge of
ground conditions during design
– Monitoring concept with all technical and organizational
provisions to allow a continuous comparison between
expected and actual conditions
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Tunnel Face in Hard Rock
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Baseline Construction Plan - Content
Construction structured into
– Step 1 – Determination of encountered Rock Mass Type
– Step 2 – Determination of Rock Mass Behaviour Type
– Step 3 – Determination of Excavation and Support
– Step 4 – Verification of System Behaviour
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Construction Monitoring
– State of the Art Data Evaluation
– The problems experienced when tunnelling through poor
rock and fault zones are well known all over the world.
– Proper modelling during design, continuous and adequate
monitoring of behaviour of rock mass and support structure
forms basis for on site decisions.
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Survey in Construction
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Monitoring Scheme in Section
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Displacement History Plots
Value of Information
– Assuming continuous face advance, displacement rate
over time has to decrease
– Displacement acceleration indicates destabilisation,
unless there are ongoing construction activities in the
monitored tunnel section (e.g. bench and invert
excavation, or shaping activities)
– Stabilisation is reached after bench and invert excavation
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Typical Displacement History Diagram
Typical displacement history diagram, showing expected behaviour and
indication of destabilisation
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Final Displacements
Final displacements extrapolated from few readings, using
previous experience and including the actual geological situation
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Deflection curves
Value of Information:
– When showing several deflection curves on the same plot,
comparison of displacements along tunnel is possible
– Information on the longitudinal extent of tunnel
deformation behaviour is provided
– Trends of relative decreasing or increasing rock mass
behaviour can be verified
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Extrapolation of Deflection Curves
The extrapolation of deflection curves to the tunnel face and the addition of the resulting
difference ("pre-displacements") to the measured values
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Typical plot of deflection curve
Typical plot of deflection curves when excavation approaches a "weak" zone
(schematically)
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Trend Lines
Value of Information
– Trend lines provide an overview of displacement
development along tunnel axis, used for extrapolation
beyond face
– Trend lines used to determine appropriate support type
and quantity for comparison of similar deformation
behaviour.
– Trend lines with increasing displacement tendency can
indicate critical situations and must be analysed
– Trend line shows settlement behind face.
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Trend Line of Settlement
Trend line of settlement when tunnelling in homogeneous rock mass and
when passing a fault zone (schematically)
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Conclusions
 Ground is viewed as integrated element of support
 Ground reactions are measured to confirm stability
 Ground should be kept undisturbed
 Rapid rigid support or slim deformable support
 Type of support to allow most economical design
 Tunnelling on ground classification system
 Agreement between Contractor and Engineer at face
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Thanks for your Attention
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ITA/AITES
Clause de non-responsabilité pour les rapports des groupes de travail de l'AITES
L’Association Internationale des Travaux en Souterrain (AITES) publie ce rapport, conformément à ses Statuts, pour faciliter les échanges d’informations afin :
d’encourager l’utilisation du sous-sol au profit du grand public, de l’environnement et du développement durable;
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The 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
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However ITA accepts no responsibility or liability whatsoever with regard to the material published in this report.
This material is:
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