concrete formwork for tunnel lining

8/9/2019 concrete formwork for tunnel lining

1/58

Geometry, concrete mixes,

formwork and concretepouring practicefor tunnel linings

GT36R1A1

www.aftes.asso.fr

ASSOCIATION FRANAISE DES TUNNELSET DE LESPACE SOUTERRAIN

Organization member of the AFTES

AAAFFFTTTEEESSS

RRReeecccooommmmmmeeennndddaaatttiiiooonnnsss


2/58


3/58

AFTES Guidelines GT36

Publication en franais dans TUNNELS ET OUVRAGES SOUTERRAINS n 202 1

Geometry, concrete mixes,formwork and concrete pouring practicefor tunnel linings

Text submitted byA. MERCUSOT (CETU) Chairman Working Group GT36and A. BOERI (ALTER ) Vice-Chairman

These Guidelines were drafted jointly withG. ABOU SLEIMAN (CHANTIERS MODERNES) -JP. ALBRECHT (BEC Frres SA) -V. AVRIL (DEMATHIEU et BARD) - H. BATAILLE (SEMI) -

W. BENEDETTO (LTF) - PP. BERNARDI (GARELLI) - P. BRIAND (RAZEL) - MME F. BUFFET (RATP) - F. CUSSIGH (GTM CONSTRUCTION ) -B. DE RIVAZ (BEKAERT France S.A.S.) - F. DEL CASTELLO (SIKA) - C. HENAULT (BOUYGUES CONSTRUCTION) -

P. HINGANT (SCETAUROUTE) - M. IMBARD (CETU) - P. LAC ( VICAT) - T. LOUGE (SETEC) - R. MARUCCO (MECSIDER SPA) -M. MELKONIAN (MELKONIAN CONSEIL) -J. MICHAUD (SIGMA BETON) - T. NALLET (EIFFAGE) - R. PARRA (CMC) -

V. PERRAUD (CARI) - H. THIEBAUT (SETEC TPI) - E. SALVI (CAMPENON BERNARD Rgions) - H. SOURON (COYNE ET BELLIER)

These Guidelines were approved by AFTES Technical Committee subsequent to a critical review byJ. BURDIN (CONSULTING ENGINEER) - G. COLOMBET (COYNE ET BELLIER) - P. DUBOIS (IGOA) - L. THEVENOT (RAZEL) -JL. REITH (CETU)

Translation : ROBERT CHADWICK- Rereading : LUCY REW

PagesPages

1 - PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 - Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 - Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 - General background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 - Administrative framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 - LININGS AND DESIGN REQUIREMENTS . . . . . . . . . . . . 5

2.1 - Functions of lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.1.1 - Support Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.1.2 - Support and Protection of Waterproof Lining System Function . . . 62.1.3 - Operating Equipment Support Function . . . . . . . . . . . . . . . . . . . 62.1.4 - Operating Cost Control Function . . . . . . . . . . . . . . . . . . . . . . . . . 62.1.5 - User Comfort Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 - Tunnel cross sectional shapes . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2.1 - Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2.2 - Examples of Profile Optimisation . . . . . . . . . . . . . . . . . . . . . . . . 72.2.3 - Consequences on operating formwork systems . . . . . . . . . . . . . . 8

2.3 - Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.3.1 - Typical cross section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.3.2 - Definition of physical and payment lines . . . . . . . . . . . . . . . . . . . 82.3.3 - Typical lines and cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.3.4 - Lining concrete volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.4 - Concrete criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.5 - Lining construction criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.6 - Criteria for the appearance of exposed concrete . . . . . . . . . . . . 10

2.6.1 - Field of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.6.2 - Characteristics and types of exposed surfaces . . . . . . . . . . . . . . . 102.6.3 - Lift joints and construction joints . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.7 - Construction practice basics . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.7.1 - Plain concrete linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.7.2 - Locally reinforced linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.7.3 - Fully-reinforced linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.7.4 - Construction in sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.7.5 - Embedded Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3 - CONCRETE FOR PERMANENT LINING . . . . . . . . . . . . . 12

3.1 - Concrete mix design and tests . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.1 - Reference document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.2 - Selecting independent inspection body . . . . . . . . . . . . . . . . . . . . 12

3.2 - Concrete components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.2.1 - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.2.2 - Aggregate quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.2.3 - Cementitious materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.2.4 - Mixing water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.2.5 - Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2.6 - Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

CONTENTS

AFTES Welcomes comments on this paper

/


4/58


Geometry, concrete mixes, formwork and concrete pouring practice for tunnel linings

Publication en franais dans TUNNELS ET OUVRAGES SOUTERRAINS n 2022

PagesPages

3.3 - Concrete definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.3.1 - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.3.2 - Specification of basic properties . . . . . . . . . . . . . . . . . . . . . . . . . 133.3.3 - Specification of supplementary properties . . . . . . . . . . . . . . . . . . 133.3.4 - Concrete classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.4 - Concrete mixing and transport . . . . . . . . . . . . . . . . . . . . . . . . . 143.4.1 - Choice of batching plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.4.2 - Concrete mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.4.3 - Concrete transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.5.1 - Monitoring concrete strength development and performance . . . . 143.5.2 - Minimum requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.5.3 - Recommended values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.5.4 - Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.6 - Surface treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.6.1 - Protection of surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.2 - Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.6.3 - Fire protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.7 - Benefits of self-compacting concrete . . . . . . . . . . . . . . . . . . . . . 16

4 - FORMWORK SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1 - Description of formwork systems and Minimum fabrication rules 164.1.1 - Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.1.2 - Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.1.3 - Different types of formwork system . . . . . . . . . . . . . . . . . . . . . . . 174.1.4 - Details of formwork system components . . . . . . . . . . . . . . . . . . . 23

4.2 - Fabrication of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294.2.1 - Contractor writen specification . . . . . . . . . . . . . . . . . . . . . . . . . . 294.2.2 - Contractor's tendering procedure for suppliers . . . . . . . . . . . . . . 304.2.3 - Contract award . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.3 - Ordering formwork by contractor . . . . . . . . . . . . . . . . . . . . . . . . 314.2.4 - Supplier's design and fabrication report . . . . . . . . . . . . . . . . . . . 314.2.5 - Transport, erection on site and acceptance in final configuration . 32

5 - FORMWORK SET-UP AND CONCRETING . . . . . . . . . . . 34

5.1 - Formwork system working configurations . . . . . . . . . . . . . . . . . 345.1.1 - Planning excavation and lining sequence . . . . . . . . . . . . . . . . . . 345.1.2 - Longitudinal planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345.1.3 - Transverse planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.2 - Q / S / E (Quality/Safety/Environment) aspects . . . . . . . . . . . . 355.2.1 - Content of quality assurance plan . . . . . . . . . . . . . . . . . . . . . . . . 355.2.2 - Safety aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2.3 - Environmental aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2.4 - Quality monitoring of works . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.3 - Lining concreting record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.4 - Operations in concreting cycle . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.4.1 - Form striking and precautions specific to this phase . . . . . . . . . . . 365.4.2 - Translation of formwork to next ring . . . . . . . . . . . . . . . . . . . . . . 375.4.3 - Concrete curing after form removal . . . . . . . . . . . . . . . . . . . . . . . 375.4.4 - Preparation of form liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.4.5 - Moving, setting up and adjustment of formwork ready for pouring 385.4.6 - End stop(s) and seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.4.7 - Concreting lining rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415.4.8 - Concrete hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425.5 - Special items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.5.1 - Portals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425.5.2 - Niches and intersections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

5.6 - Special cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445.6.1 - Contact grouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445.6.2 - Special concrete mixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445.6.3 - Special concreting conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.7 - Re-use of formwork systems . . . . . . . . . . . . . . . . . . . . . . . . . . 465.7.1 - Dismantling formwork systems . . . . . . . . . . . . . . . . . . . . . . . . . . 465.7.2 - Formwork system maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . 465.7.3 - Temporary Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465.7.4 - Re-use of Formwork Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

6 - LINING CONSTRUCTION SUPERVISION . . . . . . . . . . . . 47

6.1 - Specific testing and inspection challenges . . . . . . . . . . . . . . . . . 476.2 - Level of supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476.3 - Types of supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

6.3.1 - Internal supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476.3.2 - External supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476.3.3 - Independent supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

6.4 - Critical points and stop points . . . . . . . . . . . . . . . . . . . . . . . . . 506.5 - Treatment of non-conformities . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.5.1 - Classification of non-conformities . . . . . . . . . . . . . . . . . . . . . . . . 506.5.2 - Means for treating non-conformities . . . . . . . . . . . . . . . . . . . . . . 50

7 - SAFETY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1 - Safety and formwork system design . . . . . . . . . . . . . . . . . . . . . 517.1.1 - Moving parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1.2 - Access and working items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1.3 - Concreting tools and accessories . . . . . . . . . . . . . . . . . . . . . . . . 517.1.4 - Ancillary components for translation, positioning and form stripping 517.1.5 - Fluids pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1.6 - Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1.7 - Handling and controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.1.8 - Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527.1.9 - Emergency stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527.1.10 - Instruction manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

7.2 - Definition of risks during construction work . . . . . . . . . . . . . . . 527.3 - Protective equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

7.3.1 - Individual protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527.3.2 - Collective protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

7.4 - Trainning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53


5/58




1.1 - ObjectiveThese Guidelines are drafted as a contribution to the design andconstruction of cast-in-situ concrete linings, primarily to road andrail tunnels, but are also applicable to canal and drainage tunnels,backfilled tunnel portals, branch and cross tunnels and ancillaryworks such as niches, lay_bys, etc. They do not concern precastconcrete segmental linings, precast roof segmental linings, watertunnels and linings to special items such as underground railwaystation chambers and shafts. Finished cross sectional areas addres-sed range from 40 m2 to 120 m2.

The engineering content of the Guidelines focuses on general

lining design criteria and their consequences, and constructionalmaterials, tools and processes, as relevant to the various tunnellingspecialists, to provide them with:

information on linings, descriptions, models and recommendations, details of special requirements with respect to in situ concrete

linings, the means of formulating a sound design, assistance to contract award, assistance to works progress, the means of monitoring lining performance, etc.,

on the understanding that design studies must commence at theearliest opportunity for results to meet declared goals, such as toensure that the finished lining:

provides the functions and performance required for a functio-nal and safe structure,

is long-lasting and strong without the need for excessive main-tenance,

exhibits a general degree of quality, resulting from an apprecia-tion, at the design stage, of all the loads and stresses to which itwill be exposed over its expected lifespan,

offers a level of operational safety for its functions to be retai-ned under expected operating conditions.

The tunnelling specialists concerned are Owners and executive agencies, Consulting engineers, Regulatory bodies, Construction contractors and their subcontractors, Plant and equipment suppliers, Tunnel operators, Research institutes, Health and safety coordinators, Bodies involved in improving health and safety at the work-

place, All other parties in any way involved in project implementation.

Foundations and inverted-arch inverts, and shuttering for theseparts of the tunnel are not extensively discussed although shown onsome drawings. A suitable appendix will be issued in due course.

1.2 - ContentThe Guidelines present the sequence of operations for performingthe design studies and constructional activities involved in buil-ding a tunnel:

Technical and administrative framework; Description of linings and specific design requirements; Concrete mix design, mixing and transport; Design and construction of formwork systems; Placement of forms and concreting; Monitoring workmanship; Safety.

Topics not dealt with in these Guidelines are excluded becausethey have already been, or are to be covered by other AFTES Gui-delines on (in French):

Design computations and their application to European stan-dards;

Fire performance; Structural and superficial repairs; Surface preparation for contact with waterproofing systems or

painting.

1.3 - General background

The first guide on in situ concrete linings was issued by CETU in1976 and a second version was drafted in 1983 by a workinggroup made up of Owners, Consulting Engineers, ConstructionContractors and Manufacturers to take account of new regula-tions (such as Fascicule 69, 1980), reports from recent jobs(concerning primarily systematic flaws in appearance) and varia-bles affecting lining quality and durability.

The 1983 CETU publication (Linings, Concretes, ConcretingPlant, Waterproofing, Concreting Practice) was aimed chiefly atdesigners but did not constitute an Instruction document.

More than twenty years on, many new-build, lined, waterproofed

tunnels have been completed, often inspected on first commissio-ning and then periodically in the course of their operational life,and found to suffer from recurring flaws in appearance or evenstructural damage, which could be correlated with faulty workingpractices, poor workmanship and unsuitable working proceduresduring construction.

These present Guidelines are therefore based on: the practical knowledge of specialist tunnelling professionals, observed data on tunnels built in the last thirty years, inspection reports, as well as the available literature, specifications, standards and

other guidelines.It is also supplementary to the Guidelines issued by AFTES Wor-king Groups 7 (GT7 Use of Unreinforced Concrete in Tunnels)

1 - PRESENTATION


6/58




and 29 (GT29 Use of General Standards and Design and AnalysisRules for Reinforced and Plain Concrete).

These Guidelines are written in sections which fill the gaps bet-

ween other relatively exhaustive and very recent documents, andare presented in a descriptive manner in the form of recommen-dations or advice, so that interested parties may find the informa-tion needed for their design and construction operations.

1.4 - Administrative frameworkThe following Table shows schematically the sequence of projectimplementation activities from the initial feasibility studies up to

lining construction, naming the more representative referencedocuments as well as these present Guidelines, the design stages,and the tasks performed by the various parties.

STAGE

P

ROJECT

PLANNING

DESIGNANALYSES

AFTES GT36 GUIDELINESOTHERS AFTES GUIDELINES OR

DOCUMENTS

IMPORTANTDOCUMENTS FROMOTHER SOURCES*

PROJECTDESIGN STAGE

CONTRIBUTORS

ROLE, FUNCTIONS, SHAPES,GEOMETRY, CONVENTIONS

SPECIFIC REQUIREMENTS FOREXPOSED CONCRETE FACES

CONCRETE MIX DESIGN, PREPARATION AND POURING

FORMWORK DESIGN AND FABRICATION

FORMWORK INSTALLATION

POURING LINING

WORKMANS,HIP INSPECTION

DESIGN AND OPERATIONAL SAFETYJOBSITE ACCIDENT PREVENTION

FORMS: FAULTYWORKMANSHIPAND DISTRESS

CCTG Fascicule 69:Underground

WorksCETU Geometry

(pilot dossier) 1990

CCTG Fascicule 65Exposed surfaces

CETU Pilot DossierSNCF RATP

Eurocodes

CETU FireGuidelines 2006

CCTG Fascicule 65:Concrete

CCTG Fascicule 67:Waterproofing

Civil worksproject planning OWNERS

ENGINEERS

ENGINEERS

DESIGNOFFICES

CONSTRUCTIONCONTRACTORS

SUPPLIERS

IN-HOUSE ANDINDEPENDENTSUPERVISION

OPPBTP - CRAM

INDEPENDENTSUPERVISION

EXPERTS

SPECIALISTS

OPERATORS

Preliminarydesign

Final design

TenderDocuments

ConstructionContract

Progress reportsand inspection

reports

Inspection and

maintenancereports

Considerations on usual lining analysis methodsGT7 - TOS No.14 / 1976 (for information)

Use of general design and sizing rules and standards for reinforcedand plain concrete linings

GT29 - TOS No. 165 2001AFTES guidelines and the new EU standard

GT29 TOS No. 203 - 2007Use of Plain Concrete in Tunnels

GT7 TOS No. 149 - 1998

Use of Plain Concrete in TunnelsTOS No. 149 - 1998 Fire Performance of

Civil Engineering Structures - GT37 (Guidelines pending)

Extrados interface: Waterproofing System between TemporarySupport and LiningGT 9- TOS No. 159

Intrados interface: Painting Exposed Concrete FacesGT 31 - TOS No. 178

Catalogue of visible flaws in tunnels, supplemented withglossary of tunnel parts names 1980

Catalogue of structural damage in underground structures -GT14 HS 3 Chambry

Diagnostic Method for Lined Tunnels

Hazards and First AidGT12

CCTGFascicule 69:

Underground works

SNCF Classificationof structures.Catalogue of

Damage Livret KTunnels 1996

CETMEF Notes onmonitoring and

maintenance of canaltunnels with

catalogue 2000

Guidelines forInspection of Road

Tunnels, with

catalogue 2004CETU GTFE

(French OperatorsGroup)

CON-

CRETE

INTERFACES

CON

CRETING

INSPECTION

OPERATION

FORM-

WORK

Article TOS No. 121 Pressure during

concreting

*Standards relevant to tunnel linings cited in the Guidelines are listed in the Reference section at the end of the document


7/58




2.1 - Functions of liningThe lining to a tunnel or of a longitudinal underground openingor cross-tunnel forming part of the principal structure is a struc-ture placed directly against the ground, or the temporary supportor waterproofing system as applicable.

The lining determines the effective cross-sectional area of the tun-

nel offering the functions required by the tunnel operator. It isphysical proof of the completeness and durability of the structurein terms of the required criteria to be met for the tunnel to remainstable and fit for the purpose for which it was designed.

The lining is usually left exposed when seen from inside the tun-nel although it hides the waterproofing system and any temporaryor permanent support which may have been installed. It may belined internally to meet certain requirements concerning appea-rance or environmental considerations.

It is necessary at the tunnel design stage that a clear statement bemade of the functions the lining will be called upon to provide interms of (i) the requirement for overall stability of the structure,

chiefly as determined within the surrounding rock, and (ii) requi-rements relative to operational criteria. These functions are detai-led in this section of the Guidelines, and subsequent sections dis-cuss the resulting consequences for the construction phase.

Five functions are described and discussed (definitions, needs,benefits, etc.) in the following paragraphs, with no pretension ofbeing an exhaustive list, to highlight the constraints and theirconsequences for the construction of the lining.

2.1.1 - Support Function

2.1.1.1 - Ground Loads

The structural support provided by the tunnel lining provides therequired long-tem mechanical stability. If temporary support wasapplied immediately after excavation and this support can beconsidered sufficiently reliable over time (suitably designed andexecuted sprayed concrete, protected anchor bolts, etc.), thedesign of the permanent lining may make allowance for thecontribution of this temporary support in withstanding outsideloads.

The lining must be capable of withstanding the following loads: Its own weight, Short- and long-term external loads from the surrounding

ground, including any earthquake loads, External hydrostatic groundwater loads,

The effect of time-dependent strains (swelling, creep), Loads applied by operating equipment.

In the particular case of swelling ground, the completion schedule

does not normally allow sufficient time for letting the ground todecompress sufficiently to arrive at an equilibrium state and thelining must be designed accordingly. This quite frequently resultsin the need for a high-stress lining with inverted vault invert.

Dead weight loads may be factored to include for stresses due totemperature changes and concrete drying shrinkage. These areusually not considered to be critical items in lined tunnel design.

The lining may be poured, according to circumstances: either after excavation and installation of temporary support

when there has been time for a new equilibrium to be reachedbetween the surrounding ground and the support; in this case,the permanent lining is necessary and useful for providing longterm stability and the loads from the surrounding ground areapplied to it very gradually,

or keeping pace with excavation, by heading and benching ifnecessary, when the previously described approach is not possi-ble when, for example the tunnel is passing through poorground or there are severe settlement criteria. The design mustaccordingly include for a very complex construction sequence

and finely-tuned organisation (different items of plant allconcentrated in a small space for driving / temporary support /waterproofing / shuttering, and all well ventilated); the loadsacting on the lining will generally be higher than in the pre-vious example.

2.1.1.2 - Mobilisation of Ground / Support /Structure Interaction

It is common knowledge that, if it is to contribute to the perma-nent support, the lining must be conceived in such a way as toefficiently make use of its interaction with the surroundingground. This implies appropriate decisions as to the cross sectio-nal shape and stiffness of the lining as compared with that of the

host ground, and careful choice of construction method to ensuretight contact with the ground everywhere.

A tight interface does not in itself guarantee sufficient mobilisa-tion of the ground / support / lining interaction to control ben-ding stresses in the lining to the preferred degree. The other requi-rements are:

The mean axis of the roof arch must be appropriately shaped,which may require an iterative analytical method. A very flattop arc will keep down excavation volumes but in return, willvery frequently allow high bending stresses to develop. Suddenchanges of curvature commonly cause locally high stresses, andsmooth transitions are eminently to be desired.

The host ground must possess significant stiffness. In groundexhibiting plastic behaviour or poor stiffness, the soil/structureinteraction may be too weak not to have to resort to systematicreinforcement of the lining.

2 - LININGS AND DESIGN REQUIREMENTS

This chapter reviews the various functions which may be assigned to the tunnel lining and the requirements associated with thesefunctions, along with the chief consequences that will result in the construction phase in terms of the concrete mix, constructionmethods, formwork systems, construction of the lining and its appearance.

It does not deal with issues of tunnel shape. Only those terms necessary for an understanding of the text are defined in this chapter,accompanied by a few examples.


8/58




It is also universally accepted that, if the interaction criteria aremet, plain concrete can be used for the typical section of thetunnel.

The design thickness of the arch is based on loads computed bymethods which take account of this soil/structure interaction and,provided bending stresses are moderate, reinforcement of the liningmay be dispensed with, in accordance with AFTES Guidelines onUse of Plain Concrete in Tunnels which were published in TOS149, Sept-Oct 1980.

Cases where reinforcing steel is needed are dealt with below.

2.1.2 - Support and Protection of WaterproofLining System Function

Older tunnels (pre-1970) were not waterproofed. They often sufferfrom damp patches and leaks which become worse over time andlead to inevitable deterioration of the lining concrete (especially inroad tunnels).

More recent constructions have waterproofing systems on the outersurface (extrados); this usually consists of a PVC sheet placed bet-ween the temporary support and the permanent lining, andOwners are advised to provide such a waterproofing system.

Two cases are found: Full waterproofing which includes the invert (usually an inver-

ted arch in this case) and the lining must be designed to withs-tand groundwater loads.

Partial waterproofing of the roof and down to the bottom of thesidewalls, with drains to empty the system (this system is alsoknown as umbrella waterproofing).

Dispensing with waterproofing altogether may be considered insome rare one-off situations, e.g. where there is no water table, intunnels excavated by heading and benching with long sections ofconstruction joints multiplying the risk of flaws, or where functio-nal requirements are not severe (especially as regards dampness).

Waterproofing the crown makes it possible to produce a better qualityconcrete by keeping moisture within the concrete during the first fewdays of curing. It also prevents formation water from upsetting thephysical and chemical equilibrium of the concrete while it is settingand also reduces the problems associated with concrete shrinkage.

If there is no extrados waterproofing, the fresh concrete may lose itswater as soon as it is poured or conversely, it may take water from the

surrounding ground, even if the tunnel lies above the water table butis very wet. In both cases, its original mechanical properties may bealtered. An additional problem is that concrete shrinkage may beseverely and unevenly restrained by any serious overbreaks.

A concrete lining protects the waterproofing system against damagearising from tunnel operation and of course, care must be taken notto damage the system when building the lining.

2.1.3 - Operating Equipment Support Function

The structure of road and rail tunnel linings is tied up with thefunctions required of the tunnel, and attention must be given to:

Static and dynamic stresses concentrated by equipment (fans, ven-

tilation ducting, hangers and supports for traffic roadways and/orventilation ducts, fastenings for cable trays, lighting or signage,catenary tensioning points, lifting loads when removing crashedroad vehicles and railway trucks, etc),

Misoperation due to operating conditions.

This should result in different designs for certain sections of thetunnel lining (e.g. reinforcement of the roof at ventilation booster

sites and/or extra reinforcement in the sidewalls in typical tunnelsections) and should involve special arrangements during construc-tion for very strict inspection and supervision of the work of fixingreinforcing steel and pouring concrete in these zones.

2.1.4 - Operating Cost Control Function

Tunnel operating costs (especially for road tunnels) are largelygoverned by the cost of electricity for lighting and ventilation, etc.and maintenance (cleaning) and although more expensive initially,tunnels with in situ linings are easier and less costly to operate thantunnels lined with sprayed concrete.

In situ concrete linings reduce: friction head losses in air circulating in the tunnel (velocity

< 8 m/s) and ventilation ducting (velocity 20 25 m/s), head losses in water flowing in drainage and relief tunnels, deposits in drainage tunnels, cleaning difficulties.

They may also improve efficiency of lighting systems, especially inroad tunnels.

This "minor" function of the lining must not be overlooked in thedesign studies for the lining (the surface finish of concrete exposedto view should be specified), the formwork system (especially itsquality and strength) and concrete mixes (workability among otherfactors).

2.1.5 - User Comfort FunctionThe intrados of the tunnel remains visible and the appearance ofthe lining (especially if there are regular commuters) must be consi-dered at the design stage.

A smooth painted surface is obviously more attractive than thedepressing as-cast grey expanse where the driver can see the demarca-tions between the different pours, all with their own shade of grey.

Painting the sidewalls of road tunnels is an effective way to combatconcrete deterioration, by controlling grime deposits and makingcleaning easier.

The lining may also be of use to the road user by giving advancewarning of bends by highlighting the longitudinal construction

joints between sidewall and crown and the vertical constructionjoints between lining rings.

Tunnel type and length, and the type and extent of the traffic load,are the basis for setting a level of comfort which will be governed bythe quality and appearance of the walls. This in turn dictates theformwork system, which will be different when operating at urbanor greenfield sites.

2.2 - Tunnel cross sectional shapes2.2.1 - Definitions

This section presents a brief explanation of why the cross sectionalprofile of a road, rail, canal or sewer tunnel cannot be standardi-

sed, even if equivalent performance is required.Linings consist of one or more concrete arches enclosing an effec-tive cross sectional area such that the resulting tunnel offers the


9/58

specified functional performance. The intellectual process leadingto the elaboration of the cross sectional profile involves carefulstudy at the project planning stage, whatever the tunnel type andpurpose in question.

The line enclosing this effective cross section is called the intra-dos. The geometry of the intrados may be defined by a single arcof circle, a succession of circular arcs joined by smooth tangents ormore generally a succession of circular arcs and straight lines.

The selected intrados must be the outcome of a process of opti-misation of the effective cross section offering all the requiredfunctions, but also circumscribing rectangular or circular bodiesrepresenting machinery and equipment; it must incorporate asafety margin with respect to the civil works and utilities, cons-truction and maintenance activities, and the electric field (in thecase of rail tunnels), and construction tolerances such as to have aminimum excavated section with a generally regular geometry. Inthe design of the intrados, slightly curved or flat surfaces, sharpprojections and sudden changes in curvature must be avoided asfar as possible because they concentrate loads and stresses whichmay result in overdesigning the lining. On the basis of these

requirements, the shape of the intrados may range from a circleto five circles.

The outer line of the lining is called the extrados. It is defined with

reference to the intrados, by shifting the intrados line outwards bythe design thickness of the concrete. Concrete thickness is derivedfrom the envelopes calculated for the loads and load combinationsapplied to the lining, or complies with the minimum thickness forthe size of the cross section*. In some cases, design thickness maybe modified to allow for various design rules. For example, conc-rete thickness must be sufficient to provide adequate cover to box-outs or cable ducts required for equipment.

2.2.2 - Examples of Profile Optimisation

The examples presented below illustrate the critical points invol-ved in setting the shape of the lining intrados (smoothing the line)and extrados (intrados line shifted outwards by approximately thespecified minimum concrete thickness) and dealing with sharpprojections or hard points; this data is needed for designing theformwork system and its operating procedures, especially formstripping.




Profile of road tunnel without concrete invertand with ceiling slab forming ventilation duct Profile of road tunnel with arched invert

Profile of (rubber-tyred) metro tunnel with flat invert Profile of TGV (high speed train) tunnel with arched invert

Figure 1 - Typical Road and Rail Tunnel Shapes

*Guidelines in TOS 165. Owing to structural considerations, the minimum permissible design thickness of an in situ concrete lining is dictated by tunnel size(generally 200 mm for small tunnels and 300 mm for tunnels with a diameter of approximately 10 m).


10/58




2.2.3 - Consequences on operatingformwork systems

The geometries of tunnel cross sections may appear very similar

but the formwork needed to build the lining may be very diffe-rent. For example, there may be: No continuity of the intrados between sidewall and roof arch

and a change of curvature at the brackets carrying the ventila-tion duct ceiling slab, requiring special forms that are compli-cated to make and use when striking the forms.

No true invert (just non-structural blinding concrete) or anarched invert requiring either a runway for moving the slipforms along the tunnel or special arrangements in the form-work system itself.

Flat invert with variable (sometimes steep) angles of superele-vation requiring a shuttering system which can be adjustedover a wide angular range.

Curved upper face of foundation or no foundation to providethe reaction, so that the forms must be fastened to the invert orbe entirely independent.

2.3 - ConventionsIn general, once the design analyses have been completed, linearunderground structures are usually drawn up on a set of what areknown as Typical Cross Sections, which show temporary support,waterproofing and lining details and the conventional paymentlines.

Linings and their minimum, nominal and mean thicknesses mayraise questions for the designer and the next part of this section

presents some simple minimum rules and the most widely usedconventions adopted by design offices, consulting engineers andconstruction contractors (they will be a compromise between allthe conventions studied and accepted), always keeping in mindthe requirements in CCTG Fascicule 69 (Underground Works)specifications, with additional material when the issue of extradoswaterproofing systems arises.

2.3.1 - Typical cross section

2.3.1- Definition of physical and payment lines

2.3.2.2 - Physical Lines

Two lines are obligatory for the definition of the structure: excava-tion, temporary support and/or lining.

These are the physical lines calles I Line and A Line

The A and I lines are directly measurable. Another line is neededto determine the volumes or areas to be used for calculating pay-ment. This is the B line as defined in CCTG Fascicule 69. It isderived by shifting the A line outwards by a distance d.

Distance d can be thought of as a tolerance permitted to thecontractor based on driving method and conditions and it mustbe specified by the Engineer such as to allow the contractor toearn a fair rate for the work performed.

2.3.2.2 - Payment LinesThe B and E lines are theoretical and so cannot be measured.

2.3.3 - Typical Lines and Cases2.3.3.1 - Lining poured directly against rock,no waterproofing system

Sidewalls Vertical or curved parts between the foundationand the horizontal diameter of the roof arch

Springing Plane located on the horizontal diameter ofthe roof arch

ShoulderPart of the roof arch between the springingand the crown

CrownHighest point of the roof arch lying in the verticalplane of symmetry of the tunnel

Key Central part of the crown

Circular arch Profile in which they mean axis of the roof archis an arc of circle

Invert Lower part of the tunnel section spanning betweenthe two sidewalls

ArchedInvert which is arched downwards with the lowest

invertpoint of the invert lying in the vertical plane of symmetry of the tunnel

Figure 2 - Typical Cross Section Notation

I LineDefines the effective width and height clearances ofthe tunnels permanent lining (inside cross sectionavailable for tunnel operation).

A Line Defines the minimum size of the excavated tunnelsection before installing temporary support andpermanent lining (minimum excavation line).

B LinePayment line for excavation defined by its distanced from the A line (mean excavation line).

E LinePayment line for lining extrados determined byshifting intrados line I by the nominal thickness ofthe lining.


11/58

2.3.4 - Lining Concrete Volumes

2.3.4.1 - Quantity Estimates General Tunnel Section (Tunnel and Cross Tunnels):

The volumes of concrete poured in the lining must be estimatedon the basis of the drawings in the tender or design documents.The thickness considered is the space between theoretical lines Eand I.theoretical line E and physical line I.

Structure at junctions (lay-bys, galleries, niches, etc.)

Concrete volumes must be estimated more accurately withdimensions taken from the design drawings, lying between the Eand I lines.

2.3.4.2 - Overbreak

Overbreak volumes must be estimated well before installing thewaterproofing system. Instruments such as a profiler or 3Dscanner allow the relevant volumes to be estimated.

2.3.4.3 - Construction Tolerance

The total tolerance covering fabrication and assembly of theformwork system, moving the forms to station and concreting

must not result in the finished lining being thinner than thenominal design thickness (the thickness of concrete estimated forpayment between the E and I lines remains unchanged). Conver-gent zones must be identified well in advance before moving theslip forms to station.

2.4 - Concrete criteriaIn addition to the necessary mechanical properties of the concreteto provide the support function (contract strength of hardenedconcrete and deformation modulus), the more important proper-ties of concrete for tunnel lining applications are workability,compaction, resistance to cracking and resistance to spalling.

Workability is needed so that the concrete will flow freely into theforms despite irregularities in the rock face and the presence ofreinforcement and items to be embedded in the concrete. Com-paction is necessary to obtain a high degree of watertightness andthereby, good resistance to aggressive substances. In this case, spe-cial cements must be used.

For the same reasons, the concrete must exhibit the least possibleshrinkage, especially as shrinkage is restrained by reason of theconcrete forming a solid mass with the host rock on one side(except if a waterproofing system is installed) and the concrete isnot reinforced. The most typical case is in large tunnels in which astrong current of air might circulate after break-through. Therapid loss of moisture and temperature drop caused by this aircurrent are the leading causes of increased concrete shrinkage andconcomitant cracking, specially in green concrete.

Lastly, if the forms are to be struck quickly, high early age strengthis needed, which may be incompatible with reduced cracking.

The solution to this problem is often to find the best compromisebetween the opposing requirements and actual conditions at thesite with due consideration of the resources available there.

2.5 - Lining construction criteriaCharacteristic strength is the most important concrete property

for lining stability. Furthermore, it must be remembered that highstrength means a high modulus and therefore, a stiffer lining.

However, this is not usually the critical factor with plain concretefor which in practice the offset of the normal load determines theconcrete thickness needed. But high early strength is always adetermining factor for deciding how soon the forms can be struckafter completion of concrete pouring.

In all cases, the concrete closure must ensure a tight contact bet-ween the rock or temporary support and the lining; contact grou-ting may be needed after completion of pouring. Efficient struc-tural performance (interaction) requires good constructionpractice: good concrete workability is needed for the concrete tocompletely fill the space behind the forms and flow around geo-metrical irregularities of the rock face and embedded items, anddespite difficulties of forcing concrete into the roof crown.




Figure 5 - Lines - Steel ribs and liner plates / Packing concrete /Waterproofing system / Linin

Figure 6 Lines Steel ribs / Shotcrete / Lining

2.3.3.2 - Shotcrete, waterproofing system,permanent lining

Volume bton coffr = Vol (B) Vol (I)

Volume bton coffr = Vol(B) Vol(I) Vol(BP=BE)


12/58




Lastly, moderate shrinkage keeps early age cracking of the roofarch to a minimum, until such time as pressure from the surroun-ding ground eventually produces significant compressive stress

conditions in the roof.

2.6 - Criteria for the appearance ofexposed concrete

Apart from problems with cracking and blemishes revealed afterremoving formwork, the compaction, porosity and shrinkage cha-racteristics of the concrete will determine its propensity for pic-king up grime.

Linings in road tunnels are usually cleaned regularly; therefore,protection and maintenance must be considered necessary activi-ties. But before applying systematic preventive protection, it is

important to fully control fabrication of the formwork, prepara-tion and pouring of the concrete, and striking forms.

2.6.1 - Field of Application

The stipulations in this section of the Guidelines apply solely tothe exposed faces of in situ concrete. They deal with the appea-rance of these visible surfaces, which results from a combinationof concrete mix, successful embedment of reinforcing bars andother items, and concrete pouring practice which can lead tomany flaws liable to spoil the appearance.

The process for achieving the specified appearance and means ofarriving at this goal mainly concern:

the design, fabrication and setting up of the formwork system(the form liners must be appropriate for the quality of theresulting concrete face),

the conformity of the materials entering into the concrete mix, the concrete mix design and properties, the regularity of concrete mixes and pours (vibration and cons-

truction joints), the treatment of areas not left as-cast; this treatment must be

specified in the contract documents.

2.6.2 - Characteristics and Types of ExposedSurfaces

Briefly, in situ concrete surfaces exposed to view are judged by: Surface condition, Shape and flatness: low spots must not deviate from flat by

more than 5 mm when measured with a 2 m straight edge or 2mm measured with a 0.2 m straight edge,

Texture, representing surface condition and quality: moderateor concentrated blowholes, local defects visible from a distance(cf. French Standard NFP18 503),

Colour as assessed on a grey scale.

Most surfaces are left as-cast and these characteristics are directlydependent on concrete colour and form liner properties (type and

category). But the sidewalls of road tunnels and other structuresfrequented by users are often painted.

There are three classes of surface finish, on the basis of increasin-

gly stringent appearance requirements. The contract must stipu-late what finishes are required where.

2.6.2.1 - Plain finish

Plain or ordinary surfaces (category 3) are surfaces left as-cast forwhich the only requirement is for a regular shape. This usuallyapplies to ancillary cross galleries to the tunnel and its founda-tions.

2.6.2.2 - Fine finish

Fine surfaces (category 2) are surfaces left as-cast covered by spe-cial requirements as regards shape, and concrete texture andcolour. This finish is mostly used on sidewalls to the tunnel or by-passes and shelters.

Where light-coloured or special concretes are specified, specificdocuments can be incorporated into the contract and samples

must be produced, as follows: Specimens must be made at the same time as for the suitability

tests using reinforcement equivalent to that used in the tunnel(if necessary) and the same concrete as is to be incorporatedinto the works,

Specimens must be truly representative of the structure to beconcreted under actual field conditions in order to ascertainthat the resources (identical forms, vibration, etc.) assigned bythe Contractor are adequate to meet the contract requirements,

They must be acceptable to the Engineer.

2.6.2.3 - Featurework

Featurework surfaces are very special surfaces which must meetdecorative and architectural requirements (category 1); they areoften stipulated for the first rings of urban road tunnels.

The contract must specify precisely all the characteristics of thesesurfaces and some characteristics of the forms.

This category also includes surfaces left as-cast exhibiting somedegree of relief or special shapes, and worked surfaces.

2.6.2.4 - Unspecified finish

Except as otherwise stipulated, surfaces exposed to view have afine finish and concealed surfaces have a plain finish.

2.6.3 - Lift Joints and Construction Joints

Exposed surfaces may have joints highlighted, i.e. horizontal liftjoints at the foundation ledge, if exposed to view, horizontal liftjoints between sidewalls and roof arch, and vertical constructionjoints between lining rings. Trapezoidal joint formers are preferredfor reasons of ease of form removal, using stiff rubber or metalshapes fixed to the forms.

2.7 - CONSTRUCTION PRACTICE BASICSTunnel and gallery linings are generally made of plain concrete forstandard sections but may be locally reinforced at safety nichesand points where the tunnel is intersected by cross galleries.

Arched inverts, where necessary, may also be reinforced. In thiscase, controlling the high stresses where the sidewall meets theinvert calls for the reinforcing bars to be continued up a certaindistance into the sidewall.


13/58

2.7.1 - Plain Concrete Linings

In the majority of situations, tunnel linings are not reinforced onstandard sections except in specified conditions such as the need

to control detrimental cracking.This does however mean that the host ground must display somedegree of stiffness and that tunnel geometry is satisfactory. Thesetwo factors are not independent. A flattish roof arch tending toforce the abutments apart might be acceptable in a stiff rock butnot in deformable ground where the tendency towards outwardmovements or convergence of the abutments would result insignificant bending stresses.

2.7.2 - Locally Reinforced Linings

A plain concrete tunnel lining may be reinforced locally at: highly stressed zones such as foundation ledges, sidewalls, inter-

sections with cross galleries, niches, connecting galleries, etc. zones called upon to carry concentrated loads (extrication

rings, bearing points of ceiling slabs forming ventilation ducts,fans, suspension rod anchors, etc.),

invert (flat or arched), sharp changes of curvature, parts of structures exposed to a harmful cracking criterion.

At the stage of undertaking the structural design and tender docu-ments, profile geometry must allow for constraints associatedwith reinforcing bars (bar sizes and concrete cover) and concrete(aggregate size), and during the tendering process, the formworksystem design must address the issue of constraints associatedmore particularly with fixing bars in place and positions ofconcreting windows.

2.7.3 - Fully-reinforced Linings

Special linings reinforced around the whole section are chieflyfound on:

tunnels subject to high hydrostatic loads that have to be com-pletely waterproofed (including the invert),

tunnels driven through ground of low stiffness, displayingsignificant convergence or divergence and where there is insuf-ficient soil-structure interaction to realign the normal loads inthe sections,

drainage galleries carrying water under pressure,

intersections with geological features or special zones (swellingground, shallow tunnel),

tunnel portals built above ground and backfilled ("pseudo tun-nels").

At the structural design and contract document preparationstages, the tunnel section profile must include for constraintsassociated with the reinforcement (bar sizes, concrete cover, aggre-gate, stiffness of structures, etc.), as well as steel fixing methods (asfree standing assemblies or mounted on the shuttering) and theformwork system (design, lowering, number of forms, support ofthe steel, etc.).

2.7.4 - Construction in sections

The lining is built in sections, called rings, whose length is gover-ned by:

tunnel alignment: in curved sections the offset caused by thering length must remain within the stated tolerances,

concrete shrinkage (mix design and time before striking form-work),

control of cracking (roof arch design assumptions), whether or not there is a waterproofing system. If there is, the

lining can slide in relation to the surrounding rock, and thisreduces the tensile stresses due to restrained shrinkage. If thereis no waterproofing system, shrinkage is impeded and in addi-tion more severe temperature cracking must be considered,due to the greater mean effective thickness of the lining, asituation which is made worse when there are major over-breaks.

Less commonly, tunnel length and lining construction time.Tunnel lining ring length is generally of the order of 10 m (maxi-mum 15 m) and for long transverse galleries (lay-bys and turninggalleries, etc.) of the order of 5 m.

Basic construction principles for building the lining with amechanised formwork system must be settled in the project plan-ning stage and further addressed in the tender documents.

2.7.5 - Embedded Items

Some types of tunnel may require embedding components in thelining or at its intrados to subsequently fasten in place and operateequipment, or to strengthen parts of the lining.

In road tunnels, this concerns: Anchorages for suspension rods for ceilings and partitions for-

ming ventilation ducts, Electric cable conduit for safety lighting, signage and fans, Smoke ducts, Anchorages for extrication rings, Electrical boxes, Reinforcement to brackets carrying the ventilation duct parti-

tions, etc.

In rail tunnels: Mounting rails for catenary brackets, Anchorages for tensioners,

Electrical boxes, etc.In addition to the above, for all tunnels:

Tubes to the compartmentalisation system of the extradoswaterproofing system,

Access cables to measuring instruments in the support, Contact grouting lines, etc.

Embedded parts must be accurately described and positioned onthe tunnel ring lay-out drawing. This issue must therefore be exa-mined at the project planning and civil works and equipmentdesign stage and finalised in the tender documents.





14/58




3.1 - Concrete mix design and tests3.1.1 - Reference Document

Concrete for tunnel linings must meet the requirements of Stan-dard NF EN 206-1. This is a fundamental requirement, butcannot be considered as the one and only reference document andsome major jobs may make use of others as a supplement to theStandard for that specific job.

3.1.2 - Selecting Independent Inspection Body

The independent inspection bodies must be accredited byCOFRAC (COFRAC was instituted by the authorities so thataccredited bodies could have proof of their competence andimpartiality ISO 15189 [?]). However, it is not always possibleto find a COFRAC-accredited body and provision must be madefor waivers, provided that the prospective body operates a qualityassurance system providing an equivalent level of quality.

3.2 - Concrete components3.2.1 - General

All reports submitted by the Contractor to the Engineer forapproval of the ingredients entering into concrete must containthe results of the following tests.

3.2.2 - Aggregate Quality

Aggregates for concrete must comply with Standard XP P 18-545code B with a water absorption preferably index A except if other-wise stipulated.

Aggregates must be suitable with respect to alkali aggregate reaction.

Aggregates may be obtained by crushing and screening materialexcavated from the tunnel in so far as it meets the technical requi-rements in this section. The use of concrete rubble as aggregate isnot recommended without careful study (see AFTES GT35Guidelines on Materials Management and Re-use).

3.2.2.1 - Sand

Sands routinely used must be 0/4 mm.

Optimum fineness modulus

The specification in Standard NF EN 12620 is

The recommended value for the mean fineness modulus is 3.0.

Corrector sand

A corrector sand is by definition a sand added in a proportion ofup to 30% of the total sand mass. When used, the tests are madeon the mixture of corrector sand and natural sand in proportionsset by the producer.

3.2.2.2 - Gravel

The gravel routinely used is graded 5/20 with two gaps.

Gravel with a D (diameter) ranging from 16 mm to 31.5 mm canbe considered.

Particular specifications are required for items subject to severeabrasion (e.g. some drainage works).

3.2.3 - Cementitious materials

3.2.3.1 - Cements

Cements must comply with NF EN 197-1 or approved equivalent.

3.2.3.2 - Additions

Permissible additional ingredients are: silica fume complying with Standard NF P 18-502 and NFEN 13263-1, ground vitrified blast furnace slag complying with StandardNF P 18-506, coal fly ash complying with Standard NF P 450, calcareous admixtures complying wth Standard NF P 18-508, siliceous admixtures complying with Standard NF P 18-509.

These additions are tested with a procedure recognised as beingequivalent to the procedure employed for preparing concretes

bearing the NF mark or equivalent.3.2.3.3 - Special Features for Tunnel Linings

The cementitious material selected must achieve the best compro-mise between the rate of strength development and sensitivity tocracking (heat of hydration, shrinkage). The usual cements areCEM I plus admixtures or CEM II blended cements having atotal cementitious content of the order of 350 kg per cubic metreof concrete. Recourse to CME III or CEM IV cements is possiblebut not really compatible with the 24 hour working cycle (setformwork pour concrete concrete hardens strike forms move shuttering on to next station).

3.2.4 - Mixing WaterWater used for mixing the concrete must comply with StandardNF EN 1008; seawater must not be used and recycled water from

3 - CONCRETE FOR PERMANENT LINING

This important part of the Guidelines examines the requirements associated with materials (especially concrete), concrete transport tothe formwork system and special treatment if any (in the mass and/or exposed faces). These Guidelines do not repeat the requirementsdetailed in the Fascicules, standards and other official documents which are simply referenced.

This chapter is also a guide for the Engineer and design office for drafting the Specification in the Tender Documents and for theContractor and his Design Office in preparing the tender and design during the works, in collaboration with the concrete batchingplants laboratory and his independent auditors.

CF 4.0 to 2.4 (coarse sand)

MF 2.8 to 1.5 (medium sand)

FF 2.1 to 0.6 (fine sand)


15/58

the concrete mixing plant, if used, must meet the requirements ofAnnexe A of the standard.

3.2.5 - AdmixturesThe CE certification mark allows products to circulate freelythroughout the European Union, regardless of their country oforigin. It is proof of EC compliance. It is complusory but does notreplace the NF mark.

Standard NF EN 934-2 redefines the eleven types of concreteadmixtures (Tables 2 to 12), this is the quality mark attesting tothe quality aptitudes of the product (tested by an independentoutside body).

Having both accreditations is the new quality baseline for conc-rete admixtures.

All admixtures must bear the NF quality mark or approved equivalent.

3.2.6 - Additives

Additives, not covered by Standards, may be incorporated intothe concrete to modify some of its properties or confer specialproperties to it.

Coming under the heading of additives are natural or syntheticnon-organic dyes, fibres, pozzolana fines,, cohesion agents, etc.

Metal fibres can be mixed into the freshly-mixed concrete toimprove its properties, especially its ductility, durability and crackresistance. Metal fibres must comply with Standard EN 14889-1Fibres for Concrete Part 1 Steel Fibres Definitions, Specifi-

cations and Conformity.The unique properties of fibre-reinforced concrete may beparticularly attractive if lining thickness has to be reduced or aself-compacting concrete has to be used. Pumping fibre-reinforcedconcrete might raise a few problems.

The minimum proportion of fibres depends on fibre properties(tensile strength, anchoring system, length/diameter ratio). Itmust be determined by testing (e.g. by measuring strain energy).

The recommendations from the Brite-Euram* european projectset out the criteria for selecting steel fibre properties and use.

Steel fibres can replace all or part of the traditional concrete rein-forcement in specific structures provided that bending tensile

strength values are cross checked with appropriate tests.* Project BRPR-CT98-0813 Recommendations on Quality Assuranceof SFRC.

3.3 - Concrete definition

3.3.1 - General

Concretes must be defined in the manner described in StandardNF 206-1 except if otherwise specified.

3.3.2 - Specification of Basic Properties

The underlisted basic properties required for in situ concretelinings must always be specified:

28-day characteristic compressive strength of the concrete, level of prevention against alkali aggregate reaction,

exposure class, chloride content class, concrete consistency.

3.3.3 - Specification of SupplementaryProperties

High early strength (to allow the forms to be removed) is always asupplementary specification for lining concrete. It is specified interms of strength at a given age (equivalent age at 20C).

Other properties may be specified, such as: concrete compressive strength at ages other than 28 days

(e.g. 90 days), tensile strength by splitting tensile test, amount of blowholes.

3.3.4 - Concrete Classification3.3.4.1 - Exposure Classes

In most road and rail tunnels, the tunnel lining concrete has to complywith requirements appertaining to class XC3 XF1 exposure.

Parts of the structure subjected to de-icing salts only fall into classXF2 exposure if they are not protected by an appropriate surfacedressing.

The tunnel lining does not have any horizontal surface liable toresult in a high water saturation and exposure classes XF3 and

XF4 are not appropriate if exposed to severe subzero temperatureconditions. However, special requirements as to durability inrespect of freezing and melting agents may be necessary over adistance of several hundred metres from each portal.

For works or parts of works in contact with aggressive ground andnot protected by a waterproof sheet on the extrados, exposureclasses XA1 to XA3 can be accepted.

In a situation involving attack by melt water, as for the aggressiveground case, it is preferable not to deal with the durability issue byincreasing the binder content of the concrete (which wouldinvolve problems of shrinkage cracking) but by providing a protec-tive barrier.

In general, except as may be otherwise stated in the contract, thevalues in the following table apply. It might also be possible to

invoke the equivalent performance concept as defined in StandardNF EN 206-1 and compare the permeability of the proposedconcrete (with limited cement content) with the referenceconcrete as illustrated In Table NA.F.1 of the standard.

For other exposure classes, see specifications in NF EN 206-1.

Some drainage works may convey aggressive effluent leading totype XA exposure class, with reference to the degree of aggressivityset out in Table 2 of standard NF EN 206-1.




EXPOSURE CLASSES

XC3-XF1 XF2

Maximum water/equivalent binder ratio 0.60 0.55

Minimum equivalent binder content (kg/m3) 280 300

Minimum air content in concrete N/A 4%

Characteristic 28-day strength C25/30 C25/30


16/58




3.3.4.2 - Level of Protection in Respect of AlkaliAggregate Reaction

The AAR prevention level for all types of underground works is

generally level C.3.3.4.3 - Fire Performance

Fire resistance level is defined in the Technical Instruction appen-ded to Ministry Circular 2000-63. It may range from N0 for alining in stable ground to N3 for an underwater tunnel. Verifyinglining fire resistance requires an analysis which includes for thermalexpansion effects and loss of structural properties, and the possi-bility of spalling. Spalling assumptions must be backed up by tests.

Fire performance of these concretes can be improved by theaddition of polypropylene fibres at a rate of 1 kg to 3 kg per cubicmetre of concrete.

If the requirements concerning the durability of fire resistanceproperties are very severe, the protection provided by the concretealone may not be sufficient and special fire resistant protectionmay be required (gunite, heat insulating panels, etc.).

Further details can be found in CETU guidelines Fire Perfor-mance of Structures 2006 edition, and an article by AFTES

Working Group GT37 in TOS No. 196 entitled Contributionto Means of Preventing Spalling Damage in Tunnel Concrete.

3.3.4.4 - Consistency of Fresh Concrete

The consistency and workability properties of freshly mixedconcrete must be maintained during transport, pumping and pla-cing the concrete. These parameters must be quantified and justi-

fied by the Contractor.As a general rule, the required consistency is as pertaining to classS4 slump or class F4 or F5 spread for conventional vibratedconcrete. The reference value is then the value measured on arrivalof the concrete on site.

For self-compacting concretes, limiting values for the slump flowtest must be set at the time of finalizing the mix design (suitabilitystudy). Generally, the tolerance on either side of the target value is+ 50 mm.

3.4 - Concrete mixing and transport

3.4.1 - Choice of Batching PlantThe concrete mixing plant must comply with required conditionsfor awarding the NF-BPE mark plus requirements in Fascicule65A but formal certification must not be made compulsorybecause it is a costly process that would be incompatible with pro-

ject economics.

3.4.2 - Concrete Mixing

It is recommended to follow the technical clauses of Article 83 ofFascicule 65A of the CCTG general specification as concernsconcrete preparation.

In extreme climates, special provisions must be made to ensure atdelivery a minimum concrete temperature in winter (generally16C) and a maximum concrete temperature in summer(generally 30C).

At the very least, this means hot water (up to 60C) must beavailable for mixing concrete in winter.

It is also important when lining rings consume large amounts of

concrete, to provide a back-up batching plant capable of beingbrought on line promptly if the primary plant breaks down.

3.4.3 - Concrete Transport

3.4.3.1 - Mixer Truck Transport

A delivery note must be filled in for every batch delivered bymixer truck, stating, in addition to the requirements of StandardNF EN 206-1, complete identification of the materials used andthe detailed composition of the batch.

No water may be added on delivery or in the drum.

In the case of self-compacting concrete, every precaution must be

taken to avoid concrete losses or incomplete filling of the drum(use of a plug, etc.).

Not more than two hours may elapse between the time a batchleaves the concrete mixing plant and the time it begins to enterthe shuttering (transport time + waiting time), and must be stipu-lated in the contract specification and assumed in the concretemix design.

3.4.3.2 - Pumped Concrete, Long Lines andBooster Pump

The Contractor must propose the means of transport and pum-ping parameters from which he shall deduce any special mix

design requirements (conservation of rheology, workability, risk ofsetting, etc.).

When a priming slurry is used to start the pumps, it must not beincorporated in the works but discharged to waste.

3.5 - Concrete characteristics whenstriking forms

3.5.1 - Monitoring Concrete StrengthDevelopment and Performance

Concrete maturity measurement is recommended for justifyingthat the required strength for form stripping has been attained.

The recommendations in the guidelines on Strength of Concretein the Works, the Maturity-meter published by LCPC, March2003 is the basic text for calibrating and using this method.

The characteristics required of concrete when the forms are struckconcern two factors:

structural strength, which must be sufficient for there to be nodistress In the concrete from the application of loads it wouldnot be able to withstand (mainly form suction and self-weight),

the time the concrete must remain confined within the formsbefore being exposed to the atmosphere, in order to void preju-dicial drying out due to evaporation of surface water whichmight cause cracking and loss of concrete density near the sur-

face.Dependent on several parameters, some minimum value might beimposed on one or the other of these factors, or even both, but it


17/58

must be realised that they are closely interrelated (strength deve-lopment over time).

The parameters in question are (the list is not exhaustive):

type and proportion of cement in the concrete, water/cement ratio, air temperature at time of form removal, whether or not a curing agent is used (see next section), air velocity through tunnel at time of form removal, concrete mass (thickness), since concrete setting is an exother-

mal reaction, tunnel geometry: diameter (in small tunnels, tensile stresses in

the young concrete will be low) and shape (forms for a circularroof arch can be struck earlier than for a flatter roof shape).

In all cases to guarantee early-age structural performance, regula-rity in concrete production and control of concrete temperatureduring placing are the overriding factors.

3.5.2 - Minimum Requirement

The minimum concrete strength required before forms can beremoved must be justified by the Contractor and the concrete mixmust be optimised to obtain the necessary strength within thetime allowed. However, as a general rule, forms should not beremoved before the concrete has had ten hours to harden.

3.5.3 - Recommended Values

Recommended values for a circular arch roof 8-10 metres wide areas follows:

compressive strength 8 to 10 MPa, minimum time before stripping forms: 10 hours (knowing

that the required compressive strength is usually reachedwithin this time) under normal tunnel conditions (air velocity< 5 m/s, temperature > 15C).

These two values should be measured on the last concrete batchdelivered (filling the crown) except if there is very extensive overb-reak or other special considerations.

If the minimum compressive strength on removal of the forms isstipulated in the contract, the Contractor does not have to justifyit with his own calculations. But if no value is imposed or theContractor wishes to change it, he must justify the proposed valuewith a suitable analysis.

The minimum form removal time may be adjustable in the lightof precautions adopted after stripping (whether or not a curingagent or plastic sheets are provided, etc.). A formal procedureapproved by the Engineer is necessary for this.

The specified concrete strength value is the internal in situstrength, not the strength measured on an isolated laboratory spe-cimen.

There are several ways of making this measurement: on specimens heated to the same temperature as the concrete

in the works (hot cap method), by measuring the internal concrete temperature, correlated

with strength after calibration at the commencement of the

works (maturity-meter).The recommended method is the maturity-meter. If test speci-mens are still used, the Contractor must prove that the age of

the specimens is the same as the age of the last concrete pouredin the ring.

It is stressed that arriving at a concrete mix design with which

the targets can be attained is very important. An excessivelyprompt concrete or one containing too much cement mightdevelop the required strength quickly but only at the cost ofexcessive heat generation liable to cause cracking and deman-ding extensive precautions after removing the forms. Similarly,special precautions would have to be taken with self-compac-ting concrete (types of additions and admixtures, etc.).

3.5.4 - Curing

The exposed concrete surface must be protected against dryingout (water evaporation) and sudden temperature changeswhich might lead to significant shrinkage. Cracking can be

controlled by applying special measures, consisting of not res-training deformations, adapting concrete composition, andproviding appropriate curing. The appropriate curing methodfor lining concrete must be described in the Contractor'sQuality Assurance Plan, which must comply with the stipula-tions in Standard EN 13670.

Since most in situ tunnel linings are plain concrete, shrinkagecracking will inevitably occur sooner or later. It is acceptablein the majority of cases providing cracks are not more than0.5 mm wide.

If controlled curing is planned, it must be covered by a detailedprocedure described in the Contractor's Quality AssurancePlan; trials must be made if a chemical curing agent is to beused.

Specific rates must be included in the contract and applied toremunerate curing.

Controlled curing is strongly recommended. It must be desi-gned with reference to the intrinsic properties of the concrete(heat of hydration, etc.) and external influences (air tempera-ture, percent relative humidity, air velocity, etc.), as well as theconsequences of the curing on the following aspects:

possible changes in concrete surface conditions which mighthave to be cleaned off before painting,

congestion caused by portal frame, although not so severe asfor the formwork system,

possible influence on concreting cycles and therefore on themain lining works schedule,

possible negative environmental effects (water-sensitive envi-ronment in swelling ground for example if curing involvesspraying water).

As a general rule, water curing must be continued until suchtime as concrete strength has reached at least 35% of thespecified 28-day characteristic strength (criterion adopted inFascicule 65A).

3.6 - Surface treatment

For surfaces where the concrete is to be further treated afterstripping formwork, the treatment method and timetable mustbe described in the contract. Guarantee times inherent in thetreatment method chosen must also be specified.





18/58




3.6.1 - Protection of Surfaces

Until handover of the works the Contractor must protect all sur-faces (treated or left as-cast) against grime and flying dirt, and

spalling.

3.6.2 - Cleaning

Surfaces can be cleaned by spraying an abrasive substance or ahigh pressure water jet. The work must be done with care becauseit accentuates existing flaws such a blowholes and honeycombing.

When cleaning with abrasive substances, the Contractor must pro-vide the necessary means of protecting workmen and control pollu-tion with an efficient dust extraction system or other means.

Suitabiity tests will be needed to check the surface texture obtained,depth of treatment and effectiveness of the cleaning operation.

3.6.3 - Fire ProtectionFor existing tunnels, fire protection consists of a "special-design"lining not covered by these Guidelines. Reference might be madeto the Technical Instruction on Safety of Tunnels on the NationalRoad Network which stipulates that the material used for theinside lining must be classed as M0 for the crown and M1 for thesidewalls provided they do not consist of flammable materials.

3.7 - Benefits of self-compacting concreteThe conditions for building a conventional vibrated concrete tun-nel lining require a minimum lining thickness of at least 300 mm

approx. Using self-compacting concrete allows us to revise thislimit downwards (thicknesses of less than 300 mm are potentiallyfeasible, with 250 mm being found on a few tunnels) and at thesame time, concrete quantities and corresponding pouring timescan be reduced.

Self-compacting concrete generally exhibits better mechanicalperformance than the traditional C25/30 and can in some casesbe formulated to have characteristic strengths equal to that ofhigh performance concrete (C50/60).

Shrinkage of self-compacting concrete must be controlled (bycontrolling heat of hydration and cement paste volume) in orderto combat cracking. Methods that render the forms watertightmust be used (especially at the end stop forms).

Imposing a minimum lining thickness is not based solely onconsiderations of concrete pouring. It is an extra safety factor forplain concrete structures in which thickness is vital for withstan-ding bending stresses. The French National Annexe for the appli-cation of Eurocode 2 (incorporated in the update of the guideli-nes in TOS No.149 on unreinforced concrete already mentioned)accepts a lower safety factor on concrete compressive strengthonly if lining thickness is greater than a certain value (e.g. 400mm in tunnels 6 m in diameter and above).

Self-compacting concrete dispenses with the need for form vibra-tors and the loud noise associated with them.

Lastly, self-compacting concrete may improve appearance in terms ofblowholes, uniformity of colour and density (especially at the crown).

Self-compacting concrete displays most advantages in lining reno-vation (e.g. in the Tunnel des Monts at Chambery, France) andfor concreting panels to form ventilation ducts (e.g. upper panelin SOCATOP VL.1 tunnel or the Foix tunnel). In the renovationwork in the Tunnel des Monts (900 m twin tube in an urban set-ting), the new self-compacting concrete lining is not designed tosupport the ground.

Ultra High Performance Fibre-Reinforced Concrete is not suita-ble for cast-in-place lining and is not dealt with in these chapters.Its use in tunnel engineering might be considered for making pre-cast items such as thin panels or shells.

4.1 - Description of formwork systemsand minimum fabrication rules

4.1.1 - Functions

Forms for tunnel linings must provide the following essentialfunctions:

They must reproduce the design geometry without deformingout of shape, and remain within the specified tolerances;

They must produce the appearance required for exposed surfaces; They must facilitate fixing steel reinforcing bars and keeping

them in position while pouring concrete; They must prepare fastening points for embedded items; They must allow concrete pouring to proceed satisfactorily;

They must protect the fresh concrete against knocks and water loss; They must not leak when packing the concrete tight under

pressure;

4 - FORMWORK SYSTEMS

This Chapter of the Guidelines is in two parts:

The first focuses on the precise description of the formwork system and dimensioning principles, at the same time, giving an overviewof the plan of the tender documents. It is addressed chiefly to the Contractor and formwork system manufacturer/supplier.

The second part sets out the different steps in producing the formwork system, beginning with the formal order and ending withacceptance on site. The various steps describe the principles of interest to the Contractor, Supplier and Engineer.

In addition, this Chapter applies more particularly to the roof and sidewalls of linings to road and rail tunnels, and purposely ignoresfull-circle linings poured in a single shot (as frequently found in drainage tunnels and sewers) and telescoping forms, because the mannerin which these systems operate and construction methods in this kind of work are entirely different.


19/58

They must promote efficient hardening of the concrete underconditions as provided for in the design (thermal insulation forexample);

They must not restrain deformations in the green concrete(arrangements for this must not adversely affect the seal atexpansion joints);

They must facilitate the striking of the forms; They must withstand, without damage or any notable structu-

ral deformation, actions of all kinds occurring in the course ofthe works;

The must not apply any deleterious loads on nearby, previouslyconcreted structures (e.g. at reaction bearing points, etc.).

4.1.2 - Terminology

For convenience in reading these Guidelines, the following fivecommon terms are defined:

Form liner: the surface of the form in contact with the concrete Backing: the structure that holds and stiffens the form liner Form: form liner and backing Portal structure: the structure that allows the form (form linerand backing) to be moved to station along the tunnel Formwork or shuttering system: form and portal structure

Other terms exist for sub-assemblies and parts needed for bearingpoints, adjustments, translation and concrete pouring.

Bogey: provides for translation and rotation motions andcomprises a roller (on rail) or a rubber-tyred wheel which mayor may not be motorised (usually electrically driven);

Hydraulic cylinder or jack: used for lifting, moving and sup-

porting loads; Short strut: strengthens form backing and portal structure; Adjustable strut: lightweight load transfer beam with screwjacks or hydraulic cylinders at ends;

Collapser: closure system holding the formwork in the pouringposition and facilitating form stripping (once released, theforms drop open under their own weight);

Form end stop: radial stop at the forward end of each liningring;

Windows: openings in the form liner to pump in concrete

(must measure at least 500 mm x 500 mm); Shutters: panels closing off windows; Distributor: mechanical device facilitating distribution of the

concrete to all parts of the formwork system (windows andstub pipes);

Stub pipe: orifice and tube welded onto the form liner throughwhich the concrete is pumped into the form (generally in thekey of the crown, 100 to 150 mm diameter with a slidingclosure panel);

Skirt: lower, hinged part of formwork system.

4.1.3 - Different Types of Formwork System

Modern formwork systems are all free-standing and break downinto three main categories:

Type 1: Free standing system without portal frame, with meansof translation mounted on the form liner backing, and withouta skirt locking system built in. The Type 1 system is commonlycalled a free standing system without portal frame.

Type 2: Free standing system with portal frame independent ofthe form liner and backing, but without an incorporated skirtlocking system. The Type 2 system is commonly known as a freestanding system with independent portal frame.

Type 3: Free standing system with built-in portal frame fortranslation and skirt locking incorporated in the system. TheType 3 system is commonly known as a self-locking system

with integrated portal frame.