concrete formwork for tunnel lining

ASSOCIATION FRANÇAISE DES TUNNELS ET DE L’ESPACE SOUTERRAIN Organization member of the AFTES www.aftes.asso.fr

AFTES Recommendations Geometry, concrete mixes, formwork and concrete pouring practice for tunnel linings GT36R1A1

AFTES Guidelines GT36

Geometry, concrete mixes, formwork and concrete pouring practice for tunnel linings Text submitted by A. MERCUSOT (CETU) Chairman Working Group GT36 and A. BOERI (ALTER ) Vice-Chairman These Guidelines were drafted jointly with G. ABOU SLEIMAN (CHANTIERS MODERNES) - JP. ALBRECHT (BEC Frères 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 Régions) - H. SOURON (COYNE ET BELLIER) These Guidelines were approved by AFTES Technical Committee subsequent to a critical review by J. BURDIN (CONSULTING ENGINEER) - G. COLOMBET (COYNE ET BELLIER) - P. DUBOIS (IGOA) - L. THEVENOT (RAZEL) - JL. REITH (CETU) Translation : ROBERT CHADWICK - Rereading : LUCY REW AFTES Welcomes comments on this paper

CONTENTS Pages

Pages

1 - PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 - Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 - Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 - General background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 - Administrative framework . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 3 3 3 4

2 - LININGS AND DESIGN REQUIREMENTS . . . . . . . . . . . . 2.1 - Functions of lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 5

2.1.1 - Support Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 - Support and Protection of Waterproof Lining System Function . . . 2.1.3 - Operating Equipment Support Function . . . . . . . . . . . . . . . . . . . 2.1.4 - Operating Cost Control Function . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.5 - User Comfort Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 6 6 6 6

2.2 - Tunnel cross sectional shapes . . . . . . . . . . . . . . . . . . . . . . . . . .

6

2.2.1 - Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 - Examples of Profile Optimisation . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 - Consequences on operating formwork systems . . . . . . . . . . . . . .

6 7 8

2.3 - Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

2.3.1 - Typical cross section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 - Definition of physical and payment lines . . . . . . . . . . . . . . . . . . . 2.3.3 - Typical lines and cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 - Lining concrete volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8 8 8 9

2.4 - Concrete criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

2.5 - Lining construction criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 - Criteria for the appearance of exposed concrete . . . . . . . . . . . .

9 10

2.6.1 - Field of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.2 - Characteristics and types of exposed surfaces . . . . . . . . . . . . . . . 2.6.3 - Lift joints and construction joints . . . . . . . . . . . . . . . . . . . . . . . . .

10 10 10

2.7 - Construction practice basics . . . . . . . . . . . . . . . . . . . . . . . . . . .

10

2.7.1 - Plain concrete linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2 - Locally reinforced linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.3 - Fully-reinforced linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.4 - Construction in sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.5 - Embedded Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11 11 11 11 11

3 - CONCRETE FOR PERMANENT LINING . . . . . . . . . . . . . 3.1 - Concrete mix design and tests . . . . . . . . . . . . . . . . . . . . . . . . .

12 12

3.1.1 - Reference document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 - Selecting independent inspection body . . . . . . . . . . . . . . . . . . . .

12 12

3.2 - Concrete components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

3.2.1 - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 - Aggregate quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 - Cementitious materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4 - Mixing water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.5 - Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.6 - Additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12 12 12 12 13 13

…/…

Publication en français dans TUNNELS ET OUVRAGES SOUTERRAINS n° 202

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AFTES Guidelines GT36 Geometry, concrete mixes, formwork and concrete pouring practice for tunnel linings

Pages

Pages

2

3.3 - Concrete definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

3.3.1 - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 - Specification of basic properties . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 - Specification of supplementary properties . . . . . . . . . . . . . . . . . . 3.3.4 - Concrete classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 13 13 13

3.4 - Concrete mixing and transport . . . . . . . . . . . . . . . . . . . . . . . . .

14

3.4.1 - Choice of batching plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 - Concrete mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 - Concrete transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 - Monitoring concrete strength development and performance . . . . 3.5.2 - Minimum requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 - Recommended values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.4 - Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14 14 14 14 15 15 15

3.6 - Surface treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

3.6.1 - Protection of surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 - Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 - Fire protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 16 16

3.7 - Benefits of self-compacting concrete . . . . . . . . . . . . . . . . . . . . .

16

4 - FORMWORK SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . 4.1 - Description of formwork systems and Minimum fabrication rules

16 16

4.1.1 - Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.2 - Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.3 - Different types of formwork system . . . . . . . . . . . . . . . . . . . . . . . 4.1.4 - Details of formwork system components . . . . . . . . . . . . . . . . . . .

16 17 17 23

4.2 - Fabrication of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

4.2.1 - Contractor writen specification . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 - Contractor's tendering procedure for suppliers . . . . . . . . . . . . . . 4.2.3 - Contract award . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 - Ordering formwork by contractor . . . . . . . . . . . . . . . . . . . . . . . . 4.2.4 - Supplier's design and fabrication report . . . . . . . . . . . . . . . . . . . 4.2.5 - Transport, erection on site and acceptance in final configuration .

29 30 31 31 31 32

5 - FORMWORK SET-UP AND CONCRETING . . . . . . . . . . . 5.1 - Formwork system working configurations . . . . . . . . . . . . . . . . .

34 34

5.1.1 - Planning excavation and lining sequence . . . . . . . . . . . . . . . . . . 5.1.2 - Longitudinal planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 - Transverse planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34 34 35

5.2 - Q / S / E (Quality/Safety/Environment) aspects . . . . . . . . . . . .

35

5.2.1 - Content of quality assurance plan . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 - Safety aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 - Environmental aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 - Quality monitoring of works . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.5 - Moving, setting up and adjustment of formwork ready for pouring 5.4.6 - End stop(s) and seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.7 - Concreting lining rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.8 - Concrete hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

38 40 41 42

5.5 - Special items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

42

5.5.1 - Portals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.2 - Niches and intersections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

42 44

5.6 - Special cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

44

5.6.1 - Contact grouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.2 - Special concrete mixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.3 - Special concreting conditions . . . . . . . . . . . . . . . . . . . . . . . . . . .

44 44 45

5.7 - Re-use of formwork systems . . . . . . . . . . . . . . . . . . . . . . . . . .

46

5.7.1 - Dismantling formwork systems . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2 - Formwork system maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.3 - Temporary Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.4 - Re-use of Formwork Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .

46 46 46 46

6 - LINING CONSTRUCTION SUPERVISION . . . . . . . . . . . . 6.1 - Specific testing and inspection challenges . . . . . . . . . . . . . . . . . 6.2 - Level of supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 - Types of supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

47 47 47 47

6.3.1 - Internal supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 - External supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 - Independent supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

47 47 49

6.4 - Critical points and stop points . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 - Treatment of non-conformities . . . . . . . . . . . . . . . . . . . . . . . . .

50 50

6.5.1 - Classification of non-conformities . . . . . . . . . . . . . . . . . . . . . . . . 6.5.2 - Means for treating non-conformities . . . . . . . . . . . . . . . . . . . . . .

50 50

7 - SAFETY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 - Safety and formwork system design . . . . . . . . . . . . . . . . . . . . .

51 51

35 36 36 36

7.1.1 - Moving parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2 - Access and working items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.3 - Concreting tools and accessories . . . . . . . . . . . . . . . . . . . . . . . . 7.1.4 - Ancillary components for translation, positioning and form stripping 7.1.5 - Fluids pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.6 - Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.7 - Handling and controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.8 - Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.9 - Emergency stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.10 - Instruction manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 51 51 51 51 51 51 52 52 52

7.2 - Definition of risks during construction work . . . . . . . . . . . . . . . 7.3 - Protective equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

52 53

5.3 - Lining concreting record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 - Operations in concreting cycle . . . . . . . . . . . . . . . . . . . . . . . . .

36 36

7.3.1 - Individual protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 - Collective protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

52 52

5.4.1 - Form striking and precautions specific to this phase . . . . . . . . . . . 5.4.2 - Translation of formwork to next ring . . . . . . . . . . . . . . . . . . . . . . 5.4.3 - Concrete curing after form removal . . . . . . . . . . . . . . . . . . . . . . . 5.4.4 - Preparation of form liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36 37 37 38

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

52

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 - PRESENTATION 1.1 - Objective

1.2 - Content

These Guidelines are drafted as a contribution to the design and construction of cast-in-situ concrete linings, primarily to road and rail tunnels, but are also applicable to canal and drainage tunnels, backfilled tunnel portals, branch and cross tunnels and ancillary works such as niches, lay_bys, etc. They do not concern precast concrete segmental linings, precast roof segmental linings, water tunnels and linings to special items such as underground railway station chambers and shafts. Finished cross sectional areas addressed range from 40 m2 to 120 m2.

The Guidelines present the sequence of operations for performing the design studies and constructional activities involved in building 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.

The engineering content of the Guidelines focuses on general lining design criteria and their consequences, and constructional materials, tools and processes, as relevant to the various tunnelling specialists, 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 the earliest opportunity for results to meet declared goals, such as to ensure that the finished lining: • provides the functions and performance required for a functional and safe structure, • is long-lasting and strong without the need for excessive maintenance, • exhibits a general degree of quality, resulting from an appreciation, at the design stage, of all the loads and stresses to which it will be exposed over its expected lifespan, • offers a level of operational safety for its functions to be retained 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 workplace, • All other parties in any way involved in project implementation. Foundations and inverted-arch inverts, and shuttering for these parts of the tunnel are not extensively discussed although shown on some drawings. A suitable appendix will be issued in due course.

Topics not dealt with in these Guidelines are excluded because they have already been, or are to be covered by other AFTES Guidelines on (in French): • Design computations and their application to European standards; • 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 in 1976 and a second version was drafted in 1983 by a working group made up of Owners, Consulting Engineers, Construction Contractors and Manufacturers to take account of new regulations (such as Fascicule 69, 1980), reports from recent jobs (concerning primarily systematic flaws in appearance) and variables affecting lining quality and durability. The 1983 CETU publication (Linings, Concretes, Concreting Plant, Waterproofing, Concreting Practice) was aimed chiefly at designers 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 commissioning and then periodically in the course of their operational life, and found to suffer from recurring flaws in appearance or even structural damage, which could be correlated with faulty working practices, poor workmanship and unsuitable working procedures during 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 Working Groups 7 (GT7 Use of Unreinforced Concrete in Tunnels)


3


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

AFTES GT36 GUIDELINES

The following Table shows schematically the sequence of project implementation activities from the initial feasibility studies up to lining construction, naming the more representative reference documents as well as these present Guidelines, the design stages, and the tasks performed by the various parties.

OTHERS AFTES GUIDELINES OR DOCUMENTS

SPECIFIC REQUIREMENTS FOR EXPOSED CONCRETE FACES Considerations on usual lining analysis methods GT7 - TOS No.14 / 1976 (for information) Use of general design and sizing rules and standards for reinforced and plain concrete linings GT29 - TOS No. 165 – 2001 AFTES guidelines and the new EU standard GT29 – TOS No. 203 - 2007 Use of Plain Concrete in Tunnels GT7 – TOS No. 149 - 1998 Use of Plain Concrete in Tunnels TOS No. 149 - 1998 Fire Performance of Civil Engineering Structures - GT37 (Guidelines pending)

Extrados interface: Waterproofing System between Temporary Support and Lining GT 9- TOS No. 159 Intrados interface: Painting Exposed Concrete Faces GT 31 - TOS No. 178

POURING LINING

FORMS: FAULTY WORKMANSHIP AND DISTRESS

ENGINEERS

Preliminary design ENGINEERS CETU Pilot Dossier SNCF – RATP Eurocodes

Final design

DESIGN OFFICES

CETU Fire Guidelines 2006

CCTG Fascicule 67: Waterproofing

CCTG Fascicule 69: Article TOS No. 121 – Pressure during Underground works concreting

WORKMANS,HIP INSPECTION DESIGN AND OPERATIONAL SAFETY JOBSITE ACCIDENT PREVENTION

OWNERS

CCTG Fascicule 65 Exposed surfaces

CCTG Fascicule 65: Concrete

CONCRETE MIX DESIGN, PREPARATION AND POURING

FORMWORK DESIGN AND FABRICATION FORMWORK INSTALLATION

IMPORTANT PROJECT DOCUMENTS FROM DESIGN STAGE CONTRIBUTORS OTHER SOURCES*

CCTG Fascicule 69: Civil works Underground project planning Works CETU Geometry (pilot dossier) 1990

ROLE, FUNCTIONS, SHAPES, GEOMETRY, CONVENTIONS

Tender Documents CONSTRUCTION CONTRACTORS

SUPPLIERS Construction Contract

Hazards and First Aid GT12

IN-HOUSE AND INDEPENDENT SUPERVISION OPPBTP - CRAM

SNCF Classification of structures. Catalogue of visible flaws in tunnels, supplemented with Catalogue of glossary of tunnel parts names 1980 Damage Livret K Catalogue of structural damage in underground structures Tunnels 1996 CETMEF Notes on GT14 HS 3 Chambéry monitoring and Diagnostic Method for Lined Tunnels maintenance of canal tunnels with catalogue 2000

Guidelines for Inspection of Road Tunnels, with catalogue 2004

OPERATION

INSPECTION

CONCRETING

FORMWORK INTERFACES

CONCRETE

DESIGN ANALYSES

PROJECT PLANNING

STAGE

These Guidelines are written in sections which fill the gaps between other relatively exhaustive and very recent documents, and are presented in a descriptive manner in the form of recommendations or advice, so that interested parties may find the information needed for their design and construction operations.

1.4 - Administrative framework

CETU GTFE (French Operators Group)

Progress reports and inspection reports

Inspection and maintenance reports

INDEPENDENT SUPERVISION EXPERTS

SPECIALISTS OPERATORS

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

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2 - LININGS AND DESIGN REQUIREMENTS This chapter reviews the various functions which may be assigned to the tunnel lining and the requirements associated with these functions, along with the chief consequences that will result in the construction phase in terms of the concrete mix, construction methods, 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.

2.1 - Functions of lining The lining to a tunnel or of a longitudinal underground opening or cross-tunnel forming part of the principal structure is a structure placed directly against the ground, or the temporary support or waterproofing system as applicable. The lining determines the effective cross-sectional area of the tunnel offering the functions required by the tunnel operator. It is physical proof of the completeness and durability of the structure in terms of the required criteria to be met for the tunnel to remain stable and fit for the purpose for which it was designed. The lining is usually left exposed when seen from inside the tunnel although it hides the waterproofing system and any temporary or permanent support which may have been installed. It may be lined internally to meet certain requirements concerning appearance or environmental considerations. It is necessary at the tunnel design stage that a clear statement be made of the functions the lining will be called upon to provide in terms of (i) the requirement for overall stability of the structure, chiefly as determined within the surrounding rock, and (ii) requirements relative to operational criteria. These functions are detailed in this section of the Guidelines, and subsequent sections discuss the resulting consequences for the construction phase. Five functions are described and discussed (definitions, needs, benefits, etc.) in the following paragraphs, with no pretension of being an exhaustive list, to highlight the constraints and their consequences 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 the required long-tem mechanical stability. If temporary support was applied immediately after excavation and this support can be considered sufficiently reliable over time (suitably designed and executed sprayed concrete, protected anchor bolts, etc.), the design of the permanent lining may make allowance for the contribution of this temporary support in withstanding outside loads. 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 to decompress sufficiently to arrive at an equilibrium state and the lining must be designed accordingly. This quite frequently results in the need for a high-stress lining with inverted vault invert. Dead weight loads may be factored to include for stresses due to temperature changes and concrete drying shrinkage. These are usually 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 reached between the surrounding ground and the support; in this case, the permanent lining is necessary and useful for providing long term stability and the loads from the surrounding ground are applied to it very gradually, • or keeping pace with excavation, by heading and benching if necessary, when the previously described approach is not possible when, for example the tunnel is passing through poor ground or there are severe settlement criteria. The design must accordingly include for a very complex construction sequence and finely-tuned organisation (different items of plant all concentrated in a small space for driving / temporary support / waterproofing / shuttering, and all well ventilated); the loads acting on the lining will generally be higher than in the previous example. 2.1.1.2 - Mobilisation of Ground / Support / Structure Interaction It is common knowledge that, if it is to contribute to the permanent support, the lining must be conceived in such a way as to efficiently make use of its interaction with the surrounding ground. This implies appropriate decisions as to the cross sectional shape and stiffness of the lining as compared with that of the host ground, and careful choice of construction method to ensure tight contact with the ground everywhere. A tight interface does not in itself guarantee sufficient mobilisation of the ground / support / lining interaction to control bending stresses in the lining to the preferred degree. The other requirements are: • The mean axis of the roof arch must be appropriately shaped, which may require an iterative analytical method. A very flat top arc will keep down excavation volumes but in return, will very frequently allow high bending stresses to develop. Sudden changes of curvature commonly cause locally high stresses, and smooth transitions are eminently to be desired. • The host ground must possess significant stiffness. In ground exhibiting plastic behaviour or poor stiffness, the soil/structure interaction may be too weak not to have to resort to systematic reinforcement of the lining.


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It is also universally accepted that, if the interaction criteria are met, plain concrete can be used for the typical section of the tunnel. The design thickness of the arch is based on loads computed by methods which take account of this soil/structure interaction and, provided bending stresses are moderate, reinforcement of the lining may be dispensed with, in accordance with AFTES Guidelines on Use of Plain Concrete in Tunnels which were published in TOS 149, Sept-Oct 1980. Cases where reinforcing steel is needed are dealt with below. 2.1.2 - Support and Protection of Waterproof Lining System Function Older tunnels (pre-1970) were not waterproofed. They often suffer from damp patches and leaks which become worse over time and lead to inevitable deterioration of the lining concrete (especially in road tunnels). More recent constructions have waterproofing systems on the outer surface (extrados); this usually consists of a PVC sheet placed between the temporary support and the permanent lining, and Owners are advised to provide such a waterproofing system. Two cases are found: • Full waterproofing which includes the invert (usually an inverted arch in this case) and the lining must be designed to withstand groundwater loads. • Partial waterproofing of the roof and down to the bottom of the sidewalls, with drains to empty the system (this system is also known as umbrella waterproofing). Dispensing with waterproofing altogether may be considered in some rare one-off situations, e.g. where there is no water table, in tunnels excavated by heading and benching with long sections of construction joints multiplying the risk of flaws, or where functional requirements are not severe (especially as regards dampness). Waterproofing the crown makes it possible to produce a better quality concrete by keeping moisture within the concrete during the first few days of curing. It also prevents formation water from upsetting the physical and chemical equilibrium of the concrete while it is setting and also reduces the problems associated with concrete shrinkage. If there is no extrados waterproofing, the fresh concrete may lose its water 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 but is very wet. In both cases, its original mechanical properties may be altered. An additional problem is that concrete shrinkage may be severely and unevenly restrained by any serious overbreaks. A concrete lining protects the waterproofing system against damage arising from tunnel operation and of course, care must be taken not to 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 the functions required of the tunnel, and attention must be given to: • Static and dynamic stresses concentrated by equipment (fans, ventilation ducting, hangers and supports for traffic roadways and/or ventilation ducts, fastenings for cable trays, lighting or signage, catenary tensioning points, lifting loads when removing crashed road vehicles and railway trucks, etc),

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• Misoperation due to operating conditions. This should result in different designs for certain sections of the tunnel lining (e.g. reinforcement of the roof at ventilation booster sites and/or extra reinforcement in the sidewalls in typical tunnel sections) and should involve special arrangements during construction for very strict inspection and supervision of the work of fixing reinforcing steel and pouring concrete in these zones. 2.1.4 - Operating Cost Control Function Tunnel operating costs (especially for road tunnels) are largely governed 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 than tunnels 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 in road tunnels. This "minor" function of the lining must not be overlooked in the design studies for the lining (the surface finish of concrete exposed to view should be specified), the formwork system (especially its quality and strength) and concrete mixes (workability among other factors). 2.1.5 - User Comfort Function The intrados of the tunnel remains visible and the appearance of the lining (especially if there are regular commuters) must be considered at the design stage. A smooth painted surface is obviously more attractive than the depressing as-cast grey expanse where the driver can see the demarcations between the different pours, all with their own shade of grey. Painting the sidewalls of road tunnels is an effective way to combat concrete deterioration, by controlling grime deposits and making cleaning easier. The lining may also be of use to the road user by giving advance warning of bends by highlighting the longitudinal construction joints between sidewall and crown and the vertical construction joints 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 by the quality and appearance of the walls. This in turn dictates the formwork system, which will be different when operating at urban or greenfield sites.

2.2 - Tunnel cross sectional shapes 2.2.1 - Definitions This section presents a brief explanation of why the cross sectional profile of a road, rail, canal or sewer tunnel cannot be standardised, even if equivalent performance is required. Linings consist of one or more concrete arches enclosing an effective cross sectional area such that the resulting tunnel offers the


specified functional performance. The intellectual process leading to the elaboration of the cross sectional profile involves careful study at the project planning stage, whatever the tunnel type and purpose in question. The line enclosing this effective cross section is called the intrados. The geometry of the intrados may be defined by a single arc of circle, a succession of circular arcs joined by smooth tangents or more generally a succession of circular arcs and straight lines. The selected intrados must be the outcome of a process of optimisation of the effective cross section offering all the required functions, but also circumscribing rectangular or circular bodies representing machinery and equipment; it must incorporate a safety margin with respect to the civil works and utilities, construction and maintenance activities, and the electric field (in the case of rail tunnels), and construction tolerances such as to have a minimum excavated section with a generally regular geometry. In the design of the intrados, slightly curved or flat surfaces, sharp projections and sudden changes in curvature must be avoided as far as possible because they concentrate loads and stresses which may result in overdesigning the lining. On the basis of these

requirements, the shape of the intrados may range from a circle to 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 by the design thickness of the concrete. Concrete thickness is derived from the envelopes calculated for the loads and load combinations applied to the lining, or complies with the minimum thickness for the size of the cross section*. In some cases, design thickness may be modified to allow for various design rules. For example, concrete thickness must be sufficient to provide adequate cover to boxouts or cable ducts required for equipment. 2.2.2 - Examples of Profile Optimisation The examples presented below illustrate the critical points involved in setting the shape of the lining intrados (smoothing the line) and extrados (intrados line shifted outwards by approximately the specified minimum concrete thickness) and dealing with sharp projections or hard points; this data is needed for designing the formwork system and its operating procedures, especially form stripping.

Profile of road tunnel without concrete invert and 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).


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2.2.3 - Consequences on operating formwork systems The geometries of tunnel cross sections may appear very similar but the formwork needed to build the lining may be very different. 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 ventilation duct ceiling slab, requiring special forms that are complicated to make and use when striking the forms. • No true invert (just non-structural blinding concrete) or an arched invert requiring either a runway for moving the slip forms along the tunnel or special arrangements in the formwork system itself. • Flat invert with variable (sometimes steep) angles of superelevation requiring a shuttering system which can be adjusted over a wide angular range. • Curved upper face of foundation or no foundation to provide the reaction, so that the forms must be fastened to the invert or be entirely independent.

2.3 - Conventions In general, once the design analyses have been completed, linear underground structures are usually drawn up on a set of what are known as Typical Cross Sections, which show temporary support, waterproofing and lining details and the conventional payment lines. Linings and their minimum, nominal and mean thicknesses may raise questions for the designer and the next part of this section presents some simple minimum rules and the most widely used conventions adopted by design offices, consulting engineers and construction contractors (they will be a compromise between all the conventions studied and accepted), always keeping in mind the requirements in CCTG Fascicule 69 (Underground Works) specifications, with additional material when the issue of extrados waterproofing systems arises. 2.3.1 - Typical cross section Sidewalls Springing Shoulder Crown Key Circular arch Invert

Arched invert

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Vertical or curved parts between the foundation and the horizontal diameter of the roof arch Plane located on the horizontal diameter of the roof arch Part of the roof arch between the springing and the crown Highest point of the roof arch lying in the vertical plane of symmetry of the tunnel Central part of the crown Profile in which they mean axis of the roof arch is an arc of circle Lower part of the tunnel section spanning between the two sidewalls Invert which is arched downwards with the lowest point of the invert lying in the vertical plane of sym metry of the tunnel


Figure 2 - Typical Cross Section – Notation

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: excavation, temporary support and/or lining. These are the physical lines calles “I Line” and “A Line” I Line

Defines the effective width and height clearances of the tunnel’s permanent lining (inside cross section available for tunnel operation).

A Line

Defines the minimum size of the excavated tunnel section before installing temporary support and permanent lining (minimum excavation line).

The A and I lines are directly measurable. Another line is needed to determine the volumes or areas to be used for calculating payment. This is the B line as defined in CCTG Fascicule 69. It is derived by shifting the A line outwards by a distance d. Distance d can be thought of as a tolerance permitted to the contractor based on driving method and conditions and it must be specified by the Engineer such as to allow the contractor to earn a fair rate for the work performed. 2.3.2.2 - Payment Lines The B and E lines are theoretical and so cannot be measured.

B Line

Payment line for excavation defined by its distance “d” from the A line (mean excavation line).

E Line

Payment line for lining extrados determined by shifting intrados line I by the nominal thickness of the lining.

2.3.3 - Typical Lines and Cases 2.3.3.1 - Lining poured directly against rock, no waterproofing system


2.3.4.3 - Construction Tolerance The total tolerance covering fabrication and assembly of the formwork system, moving the forms to station and concreting must not result in the finished lining being thinner than the nominal design thickness (the thickness of concrete estimated for payment between the E and I lines remains unchanged). Convergent zones must be identified well in advance before moving the slip forms to station.

2.4 - Concrete criteria

Volume béton coffré = Vol (B) – Vol (I) Figure 5 - Lines - Steel ribs and liner plates / Packing concrete / Waterproofing system / Linin

2.3.3.2 - Shotcrete, waterproofing system, permanent lining

Volume béton coffré = Vol(B) – Vol(I) – Vol(BP=BE) Figure 6 – Lines – Steel ribs / Shotcrete / Lining

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 estimated on the basis of the drawings in the tender or design documents. The thickness considered is the space between theoretical lines E and I.theoretical line E and physical line I. • Structure at junctions (lay-bys, galleries, niches, etc.) Concrete volumes must be estimated more accurately with dimensions taken from the design drawings, lying between the E and I lines. 2.3.4.2 - Overbreak Overbreak volumes must be estimated well before installing the waterproofing system. Instruments such as a profiler or 3D scanner allow the relevant volumes to be estimated.

In addition to the necessary mechanical properties of the concrete to provide the support function (contract strength of hardened concrete and deformation modulus), the more important properties 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 the forms despite irregularities in the rock face and the presence of reinforcement and items to be embedded in the concrete. Compaction is necessary to obtain a high degree of watertightness and thereby, good resistance to aggressive substances. In this case, special cements must be used. For the same reasons, the concrete must exhibit the least possible shrinkage, especially as shrinkage is restrained by reason of the concrete forming a solid mass with the host rock on one side (except if a waterproofing system is installed) and the concrete is not reinforced. The most typical case is in large tunnels in which a strong current of air might circulate after break-through. The rapid loss of moisture and temperature drop caused by this air current are the leading causes of increased concrete shrinkage and concomitant cracking, specially in green concrete. Lastly, if the forms are to be struck quickly, high early age strength is needed, which may be incompatible with reduced cracking. The solution to this problem is often to find the best compromise between the opposing requirements and actual conditions at the site with due consideration of the resources available there.

2.5 - Lining construction criteria Characteristic strength is the most important concrete property for lining stability. Furthermore, it must be remembered that high strength means a high modulus and therefore, a stiffer lining. However, this is not usually the critical factor with plain concrete for which in practice the offset of the normal load determines the concrete thickness needed. But high early strength is always a determining factor for deciding how soon the forms can be struck after completion of concrete pouring. In all cases, the concrete closure must ensure a tight contact between the rock or temporary support and the lining; contact grouting may be needed after completion of pouring. Efficient structural performance (interaction) requires good construction practice: good concrete workability is needed for the concrete to completely fill the space behind the forms and flow around geometrical irregularities of the rock face and embedded items, and despite difficulties of forcing concrete into the roof crown.


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Lastly, moderate shrinkage keeps early age cracking of the roof arch to a minimum, until such time as pressure from the surrounding ground eventually produces significant compressive stress conditions in the roof.

2.6 - Criteria for the appearance of exposed concrete Apart from problems with cracking and blemishes revealed after removing formwork, the compaction, porosity and shrinkage characteristics of the concrete will determine its propensity for picking up grime. Linings in road tunnels are usually cleaned regularly; therefore, protection and maintenance must be considered necessary activities. But before applying systematic preventive protection, it is important to fully control fabrication of the formwork, preparation and pouring of the concrete, and striking forms. 2.6.1 - Field of Application The stipulations in this section of the Guidelines apply solely to the exposed faces of in situ concrete. They deal with the appearance of these visible surfaces, which results from a combination of concrete mix, successful embedment of reinforcing bars and other items, and concrete pouring practice which can lead to many flaws liable to spoil the appearance. The process for achieving the specified appearance and means of arriving 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 the resulting 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 construction 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 Exposed Surfaces 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 2 mm measured with a 0.2 m straight edge, • Texture, representing surface condition and quality: moderate or 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 directly dependent on concrete colour and form liner properties (type and category). But the sidewalls of road tunnels and other structures frequented by users are often painted. There are three classes of surface finish, on the basis of increasin-

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gly stringent appearance requirements. The contract must stipulate what finishes are required where. 2.6.2.1 - Plain finish Plain or ordinary surfaces (category 3) are surfaces left as-cast for which the only requirement is for a regular shape. This usually applies to ancillary cross galleries to the tunnel and its foundations. 2.6.2.2 - Fine finish Fine surfaces (category 2) are surfaces left as-cast covered by special requirements as regards shape, and concrete texture and colour. This finish is mostly used on sidewalls to the tunnel or bypasses and shelters. Where light-coloured or special concretes are specified, specific documents 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 incorporated into the works, • Specimens must be truly representative of the structure to be concreted under actual field conditions in order to ascertain that the resources (identical forms, vibration, etc.) assigned by the 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 meet decorative and architectural requirements (category 1); they are often stipulated for the first rings of urban road tunnels. The contract must specify precisely all the characteristics of these surfaces and some characteristics of the forms. This category also includes surfaces left as-cast exhibiting some degree of relief or special shapes, and worked surfaces. 2.6.2.4 - Unspecified finish Except as otherwise stipulated, surfaces exposed to view have a fine 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 lift joints at the foundation ledge, if exposed to view, horizontal lift joints between sidewalls and roof arch, and vertical construction joints between lining rings. Trapezoidal joint formers are preferred for reasons of ease of form removal, using stiff rubber or metal shapes fixed to the forms.

2.7 - CONSTRUCTION PRACTICE BASICS Tunnel and gallery linings are generally made of plain concrete for standard sections but may be locally reinforced at safety niches and points where the tunnel is intersected by cross galleries. Arched inverts, where necessary, may also be reinforced. In this case, controlling the high stresses where the sidewall meets the invert calls for the reinforcing bars to be continued up a certain distance into the sidewall.


2.7.1 - Plain Concrete Linings In the majority of situations, tunnel linings are not reinforced on standard sections except in specified conditions such as the need to control detrimental cracking. This does however mean that the host ground must display some degree of stiffness and that tunnel geometry is satisfactory. These two factors are not independent. A flattish roof arch tending to force the abutments apart might be acceptable in a stiff rock but not in deformable ground where the tendency towards outward movements or convergence of the abutments would result in significant 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, intersections 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 documents, profile geometry must allow for constraints associated with reinforcing bars (bar sizes and concrete cover) and concrete (aggregate size), and during the tendering process, the formwork system design must address the issue of constraints associated more particularly with fixing bars in place and positions of concreting windows. 2.7.3 - Fully-reinforced Linings Special linings reinforced around the whole section are chiefly found on: • tunnels subject to high hydrostatic loads that have to be completely waterproofed (including the invert), • tunnels driven through ground of low stiffness, displaying significant convergence or divergence and where there is insufficient soil-structure interaction to realign the normal loads in the sections, • drainage galleries carrying water under pressure, • intersections with geological features or special zones (swelling ground, shallow tunnel), • tunnel portals built above ground and backfilled ("pseudo tunnels"). At the structural design and contract document preparation stages, the tunnel section profile must include for constraints associated with the reinforcement (bar sizes, concrete cover, aggregate, stiffness of structures, etc.), as well as steel fixing methods (as free standing assemblies or mounted on the shuttering) and the formwork system (design, lowering, number of forms, support of the steel, etc.).

2.7.4 - Construction in sections The lining is built in sections, called rings, whose length is governed by: • tunnel alignment: in curved sections the offset caused by the ring length must remain within the stated tolerances, • concrete shrinkage (mix design and time before striking formwork), • 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 this reduces the tensile stresses due to restrained shrinkage. If there is no waterproofing system, shrinkage is impeded and in addition more severe temperature cracking must be considered, due to the greater mean effective thickness of the lining, a situation which is made worse when there are major overbreaks. • Less commonly, tunnel length and lining construction time. Tunnel lining ring length is generally of the order of 10 m (maximum 15 m) and for long transverse galleries (lay-bys and turning galleries, etc.) of the order of 5 m. Basic construction principles for building the lining with a mechanised formwork system must be settled in the project planning stage and further addressed in the tender documents. 2.7.5 - Embedded Items Some types of tunnel may require embedding components in the lining or at its intrados to subsequently fasten in place and operate equipment, or to strengthen parts of the lining. In road tunnels, this concerns: • Anchorages for suspension rods for ceilings and partitions forming 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 partitions, 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 extrados waterproofing system, • Access cables to measuring instruments in the support, • Contact grouting lines, etc. Embedded parts must be accurately described and positioned on the tunnel ring lay-out drawing. This issue must therefore be examined at the project planning and civil works and equipment design stage and finalised in the tender documents.


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3 - CONCRETE FOR PERMANENT LINING This important part of the Guidelines examines the requirements associated with materials (especially concrete), concrete transport to the formwork system and special treatment if any (in the mass and/or exposed faces). These Guidelines do not repeat the requirements detailed 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 the Contractor and his Design Office in preparing the tender and design during the works, in collaboration with the concrete batching plant’s laboratory and his independent auditors.

3.1 - Concrete mix design and tests 3.1.1 - Reference Document Concrete for tunnel linings must meet the requirements of Standard NF EN 206-1. This is a fundamental requirement, but cannot be considered as the one and only reference document and some major jobs may make use of others as a supplement to the Standard for that specific job. 3.1.2 - Selecting Independent Inspection Body The independent inspection bodies must be accredited by COFRAC (COFRAC was instituted by the authorities so that accredited bodies could have proof of their competence and impartiality – ISO 15189 [?]). However, it is not always possible to find a COFRAC-accredited body and provision must be made for waivers, provided that the prospective body operates a quality assurance system providing an equivalent level of quality.

3.2 - Concrete components 3.2.1 - General All reports submitted by the Contractor to the Engineer for approval of the ingredients entering into concrete must contain the results of the following tests. 3.2.2 - Aggregate Quality Aggregates for concrete must comply with Standard XP P 18-545 code B with a water absorption preferably index A except if otherwise stipulated. Aggregates must be suitable with respect to alkali aggregate reaction. Aggregates may be obtained by crushing and screening material excavated from the tunnel in so far as it meets the technical requirements in this section. The use of concrete rubble as aggregate is not recommended without careful study (see AFTES GT35 Guidelines 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 CF

4.0 to 2.4

(coarse sand)

MF

2.8 to 1.5

(medium sand)

FF

2.1 to 0.6

(fine sand)

The recommended value for the mean fineness modulus is 3.0.

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• Corrector sand A corrector sand is by definition a sand added in a proportion of up to 30% of the total sand mass. When used, the tests are made on the mixture of corrector sand and natural sand in proportions set 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 can be considered. Particular specifications are required for items subject to severe abrasion (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 NF EN 13263-1, • ground vitrified blast furnace slag complying with Standard NF 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 being equivalent 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 compromise between the rate of strength development and sensitivity to cracking (heat of hydration, shrinkage). The usual cements are CEM I plus admixtures or CEM II blended cements having a total cementitious content of the order of 350 kg per cubic metre of concrete. Recourse to CME III or CEM IV cements is possible but not really compatible with the 24 hour working cycle (set formwork – pour concrete – concrete hardens – strike forms – move shuttering on to next station). 3.2.4 - Mixing Water Water used for mixing the concrete must comply with Standard NF EN 1008; seawater must not be used and recycled water from


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

• exposure class, • chloride content class, • concrete consistency.

3.2.5 - Admixtures The CE certification mark allows products to circulate freely throughout the European Union, regardless of their country of origin. It is proof of EC compliance. It is complusory but does not replace the NF mark. Standard NF EN 934-2 redefines the eleven types of concrete admixtures (Tables 2 to 12), this is the quality mark attesting to the quality aptitudes of the product (tested by an independent outside body). Having both accreditations is the new quality baseline for concrete admixtures. All admixtures must bear the NF quality mark or approved equivalent.

3.3.3 - Specification of Supplementary Properties High early strength (to allow the forms to be removed) is always a supplementary specification for lining concrete. It is specified in terms of strength at a given age (equivalent age at 20°C). 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.

3.2.6 - Additives Additives, not covered by Standards, may be incorporated into the concrete to modify some of its properties or confer special properties to it. Coming under the heading of additives are natural or synthetic non-organic dyes, fibres, pozzolana fines,, cohesion agents, etc. Metal fibres can be mixed into the freshly-mixed concrete to improve its properties, especially its ductility, durability and crack resistance. Metal fibres must comply with Standard EN 14889-1 Fibres for Concrete – Part 1 – Steel Fibres – Definitions, Specifications and Conformity. The unique properties of fibre-reinforced concrete may be particularly attractive if lining thickness has to be reduced or a self-compacting concrete has to be used. Pumping fibre-reinforced concrete might raise a few problems. The minimum proportion of fibres depends on fibre properties (tensile strength, anchoring system, length/diameter ratio). It must be determined by testing (e.g. by measuring strain energy). The recommendations from the Brite-Euram* european project set out the criteria for selecting steel fibre properties and use. Steel fibres can replace all or part of the traditional concrete reinforcement in specific structures provided that bending tensile strength values are cross checked with appropriate tests. * Project BRPR-CT98-0813 “Recommendations on Quality Assurance of SFRC”.

3.3.4.1 - Exposure Classes In most road and rail tunnels, the tunnel lining concrete has to comply with requirements appertaining to class XC3 – XF1 exposure. Parts of the structure subjected to de-icing salts only fall into class XF2 exposure if they are not protected by an appropriate surface dressing. The tunnel lining does not have any horizontal surface liable to result in a high water saturation and exposure classes XF3 and XF4 are not appropriate if exposed to severe subzero temperature conditions. However, special requirements as to durability in respect of freezing and melting agents may be necessary over a distance of several hundred metres from each portal. For works or parts of works in contact with aggressive ground and not protected by a waterproof sheet on the extrados, exposure classes XA1 to XA3 can be accepted. In a situation involving attack by melt water, as for the aggressive ground case, it is preferable not to deal with the durability issue by increasing the binder content of the concrete (which would involve problems of shrinkage cracking) but by providing a protective barrier. In general, except as may be otherwise stated in the contract, the values in the following table apply. It might also be possible to invoke the equivalent performance concept as defined in Standard NF EN 206-1 and compare the permeability of the proposed concrete (with limited cement content) with the reference concrete as illustrated In Table NA.F.1 of the standard.

3.3.4 - Concrete Classification

3.3 - Concrete definition 3.3.1 - General Concretes must be defined in the manner described in Standard NF 206-1 except if otherwise specified. 3.3.2 - Specification of Basic Properties The underlisted basic properties required for in situ concrete linings must always be specified: • 28-day characteristic compressive strength of the concrete, • level of prevention against alkali aggregate reaction,

EXPOSURE CLASSES XC3-XF1 XF2 Maximum water/equivalent binder ratio Minimum equivalent binder content (kg/m3) Minimum air content in concrete Characteristic 28-day strength

0.60 280 N/A C25/30

0.55 300 4% C25/30

For other exposure classes, see specifications in NF EN 206-1. Some drainage works may convey aggressive effluent leading to type XA exposure class, with reference to the degree of aggressivity set out in Table 2 of standard NF EN 206-1.


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3.3.4.2 - Level of Protection in Respect of Alkali Aggregate 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 appended to Ministry Circular 2000-63. It may range from N0 for a lining in stable ground to N3 for an underwater tunnel. Verifying lining fire resistance requires an analysis which includes for thermal expansion effects and loss of structural properties, and the possibility of spalling. Spalling assumptions must be backed up by tests. Fire performance of these concretes can be improved by the addition of polypropylene fibres at a rate of 1 kg to 3 kg per cubic metre of concrete. If the requirements concerning the durability of fire resistance properties are very severe, the protection provided by the concrete alone may not be sufficient and special fire resistant protection may be required (gunite, heat insulating panels, etc.). Further details can be found in CETU guidelines “Fire Performance of Structures – 2006 edition”, and an article by AFTES Working Group GT37 in TOS No. 196 entitled “Contribution to Means of Preventing Spalling Damage in Tunnel Concrete”. 3.3.4.4 - Consistency of Fresh Concrete The consistency and workability properties of freshly mixed concrete must be maintained during transport, pumping and placing the concrete. These parameters must be quantified and justified by the Contractor. As a general rule, the required consistency is as pertaining to class S4 slump or class F4 or F5 spread for conventional vibrated concrete. The reference value is then the value measured on arrival of the concrete on site. For self-compacting concretes, limiting values for the slump flow test must be set at the time of finalizing the mix design (suitability study). 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 Plant The concrete mixing plant must comply with required conditions for awarding the NF-BPE mark plus requirements in Fascicule 65A but formal certification must not be made compulsory because it is a costly process that would be incompatible with project economics. 3.4.2 - Concrete Mixing It is recommended to follow the technical clauses of Article 83 of Fascicule 65A of the CCTG general specification as concerns concrete preparation. In extreme climates, special provisions must be made to ensure at delivery a minimum concrete temperature in winter (generally 16°C) and a maximum concrete temperature in summer (generally 30°C).

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At the very least, this means hot water (up to 60°C) must be available 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 being brought 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 by mixer truck, stating, in addition to the requirements of Standard NF EN 206-1, complete identification of the materials used and the 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 batch leaves the concrete mixing plant and the time it begins to enter the shuttering (transport time + waiting time), and must be stipulated in the contract specification and assumed in the concrete mix design. 3.4.3.2 - Pumped Concrete, Long Lines and Booster Pump The Contractor must propose the means of transport and pumping parameters from which he shall deduce any special mix design requirements (conservation of rheology, workability, risk of setting, etc.). When a priming slurry is used to start the pumps, it must not be incorporated in the works but discharged to waste.

3.5 - Concrete characteristics when striking forms 3.5.1 - Monitoring Concrete Strength Development and Performance Concrete maturity measurement is recommended for justifying that the required strength for form stripping has been attained. The recommendations in the guidelines on Strength of Concrete in the Works, the Maturity-meter published by LCPC, March 2003 is the basic text for calibrating and using this method. The characteristics required of concrete when the forms are struck concern two factors: • structural strength, which must be sufficient for there to be no distress In the concrete from the application of loads it would not be able to withstand (mainly form suction and selfweight), • the time the concrete must remain confined within the forms before being exposed to the atmosphere, in order to void prejudicial drying out due to evaporation of surface water which might cause cracking and loss of concrete density near the surface. Dependent on several parameters, some minimum value might be imposed on one or the other of these factors, or even both, but it


must be realised that they are closely interrelated (strength development 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 exothermal reaction, • tunnel geometry: diameter (in small tunnels, tensile stresses in the young concrete will be low) and shape (forms for a circular roof arch can be struck earlier than for a flatter roof shape). In all cases to guarantee early-age structural performance, regularity in concrete production and control of concrete temperature during placing are the overriding factors. 3.5.2 - Minimum Requirement The minimum concrete strength required before forms can be removed must be justified by the Contractor and the concrete mix must be optimised to obtain the necessary strength within the time allowed. However, as a general rule, forms should not be removed 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 are as follows: • compressive strength 8 to 10 MPa, • minimum time before stripping forms: 10 hours (knowing that the required compressive strength is usually reached within this time) under normal tunnel conditions (air velocity < 5 m/s, temperature > 15°C). These two values should be measured on the last concrete batch delivered (filling the crown) except if there is very extensive overbreak or other special considerations. If the minimum compressive strength on removal of the forms is stipulated in the contract, the Contractor does not have to justify it with his own calculations. But if no value is imposed or the Contractor wishes to change it, he must justify the proposed value with a suitable analysis. The minimum form removal time may be adjustable in the light of precautions adopted after stripping (whether or not a curing agent or plastic sheets are provided, etc.). A formal procedure approved by the Engineer is necessary for this. The specified concrete strength value is the internal in situ strength, not the strength measured on an isolated laboratory specimen. 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 specimens are still used, the Contractor must prove that the age of

the specimens is the same as the age of the last concrete poured in the ring. It is stressed that arriving at a concrete mix design with which the targets can be attained is very important. An excessively prompt concrete or one containing too much cement might develop the required strength quickly but only at the cost of excessive heat generation liable to cause cracking and demanding extensive precautions after removing the forms. Similarly, special precautions would have to be taken with self-compacting concrete (types of additions and admixtures, etc.). 3.5.4 - Curing The exposed concrete surface must be protected against drying out (water evaporation) and sudden temperature changes which might lead to significant shrinkage. Cracking can be controlled by applying special measures, consisting of not restraining deformations, adapting concrete composition, and providing appropriate curing. The appropriate curing method for lining concrete must be described in the Contractor's Quality Assurance Plan, which must comply with the stipulations in Standard EN 13670. Since most in situ tunnel linings are plain concrete, shrinkage cracking will inevitably occur sooner or later. It is acceptable in the majority of cases providing cracks are not more than 0.5 mm wide. If controlled curing is planned, it must be covered by a detailed procedure described in the Contractor's Quality Assurance Plan; trials must be made if a chemical curing agent is to be used. Specific rates must be included in the contract and applied to remunerate curing. Controlled curing is strongly recommended. It must be designed with reference to the intrinsic properties of the concrete (heat of hydration, etc.) and external influences (air temperature, percent relative humidity, air velocity, etc.), as well as the consequences of the curing on the following aspects: • possible changes in concrete surface conditions which might have to be cleaned off before painting, • congestion caused by portal frame, although not so severe as for the formwork system, • possible influence on concreting cycles and therefore on the main lining works schedule, • possible negative environmental effects (water-sensitive environment in swelling ground for example if curing involves spraying water). As a general rule, water curing must be continued until such time as concrete strength has reached at least 35% of the specified 28-day characteristic strength (criterion adopted in Fascicule 65A).

3.6 - Surface treatment For surfaces where the concrete is to be further treated after stripping formwork, the treatment method and timetable must be described in the contract. Guarantee times inherent in the treatment method chosen must also be specified.


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3.6.1 - Protection of Surfaces Until handover of the works the Contractor must protect all surfaces (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 a high pressure water jet. The work must be done with care because it accentuates existing flaws such a blowholes and honeycombing. When cleaning with abrasive substances, the Contractor must provide the necessary means of protecting workmen and control pollution 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 Protection For existing tunnels, fire protection consists of a "special-design" lining not covered by these Guidelines. Reference might be made to the Technical Instruction on Safety of Tunnels on the National Road Network which stipulates that the material used for the inside lining must be classed as M0 for the crown and M1 for the sidewalls provided they do not consist of flammable materials.

3.7 - Benefits of self-compacting concrete The conditions for building a conventional vibrated concrete tunnel lining require a minimum lining thickness of at least 300 mm approx. Using self-compacting concrete allows us to revise this limit downwards (thicknesses of less than 300 mm are potentially feasible, with 250 mm being found on a few tunnels) and at the same time, concrete quantities and corresponding pouring times can be reduced.

Self-compacting concrete generally exhibits better mechanical performance than the traditional C25/30 and can in some cases be formulated to have characteristic strengths equal to that of high performance concrete (C50/60). Shrinkage of self-compacting concrete must be controlled (by controlling heat of hydration and cement paste volume) in order to combat cracking. Methods that render the forms watertight must be used (especially at the end stop forms). Imposing a minimum lining thickness is not based solely on considerations of concrete pouring. It is an extra safety factor for plain concrete structures in which thickness is vital for withstanding bending stresses. The French National Annexe for the application of Eurocode 2 (incorporated in the update of the guidelines in TOS No.149 on unreinforced concrete already mentioned) accepts a lower safety factor on concrete compressive strength only if lining thickness is greater than a certain value (e.g. 400 mm in tunnels 6 m in diameter and above). Self-compacting concrete dispenses with the need for form vibrators and the loud noise associated with them. Lastly, self-compacting concrete may improve appearance in terms of blowholes, uniformity of colour and density (especially at the crown). Self-compacting concrete displays most advantages in lining renovation (e.g. in the Tunnel des Monts at Chambery, France) and for concreting panels to form ventilation ducts (e.g. upper panel in SOCATOP VL.1 tunnel or the Foix tunnel). In the renovation work in the Tunnel des Monts (900 m twin tube in an urban setting), the new self-compacting concrete lining is not designed to support the ground. Ultra High Performance Fibre-Reinforced Concrete is not suitable for cast-in-place lining and is not dealt with in these chapters. Its use in tunnel engineering might be considered for making precast items such as thin panels or shells.

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 overview of 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 with acceptance 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 ignores full-circle linings poured in a single shot (as frequently found in drainage tunnels and sewers) and telescoping forms, because the manner in which these systems operate and construction methods in this kind of work are entirely different.

4.1 - Description of formwork systems and minimum fabrication rules 4.1.1 - Functions Forms for tunnel linings must provide the following essential functions: • They must reproduce the design geometry without deforming out of shape, and remain within the specified tolerances;

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• 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;


• They must promote efficient hardening of the concrete under conditions as provided for in the design (thermal insulation for example); • They must not restrain deformations in the green concrete (arrangements for this must not adversely affect the seal at expansion joints); • They must facilitate the striking of the forms; • They must withstand, without damage or any notable structural deformation, actions of all kinds occurring in the course of the works; • The must not apply any deleterious loads on nearby, previously concreted structures (e.g. at reaction bearing points, etc.). 4.1.2 - Terminology For convenience in reading these Guidelines, the following five common 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 liner and 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 bearing points, adjustments, translation and concrete pouring. • Bogey: provides for translation and rotation motions and comprises a roller (on rail) or a rubber-tyred wheel which may or may not be motorised (usually electrically driven); • Hydraulic cylinder or jack: used for lifting, moving and supporting loads; • Short strut: strengthens form backing and portal structure; • Adjustable strut: lightweight load transfer beam with screw jacks or hydraulic cylinders at ends; • Collapser: closure system holding the formwork in the pouring position and facilitating form stripping (once released, the forms drop open under their own weight);

• Form end stop: radial stop at the forward end of each lining ring; • 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 and stub pipes); • Stub pipe: orifice and tube welded onto the form liner through which the concrete is pumped into the form (generally in the key of the crown, 100 to 150 mm diameter with a sliding closure 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 down into three main categories: • Type 1: Free standing system without portal frame, with means of translation mounted on the form liner backing, and without a skirt locking system built in. The Type 1 system is commonly called a free standing system without portal frame. • Type 2: Free standing system with portal frame independent of the form liner and backing, but without an incorporated skirt locking system. The Type 2 system is commonly known as a free standing system with independent portal frame. • Type 3: Free standing system with built-in portal frame for translation and skirt locking incorporated in the system. The Type 3 system is commonly known as a self-locking system with integrated portal frame. Free standing systems with portal frames are more complex than systems without this frame but they do shorten the cycle time, making them especially attractive on moderate to large tunnels, despite the higher cost involved.

Figure 7 - Leg (wheel and winch) and sidewall (collapsers, hydraulic cylinders, short struts) on the formwork system


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4.1.3.1 - Type 1: Free Standing System without Portal Frame or Skirt Locking System a) Definition This free standing system does not use a portal frame. It consists of a form liner and backing only but it is hinged at the crown or shoulders, freeing it to move to the next station, for setting out and for releasing the form. The travelling system is mounted directly on the legs of the form liner backing, and systems for locking the legs of the skirts against the lining foundation are located on the outside. The built-in translation system (hydraulic cylinders, wheels, pivots, etc.) provides for advancing the formwork to the next location, adjusting the fit (longitudinally, transversally, vertically and obliquely), and collapsing the hinged formwork once the concrete has set.

TYPE 1 HINGES TRANSLATION SYSTEM SKIRT MOVEMENT POSITIONING DEVICES LOCKING FORMWORK IN PLACE BEARING POINTS FOR CONCRETING (Forms & Concrete)

The lower parts of the shuttering at the bottom of the skirts are fixed to the foundations by anchor bolts in the ledges or held in place by short and long horizontal struts spanning from sidewall to sidewall. When pouring concrete, the weight of the formwork and concrete is transmitted through the collapsers. The hinges at shoulders or crown are locked by means of linkages (generally hand-operated) and the adjustment devices on the legs are raised off the floor. Free standing formwork systems without portal frame are generally used in short tunnels and for small transverse structures with a flat or arched invert (lay-bys, niches, galleries, etc.). Form liners and backings must be designed to have sufficient stiffness during translation and remain undeformed when pouring the concrete. The various functions and variants of Type 1 shuttering systems appear in the following table.

FREE STANDING FORMWORK SYSTEM, NO PORTAL FRAME TWO PART SYSTEM THREE PART SYSTEM 1 hinge and 1 linkage 2 hinges and 2 linkages at crown (braces) at shoulders (braces) Rollers or pneumatic tyres mounted directly on legs built into the formwork (electric drive, ratchet jack, site plant, etc.) Leg-to-leg spreader strut (mechanical jacks, Oblique bars from top cross member to bottom of leg hydraulic cylinders, screw jacks) (mechanical jacks, hydraulic cylinders, screw jacks) Transverse orientation of translation system Vertical and transverse motions powered by mechanical jacks, hydraulic cylinders or screw jacks and leg-mounted translation devices Long horizontal leg-to-leg strut Short horizontal struts from pressing formwork against edge of excavation and formwork Formwork pressed foundation (mechanical jacks, pressed against foundation against and fixed to foundation hydraulic cylinders, (mechanical jacks, hydraulic cylinders, with anchor bolts screw jacks) screw jacks) Crown hinge linkage closed

Shoulder hinges linkages closed

Vertical collapsers under formwork legs Figure 8 - Details of Type 1 Formwork

b) Type 1 Plan 1 2 3 4 5 6 7 8 9

- Lining extrados - Lining intrados - Form liner backing - Crown hinge - Form release motion / Concrete stub pipe - Collapser - Concreting window - Leg-to-leg strut - Translation wheel

Examples of longitudinal translation, transverse positioning and form stripping systems on flat and arched invert

Figure 9 : Sketch and Key for Type 1 Formwork

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Figure 10 : Typical Type 1 Formwork Bearing

c) Advantages • simple design, easy to build, • attractive for re-use, especially for ancillary works, • very quick field assembly and dismantling time, • maximum clearance for traffic under formwork (when struts are not in place), • simplified forward translation system, • unequalled quality for price (cheaper than portal frame types). d) Drawbacks • limited transverse movement and back-off due to short strokes of hydraulics or screw jacks, • need for additional means of translation (site plant for example), • no platforms or walkways on formwork, • interference with site traffic. 4.1.3.2 - Type 2: Free standing system with portal frame independent of the form liner and backing assembly, but without an incorporated skirt locking system

TYPE 2 HINGES TRANSLATION SYSTEM SKIRT MOVEMENT

POSITIONING DEVICES

LOCKING FORMWORK IN PLACE BEARING POINTS FOR CONCRETING (Forms & Concrete)

a) Definition Independent portal frame formwork systems are only hinged at the shoulders, not at the crown. Due to the portal frame with its various functions, the formwork has full degrees of freedom in translation and transverse, horizontal and inclined adjustments, but the system remains conventional because the bottoms of the skirts (hinged at the shoulders) are held in position by anchors in the ledges or by horizontal spreader struts. The working platform is built into the formwork, forming part of the form liner backing assembly (transverse beams and bracing); the portal frame is supported under the platform. The most widely used independent portal frames come in two categories: fixed and adjustable. There is a third hybrid category because the functions of the two types are often "mixed." • Formwork system with independent fixed-dimensions portal frame The portal frame legs and transverse beams are fixed and vertical and transverse (horizontal and inclined) movements of the formwork system are obtained by telescoping components, hinges, pivots and screw jacks on the upper beams of the portal frame.

FREE STANDING FORMWORK WITH INDEPENDENT PORTAL FRAME THREE PART SYSTEM 2 hinges and 2 linkages at shoulders (stiffeners) Fixed-dimension portal frame Variable-dimension portal frame Rollers or pneumatic tyres mounted on portal leg built into the portal structure (electric motors, ratchet jacks, site plant, etc.) Oblique struts from portal frame Oblique struts from top cross member to legs to bottom of formwork bottom of formwork (mechanical jacks or hydraulic cylinders) (mechanical jacks or hydraulic cylinders) Transverse position of translation system Vertical and transverse movements Vertical movement with hydraulic Part of vertical movement with obtained with hinges, pivots, cylinders of portal frame legs, hydraulic cylinders of portal fram hydraulic cylinders on portal top transverse movements with horizontal legs; fine vertical adjustments cross members hydraulic cylinder on and transverse movements with top portal members horizontal hydraulic cylinders on top portal members Hinges at shoulders (screw braces) Long horizontal leg-to-leg Short horizontal struts spreader strut presses forms between edge of excavation Bottom of form pressed against foundations and formwork pressed against foundation and held (mechanical jacks, against foundations (mechanical in place with anchor bolts hydraulic cylinder, screw jacks) jacks, hydraulic cylinder, screw jacks) Vertical collapsers under formwork legs loaded Skirt movement struts disabled / Portal frame lowered down from formwork or portal frame removed Figure 11 - Details of Type 2 Formwork


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• Formwork system with independent variable-dimension portal frame Vertical movement of the shuttering is obtained with the legs (telescoping components and jacks) and the horizontal and inclined adjustments are made with horizontal jacks fixed on the upper beams of the portal frame. • Formwork system with independent variable-dimension mixed-function portal frames Vertical movements of the shuttering are obtained with the legs (telescoping components and jacks) of the portal frame, and vertical and transverse (horizontal and inclined) movements are provided for by telescopic components, hinges, pivots or horizontal jacks fixed on the upper beams of the portal frame. When concreting, the weight of the formwork and concrete is transmitted to the collapsers. The hinges are locked by means of mechanical linkages, and the portal structure and its adjustment controls must be disabled. After checking that the formwork functions have been locked out, the portal frame can be removed to serve another formwork system in the same tunnel.

c) Additional functions compared with Type 2 formwork system and advantages This type of shuttering is designed as a free-standing structure (like Type 1) with the portal frames providing only extra functions to compensate for the inconvenience of not having a portal frame, in particular: • wider back-off gap when striking forms, • improves usage and shorter transfer times, • can accommodate changes in longitudinal profile, • shuttering (or two sets of shuttering) can be leapfrogged to concrete alternate lining rings, • extra functions can be added to the portal frame to suit the Contractor's needs, • can more easily accept invert superelevation and arched invert shape, • possibility of permanent platform and walkways, • will easily accept a front walkway with service access, • it can be mounted on pneumatic tyres without any special steering system, • it can combine a variety of functions simultaneously, • etc.

b) Type 2 Plan 1 2 3 4 5 6 7 8 9 10 11

- Lining extrados - Lining intrados - Form - Shuttering hinge (shoulders) - Upper formwork positioning system (V = vertical, H =horizontal) - Hinge locking linkage - Portal frame - Skirt struts - Bottom shuttering prepositioning system - Transverse screw strut - Collapser / support device

Figure 12 – Sketch and Key for Type 2 Formwork

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Figure 13 – Type 2 formwork system – Butte d'Osse Tunnel – France, RN64 Oblique struts from portal frame legs to bottom of shuttering – Transverse leg-to-leg struts

Figure 14 – Type 2 formwork system – Lotschberg Tunnel – Switzerland – Short struts from foundation to edge of excavation

d) Drawbacks • needs a concrete base, • demands an extra set of shuttering, relatively expensive but very useful, • less need for telescoping legs on gradients (risk of sliding members jamming), • may block passage through shuttering if left in place. 4.1.3.3 - Type 3: Self-locking shuttering with integral portal frame and skirt locking a) Definition With this type of shuttering (form liners + backing + portal frame), the stiff portal frame is intimately merged with the shuttering and the devices for holding and locking the skirt bottoms are also integral with the shuttering. The Type 3 formwork system is also known as “the free-standing formwork system with integral portal frame”. Devices for moving and positioning the shuttering are mounted on the portal frame and provide for all longitudinal, transverse, height and banking adjustments. The formwork system must be powered and advance at very slow speed. The telescoping stanchions forming the legs of the portal frame (beams with powerful vertical hydraulic cylinders) provide for rough height adjustment of the shuttering; the devices (hin-

Figure 15 – Type 2 formwork system – Independent portal frame – Oblique hydraulic struts between top cross member and shuttering legs

Figure 16 – Type 2 formwork system – Independent portal frame on rails – Rail tunnel

ges, pivots, smaller hydraulic cylinders) on the upper members of the portal frame's transverse beams are only used for fine transverse and vertical positioning. The skirts may be locked in two ways: • The hydraulic cylinders of the inclined struts between the upper beam of the formwork system and the bottom of the skirt press the skirt bottom against the tunnel ledge (vertical faces of the foundation). It is this compressive force which provides the seal and transmits the pressure from the fresh concrete, and prevents structural deformations. These hydraulic cylinders apply heavy loads to the formwork system and foundation, a fact which must be given due consideration in the design. • Alternatively, the inclined struts from the upper members to the legs of the formwork system gently press the skirt against the vertical faces of the foundations and the skirt hinges are locked tight through the shoulder linkages. The oblique struts are therefore compressed and apply an internal force (prestress) to the circular form backing to prevent it deforming when the concrete is poured. This arrangement also avoids stray forces being applied to the ledges, otherwise the seal at the bottom of the skirt would have to be formed by an independent device. During concring, the combined weight of the formwork and fresh concrete must be taken by the collapsers; for this to happen, the portal frame's positioning function must be disabled.


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When striking the forms, the portal frame must take the load and the hinge linkages must be removed. This will cause the collapsers to unstick the formwork from the concrete, the sidewall skirts are lifted off from the lining by the oblique hydraulic cylinders and the portal frame lowers the complete form. This highly mechanised self-locking formwork system requires less labour but operations require some skill, especially when unsticking the forms, in order not to lift off the adhering green concrete.

TYPE 3 HINGES TRANSLATION SYSTEM SKIRT MOVEMENT POSITIONING DEVICES LOCKING FORMWORK IN PLACE

• very wide back-off gap between liner and freshly exposed concrete face, • dispenses with the need for fixings in the foundation, • strokes of hydraulic cylinders on legs and skirts such as to leave a clear passage underneath the formwork, • less labour needed, • possibility of semi-automated concrete distribution, • increased safety,

SELF-LOCKING FORMWORK SYSTEM WITH INTEGRAL PORTAL FRAME THREE PART SYSTEM 2 hinges and 2 locking linkages at shoulders (stiffeners) Heavy, variable dimension, long stroke portal frame Rollers or pneumatic tyres on legs integral with portal frame (electric drive) Oblique struts from top cross member to bottom of formwork system (bars or braces with hydraulic cylinders) Vertical movement by hydraulic cylinders acting on portal frame legs – Additional vertical movement plus transverse movements by devices (hinges, pivots, hydraulic cylinders) on top portal members Bottom of formwork forced against foundation Bottom of formwork pressed lightly against the by oblique struts from top cross member foundation by oblique struts from top cross member to formwork legs to leg of formwork Hinge linkages locked (bars with powerful hydraulic cylinders) (screw or mechanical jacks) Oblique braces Hinge linkages locked (screw jacks or mechanical jacks) in compression and structures are prestressed

BEARING POINTS FOR CONCRETING (Forms & Concrete)

Vertical collapsers under formwork legs Formwork positioning system disabled Figure 17 – Details of Type 3 Formwork

b) Type 3 Plan 1 2 3 4 5 6 7 8 9 10 11

- Lining extrados - Lining intrados - Form liner backing - Formwork hinge (shoulders) - Upper formwork positioning system (H = horizontal) - Concreting windows - Integral portal frame with positioning device (V = vertical) - Oblique skirt movement braces - Formwork pre-positioning system (formwork legs) - Motorised translation bogey - Collapser / Support device

Figure 18 – Sketch and key for Type 3 formwork

c) Additional functions compared with Type 2 shuttering and advantages The Type 3 formwork system is designed, like Types 1 and 2, as a free-standing structure but remedies their weaknesses. In particular, it features: • more robust formwork system, better for long tunnels,

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• portal frame can be re-used, • etc. d) Drawbacks • more complex design (especially for prestressed structures), • cost, • risk of damage to previously poured lining ring, • skill and training essential.


Figure 19 – Type 3 Formwork System – Lioran Road Tunnel - 2006 – Cantal, France – Oblique hydraulic cylinders from portal frame top member to skirts (movement and lock on foundations)

Figure 20 – Type 3 Formwork System – Vierge Tunnel – 2005 – Lodève, France

4.1.3.4 - Shuttering to Ancillary Works Formwork should be a variety of Type 1 for niches, short branches and lay-bys, and Type 2 for long connecting galleries to transport the formwork system more easily than with lightweight translation systems.

• Plywood sheets Plywood sheets must be mounted on a rigid backing. In so far as these liners are used several times, they may have to be protected against damage to edges and leakage of laitance. Plywood liners are often used for the headwalls of lay-bys, niches, or boxes. With both timber and plywood liners, the final colour of the concrete may be affected by certain varieties of wood and the number of times the liner is used (tannin seeping out). • Sheet metal Sheet metal liner panels usually come in standard sizes. They are assembled by welding onto frames, not to each other. Thickness is generally 8 mm – 10 mm and must be compatible with pressure from the fresh concrete and the number of times they are to be used; they must be free from deformations unacceptable for the type of concrete finish required. These liners are used for the tunnel intrados (sidewalls, roof arches) and transverse works repeated many times on the same project. Various styles of sheet steel are available: black steel, zinc electroplated, hot dip galvanised, stainless. Black steel is recommended. • Panels faced with synthetic materials No recommendations can be made on this type of formwork material because there are too few reported instances of its use. Whatever materials are chosen, the required finish for the concrete surface will only be achieved if the following minimum rules are observed: - Cutting, positioning and orientation of the joints must be decided on the basis of the results specified for architectural appearance, if applicable. - Materials for form liners must be selected on the basis of the results specified for concrete surface quality. - The feasibility of re-using form liners must be examined with reference to the required regularity of colouring, texture and geometrical shape specified for the concrete surface.

4.1.4 - Details of Formwork System Components The three types of formwork system briefly described in the foregoing paragraphs consist of four main parts. 4.1.4.1 - Form Liners The form liner determines the intrados line and governs the quality of the finished surface in terms of appearance (user comfort, cleaning) and technical performance (fastenings, equipment, painting, etc.). The material used for form liners may be sheet steel (generally) or lighter alloy (sometimes), or wood (more rarely). Form liner materials are classified in order of increasing quality corresponding to the categories of surface finishes: ordinary liners for plain surfaces, superior liners for fine finishes and special liners for featurework. a) Ordinary Form Liners for Plain Surface Finishes Ordinary form liners are not usually acceptable for exposed concrete. They consist of plain sawn boards or planks placed side-byside or continuous joined plywood panels. Liners to be used only once often have no particular removal / refitting system. If the liners are to be re-used a few times, they are frequently of mixed construction with either a steel frame with timber facing or more rarely a wooden frame with metal liner. End stops are made this way. b) Superior Form Liners for Fine Concrete Finish • Boards Sawcuts must be aligned and parallel, edges must be sharp and the boards must be planed on all four faces. They must all have the same thickness, at least 27 mm. This may concern drainage niches.


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- Form liner components must be assembled in such a manner as to comply with the specified tolerances on concrete surfaces. In the absence of any particular specifications on concrete surface condition, joints between lining rings and lift joints that are to remain visible on the exposed concrete surface must be highlighted by using a suitably shaped joint strip. c) Special Form Liners Special form liners are used where the concrete surface is to feature patterns or motifs, especially at tunnel portals. Featurework is often in relief or intaglio (special dies are used). The design of the geometrical pattern must allow for the inclusion of these shallow dies (depth not more than 20 mm, with draft) and at the same time, must not interfere with form stripping (no suction forces). The quality of the material used for the dies must be such that they cannot deform and are suitable for the number of times the forms are to be used. Special care must be given to making the model if polystyrene is used for the dies. When using metal form liners, black steel should be the preferred material because of the fact that corrosion is slower due to the presence of the black mill scale that gives it its name. In certain cases, this sheet is faced in the works with Pieri resin or similar. This coating is easily removed without leaving any marks on the concreting for the first few rings. The mill scale must not be removed, because of the rapid rusting that would ensue. 4.1.4.2 - Backing The form itself is a structural component of the formwork system. It must sustain the dimensional stability of the form liner, maintain design clearances in the tunnel lining and for access to the works, and transmit the loads associated with setting up the formwork system, pouring concrete and striking the forms. a) Role of Backing The backing of the formwork system must: • support the form liners so that they do not deform beyond the specified tolerances (despite repetitive use), and more generally, they are composed of (i) primary structures conferring local stiffness on the liners and (ii) secondary structures supporting the global shuttering system (arches), • transmit pressure loads and the weight of the concrete to the various bearing points. Stress paths must be carefully controlled in order to avoid applying excessive loads which would be prejudicial to the stability of the bearing points (ledge stability, concrete cracking, especially in young concrete),

• provide safe access to the work stations, • allow traffic to pass under the formwork system if necessary (clearance needed for vehicles and ventilation ducting, compressed air lines, water pipes, cables, etc.), • allow the formwork to be struck and moved to the next lining ring. b) Component Parts of Backing Generally speaking, the backing, made up with curved, straight and ribbed components, comprises the following parts: • the upper structure for the roof (crown between shoulders), • the side skirts (sidewalls) fixed and pinned to the roof frame, moved with hydraulic cylinders or mechanically when striking the formwork and moving on to the next lining ring, • vertical and horizontal stress transmission parts: - vertically, the weight of the concrete and formwork system is transmitted to the foot of the system (usually onto the ledges at footings or invert slabs) to points in line with the ribs of the formwork, through mechanical jacks, hydraulic cylinders or collapsers. - horizontally, thrust loads are transmitted: - through a long cross strut at the top, - at the bottom, either by being anchored in the foundations, by long or short horizontal passive transverse braces which must be heavy enough to prevent elastic compression strains, or by passive or active prestressed inclined braces. The designer must find the best compromise between strut stiffness and their prestressing in order to (i) avoid displacement of the skirts when pouring concrete and (ii) avoid applying excessive loads to young, previously cast concrete (especially at the foundations). Procedures describing the planned method of avoiding damaging loads being applied to the structures must be included in the formwork system calculations. 4.1.4.3 - Portal Structure The portal structure provides for striking formwork, transporting it (longitudinally and transversally) and setting up the forms for the concreting of the next lining ring. The two types of portal frame (independent and integrated) are defined in these Guidelines. a) Role of Portal Structure Both types of portal frame basically provide for moving the formwork system to the next tunnel lining ring and its precise positioning there. The portal frame can also overcome certain obstacles (see Figure 21).

Figure 21 – Formwork system travelling under roof-mounte d utilities – Type 3 formwork system – (Monts tunnel - 2005-2006, Savoie, France)

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Obstacles and clearances to be considered and described in the Contractor's specification when designing the portal frame include: • Clearances underneath formwork system for site traffic, normal traffic (at walking pace) and emergency vehicles and rescue services, • External limits for the passage of utilities if the tunnel is kept open to traffic, in both new-build situations as well as in renovating work (lighting, signage, ventilation*¸ etc.) • Space needed inside for the passage of supply lines (water, electricity, etc.). Under normal operating conditions, the load on the portal is confined to the formwork system only, but in some exceptional cases, it may have to carry the weight of the concrete also, and so must be designed with allowance for the weight of the nominal design lining thickness plus overbreak that occurred during boring. b) Component Parts The portal frame is usually built of longitudinal and transverse steel beams (H, I, rectangular, trussed). These horizontal members rest on vertical stanchions (legs) strengthened with braces and gussets. The beams are preferably of bolted rather than welded construction for ease of transport and disassembly on site. c) Travelling Systems The portal frames are equipped with systems for travelling along the tunnel (or handling mechanisms) consisting of one of the following: • rails (Vignole, Burbach or other types) upon which the wheels or bogeys run. Burbach** rails are preferred because of their lower profile. When laying the rails, it is important to keep them parallel and attention must be given to ensuring that the track is flat with smooth gradients. For repeated use, replacing the rails should be allowed for as they will tend to deform under the loads applied to them. When a rail-based system is used, it is preferable to build a concrete invert or base on which to lay the rails. • pneumatic or solid tyres which can travel directly on the excavated surface. If there is no guiding system, the portal must have means of moving the backing laterally on the portal frame, with a greater movement required than for rail-mounted portal frames; • a walking system, with hydraulic feet instead of wheels. The translation mechanism (wheels on rail, pneumatic tyres, walking feet) may be motorised (hydraulic or electric power) or mechanical (winch, ratchet hoist). Cable systems cannot accommodate reverse travel. The braking system must be designed and installed and a redundant braking system is strongly recommended. A brake must always be provided when the system is on a gradient.

Figure 22 – Bouygues Type 3 walking formwork system – Grands Goulets road tunnel 2007 – Drôme, France

d) Adjustments The legs (vertical stanchions) of the portal frame are generally fitted with main primary hydraulics for raising, lowering, striking forms and the lowering of the whole system. Secondary and fine (vertical, horizontal and inclined) adjustments can be effected by systems mounted on the upper horizontal members of the portal frame. These jacks, hinges and pivots must enable the structure to move at very slow speed (inching) and to position the system accurately to within one millimetre, without jerks. These devices are essential for staying within the construction tolerances and also for avoiding the risk of cracking the previous lining ring. e) Access and walkways • Roles - Access ways and walkways must provide for safe access to all workstations for the following operations: - Longitudinal travel (translation), - Placing and striking forms, - Placing and striking end stops, - Concrete pouring and vibration, - Cleaning and oiling the forms, - Fixing through bars when the forms are used for casting twosided walls at portals. • Design The formwork must have at least the following items: - A platform level with the top strut of the form providing access to all workstations on the upper part of the roof, - Side walkways on brackets on the side skirts providing access to the concrete pouring windows, - Main access giving onto the top platform consisting of a stair or ladder which must move with the form, - Secondary access for the side walkways consisting of ladders or steps from floor level or from the upper platform,

*For a 3 km long tunnel with the lining being carried out while boring is ongoing at the face, two ventilation ducts measuring 2 and 1.5 m are required for supplying fresh air to the face and must pass “through” the formwork system(s). ** Burbach rails are used on overhead travelling cranes


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- Access to the perimeter of the form stop for fitting and removing the end stop. In addition, the general design of the formwork must consider all phases of the shuttering process (folding skirts, lowering the form, longitudinal travel, etc.) in order to avoid having to remove parts of the access ways or walkways. • Configuration Access ways and walkways must provide for the following essential configurations: - Forward and backward longitudinal travel with the form in the lowered position, - Lowering the formwork system to pass beneath utilities suspended from the roof if necessary, - Maintaining nominal clearances for traffic, - Passage of supply lines and ventilation ducting if necessary, - Folding side skirts without encroaching on the traffic clearances and allowing collateral activities to proceed, - Assembly and disassembly.

• Ergonomics The ergonomics of the formwork system at each workstation must be designed with reference to the needs of each workstation, to be specified at the time of inviting tenders. The design of access ways must meet very stringent criteria. For example, the portal frame must be designed around the forms and the following points must be considered: - keep some minimum distance between any two stairs (perpendicular to the slope of the stair) and walkways, - provide for ease of workforce movement inside the structure, - provide a fast emergency exit route free from obstacles in the event of an accident, - use solid steel chequerplate with expanded metal surface pattern, - provide for independent lighting for all walkways, - provide flights of stairs to the top landing instead of the usual ladders, - fix the end stop stairs and access landings to the frame rather than the form, etc.

Figure 24 Minimum Access Function - Stair Access to Forms

Figure 23 - Type 2 Formwork System Saint Henri Tunnel – Marseilles, France

Figure 25 - Access Walkway to Top Lining End Stop

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Figure 26 - Passage on Upper Platform of Formwork System


4.1.4.4 - Equipment and Special Points a) Windows Openings must be provided at regular intervals in the form linings for concreting and to ensure the concrete fills the form correctly, for providing access to the ducts and box-outs placed or to be placed in the roof and for introducing poker vibrators to supplement the form vibrating system. Window numbers and sizes must be appropriate for the roof geometry and for complying with concrete pouring rules (especially height of drop). The windows are closed off as the concrete level increases by means of hinged panels provided for this purpose. The panels must be made of the same material as the form liner and must not leave too obvious a mark on the finished concrete surface. Concreting Window Closure Panel

Compressed Air Form Vibrator

king platform when concrete-filled lines are being moved from one window to the next. - Distributor Arm The hydraulically-operated and manually moved distributor arm delivers concrete to the concreting points at the windows or grouting pipes at the crown, without any heavy manhandling. The system is most suitable on long forms using low slump concrete. - Self-Compacting Concrete When pouring self-compacting concrete, grouting pipes are used instead of windows. Concrete is delivered through the distributor arm connected to the pipes. In this case, the system must be semiautomated. The operator simply opens and closes the pipe, keeping pace with the rising concrete. - Cleaning Lines The most widely reported method of cleaning concrete delivery lines is to force through a foam pig with compressed air. High pressure water is another alternative which may also be used as a complement to the first method.

Crown Concreting Pipe with Sliding Closure Panel

Figure 27

b) Concreting Equipment Concrete is placed with a concrete pump. Depending on the size of the tunnel cross section and length, formwork system type, working conditions and concrete mix, the concrete may be placed directly through the pump delivery line or via a semi-automatic distributor. • Direct Pumping For the lower part of the formwork (roughly up to the height of the shoulders), the concrete is placed by inserting the concrete delivery line into a window or connecting this line to a stub pipe on the window closure panel. For the upper part of the roof, the concrete is introduced through the grouting pipes on the form liners with sliding closure panels as close as possible to the form liner. Manoeuvring the heavy, stiff pump delivery lines is extremely tiring for the workmen. • Placing via Distributor The chief incentive for using a distributor is that it does away with nearly all the manhandling of the concrete delivery line. It also has a very beneficial impact in reducing concrete spillage on the wor-

Figure 28 - Semi-automatic Concrete Distributor - Monts Tunnel - France

Figure 29 - Concrete Lines Connected to Windows - Concrete Distributor on Portal Frame Top Platform - Monts Tunnel - France


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Figure 30 - Concrete line - Semi-Automatic Concrete Distributor - Glion Tunnel - Switzerland

c) End Stops End stops placed at the ends of the forms must be designed with the following points in mind: - The materials used for the panels must be strong enough with respect to concrete slump (especially with self-compacting concrete mixes) and the rate of rise of the concrete, - The forms must not leak especially where they are in contact with a waterproofing system (where present or the primary support system), in order to prevent loss of laitance, - They must not damage the waterproofing system. End stops may be made of: - the usual materials (mainly boards) fixed to the formwork, - metal, bolted and/or hinged on the backing structure, - or metal bolted or welded to the form with a Satujo type inflatable seal at the extrados intrados??; only suitable where there are no excessive variations in concrete thickness (e.g. in tunnel renovations where a second internal lining is being added). d) Vibration Formwork design must consider the effects of vibrating the forms unless self-compacting concrete is used. When using conventional mixes, the fresh concrete is vibrated to ensure it completely fills the forms (primarily that it flows around reinforcement and box-outs), consolidates to obtain a dense, compact concrete, and produces the required surface finish. Two alternatives are available: - internal vibration (poker vibrators inserted through the concrete pouring openings in the forms), - external vibration (used with metal form liners). In large tunnels, both methods are used simultaneously. However, there are no scientific rules for the number of vibrators needed and the length of time vibration is applied. One must rely on the practical experience of equipment suppliers working closely with formwork manufacturers. They usually determine the num-

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ber and method of mounting vibrators, vibration frequency, power rating (which depends on concrete thickness, slump, etc.), planned pouring rate and formwork design. The empirical rule is to vibrate often for a few seconds rather than operate for several minutes with longer pauses.

Figure 31 - Metal end stop and inflatable seal (renovation by adding a second internal lining)

Figure 32 - Wood end stops


Figure 33 - High frequency poker vibrator

Figure 34 - Form-mounted compressed air vibrator

Figure 35 - Electrical box-outs and conduits - Formwork for niche with release keys

4.1.4.5 - Fixing box-outs and forms for niches and transverse gallery openings Depending on their size, box-outs and embedded items may be welded or glued to the form liners or may be bolted on, so that they are removable. Their shapes must be suitable for the kinematics of the form striking operation and bulky inserts must be bolted in place, and be removable. The sizes and shapes of embedded items and forms for niches and transverse gallery openings must be designed for easy form removal (there must be a batter or relief angle of at least 5%). Box-outs should preferably be fitted with seals where they mate with the form liner (fitted on the inside faces of the box-outs) in order to have sharp angles. Forms for service and safety niches and the junctions with small cross tunnels may also be fixed to the main forms by bolting. For larger service items (lay-bys, turnaround chambers), it is preferable to ensure the forms are stable and leak-proof when pouring concrete by providing a small kicker on the foundation to provide the reaction for the base of the formwork. Proper attention must also be given to designing the bracing of the roofs of these ancillary works because of their potentially large spans. A relief angle of between 1% and 5% is provided to facilitate form removal; this angle may be smaller or non-existent if a suitable form release key, hinge, etc. is provided.

4.2 - Fabrication of formwork Building a formwork system involves an essential series of steps that require the drafting of documents by the Contractor or Supplier and their submission to the Engineer for approval: • Contractor writen specification, • Tenders invited from potential Suppliers,

• Contractor places formal order, • Supplier submits design and manufacture project, • Formwork delivery, assembly on site and acceptance procedure. The time required for these activities can be estimated at ten months for a conventional rail or road tunnel formwork system. 4.2.1 - Contractor writen specification The specification must address at least the following points: 4.2.1.1 - Site-specific factors The baseline general design assumptions to be provided for the Supplier to design the formwork are as follows: • General sequencing for construction of the Works and particular features, • Deadlines (or partial dates) for construction of the lining, • Particular constraints associated with works scheduling (e.g. for long tunnels, lining construction to start before boring completed), • Particular constraints associated with site organisation. 4.2.1.2 - Geometric data for project The leading design assumptions to be used by the Supplier are the same as those used for the design of the tunnel, determined by the Engineer and described in the Contractor's construction contract specification. They include: • Cross section showing the intrados and extrados (host ground, temporary support or old lining), • Plan view (showing positions of embedded items, box-outs and special details), • Longitudinal profile (radii and lengths of curves, gradients and superelevation),


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• Total length of tunnel, • Lengths of bored tunnel to be lined, • Lengths and geometries of portals (pseudo tunnels), • Lengths requiring reinforcement (pseudo tunnels and starter rings of bored tunnels for example), • Type, geometry and details of joints between lining rings, • General geometrical tolerances on finished work, • Clearances and acceptable tolerances, • Lining surface quality. 4.2.1.3 - Kinematics of Formwork System Before inviting tenders, the Contractor must specify the detailed kinematics of the formwork system in operation, with schematic cross sections showing gap when forms are lowered, back-off distance of collapsed skirts, turnaround area needed if applicable, etc. This determines the space needed for correct operation of the formwork system and its compatibility with the structures to be built, both in the tunnel and on the surface yard. Particular attention must be given to interlinkages between portal frame and forms in so far as they affect workmen's access for operating the formwork system and the needs, if any, of other activities (tunnel driving for example). This part of the contract specification is of major importance for the Supplier. 4.2.1.4 - Special Constraints on Formwork Systems in connection with the main works schedule Special constraints regarding the works schedule may be governed by the stipulations in the main construction contract but it is possible to propose modifications which might have an impact on overall project completion time or completion time for the lining alone. The Contractor may accept variants proposed by the Supplier on the following points: • Number of formwork systems and lengths (if stated in contract), • Length of concreting cycle, • Breakdown of concreting sequence on cross section (ledges, foundations, sidewalls, crown, etc.), • Details of lining concreting cycle, • Obstacles to be passed and traffic under portal frame (utilities, ventilation, mucking, etc.), • Passage of ventilation ducts before boring is finished, • Type and mechanical properties of support for advancing formwork, • Any other particular constraints (erection of formwork system underground or on the surface, translation, etc.). 4.2.1.5 - Relevant Concreting Parameters The Contractor must provide the Supplier responsible for building the formwork system with the concreting parameters considered in the project design phase: • Concreting rate in m3/hr, • Maximum thickness of overbreak to be considered (position, size), • Concrete mix properties (consistency, temperature, setting time, etc.), • Refusal pressure when forcing concrete into remotest corners at the end of the pour,

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• Special points, if any (intersections with other galleries, unbalanced pouring, etc.). 4.2.1.6 - Formwork Characteristics to be Provided by Supplier In his design report, the Supplier must state: • Formwork type (type 1, 2 or 3), • Formwork system dimensions and weights, • Form liner type (minimum metal gauge for crown 8 mm), • Effective length of lining ring, • Method of fixing on foundation (skirt reaction), • Kinematics of lining formwork system (this section must describe in detail the motions necessary for operating the formwork), • Size of transverse adjustments (vertical, horizontal, inclined) and translation adjustments, • Floor bearing points (pressure and material), • Required construction sequence. 4.2.1.7 - Formwork System Equipment Required The items listed below (especially for the primary formwork but also for the forms for ancillary works) must be described in detail by the Supplier and comply with safety rules: • walkways, • access stairs or ladders, • windows (numbers and dimensions), • stub pipes and sliding closure panels (number and details), • items for fixing reinforcement and/or box-outs, • embedded items and grout lines for subsequent contact grouting, • miscellaneous items (lighting, telephone, plastic sheeting), • end stops (metal, timber, Satujo seals, etc.) • vibration equipment (vibrator types and numbers if separate order from formwork system), • concrete placement technique (distributor, concrete pump lines, etc.). 4.2.2 - Contractor's Tendering Procedure for Suppliers 4.2.2.1 - Invitation to Tender for Suppliers The Contractor invites tenders from tunnel formwork manufacturers/suppliers on the basis of the specification as described above. Tender documents must present the general background to the Construction Contract (i.e. define the Works, Owner, Engineer, Main Contractor, project completion time, interim deadlines and required date of delivery of the machinery and equipment to be supplied) and clearly state the anticipated supply order. 4.2.2.2 - Suppliers' Tenders Manufacture and supply tenders must contain • Company description (fields of competence, personnel, factory, offices, contact details, etc.), • Details of recent similar projects, • Brief technical report, • A costed tender, • Deadlines for manufacture and delivery.


4.2.3 - Contract Award After scrutinising the tenders submitted, the Contractor issues a report with a recommendation as to the tenderer to be awarded the contract and submits it to the Engineer for information or approval, depending on the complexity of the lining to be built. For very complex projects, this report should be highly detailed. 4.2.3 - Ordering Formwork by Contractor By reason of the capital importance of formwork for the final quality of the structure, all engineering documents leading up to the design and operation of the formwork must be included in the order after being submitted to the Engineer for approval. The official order may take the form of the letter accompanied by explanatory documents and forms to be completed as appropriate. 4.2.3.1 - Order Letter The Contractor notifies the successful tenderer by letter, which becomes the official order for the formwork. 4.2.3.2 - Informative Documents At this stage, the general overview of the Works and the tendering procedure for formwork is described. In particular: • the Contracting parties, • the general terms and conditions of purchase of the formwork system by the Contractor, • the contract documents: - schedule of components of main contract, - main works schedule, - schedule of formwork systems to be fabricated, - safety and quality documents, • services provided and not provided by the Main Contractor, • services to be provided and not provided by the Manufacturer, • site conditions imposed by contract deadline and concreting programme, • specification (already forwarded in the tendering process), • procedures for the Contractor passing documents to the Engineer for approval, • etc… 4.2.3.3 - Supplier's Design The Contractor invites the Supplier to complete his project, stating: • prices and price breakdowns for the formwork systems, terms and conditions of payment, late penalties, retention money, if any, • time schedule for design, manufacture, erection and acceptance procedure, • design of formwork system: - drawings, - notes on design, fabrication and use of formwork system, - requirements for erection and transport, - notes on hydraulic and electrical systems, - calculations (framework described below), - design codes and standards used, - sundry documents including the Contractor's specification.

4.2.3.4 - Regulatory Conditions of Manufacture Formwork systems are considered to be in the category of machinery for underground engineering works, and the design of operational equipment and protective measures must comply with the technical rules listed in Annexe 1 of Article R223 84 of the Employment Law code. The Manufacturer must show his equipment and machinery is compliant by affixing the CE mark accompanied by the following: • Manufacturer's name and address, • Type of formwork system, • Serial number, • Year built. Before the formwork system becomes operational, it must be inspected and passed by the Manufacturer's own inspection organisation and an independent certification body. The Manufacturer must provide the Contractor with operation and maintenance manuals. 4.2.4 - Supplier's Design and Fabrication Report The design report for the Supplier's formwork systems (to be drawn up by the Supplier) must include general arrangement drawings, calculations, detailed working drawings, erection drawings and rules for pre-delivery acceptance in the Supplier's works. This report must be submitted to the Contractor and then the Engineer for approval and/or validation before manufacture begins. 4.2.4.1 - Loads to be Considered in the Structural Design Computations Based on the geometry and length of the proposed formwork system, the Supplier's structural analyses must include loads due to: • thickness of concrete (including overbreak), • concrete consistency and density, • pressure due to concreting, • unavoidable imbalance during concrete pouring, • consolidation pressure at end of pour, • self weight of forms, portal frame, ancillary structures, walkways and superimposed loads thereon, • secondary loads due to resistance of form striking (suction), form travel and adjustment, bracing and prestressing. 4.2.4.2 - Applicable Rules The necessary and compulsory formwork design calculations must at least comply with the following minimum rules: • Structural strength and strain design rules, • Standards on design analyses to be used are CM 66 addendum 80 or Eurocode 3 (Eurocodes preferred), • Safety standards for formwork. 4.2.4.3 - Calculation Principles a) Structural analysis of formwork during concreting Whatever type of formwork system is involved, the formwork must be analysed as simply supported on the collapsers (generally individual bearing points at one-metre intervals on the sidewalls) and pressed against the tunnel foundations (spacing of anchors or points of load application every one or two metres along the formwork side).


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In addition to the self-weight of the structures and internal prestress of the backing (if any), the concrete pressure to be considered is the hydrostatic pressure over the whole height of the concrete lift except if limited to a lesser value determined and justified by the manufacturer and user, plus a maximum pumping pressure of 3 bars at each stub pipe and contact grouting pipe and at overbreaks at the crown, if any. Form liners must be analysed without any pressure reduction. After the first rough models, the real structure with a variety of loads and load combinations can be addressed; these analyses provide information on stresses and strains, from which the structures can be modified or strengthened: • during translation, • when setting up formwork on station with prestress, • during concrete pouring, including for unbalanced concrete load and when filling voids at the crown. All internal mechanical parts of the formwork system must be checked, plus all linkages with external items (shafts, fastenings, collapsers, hydraulic cylinders, etc.). Simple tests can be run for special parts not amenable to analysis. b) Structural analysis of portal frame For Type 2 and 3 formwork systems as described in these Guidelines, two analyses might be needed. The first concerns the "normal" situation: type 2 and 3 portal frames are analysed on the basis of the weight of the formwork and accessories during "slow" translation and when setting up the formwork on station. The portal frame must have ample strength and not allow the forms to deform out of true. The second concerns the concrete pouring situation (exceptional case). The Type 2 portal frame never carries the weight of the concrete, whereas the Type 3 portal frame may under exceptional circumstances have to carry the weight of the concrete, accidental pressures and loads. The formwork is considered as fixed on the portal frame and it must be analysed as simply supported on the four portal frame legs and on the "n" number of collapsers. Allowable deformation limits are set in the specification and the structures must be verified. 4.2.4.4 - Tolerances on formwork construction and use There are various types of tolerances associated with the functions of the different parts of the formwork system and they are not cumulative. Tolerances on manufacture, installation and operation presented hereunder are examples only. a) Manufacture • Tolerance on cutting parts of formwork system: <1 mm • Tolerance on construction of parts of formwork systems: <3 mm • General tolerance on geometry of assembled formwork system: <10 mm b) Installation • Tolerance on installation and setting-up: <5 mm • Tolerance on bending of the formwork during concrete pouring: acceptable deflection 1 mm • Geometrical tolerance with reference to the design curve and formwork length: <10 mm.

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c) Lining I line and Radius The contract specification sets only the tolerance on lining construction. This tolerance is applied to the intrados radius (I line) and more particularly, at the upper corners of the effective clearance line. Tolerances must not be applied such as to reduce lining thickness to less than the minimum design value. For a tunnel with 20-75 m2 effective cross section, the tolerance will be R + 0 cm / R – 4 cm; for a cross section of 75-120 m2, the tolerance will be R + 0 cm / R-6 cm. Because of the special features of tunnelling work, the above values are substantially different from what may be arrived at from Chapter 10 of Fascicule 65A. If the tunnel cross section is larger than 75m2, it is advisable to provide a convergence-metering system to monitor formwork deformation during the first concrete pours. 4.2.4.5 - Draughting rules The thickness and shape of sheet metal, rolled sections and fabricated sheet must be defined and minimum weld beads (6x6 mm min) must be shown. All mechanical items (hydraulic cylinders, collapsers, etc.) must be detailed. Predicted deformations must be determined in the design analysis and shown on a specific drawing. 4.2.4.6 - Manufacture Manufacturing control must be very strict and major items and accessories must be checked (lines, geometry, welds, etc.). The Contractor must attend all trial mock-ups and final assembly. Assembled and accepted items must be stored in the factory while awaiting transport. 4.2.5 - Transport, Erection on Site and Acceptance in Final Configuration Transport to, and erection on site (on the working platform) is a job for the specialist structural steel engineer and an agreement must be signed between the Contractor, Manufacturer and Erector. The formwork Manufacturer must provide the Erector with sufficient information so that there is no distortion of the parts during transport, lifting and assembling. This must take the form of a detailed document comprising a schedule of parts (items, numbers, weights, etc.), general arrangement drawing and plans for loading, offloading and erection. At the tunnel site, the Contractor and the person(s) responsible for using the formwork system must monitor the assembling of the parts and operation of moving parts before the final-configuration acceptance process can go ahead. The Engineer will not issue the acceptance certificate until all manoeuvres (travel, adjustments, unsticking, etc.) have been fully mastered by the relevant person both aboveground and underground.


Figure 36 - Road transport (parts same width as trailer length) - Offloading (erection yard to be specified in contract).

Figure 37 - Setting up formwork for tunnel portal (intrados and extrados)


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5 - FORMWORK SET-UP AND CONCRETING This section of the Guidelines is intended to offer guidance to the Contractor in preparing engineering documents, Quality Assurance Plan, working procedures and supervision procedure and safety document. The parts listed hereunder and detailed subsequently in this chapter must be approved and/or signed out by the Engineer before for warding them to the Safety Officer and Job Superintendent: • Formwork working configurations • Q/S/E aspect (Quality/Safety/Environment) • Operations in concreting cycle • Special structures • Special cases (where applicable).

5.1 - FORMWORK SYSTEM WORKING CONFIGURATIONS 5.1.1 - Planning Excavation and Lining Sequence In new-build tunnels, a section of lining is poured after the working face has receded a set distance; in renovation and rehabilitation work, the tunnel has to be closed to traffic for a short or long length of time. The working conditions attached to each approach exert a strong influence on lining construction and type of plant needed, formwork system, accessories and erection machinery. The Contractor must describe clearly the expected procedure for tunnel lining construction. The most frequently encountered scenarios are: • Lining is built after the excavation has been finished, using one or more formwork systems (the most common scenario, and the basis for the proposed specifications), • Lining construction commences before excavation has finished; the above conditions apply, plus: - effect of blasting, - mucking traffic, - bringing up utilities (water, compressed air, electricity, ventilation ducts). • Lining is built in operational tunnel partially or completely closed to traffic for a variable time; the following constraints must be considered: - existing equipment and utilities (ventilation, lighting, signage, etc.), - clearances required by this equipment, - allowance for traffic in the tube in progress (if it is kept open to traffic) and in unaffected tube, - management of site access.

5.1.2.2 - Portal Structures The basic cycle may be drastically amended for tunnel portals, both in method and sequencing and must be addressed in detail at the tendering stage, and afterwards as part of the Supplier's design activities. The more important points are: • Different geometry (the ring may extend further at the crown than at ground level, it may be skewed or of a different length), • Reinforced concrete (affecting access to workstations, end stops with construction joints), • The extrados of the section must be shuttered, • Extra work may be involved in architectural treatment of the tunnel entrance or for sound-proofing measures, • Special end stops may be necessary, • It may be necessary for the portal to join up with ancillary works (avalanche structures, headwalls, walls, etc.).

Figure 38 Shuttering for a skewed "architectural" lining section (Grands Goulets tunnel -Drôme, France)

5.1.2 - Longitudinal Planning Building a tunnel lining consists of pouring lining rings one after the other but the characteristics of these rings (both standard and special rings) have an impact on formwork design and working conditions must be examined very early in the design process. 5.1.2.1 - Standard Rings The operations in the cycle are described for a basic lining ring; nevertheless working conditions for special rings must be considered.

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Figure 39 - End works for tunnel portal (Utelle tunnel - Alpes Maritimes, France)


5.1.2.3 - Other Special Rings Although simpler to deal with than portal sections, some special lining rings still call for detailed study on a case-by-case basis. The Supplier's design must include for: • Junctions with minor tunnels and safety refuges, • Extra reinforcement at fan sites, places where crown thickness is insufficient, etc., • Ducts, vents and other box-outs to be embedded, • Different or variable dimensions, • Etc. 5.1.3 - Transverse Planning Implementation of the formwork system is frequently dictated by the method of building the lining, which in turn derives from the design cross section of the tunnel described in the contract documents. The method to be adopted may be specified by the Engineer in the contract document, allowing for the requirements of standard formwork systems. Otherwise, the Contractor is allowed to suggest a variant to the basic design resulting in a cost saving. 5.1.3.1 - Foundation Ledges The lining foundations must be dimensioned with reference to the constraints caused by the use of the formwork system. • The shape and dimensions of the ledges (footing + rectangular foundation or L-shaped foundation or rectangular foundation without footing) influence arrangements for moving the formwork system. Having the formwork running on footings is easier and faster than on the bare tunnel floor, even if overlain by a layer of blinding concrete. • Foundations designed on this basis will make load transfer of pressure from the weight of the fresh concrete more efficient. It only requires bolting the formwork into the foundation. This dispenses with the need to find the necessary reaction by means of struts bearing on the sides of the excavation or running across the tunnel, hampering traffic. • Adjusting the formwork system to obtain the most accurate fit for setting-out the crown is largely dependent on the quality of these bearing points, which is better if an appropriate concrete is used; concrete also has the added benefit of controlling the escape of laitance and reducing the sealing work needed. 5.1.3.2 - Flat and Arched Inverts A flat or arched invert poured before the lining is built substantially improves access and working conditions and the jobsite is tidier. Under these circumstances, much less time may be spent on moving the formwork system forward. If the tunnel has a flat floor, the items in the translation system need not necessarily be positioned on the foundation footings; this provides greater freedom in choosing the portal frame type (a narrower gauge for the translation system leaves more room for working on the side skirts for example). Conversely, with an arched invert, the designer of the formwork system must cope with the curved floor when designing the translation system, and the legs are commonly positioned on foundation footings.

5.1.3.3 - Sidewalls If the sidewalls are lined first, as is frequently the case on renovation jobs or when the sidewalls are heavily reinforced, it is preferable to optimise the cycle by incorporating the majority of boxouts and inserts in the sidewalls. 5.1.3.4 - Crown(semi-circular arch) Crown forms must not bear on sidewalls that have been built previously. The best way of ensuring this is to use a free-standing formwork system with incorporated portal frame or the alternative prestressed model (as for the Monts tunnel rehabilitation project). In this set-up, the forms are supported by false sidewalls (sidewall forms without form liners or collapsers), forced against the top of the sidewalls by means of struts placed obliquely between the cross members and the bottom of the formwork system. This type of system is easier to position in the transverse direction than a complete formwork system but the overall positioning task is much more complex. Planning the job must make allowance (as for the foundations) for concrete hardening and obtaining the required strength to withstand loads applied by the formwork system. 5.1.3.5 - Sidewalls and Crown The sidewalls and crown are built with one formwork and in a single operation, as in most conventional new-build tunnels. 5.1.3.6 - Slabs and Partition Walls The presence of slabs and partition walls in most cases has an impact on the construction approach for the crown (because brackets, hangers, etc. needed). The time taken to set-up the formwork system on station is longer than in the standard arrangement.

5.2 - Q / S / E (Quality/Safety/Environment) aspects The Q/S/E section of this chapter is very important and these aspects are dealt with in greater detail than the other parts. The Contractor can therefore use the following points directly in his draft. 5.2.1 - Content of Quality Assurance Plan The object of the Contractor's Quality Assurance Plan in so far as it concerns the tunnel lining is to describe: • the organisation to be set up in order to obtain the required level of quality and safety, • the means and resources needed to achieve this objective (manpower, plant and equipment, planning, etc.) • the supervisory resources needed. Quality Assurance Plans for tunnel linings are based on two types of document: • General and specific organisation memorandums which define: - the general organisation and sharing of responsibility, - the quality assurance system, - document management system used, - procurement processes (tendering, selection, ordering), - resources management (staff training and qualifications, provision and upkeep of plant and equipment), - control of measurement systems (field survey and laboratory), - organisation for dealing with non-conformities.


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• Method statements describing, for each operation (performed directly or subcontracted): - manpower and machinery resources needed to perform the tasks, - staff training (in formwork system theory), - materials used in the works, - documents used, - construction procedure, - inspection organisation plan, - organisation for shift and night work (if necessary), - means for ensuring safety at the workplace, - formwork system acceptance formalities to be performed by accredited supervisory body, - risk analyses and associated preventive measures, - critical points, especially those concerning acts that could result in structural damage, - internal control (type, frequency, result required, individual responsibilities, records), - external control (choice of laboratory, selection of person responsible for temporary works, etc.), - procedures for dealing with non-conformities. Construction procedures in connection with the formwork system must be modified to suit the specific structure, referring to the Quality Assurance Plan included in the contract.

transport, pouring, compaction, hardening, form removal, curing, etc.) involve referral to standards, fascicules and guidelines as well as rules of good workmanship or codes of practice. The Contractor's records must therefore provide the Engineer with the following minimum information: • Design calculations and drawings for the formwork systems (provided by Supplier), • Concrete mix formulation with details of quantities of water and admixtures, • Concrete mixing machinery, • Production capacity, • Means of transport (inside and outside tunnel), carrying capacity, delivery time, • Concrete pumping equipment with concreting rates, • Alternative provisions in the event of breakdowns, • Overall concreting cycle, • Impact of concrete pouring on other activities, • In-house quality control, • Additional grouting if needed. Apart from this information, the concreting programme must also identify the activities dependent on the lining construction and the traffic that has to pass under the formwork, bearing in mind that movements of plant and materials will only be possible outside periods of concrete pouring.

5.2.2 - Safety Aspects All risks arising from the use of the formwork system and its ergonomics must be assessed and special rules put in place as described in the method statements.

5.4 - Operations in concreting cycle

5.2.3 - Environmental Aspects Operation of the formwork system must comply with the requirements of the Contract Specification. Special attention must be given to compliance with water law as regards runoff (which might be contaminated with lubricants and form oil) outside the tunnel and a suitable settling and oil separation system must be provided. Noise from the construction site must not exceed regulation levels described in the Specification for worksites in an urban or rural setting or set by the local authorities. This might require the use of electrically-powered vibrators or a noise insulating door at the tunnel entrance. 5.2.4 - Quality Monitoring of Works Quality monitoring activities must be carried out with reference to the in-house inspection organisation plan which identifies the tests and inspections required on each lining ring. A monitoring form must be completed with the findings of each test and inspection. The field quality assurance manager collects and collates the completed monitoring forms and all these records must form part of the as-built report.

5.3 - Lining concreting record The lining concreting record is an essential document. The various phases in the life of the concrete (mix design, mixing,

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The procedure for setting up the formwork system(s) must describe the tasks to be performed, in chronological order. Details of the phases mentioned below, accompanied if need be by data on constraints or design assumptions, must be given in the method statements: • Removal of forms from the last ring poured, along with precautions specific to this phase, • Translation of formwork system to next ring site to be concreted, • Curing of struck ring, • Preparation of form liners, • Setting up and final adjustment of formwork system ready for concreting, • Setting up and checking formwork locking points, • Steel fixing if applicable, • Fitting end stop(s) and seals, • Concrete pouring, • Concrete hardening. The following should also be mentioned: • Project-specific features and constraints, • Unit times for each operation, the sum of these times being the cycle time, • The level of automation of the formwork system, which is dependent on the number of times it is re-used and the cycle time (some highly automated systems drastically reduce the heavier tasks to be performed by the workmen and the dangers to which they are exposed). 5.4.1 - Form Striking and Precautions Specific to this Phase When pouring the crown, the formwork system rests (and must


be at rest) on the form stripping devices (hydraulic cylinders, screw jacks, collapsers, etc.). After removing the end stop(s), form striking involves the following operations: • The form striking system is released so that the formwork rests on the portal frame on both the integrated and independent portal frame systems or on the translation system in the selfsupporting type without portal frame; the formwork just lowers by a few millimetres, • The side skirts are freed and fold towards the interior of the formwork system, • The formwork is lowered several centimetres. This operation of freeing the formwork must not be allowed to stress the newly poured crown. On this point, the leg cylinders and oblique stays, linkages, etc. must be operated with care. Again, when there are prestressed struts or linkages, it is very important, when striking the forms, to avoid increasing the prestress load in these parts. Poor practice frequently results in localised cracking in the fresh concrete at this stage. 5.4.2 - Translation of Formwork to Next Ring The formwork system translation operation in the tunnel is an important part of the production cycle. It requires preparatory work such as laying a suitable track for wheeled or skid-mounted machinery or dismantling electric cables, other utilities, ventilation ducting, etc. The translation system must be suitably robust and its design must make due allowance for: • Tunnel geometry (ramps, superelevation, horizontal bends), • Dimensions of free passage needed, • Nature of the base supporting the track, • Longitudinal gradient (as a general rule, concreting proceeds in the upward direction in order to ensure concrete completely fills the forms, so that only the minimum of contact grouting is needed), • Translation rail type, • Motor size, with allowance for the weight of the formwork, • Sufficient rail length to maintain the cycle, • Accurate positioning of rails so as to avoid having to make good defects, • Current regulations at time of design and use of mobile translation gear. and it must include: • Braking system (whatever the gradient), • Emergency stop system, • Locking system when at standstill, • Backing and holding system on steep slopes (>5%). All translation devices must comply fully with regulations in force. 5.4.3 - Concrete Curing after Form Removal Proper curing of concrete limits the cracking which sometimes occurs with certain concrete mix formulations and working practices. Concrete in tunnel linings is not usually thought to need sophisticated curing practices although working conditions and environmental

factors (high ambient temperatures, strong draughts, etc.) generally justify it. With some types of concrete (high heat of hydration cements, self-compacting concrete), a curing agent must be applied immediately after form striking. Curing may be effected by: • Spraying a curing agent directly onto the concrete surface to prevent the escape of water vapour. These products must have the Engineer's approval and be compatible with the required quality and colour of the exposed surface and with subsequent paints, if any. They may be cleaned off after the concrete has hardened if the surface is to be painted. • Leaving the formwork in place for longer than the time needed for a daily concreting cycle. • By building a curing chamber with controlled temperature and humidity. It usually takes the form of a portal frame the same length as the lining ring installed immediately after removal of the formwork (wheeled steel frame and plastic or non-woven sheeting) to create an annular space of controlled humidity in contact with the concrete surface (with or without water spraying). The sheeting also insulates the concrete from the air currents in the tunnel. 5.4.3.1 - Curing with commercial curing agent Curing agents must be submitted to the Engineer for approval, who may require a trial application. The curing agent is applied by spraying immediately after form removal, keeping pace with the advance of the formwork system. Wheeled scaffolding or hydraulic elevated platforms are the safest way to perform this job. If the curing agent is found to be incompatible with a painted finish, it may be removed by light sandblasting or rubbing down, although this may alter the appearance of the concrete surface, as it becomes less smooth. Similarly, stains left by the curing agent are not always compatible with the required architectural finish. 5.4.3.2 - Leaving forms in place Leaving the forms in place prevents the too rapid loss of water from the concrete and so helps in controlling shrinkage cracking. The length of time the formwork is left in place may vary from one lining ring to another according to the cycle time, ambient temperature, etc., but as a general rule, the extra time as compared with the normal cycle can be limited to 24 hours. Using this method generally doubles the cycle time (48 instead of 24 hours) and only applies to short-repetition cycles. To achieve the daily cycle time, there would have to be twice as many formwork systems on the job. Furthermore, curing with the forms in place may cause mottling or stains on the surface. Experimental French standard AFNOR (XP 18-325) "Placing Concrete" cites curing times of one to ten days. 5.4.3.3 - Curing Frame If it is to be truly effective, the use of a water-spraying portal frame should be done as close as possible behind the formwork


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(less than one-half metre behind), with the frame preferably being towed by the formwork system. If the rate of advance of the formwork system is fast, the curing frame should cover two rings. The two must be designed to move simultaneously in order to avoid untreated strips being left between the two units. This requirement must be allowed for in cycle scheduling and definition. Curing with a semi-heavy or lightweight portal frame with continuous siding may take the following forms: • Spraying cold or warm water (or mist) but this is not advisable in some cases, when there is a likelihood of freezing weather, pollution of the platform (invert or roadway), presence of lighting systems, • The newly-exposed lining ring can be confined with a damp membrane hanging from the siding a few centimetres from the concrete surface, closed off at both ends. The curing frame approach may be cumbersome but may be made necessary in some particular cases when shrinkage cracking is a major risk for the durability of the tunnel or when the required level of quality is particularly high. If this approach is calles for, it must be clearly stated in the Specification (choice of technique) and a special rate provided therefor in the Schedule of Rates and Prices.

Figure 40 - Spray curing system towed behind formwork (Monts Tunnel, 2005/2006, France

5.4.4 - Preparation of form liners Preparation of form liners is a parameter influencing the final quality of the concrete surface. When the formwork system is brought up to the next ring, the form liners must be checked, cleaned and oiled before re-use. 5.4.4.1 - Cleaning Form Liners The shortage of space between the host ground (supported and waterproofed) and the formwork makes it very difficult to remove the laitance adhering to the form liners. For this reason, it is very important to take the very greatest care in cleaning and oiling them. But cleaning the liners by grinding should be avoided because this would leave marks which might be reproduced on the concrete surface during subsequent concrete pours. A good cleaning method is to take a length of nylon webbing 100 mm wide, and as long as the perimeter of the form. Two men rub the form with this, in a to-and-fro movement, working right across the form. Results are very convincing. 5.4.4.2 - Damaged Liners Damaged wooden form liners are difficult to repair and if they are to be used many times, it is best to use metal liners. 5.4.4.3 - Spraying Only wooden form liners (apart from bakelite-finished plywood liners) should be wetted. 5.4.4.4 - Release Agent Generally, commercial release products used are biodegradable oil-based liquid emulsions. The chosen product is sprayed into the available space behind the formwork and through the concreting windows. Insofar as possible, an even coating should be applied, in order not to leave marks on the finished concrete surface. The oil to be used must be submitted to the Engineer, who may order suitability tests. The Contractor's attention is drawn to the fact that spraying form oil into formwork where reinforcing steel has been set in place inevitably soils the bars with oil. For this reason, it is recommended whenever possible to oil the forms before the steel is fixed in place or to avoid applying release agent to these particular rings if they are to be concreted in a 24-hour cycle time. 5.4.5 - Moving, Setting up and Adjustment of formwork ready for pouring

Figure 41 - Cure-meter probe and readout

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5.4.5.1 - Translation and Setting Up Setting up the formwork system: • In the longitudinal, up-gradient direction, advancing and setting up the formwork must be achieved to within one centimetre (translation by motor-driven bogies, ratchet hoist, etc.), • In the transverse direction, it is the accurate positioning of the translation rails that provides the initial positioning of the formwork to within the prescribed tolerances, • Setting up the formwork for the correct level (to within a centimetre) must make use of the hydraulic cylinders at the bottom of the legs.


5.4.5.2 - Positioning Before final positioning, it is advisable to check that the geometry of the trailing edge transverse profile of the formwork system matches the mating leading edge profile so that the formwork system can achieve a tight fit without excessive voids or hard points. When setting up the formwork, the end zones of the preceding ring with its foundation must therefore be treated with care. At this stage, the trailing edge of the formwork mates with the previously poured ring with a few centimetres' overlap; for the final settings, it is preferable to provide a device for making small movements of the formwork system while the portal frame remains stationary (horizontal transverse hydraulic cylinders and vertical altitude-adjustment hydraulic cylinders with a type 3 system). If the formwork system has long-stroke hydraulic cylinders or prestressed struts, it is most strongly recommended not to use the previously poured crown as the reaction for positioning the system, for fear of cracking or breaking the fresh concrete; this is a frequent error and can be recognised by the crescent-shaped cracking. Once the formwork system is in its final position, its position must be checked in the manner described in the chapter of these Guidelines on testing and inspection. 5.4.5.3 - Contact with previous ring and foundations The seals necessary for preventing leakage of laitance must never be obtained by forcing the forms hard against the concrete to get rid of all voids. This might rupture the previously-poured concrete. Tunnel inspection frequently comes across lining rings with cracks caused by this poor work practice. A good seal can be obtained by fixing compressible rubber joint seals to the forms. As described above, excessive pressure must not be used for fear of cracking the concrete. Seals must be submitted to the Engineer for approval. The match between capacity of the seal to deform and the tolerance on misalignment at the joint must be checked. The quality of the seals must be regularly checked and the seals changed if necessary.

Figure 42 Contact between formwork and previously-poured ring

5.4.5.4 - Chases or joints between rings Construction joints that are hollow at the surface are recommended to conceal any misalignment between lining rings. The size of the chase must suit the horizontal curves of the tunnel, and the size and flexibility of the forms. Deformable materials should preferably be used (Neoprene), plugged and screwed into the leading edge of the previous ring’s concrete (full joint), or a half steel joint can be welded onto the formwork’s leading edge. 5.4.5.5 - Fixing formwork system in position and geometry check Once the formwork system is in position, it must be held in place by means of: • anchor bolts at the foot of the sidewalls (type 1 and 2 systems), • stays and/or adjustable struts at the edge of the concrete invert, if any (type 1 and 2 systems), • adjustable transverse struts between the legs of the formwork system (type 1 and 2 systems), • oblique strut or short struts between the top member and the legs of the formwork system (type 3 system). Final adjustments of the formwork ready for pouring must be made under the supervision of a surveyor who must be provided with reference points of known altitude at the bottom of the sidewalls, on the floor or at the edges of the pedestrian walkway and reference points on the formwork (legs, crown, shoulders or slab bearing points, etc.). The method of making fine adjustments to the formwork position must be capable of working within the specified tolerances and be subject to the Engineer's approval. The Contractor must check in particular the position in line and level of the extremities of the formwork system. Field results must match predefined (x, y, z) values based on the theoretical setting out of the tunnel and construction tolerances. The pre-concreting optical survey must be added to the inspection form forwarded to the Engineer (stop point). 5.4.5.6 - Load transfer during concrete pouring a) Loads When pouring concrete, the formwork system must carry the following loads in addition to its own weight: • vertical loads due to the weight of concrete, • horizontal loads due to hydrostatic pressure of wet concrete. These are very heavy loads and the system must be designed accordingly and the necessary operational precautions must be taken. b) Vertical loads Loads are carried by the formwork system and transferred down the hinged side skirts. The formwork system bears on the floor (invert or beam) via hydraulic cylinders or screw jacks, collapsers or some other high capacity means. The floor must therefore be carefully checked; it may be footings or blinding concrete and if it has insufficient bearing capacity, the number of bearing points (collapsers) must be increased or the loads better distributed by means of beams fixed on the footings.


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With integrated portal frame type formwork systems (but not systems with independent portal frame), vertical loads are either all transferred through the formwork system (in the same way as for types 1 and 2 systems, transferred through collapsers) or partially transferred through the portal frame which provides a partial stress path to the track (rails). In general, this latter arrangement is only used for small sections where the loads transferred through the legs are small. In the same way as for type 1 and 2 systems, the support to the track and collapsers must be checked and strengthened if necessary. An incorrectly stabilised system will inevitably adversely affect the concreting through unstoppable leaks of concrete, especially when pouring high slump or self-compacting mixes. c) Horizontal loads Horizontal loads due to the pressure of the wet concrete on the side skirts are not carried by the portal frames but: • at the top, by struts between the skirts (top members of the formwork system at the shoulder hinges), • at the bottom, by one of the following arrangements: - high capacity anchors in the ledge. Horizontal loads may be accompanied by heave due to the shape of the sidewalls. In this case, a means of distributing the load at the bottom of the skirt must be provided and the positioning of the anchors must be carefully checked. - horizontal struts at the bottom of the skirts. This approach is only possible on jobs where there is no need to provide for traffic passing under the formwork system, except if a bridge is provided over the struts, and the heave is countered by the weight of the formwork alone. - prestressed inclined struts. These struts, fitted with high capacity hydraulic cylinders, provide a horizontal component at the bottom of the skirts which balances out the pressure from the wet concrete, and a symmetrical horizontal component at the top which balances out in the horizontal member of the formwork system. The vertical components in the struts act at the bottom on the collapsers and at the top are countered by the weight of the formwork system. Prestressing the struts must not be allowed to cause distress at the top of the ledges and must be increased steadily to keep pace with the rising concrete. 5.4.5.7 - Reinforcement, fastenings and other embedded items Devices used for fastening or positioning items to be embedded in the concrete, including steel reinforcement, must not be allowed to adversely affect the strength or durability of the works. Metal fastenings must not be nearer the outside face than the minimum depth of concrete cover prescribed for reinforcing steel. In particular, rods or ties cut off just below the surface are not allowed. Starter bars must be treated to prevent rust stains on the exposed concrete. Holes left by the construction process must not be filled in, except as otherwise provided for in the contract. Details of the positions, shapes and dimensions of these holes must be submitted to the Engineer for approval after examining their appearance. Where a fine or featurework finish is required, plastic blocks must not be used in in situ concrete.

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5.4.5.8 - Small box-outs, joints, inserts and arrises All box-outs made from appropriate shuttering material must be designed to be easily removed when stripping the form. Small box-outs must have suitable tapers to aid extraction; expanded polystyrene is easily removed after the concrete has hardened and is a suitable material for forming box-outs. Water must not be allowed to stand in construction holes in freezing weather. Making holes with a jack-hammer in completed works should be avoided. Parts of the forms can be embedded to form openings. They must be firmly fixed in position so that they do not move while pouring concrete, and bleed water or infiltration must be drained away. Box-outs of all kinds generally needed for ventilation, lighting, signage and other equipment must be shown on the construction drawings. Fastenings for box-outs and inserts are critical points where movement must not occur when pouring concrete and their design must be addressed during the design stage of the formwork system. When determining the construction cycle, all box-outs and inserts needed must be considered and if possible, inserts should be identified individually and scheduled, so that they can be positioned against the forms. The impact of this cycle on the completion time per lining ring must not be overlooked and it is important to investigate every alternative for optimising the time required for dealing with these issues. Last-minute improvisations when the concrete is being poured are often the cause of mishaps. Sharp arrises should preferably be chamfered (to the order of 30 mm) except as otherwise provided for in the Contract; the Contractor submits to the Engineer his proposed method (chamfer or fillet), which must be shown on the working drawings. 5.4.6 - End stop(s) and seals End stops must not bear directly on waterproofing without suitable protection. A PVC sheet, even used, welded on the waterproof membrane (products submitted to Engineer for approval) is preferred to all other alternatives. For conventional wood form stops, extra protective geotextile is added at the interface with the wooden parts when they are being fitted and provides added protection against loss of laitance. Controlling leakage at end stops is one of the most critical points, especially if the end stop is fitted on site (different form shape for each lining ring) and it is a welcome precaution for the boards to be cut (and numbered) in advance, and suitably stiffened when fitted in place to avoid excessive deformations from concrete pressure when pouring and forcing in the final concrete. Where the end stop has the added protection of an inflatable tube seal, the tube must be inspected before use in each lining ring. During concreting, means of inflating and repairing the seals must be on hand at all times. A window must be left in the end stops at the crown in order to be able to see that concrete fills the forms and that there is no buildup of pressure at the end of the pour.


5.4.7 - Concreting Lining Rings 5.4.7.1 - Concrete Supply Transporting the concrete from the mixing plant must not alter its characteristics beyond the limits determined in the suitability tests. Particular points to be watched are: • Avoid sharp knocks or jerks which might cause segregation in the concrete, • Ensure that the transport and waiting time before pouring is not such as to be liable to lead to a loss of workability and the onset of initial set (especially in warm weather), • Protect the concrete against sub-zero weather if applicable, • Clean the equipment frequently in order to avoid contamination of the concrete. Where concrete is pumped over a considerable distance (up to 1000 m between the offloading point and the formwork), suitability tests must be run, as much as for confirming the required concrete characteristics as for verifying the actual flow of concrete into the forms. Booster pumps may be needed. 5.4.7.2 - Concrete Lines As a general rule, the concrete is placed by pumping through the concreting hatches and stub pipes provided for this purpose on the forms. The concrete must not be dropped from any considerable height when it emerges from the concrete line. This is particularly important when pumping self-compacting concrete because it tends to entrain more air than a conventional concrete. The following points must be addressed when designing the formwork system and preparing the job: • Designate concrete pump locations and mixer truck manœuvring areas, especially if the trucks have to pass through the formwork system during concreting, • Select positions for mixer truck arrival, offloading and washing points, • Lighten the men's workload by promoting mechanisation, by using hydraulic distributors. If it is necessary to comply with general and special specifications and working procedures, the concreting schedule must be confirmed on the first lining rings poured, especially as regards the following points: • Regularity of concrete deliveries and transport time, • Possibility of emergency services arriving at all times, • Tests on fresh concrete and preparation of specimens for mechanical tests, • Checking strength and watertightness of form end stops (if inflatable tube seals are used, it must be possible to monitor inflation pressure). 5.4.7.3 - Concreting Permission to start concreting is usually given by the Engineer. Concrete must not be retempered by adding extra water but certain liquid admixtures (superplasticizer for example) are not considered as adding extra water to the mix. a) Basics The following particular points must be addressed by the Contractor: • Always perform all tests and checks required before each concrete pour, even if operations are cyclic and repetitive,

• Choose mechanised distribution systems to reduce the amount of heavy manhandling in often congested spaces, • Keep watch on the rise of the concrete in the forms in order not to exceed the rate of rise allowed in the formwork design (maximum rate acceptable to manufacturers is 2.50 m/hr), • Keep the difference in concrete level between the sidewalls (this is another formwork design parameter) to less than 1 metre (height is often determined by the concrete load being poured, one truckload on the left, then one on the right sidewall), • Pay special attention to local singularities such as large overbreaks, safety niches, tunnel intersections which may require amendments to the cycle and concreting rules, • Vibrate in the manner specified in the concreting programme, • Follow the rules for consolidating the concrete at the end of the pour in order to fill all voids (designers generally assume 0.2 MPa pressure for the formwork and 0.1 MPa for the consolidation and void-filling), • Limit the pressure during later void-filling operations (contact grouting with mortar and normal concreting methods using the stub pipes and concrete pump). Examples of concreting times For 120 m3 lining rings, average time for filling the form is of the order of 4.00 hours or approximately 30 m3/hr. For 200-250 m3 lining rings, it is approximately 6.00 hrs, or approximately 40 m3/hr. Mixer truck capacity is 6 – 8 m3. Note. A steady concrete delivery rate makes for a good concrete finish but it must be specified and trialed before work begins. The calculation must take account of the maximum rate allowed by the formwork system manufacturer and mixing plant capacity.

Figure 43 - Concrete pump

Figure 44 - Concreting through a window


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b) Form monitoring While pouring concrete, the following points in particular must be constantly monitored: • The formwork must remain in intimate contact with the previously poured lining ring, it must not be displaced causing uncontrolled leakage, • Side skirt fastening (anchors or struts), • Concrete workability time limit (usually 2 hours), • Correct placing of concrete, without segregation, without displacing reinforcement or box-outs, and without the forms deforming, • Pumping must proceed without excessive pressure rise, • Concrete falling from windows must not segregate. Note. Concrete placement can commence before the fitting of the end stop has been completed provided it has a sufficient lead not to interfere with the concrete pour. 5.4.7.4 - Vibration All concrete (except self-compacting concrete) must be vibrated so that it completely fills the forms with dense concrete. Self-compacting concretes must not be vibrated, they compact under their own weight. The stipulations in the CCTG General Specifications (Fascicule 65A) apply along with the following recommendations. a) Internal vibration When internal vibration is achieved with electric, compressed air or other type of poker vibrator (poker diameter 25 mm to 86 mm), the following rules apply: • Choose the right poker size to suit the amount of concrete to be consolidated, on the basis of the radius of action of the poker being ten times its diameter, • Do not let the poker touch the side of the form or reinforcing bars, • The vibrator should be lowered into the concrete quickly and withdrawn slowly, • Do not use the vibrator to shift concrete laterally (it should remain upright as it is lowered and withdrawn), • When pouring concrete in layers, the vibrator should penetrate 100 mm into the previous layer, • Layers should not be more than 450 mm thick, • When metal forms are used, external vibration should be used as well as poker vibrators where sidewalls are more than 400 mm thick, • Where the lining rings are reinforced, provide "vibration wells" with guidance devices if necessary (this arrangement is recommended when concreting the first few metres from the portals with their reinforcement, box-outs and special lining ring shapes). b) External vibration External vibrators are usually employed on metal forms, plus internal vibration as necessary. Concrete should not be poured in layers more than 400 mm deep. While external vibrators can be moved to keep pace with the rising concrete, it is advisable to fit the forms with a sufficient number of units so that they do not need to be moved during the pour; only those vibrators on the part of the formwork being filled are switched on. 42


It is not advisable to vibrate near the bottoms of the formwork legs fixed to the foundation. Empty or partially-filled forms should not be vibrated. Vibrators may be started singly or in rows, but only level with the newly-poured layer, not lower than the previous layer. The Contractor must submit to the Engineer a file showing: • that the formwork system is sufficiently robust and rigid, • that the assemblies are reliable, • that the joints are leak-proof, • that the vibrators are shown on the drawings of the formwork system (numbers and positions), • that vibration times and frequencies have been stated and justified, • that the start and stop commands are given in the working procedure, • that the form filling rate will be fully controlled. In all cases, suitability tests must be run. 5.4.8 - Concrete Hardening Minimum concrete strength before striking forms must have been justified in design notes furnished by the Contractor. Strength must be sufficient to ensure that the various parts of the concreted structure will not be subjected to excessive loads or cracking caused by stresses in the structure when striking formwork. The minimum compressive strength generally adopted for striking crown forms is 10 MPa and the minimum time for circular forms to be left in place is 10 hours (to be amended according to actual section geometry and concrete properties). A cure-meter must be used when the work rate is one cycle per day, in order to check that the required strength has been reached. Recommendations in the Technical Guide entitled "Structural Concrete Strength – Maturity Meter" (in French) published by LCPC, March 2003, will become part of the Contract. This method will in this case be preferred to crushing concrete specimens. It must be remembered that premature form striking may cause: • excessive deformations liable to render the part concerned unfit for the purpose for which it was designed, • abnormal and early cracking of parts in tension, • long term deleterious micro cracking. Conversely, overdue striking may also detract from concrete quality. (See fig. 45 and 46)

5.5 - Special items 5.5.1 - Portals We shall only concern ourselves here with parts of portal structures concreted with the tunnel formwork, involving in most cases modifications to the formwork structure. Particular points to be addressed are: • Bracing the two forms (intrados and extrados) together with through rods or with rods at the bottom and a tendon at the top joining the two forms together, • The extrados usually has to be fitted with concreting windows, vibrators and safety walkways,

AFTES Guidelines GT36

Examples of Typical Full Cycle

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

Figure 45 - Concreting of Schirmeck Tunnel Lining

Ring length 10m, Concrete Volume 60 m3 approx. – 1 no. 30 m3/hr pump, 24 hours full cycle

Figure 46 - Concreting Record for Monts Tunnel Lining


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• The reinforcing steel, whose fixing requires some extra precautions, • It may be possible to pre-assemble the steelwork provided this has been considered in good time in the design process, • Concreting conditions, which will differ from those associated with the main lining rings, • Architectural features must be incorporated with little or no modification to the formwork, • Special form end stops must be made up, and also incorporate any special architectural treatment, • The extrados sometimes has to be amended to suit conditions with the surrounding ground. 5.5.2 - Niches and Intersections The particular points requiring precise study in connection with niches and intersections with other minor tunnels are: • Fixing forms to formwork system and seals at points of contact, • Steel fixing if applicable, • Impact on basic concreting cycle, • Possibility of large niches or cross galleries leading to unbalanced loads on formwork, with the prestressing struts on the opposite side having no reaction, • Workability of a concrete mix capable of flowing into all voids. (See fig. 47, 48 and 49)

5.6 - Special cases 5.6.1 - Contact Grouting Any remaining voids, chiefly at the crown, between the lining and the sealing/support system or bare host rock, must be filled with grout using a fine sand mortar mix; the same cementitious material must be used as for the lining. In general, grout and vent holes or grouting stub pipes fitted into the forms (50 mm dia.) are arranged in a three-arm fan pattern around the roof arch. Grouting pressures must be kept moderate (0.3 MPa at the manchette valve) because it is only a matter of filling voids. The grout pipe stubs must be fixed to the forms (this requirement must be kept in mind when designing the formwork system); they must not penetrate the waterproofing system and must not collapse during concrete pouring. Rigid plastic tube is better than metal pipe. A few precautions must be taken to control the formation of voids between the host rock with its temporary support and the permanent lining and so keep the amount of grouting to a minimum: • Partially fill any serious overbreaks produced during excavation, by spraying shotcrete. In the particular case of large overbreaks at the crown, these should be filled with concrete after the permanent lining is in place, and grouting stub pipes must be provided at the appropriate spot (diameter 100 mm or 125 mm). • Build the permanent lining from the lower end of the tunnel and work upwards, and inspect the crown end stop to see that the concrete is flowing into this part. • Finish by pressure pumping, using two crown pipes instead of one, without exceeding the specified refusal pressure used in designing the formwork (localised and general effects). Void-filling grouting must the done with care and be monitored. The necessary plant and equipment must be planned for in the main works schedule and the job may be done in a single operation or in sections, depending on tunnel length.

Figure 47 - Shuttering for asymmetrical fire niche with false sidewall (at back, interconnecting gallery between tubes)

Figure 50 - ??????????

5.6.2 - Special Concrete Mixes Figure 48 - Forms for symmetrical safety niche

Figure 49 – Installing wood form for niche

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5.6.2.1 - Self-Compacting Concrete The special features of self-compacting concrete to be considered in the design are as follows: • The very fluid consistency calls for special joint sealing arrangements (end stops, interface between formwork and parts of the tunnel already concreted),


• Filling may proceed through low-level grout pipes in the sidewalls, • Self-compacting concrete must not be allowed to fall from any significant height into the formwork, • The absence of vibration improves completion times and working conditions (less noise), • Filling can be done through pipes alone, although the windows are still needed in order to supervise the rising concrete level. It is important to concrete a test ring to check that there is no segregation in pumped self-compacting concrete. 5.6.2.2 - Lightweight Concrete The general principles discussed above for conventional concretes remain valid for lightweight concretes. However, consideration must be given to the light weight of the aggregate which means less spread, reduced consolidation and void-filling efficiency, and reverses the segregation problem. Lightweight concrete is recommended for filling voids in the crown (especially overbreaks). Therefore, the Contractor must: • provide more concreting windows than for standard concretes, • place tubes through the lining, especially in the crown, • increase the number of vibration points, • check and adapt the vibration equipment if necessary (e.g. use high frequency poker vibrators), reduce vibration time. 5.6.2.3 - Heavyweight Concrete The general principles discussed above for conventional concretes remain valid for heavy concretes. However, consideration must be given to the problem of high density aggravating the segregation problem. This type of concrete is not recommended. 5.6.3 - Special Concreting Conditions 5.6.3.1 - Heat Treatment If the contract so specifies, the Contractor may propose heat treatments to speed up concrete hardening provided it has no deleterious effect on the medium- and long-term performance of the concrete. The proposed treatment must be justified in a memorandum with references and instructions to be followed in order to achieve the claimed results. In all cases, the concreting procedure must state the technique, equipment and supervision proposed. Generally, heat treatment may consist simply of hanging flexible screens at the ends of the formwork system to stop air currents (consideration must be given to the possibility of interfering with vehicular traffic) with an electric or other type of space heater or electrical resistance heaters for the form liners. This type of system may be supplemented by applying heat insulation to the form liners (sprayed insulation for example). This type of heating treatment must be accompanied by monitoring concrete conditions with the aid of a cure-meter, thermometers for monitoring ambient air temperature and a control system for regulating heating system output.

5.6.3.2 - Cold Weather Concreting Rules for placing concrete in cold weather are fully described in the regulatory documents relating to concrete. The main points are however repeated in these Guidelines. A considerable proportion of lining concreting work is often carried out in winter with a low air temperature. When the air temperature measured at the place of work falls below - 5°C, no concrete placement will be allowed except as otherwise provided for in the contract, such as when long interruptions to activities at sites subject to severe weather are to be avoided. When temperatures lie between –5°C and 5°C, concrete placement may be permitted provided suitable steps are taken to protect the concrete from the deleterious effects of the cold. In all cases, the Contractor must make the following minimum arrangements: • The concrete must be kept within a temperature range of 10°C to 20°C when mixing, transporting, pouring and setting. • The required temperature of concrete being mixed may be achieved by heating the ingredients or the whole mix (in the first case, mixing water should not be hotter than 60°C and aggregate should not be hotter than 80°C). • Adequate instrumentation must be provided to check the internal temperature of the concrete by casting specimens to verify concrete strength. The required results can also be achieved by: • using, if the nature of the works permits, high heat of hydration, high early strength concretes (CPA CEM I 52.5 or 52.5R, CPA CEM I 42.5R), • preventing heat loss from the heating systems: - either by insulating the concrete and/or the forms by means of materials exhibiting low heat conductivity and hanging screens to prevent cooling, - or by providing additional heat energy input by using heated forms and screens or heating the concrete directly by means of heating coils embedded in the concrete, or by autoclaving (concrete temperature must not exceed 60°C). The corresponding working procedure must mention the arrangements and resources the Contractor is intending to assign if there is a danger of the outdoor temperature dropping below +5°C at any time during the construction period. The Contractor may decide to design a special concrete mix, based on a reduced water content and incorporation of the appropriate admixtures, a higher cement content or changing to cements of the kind mentioned above. If concrete pouring is interrupted due to cold weather and there is no protection, any damaged concrete must be demolished. 5.6.3.3 - Hot Weather Concreting Hot weather is frequently a problem in short urban tunnels in which the tunnel ambient temperature is the same as that aboveground. Because of the risk of cracking due to thermal gradients, if the temperature measured at the spot where concrete is to be poured is greater than 25°C, the Contractor must submit to the


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Engineer (with reference to the concreting schedule) the remedies he proposes to adopt. Such remedies include: • use of chilled mixing water, • reduced time for mixing, transport and pouring, • use of different cement if possible, selected from those generating the least heat of hydration. This possibility must be planned for in order to avoid changing cement in the course of the works.

5.7 - Re-use of formwork systems 5.7.1 - Dismantling Formwork Systems Activities involved in dismantling the formwork system for re-use must be studied while the system is being designed, because certain factors may impact on the design. This is particularly true where items have to be bolted rather than welded. A special procedure drawn up jointly by the Contractor and Supplier must be submitted for approval to the Engineer in Charge of Temporary Works before being submitted to the Engineer. The procedure must state: • The location of the dismantling yard with a description of the surrounding environment, and identifying external constraints, • The dismantling operating procedure, • Means of controlling noise and other nuisances, • Lifting and handling machinery to be used, • Temporary means of ensuring stability of the system, • Means of transport required, • Means of reinstating the dismantling yard on completion, • Time required, etc. If the formwork system is to be written off, it must be removed from site in the manner specified for disposing of waste in the general Quality Assurance Plan for the tunnel project. 5.7.2 - Formwork System Maintenance Use of the tunnel formwork systems must be integrated into the general production cycle and overall works sequencing for other activities after the tunnel lining works have been completed. Maintenance of the production tool is therefore vital for meeting the partial completion times and for the safety of the workforce. Maintenance must be performed regularly to check the condition of the various parts of the system, according to a predetermined list. The more important checks to be made are: • Safety-critical items for workmen: access, safety barriers, signage, lighting, etc., • Electrical and hydraulic systems, • Safety controls (remote controls, emergency stop on translation motion, etc.), • Sliding parts and contact surfaces, • Etc. 5.7.3 - Temporary Storage In the event that the formwork system is put into temporary storage or is to stand idle for any prolonged period of time, it is preferable to protect the form surface against corrosion.

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Protection may consist of applying a plastic film (although there would be a danger of condensation) or wax; both products must be completely harmless for workmen and the form surfaces. The user must have considered beforehand how the formwork system is to be cleaned before re-entering service. High pressure water (hot or cold water, with added inert soap for example) should be preferred over any other method; solvents must not be used. Preparation for storage must be covered by a procedure prepared jointly by the Contractor and Supplier and submitted to the Engineer for approval. It must address among other things: • Temporary elements needed for stability, • Location of the storage yard, with system of collecting and disposing of waste water, • Safety-critical items (special signage, access), • Protection products, • Operating procedure for applying and removing protection from form surfaces, • List of activities for safeguarding the equipment incorporated in the formwork system (electrical and hydraulic equipment). 5.7.4 - Re-use of Formwork Systems If tunnel geometry is relatively similar, re-use of the formwork system may be considered under certain conditions. The main points to be checked are listed below, and it may be necessary to prepare a design modification project to be submitted to the Engineer and Owner if there is an impact on the final geometry. In particular: • compatibility of formwork system geometry with project, • feasibility of modifications to be made to the formwork system for the purposes of adaptation (clearances, sidewall height, radii of curvature, etc.), • compatibility with existing pivot points, • condition of: - form liner, - mechanical framework and adjustment devices, - jacking (mechanical or hydraulic) and translation (bogies, motors) systems, - safety items (safety barriers, etc.), - electrical, hydraulic and pneumatic interlocks, - concreting hatches and stub pipes. Re-using an existing formwork system is not necessarily more economical than having a new one and a special study is necessary before starting on renovating an existing system. If re-use is a possibility, the Contractor must check that the original design calculations are concordant with the new criteria (concrete thickness, concrete pouring rate, unbalanced sidewaysacting loads) and preferably award the job of making the necessary modifications to the Supplier who built the original system.


6 - LINING CONSTRUCTION SUPERVISION 6.1 - Specific testing and inspection challenges Building a lining in a tunnel has a major impact on the project construction programme and the critical path in the works schedule, as well as on the final appearance of the tunnel, i.e. the visible part of the underground structure. Testing and inspection activities specific to the tunnel lining demand as much thought and care as other aspects of the project and the resources allocated to it must not be diminished at each level.

6.2 - Level of supervision In every underground engineering project (road, rail, water and wastewater tunnels), testing and inspection is always necessary and as a general rule, both in-house and independent inspection organisations are involved. For the tunnel lining work, the various levels of supervision (internal, external and independent) ensure that the lining is built in accordance with the contract. • Works quality control is exercised by the Contractor's in-house (internal and external) supervision organisation. • The cost of internal supervision is included in the Contract rates and prices and there are specific items for external supervision in the Schedule. • The independent supervision body has the duty of checking the performance of the in-house supervision organisation and the cost is borne by the Client.

6.3 - Types of supervision 6.3.1 - Internal Supervision The internal supervision organisation must be described in the Contractor's Quality Assurance Plan, and is normally determined by the Contractor's undertaking with respect to his ISO certification. Internal supervision is exercised by the personnel performing the work and their superiors. The paperwork involved consists of forms, reports or a journal. 6.3.1.1 - Concrete Testing and inspection of concrete mixes is performed as described in the documents applicable to the contract: • Standard NF EN 206-1 • Fascicule 65A or other standard specification • The particular specification written as part of the contract documents. If self-compacting concrete (SCC) is used, special procedures to be followed are mentioned in part in these Guidelines or, failing that, in the typical contract specifications written by the SCC National Project. The main focus of the internal supervisory organisation's attention concerns: • design,

• suitability (fit-for-purpose) tests and information tests, • breakdown of activities, • curing system design and monitoring. 6.3.1.2 - Operation of Formwork System and Concreting The internal supervision organisation must monitor the following points in particular: • Setting up formwork system on station (tolerance, seals, locking, contact under previous lining ring), • Seals around end stops (including protective strip), • Concrete pouring rate (rate of rise behind the form) and alternating truckloads between left and right sidewalls, • Concrete quantities, consistency, duration, waiting times, etc., • Concrete consolidation (refusal pressure), • Form striking (effect of suction and asymmetrical lowering). 6.3.2 - External Supervision The Contractor must submit to the Engineer an external supervision scheme and the arrangements he has made for ensuring these supervisors are truly independent of the production personnel. Once the external supervision organisation has been finalised, the manager must select competent design offices and/or testing laboratories (for concrete especially); these services demand a high level of organisation and coordination. 6.3.2.1 - Verification of Formwork System Drawings and Design Notes Drawings and design notes for the formwork system must be checked by a design office specialising in steel structures, unconnected with the project workforce, design personnel and formwork system manufacturers. The external supervision organisation must check the technical documents and its verdict may require repeated exchanges between the supervisory body and the Supplier of the formwork system. Once the document has been finalised, it is forwarded to the Engineer for approval. 6.3.2.2 - Monitoring Manufacture of Formwork System Formwork manufacturing tolerance must not be more than half the acceptable corresponding tolerance on the finished structure and the external supervision organisation must assess and measure if necessary deviations from nominal dimensions, lines and levels, particularly on critical parts of the formwork system, small parts, slack and accuracy of assembly. 6.3.2.3 - Performance of Concrete Suitability Tests The purpose of the suitability test is to check that the concrete mixed (i) according to the nominal formulation specified in the design and checked by the internal supervision organisation, or (ii) on the basis of a standard composition having references to support it, is placed under the conditions obtained on site in accordance with the requirements of the Contract. The suitability test must address the actual time for transporting


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the concrete and the material resources planned for transporting and pouring it, in accordance with stipulated temperature and waiting time parameters. If an air entraining admixture is to be used, the concrete must be placed with the plant and equipment to be actually used for the job. 6.3.2.4 - Validation of Concrete Plant and Machinery Depending on the complexity of working conditions, attention must be given to the following: • mixing plant installations, in particular, aggregate stockpiling and means of heating aggregate if applicable, • concrete transport, especially over long distances and in hot weather, • temperature, humidity, airspeed at the place where the concrete is to be placed, • availability and condition of concreting plant and machinery (including replacement plant on stand-by), • aids to filling form with concrete (distributor system for example). 6.3.2.5 - Checks on Next Ring to be Poured before Moving Formwork System Forward a) Geometry of Cross Section Profile The transverse profile as-driven (with or without temporary support) must be checked before installing the waterproofing system or before moving the formwork system forward if the tunnel is not waterproofed, the purpose of the checks being to ensure that the concrete lining will possess the minimum design thickness everywhere. The test may consist of moving a template along the whole tunnel from one end to the other, consisting of a hoop and stiff adjustable rubber slats (capable of being adjusted if necessary to fit nonstandard profiles) or laser profiler. This profile check must be made at least 100 metres ahead of the lining or waterproofing installation in order to leave time for any trimming that might be needed (with the Engineer's permission) at tight spots. The external supervision organisation must produce a clear, legible inspection report showing deviations from the design line (intrados + nominal concrete lining thickness). The distance between check points on the perimeter should be of the order of 150 mm or be continuous if using a profiler, and in this case, profiles must be recorded every metre. b) Host ground with or without temporary support and before installing waterproofing system The external supervision organisation must check, among other things: • the cleanliness and condition of the host ground (no sharp metal projections, no bolt heads not cut back, appearance of shotcrete compliant with the requirements of the Waterproofing System Specification), • that leakage into the tunnel (either as concentrated flows or damp oozing patches) is collected and drained away, • position and geometries of foundation ledges, • and, if the design does not include a waterproofing complex: - positions of reinforcement and spacers, - positions of inserts set in place with the reinforcement.

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c) Host ground after installing waterproofing system The external supervision organisation checks the following points: • Quality of the waterproofing, referring to the internal supervision documents, more particularly welds, anchorage on foundation and compartmentalisation, • Method of dealing with any leaks and drainage, • Installation of protective strips at joints between lining rings, • Position of reinforcement, if any, and spacers, • Position of inserts set in place with the reinforcement, • Seal at contact between sidewalls and ledges. 6.3.2.6 - Acceptance of Formwork System before Commencing Lining External supervision consists of checking successful completion of the following tasks: • Transport of parts from manufacturing works, • Temporary storage on site, • Erection and adjustment of parts, • Building running tracks, • Translation of formwork system to site of lining ring to be built, • Formwork system turnaround if applicable. The external supervision must check compliance of: • the general geometry of the assembled formwork system (respect of tolerances), • the various operations carried out with the formwork system. 6.3.2.7 - Testing Positioning of Formwork System The following must be verified in connection with the operations necessary for positioning the formwork system where the next lining ring is to be built: • Results of the optical survey of the foundation and shoulder / crown interface, • Accurate positioning of the formwork system on all three axes, • Levels of brackets for ventilation duct slab (if any), • Positioning of secondary forms (niches, galleries, refuges, branches off), • Condition of form liner (clean, smooth, oiled, seals at joints), • Placing of inserts, box-outs and reinforcement if applicable, • End stop quality and protection for waterproofing system, • Placing concreting vents, • Condition of seals on formwork system and concreting windows, • Condition of vibration system, • Condition of concrete placing plant and machinery (including stand-by gear). Concurrently with these operations, the formwork runways must be built and checked with sufficient lead time. 6.3.2.8 - Verifications while Pouring Lining Ring a) Monitoring concrete deliveries The external supervision collects the concrete mixing plant delivery chits showing at least the following information: • Nominal concrete mix formulation, • Actual quantities of each ingredient in every batch,


• Date and time mixed, • Duration of mixing, • Wattmeter reading, • Concrete consistency using slump test or spreading table methods, • Entrained air if applicable, • Volume of load, • Transport and waiting times, • Concrete temperature when poured, especially in very hot or cold weather. Besides sampling for mechanical tests, there must be at least one slump test at the start of each pour and regularly thereafter (e.g. every 30 m3 to 50 m3 or two tests per lining ring) or if and when visual inspection is inconclusive. For all works or parts of works classifying as exposure class XF2, the entrained air content of the fresh concrete must be measured at the same time as the consistency determinations. b) Supervision of concrete pouring Alongside these measurements in connection with the concrete, the external supervision organisation must check: • Operation of the pressure limiters on hydraulic cylinders, • Correct form filling through the concreting windows, • Actual pouring conditions must comply with the design assumptions (rate of rise per hour per sidewall, differing level of concrete between sidewalls), • Deformations of forms (visual inspection and/or optical survey), • Possible need to provide vents where there were major overbreaks, vents to be fixed on the temporary tunnel support or waterproofing system, • Reinforcement and embedded items must not be displaced, • Crown must always be finished off by contact grouting, • Rules for striking formwork (hardening time, concrete strength development, etc.), • Concrete curing (product, water, tools, curing time, etc.). 6.3.3 - Independent Supervision The primary duty of the design office or expert laboratory engaged by the Client is to oversee the performance of the Contractor's internal and external testing and inspection organisation, using spot tests if necessary. The independent body may also perform unannounced tests but these test results may not substitute the tests performed by the Contractor's concrete laboratory or surveyor. The independent supervision body may also address: • Formwork quality: condition of surfaces, geometry, • Concrete quality: form filling, strength at time of striking forms, 28-day strength, • Final clearances as designed: nominal geometry as specified in contract, • Condition of box-outs: numbers, positions, • Quality of exposed concrete surfaces, and parts moulded in relief (brackets) and recessed (chases). This list is merely an illustration of what might be required. Points to be checked must be relevant to the Client's criteria (importance of clearances being as designed, quality of exposed concrete, etc.).

6.3.3.1 - Concrete Control Tests Concrete control tests are the primary means of ensuring that every batch of concrete incorporated into the works meets the requirements of the contract specifications. They address concrete strength in particular, sometimes also concrete consistency and if necessary entrained air content. Control test specimens must be prepared and kept in the manner described in Standard NF EN 12390-2 and documentation Fascicule FD P 18-457, which set forth the requirements stemming from French experience. Standard NF EN 206-1 authorises reference being made to other nations' experience, where an agreement between users and producers explains the procedure for performing some of the control tests. Concrete test specimens must be kept out of the weather, in a place where the temperature remains between 15°C and 30°C. If suitable premises are not available, it is acceptable for the specimens to be kept in heat-insulated boxes on site when the ambient temperature falls below 15°C. Specimens must be placed in a controlled atmosphere within three (3) hours of removal from the moulds. The concrete modulus must be checked to ensure it remains within the design envelope. 6.3.3.2 - Post-placement Vérifications a) Exposed concrete surfaces Contract compliance is checked at different stages in the construction process, particularly on the first few lining rings concreted. • If any intermediate inspection is found to be non-compliant, the Contractor must submit his proposed corrective measures to the Engineer for approval. • If the final inspection of the completed work is found to be noncompliant, the Contractor must submit to the Engineer the methods and procedures he proposes to use in order to comply with the contract. Surfaces are considered compliant when they comply with shape, texture and colour criteria for the categories into which they fall. Since the lining is curved, the general appearance of the visible surfaces will be judged by standing back from the surface under inspection, at a distance of 10 m in principle or closer if there is not enough room. The use of a 2 m-long straight edge as stipulated in Fascicule 65A is inappropriate in tunnelling work, even though it is mentioned in this document. The inspection must be done in dry weather not sooner than fifteen days after striking the formwork, with sufficient lighting, similar to the permanent lighting to be installed subsequently. The 20 cm straight edge described in Fascicule 65A will be used to check small flaws. b) Acceptance of exposed concrete surfaces • Plain finish Surfaces must be free from exposed reinforcement, significant segregation of the aggregate and honeycombing.


49


• Fine finish Fine finish surfaces must be free from the following defects: - Exposed reinforcement, segregation or honeycombing, - Deformation such that f > 3 mm or F > 4 mm, - Misalignment between adjacent panels greater than 1 mm, - Wood fibre or other foreign matter trapped in concrete, - Patches where concrete skin has been torn off, - Spalls, - Rust stains, - Runs of laitance, - Layering and mottling showing the different batches poured, - Obvious cold joint between concrete lifts, - Severe colour discrepancies between form panels, - Extensive air pitting (blowholes), - Bleed line. • Featurework In addition to the above defects, wrought surfaces must also be free from the following: - Cracks, - Small scale mottling, - Circular stains due to laitance leaks. Tasks involved in building the tunnel lining Excavation - Check clearances - Acceptance of excavation - Trim profile if necessary Waterproofing system behind permanent lining - Inspect before concreting - Waterproofing system protection present Formwork, embedded pipe and ducting, etc. - Geometry of formwork system - Cleanliness - Positioning - Box-outs, inserts - Ducting

Critical points (internal and external supervision)

Stop points cleared by Engineer

x x x

x x

x x

x x

x

x x

x x

Reinforcement

x

x

Concrete - Approved mix - Suitability (fit for purpose) - Supervision of mixing - Supervision of pouring - Striking forms

x x x x x

x x

Contact grouting (if applicable) - Approval of mortar or slurry mix - Suitability (fit for purpose) - Supervision of mixing - Supervision of grouting lining rings des plotsa

50

x

x x x

x x

x

x


c) Checking form filling In some cases, it may be necessary to check that the forms are completely filled with concrete, and this may be done with ground penetrating radar apparatus.

6.4 - Critical points and stop points The following list of critical and stop points are mostly taken from the contract documents and Quality Assurance Plans of the parties involved: • Critical points require the Engineer to be notified in advance in order to enable him, if he judges it useful, to perform his independent inspection, although this does not place any restriction on the continuance of the activity. • Stop points are critical points requiring formal permission from the Engineer or from a body empowered by the Engineer before the activity in question may proceed. A general list is tabulated. It has to be adapted to suit the type of works in question and be incorporated into the contract specification by the Engineer.

6.5 - Treatment of non-conformities 6.5.1 - Classification of Non-Conformities Two levels of non-conformity can be identified: • Minor non-conformities that do not interrupt the work and can be dealt with by modifying the design (resurfacing, filling, modifications to equipment to suit critical clearances, minor groutable cracking, etc.) • Major non-conformities that entail demolition of all or part of the affected works. The non-conformity report form must state the level of gravity of the defect so that the time required for making good can be set. 6.5.2 - Means for Treating Non-Conformities Non-conformities are recorded on the non-conformity report form by the internal supervision organisation or on a works inspection form by the independent supervision body. Also shown on the non-conformity report form are the means, materials and method for making good the defect. In view of the activities which come after the construction of a road tunnel lining for example (concrete slab to form ventilation duct, civil works for utilities contractors, carriageways, etc.), the Contractor must be given an appropriate deadline for making good the defect before the next task can start in the relevant area. The Engineer sets the time allowed for the Contractor's response on the basis of the objective of the type of works in question. If there is an overrun, the Works Engineer must issue a formal order for the repairs or demolition of the works.


7 - SAFETY 7.1 - Safety and formwork system design The structures used for building tunnel linings are classed as machines and as such they must be designed in keeping with the regulations, which impose two types of duty: • The design must comply with the technical requirements for new machines, according to the design rules in Annex 1 of Article R233-84, • Design must follow procedures for conformity certification as relating to EC self-certification as described in Article R233-53. General requirements are set forth in the IMRS document entitled Design of Working Equipment and Means of Protection. The designer must analyse identified risks to eliminate them, inform users of any residual risks, state what special training is needed and whether or not individual or collective protective equipment is necessary. The designer's attention must focus on the undermentioned items, among others. 7.1.1 - Moving Parts Moving parts must be designed, made and positioned in such a way as to avoid any risks and, if risks subsist, the parts must be provided with protective devices. Parts of the machine on which people are liable to have to walk or stand must be designed in such a way that they cannot slip, trip or fall. Furthermore, the machine must be designed in such a way that there can be no possibility of contact with the wheels or tracks when the driver or other on-board operatives are in the operating position. 7.1.2 - Access and Working Items All stairs, ladders, landings and walkways must allow the workforce to reach their workstations and perform their jobs in safety anywhere on or in the machine, allowing for the lack of space in some parts the machine. Where there is danger of falling objects, the machine must be equipped with the necessary protective devices. The design and fabrication of formwork systems must take account of the following requirements: • Minimum width of working platforms: 1.00 m • Minimum width of access walkways and stairs: 0.60 m • Headroom: 1.90 m • Minimum height of safety barriers: 1.10 m • Minimum height of toeboard: 0.15 m • Avoid salient corners in the load-bearing structure and supporting components to the form liners, provide protective devices if necessary, • Landings and floors must be solid non-slip chequer plate (try to avoid the use of wooden boards), • There must be elevated landings at the front and rear of the formwork system providing convenient access to the front end form stop and the construction joint at the rear,

• Access ladders must have safety hoops and landings for heights greater than 4 m. 7.1.3 - Concreting Tools and Accessories The tools and accessories needed for concrete pouring must be selected such as to limit manual work and its strenuous nature. This applies to: • Routing the concrete pour by manhandling large heavy hoses; a monorail with hoists should be provided, or better still, a concrete distributor, • Use electric poker vibrators and form vibrators to keep down noise, • Use water to clean concrete delivery lines rather than a foam pig pushed through by compressed air, • Keep the use of compressed air to a minimum, because it raises dust and is noisy. 7.1.4 - Ancillary Components for Translation, Positioning and Form Stripping These are complex and delicate operations; even if the formwork system operator is fully conversant with the controls, he must know and fully control the range of operations he must perform, especially: • Coordination of vertical, horizontal, transverse and longitudinal motions which may be manual or electric/hydraulic powered motions, • Sound alarm to warn workforce before starting a manoeuvre, • Check the track has been laid correctly, and is firmly fixed and stable, • Check safety pins which must be provided on certain moving parts such as the skirt props, adjustable feet, etc.; they must be easy to pull, • Inspect braking and blocking systems, make sure they are capable of holding the machine stationary, whatever the gradient. 7.1.5 - Fluids Pressure Pipes and hoses carrying fluids under pressure must be able to withstand external loads without damage and must be firmly attached and protected. Emergency stop controls must always be provided. They must be highly visible and all workmen must know where to find them. 7.1.6 - Lighting Lighting suitable for all manoeuvres of the formwork system and associated tasks must be provided. The lighting installation must be inspected at the time of acceptance of the formwork system. 7.1.7 - Handling and Controls The various handling operations needed for the correct working of the formwork system must be incorporated at the design stage (remember to provide lifting handles). Controls must be designed so that no dangerous situation can


51


develop through incorrect manoeuvres. The machine operator must be able to see from the operating position that there are no people in the whole danger zone. A special warning should be provided for all dangerous manoeuvres (Figure 51).

7.2 - Definition of risks during construction work In view of the wide range of different geometries in the different types of tunnel, and the special features of each phase, a risks review should be carried out at the design stage, before work begins. The more important risks are: • body parts getting nipped or crushed, • eyes hit by flying solids and liquids, • back injury, • being run over or hit, • falls from heights, • burns, • damp, cold, heat, harmful fumes, etc. from the atmosphere, • assembly of formwork system (crane, trucks, digger arm, etc.), • when pouring concrete: - concrete distributor (manhandling hoses filled with concrete and at height), - cleaning lines on completion of pour (with air or water), - form vibration (electric or compressed air vibrators), • when moving to next station, setting up and form striking, • etc.

7.3 - Protective equipment 7.3.1 - Individual Protection Compulsory personal protection includes at least: • hard hat, • gloves, • safety boots, • goggles or safety glasses, • ear protectors and defenders.

Figure 51 - Formwork circuit diagram and controls

7.1.8 - Starting The machine must only start as the result of a voluntary action on a control specially provided for this purpose. 7.1.9 - Emergency Stop An emergency stop control must be provided except if the control being used returns automatically to its neutral position when released by the operator. 7.1.10 - Instruction Manual The geometry of the formwork system must consider safety issues from the earliest design stages, and lighten the men's workload. All machines must be accompanied by a highly detailed and very easy to understand instruction manual, drafted jointly by the formwork system supplier / manufacturer and Contractor. The manual is issued to the works director and formwork system manager.

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7.3.2 - Collective Protection Collective protection comprises (i) all the systems and devices built into the formwork system as already described, and (ii) the following: • Fire-fighting equipment based on all types of fire extinguishers (electric fires, hydrocarbons, etc.), • Audible alarms during movements of the formwork system and potentially dangerous manoeuvres of the forms for hydraulicallypowered formwork systems, • Plastic or canvas sheeting at the ends of the formwork system such as to confine a clean working area free from draughts and preventing unannounced traffic movements through the portal frame, • Traffic lights controlling movements of machinery and vehicles through the portal frame of the formwork system and physically separate areas for formwork and concrete pouring activities and traffic movements, • Warning system based on air monitors for identified risks from harmful fumes.

7.4. Training There is no nationwide training scheme; the only effective training is dispensed within the company by site foremen, experienced workers and senior staff.


Before shuttering and pouring concrete for the lining crown but after the Manufacturer has issued the formwork system operating manual and the Contractor has issued a job-specific health and safety plan, the Manufacturer must organise a demonstration of the motions of the formwork system and safety conditions to be observed. The senior staff in charge of the tunnel lining work must train the workforce in the proper use of the formwork system and safety rules before commencement of the lining works.

Training, awareness enhancement and repeated safety announcements must be continually provided with back-up, if necessary, by contributions from the CRAM (regional sickness insurance fund), OPPBTP (construction industry professional prevention organisation), occupational doctor, Engineer, Safety Coordinator, etc.

s REFERENCES Fascicules • Fascicule 65 du CCTG : Bétons… • Fascicule 67 du CCTG : Etanchéité • Fascicule 69 du CCTG : Travaux en souterrains Dossiers, catalogues, notices, proceedings and guidelines • Annales de l’Institut du bâtiment et des travaux publics N°526 - Septembre 1994 - Etude de la fissuration du béton dans le cas des revêtement de tunnels • CETMEF - Notice sur la surveillance et l’entretien des tunnels canaux avec catalogue - 2000 • Dossier Pilote du CETU Géométrie 1990 • GTFE (Groupe [permanent] de Travail Francophone des Exploitants) – Ministère des Transports - CETU • Guide technique " Résistance du béton dans l’ouvrage, la maturométrie " - Ministère des Transports - LCPC - 2003 • Guide du béton coffré en tunnel – CETU Centre d’Etudes es Tunnels - Direction des routes - 1983 • Guide de l’inspection du génie civil des tunnels routiers - Ministère des Transports - CETU - 2004 • Guide technique du LCPC - Défauts d’aspect des parements en béton - Ministère des Transports - 1991 • Catalogue des avaries Tunnels ferroviaires (Livret K) - Cotation des OA - SNCF - 1996 AFTES Guidelines • GT7 : Réflexions sur les méthodes usuelles de calcul des revêtements - TOS N°14 / 1976 • GT7 : L’utilisation du béton non armé - TOS N° 149 / 1998 • GT9 : Etanchéité - TOS N° 159 / ???? • GT14 : Catalogue des défauts apparents des tunnels complété par une nomenclature des parties d’ouvrages en tunnels - 1980 • GT14 : Méthode de diagnostic pour les tunnels revêtus - HS 3 Chambéry • GT29 : Utilisation des règles et normes générales de conception et de dimensionnement pour les revêtements en béton armés et non armés TOS N°165 / 2001 • GT31 : Peinture des parements en béton - TOS N°178 / 200…. • GT35 : Gestion et valorisation des matériaux - TOS N°199 / 2007 • GT37 : Comportement au feu des structures de génie civil (Recommandation en cours) • Article "Vers les moyens de prévenir l’écaillage du béton en tunnel" - TOS N°196 / 2006 • Article "Pression au bétonnage" - TOS N° 121/ 1994 • Article "Utilisation du béton non armé en tunnel" - TOS N°149 / 1998 Standards • NF EN 197- 1 : Composition, spécifications et critères de conformité des ciments courants - Février 2001 • NF EN 206-1/A1 : Béton - Partie 1 : Spécifications, performances, production et conformité (amendement à la norme NF EN 206 -1 avril 2004 et IDC P18-325 -1/A1 - avril 2005 • NF EN 206-1/A2 (IDC P 18-325-1/A2 - Amendement 2) - Béton - Partie 1 : Spécification, performances, production et conformité - Oct. 2005 .../...


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• NF EN 450 : Cendres volantes pour béton / Partie 1 : Définition, spécifications et critères de conformité (IC : P18-050-1) - Octobre 2005 • NF EN 934 - 2 - Adjuvants pour béton, mortier et coulis - Partie 2 : adjuvants pour bétons. Définitions et exigences - Avril 1998 • NF EN 1008 - Eau de gâchage pour bétons - Spécifications d'échantillonnage, d'essais et d'évaluation de l'aptitude à l'emploi, y compris les eaux des processus de l'industrie du béton, telle que l'eau de gâchage pour béton (P18-211) - Juillet 2003 • NF EN 12390 - 2 : Essai pour béton durci Partie 2 : confection et conservation des éprouvettes pour essais de résistance - Octobre 2001 • NF EN 13263 - 1 : Fumées de silice pour béton / Partie 1 : Définitions, exigences et critères de conformité (IC : P18-502-1) - Septembre 2005 • NF EN 13670 - 1 : .Exécution des ouvrages en béton - Juin 2003 • NF EN 14889 - 1 : Fibres pour béton. - Partie 1 : Fibres d'acier - Définitions, spécifications et conformité (indice de classement : P18-328-1). Octobre 2006 • NF- LH ou équivalent : Ciments conformes aux normes EN 197-1, NF P 15-317 (Prise Mer) et NF P 15-319 (Eaux sulfatées) • NF P 18 - 502 : Additions pour béton hydraulique - Fumées de silice - Mai 1992 • NF P 18 - 503 : Surfaces et parements de béton - Eléments d'identification - Novembre 1989 • NF P 18 - 506 : Béton - Réactivité d'une formule de béton vis-à-vis de l'alcali-réaction - Critères d'interprétation des résultats de l'essai de performance - Novembre 2004 • NF P 18 - 508 : Additions pour béton hydraulique - Additions calcaires - Spécifications et critères de conformité - Juillet 1995 • NF P 18 - 509 : Additions pour béton hydraulique - Additions siliceuses - Spécifications et critères de conformité - Décembre 1998 • FD P 18 - 457 (Fascicule de documentation) : Béton - Guide d'application des méthodes d'essais - Juin 2005 • Projet BRPR-CT98 - 0813 : Test and design methods for steel fibre reinforced concrete • Circulaire interministérielle n° 2000- 63 (du 25 août 2000) relative à la sécurité dans les tunnels du réseau routier national • ISO 15189 COFRAC : Organisme mis en place par les pouvoirs publics pour permettre aux laboratoires qu'il accrédite d'apporter la preuve de leur compétence et de leur impartialité • ISO 1518 : Test de résistance à la rayure • R233 84 du Code du travail. Décret no 92-767 du 29 juillet 1992 relatif aux règles techniques et aux procédures de certification de conformité applicables aux équipements de travail et modifiant le code du travail (deuxième partie: Décrets en Conseil d'Etat) • CM 66 additif 80 : Règles de calcul des constructions en acier • Eurocode 2 : Annexe Nationale française • Eurocode 3 : Construction métallique - Calcul des structures en acier et Document d'Application Nationale dont : • NF EN 1993 - 1 - 1 : Eurocode 3 - Calcul des structures en acier - Partie 1 - 1 : règles générales et règles pour les bâtiments (P22-311-1) Octobre 2005 • NF EN 1993 - 1 - 2 : Eurocode 3 - Calcul des structures en acier - Partie 1 - 2 : règles générales - Calcul du comportement au feu (P22-312-1) - Novembre 2005 • NF EN 1993 - 1 - 8 : Eurocode 3 - Calcul des structures en acier - Partie 1 - 8 : calcul des assemblages (P22-318-1) - Décembre 2005 • NF EN 1993 - 1 - 9 : Eurocode 3 - Calcul des structures en acier - Partie 1 - 9 : fatigue (P22-319-1) - Décembre 2005 • XP ENV 1993 - 6 : Eurocode 3 - Calcul des structures en acier - Partie 6 : chemins de roulement. (P22-360) - Avril 2002 • P22380 - 1 : Euro code 3 - Calcul des structures en acier - Partie 1 -10 : choix des qualités d'acier - Décembre 2005

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