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Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 2010

223

Fire protection options for concrete tunnel linings

Frank Clement

MEYCO Global Underground Construction,Division of BASF Construction Chemicals, Switzerland

DESIGN LIFE

The modern, reliability-based service life design for tunnels is implemented in most new designs and in re-

design of existing structures and has been adopted by national authorities and individual clients in

countries all over the world. Currently there are no real standards on how to design concrete for a specific

design life. The current concrete codes are recommending various mix designs and reinforcement cover for

design life of approx. 50 years

Tunnels are now usually designed for a service life of 100, 120 or even 200 years. This by far surpasses theassumed design life according to most codes and standards. All uncertainties regarding, the designer has to

take into account environmental exposure, material properties and deterioration modeling in order to meet

the required design life.

Thus service life design, based on functional requirements, can be carried out by sticking to the same

mechanical concept as the one that is used for structural design. Other issues that need to be considered in

relation to the required design life are water tightness of the lining and its behavior under a fire. Both will

influence the design life of a permanent concrete tunnel lining. By design concrete with high durability the

designer should also consider the behavior of the concrete during a tunnel fire and in some cases this

behavior is negatively influenced by the concrete mix properties and the used materials.

PRECAST SEGMENTS

Excavations of tunnels using an EPB or slurry TBM are requiring a high volume of segments [1]. These

segments are produced in specialized precast plants. Advantages of precast plants are the speed of

production in a controlled working environment ensuring constant quality of the concrete segment. Most

precast plants use computer controlled systems for the batch and mixing equipment with automatic

moisture control of the aggregates. This leads to a better quality, homogeneous mix with fewer variations in

workability and strength.

In order to comply with the required design life, sometimes more than 100 years, higher structural

performances and increased durability of precast structures are necessary. This is requiring a optimal use of

the materials and production techniques. State of the art admixtures are used in the concrete to provide

specific performances in the fresh, hardening and hardened stage for each application. Casting, compaction

and curing are carried out in controlled circumstances. This allows the concrete to reach the requiredperformances at a very early stage in the most efficient manner. It is now possible to produce precast

concrete elements having compressive strength grade higher than 100 MPa.

All precast producers have specific requirements and the aim is to produce elements in the most cost

effective manner but still complying with the national and international norms and the required life time.

To achieve this objective, the precast concrete producer must optimize his production process; reduce

material, labor and energy costs. In this process he may opt for a daily turn around of the casting beds using

relatively long curing cycles or he may opt for two or more production cycles per day. The main factor

which controls the production cycle is the compressive strength required for de-moulding, eventual pre-

stress transfer and handling of the elements. The requirements for compressive strength may vary from 20

MPa for ordinary reinforced concrete elements, to up to 45 MPa for certain pre-stressed concrete structures.

Superplasticisers are commonly used to enhance the workability of the fresh concrete for easy placement

and to lower the water cement ratio for increasing the strength using relatively low cement content. Heat


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curing (steam or electrical) is often used to accelerate the strength development for releasing the bed for the

successive cycle.

Typically, a precast process includes designing and producing a concrete mixture to achieve specific

properties such as high early strengths, placing the concrete in the forms, heat or ambient curing

(depending upon the climatic conditions) of the concrete elements, removal from the forms and handling of

the elements during transport and erection. In a state of the art plant the placing and consolidation ofconcrete is facilitated by utilizing the new generation of superplaticizers based on PCEs ( Poly Carboxylic

Ethers) and efficient vibration. Heat curing is normally applied to obtain the required strengths at the

desired early age.

The PCE polymers of the second generation (Admixture Controlled Energy, Glenium ACE) have been

designed according to a specific balance between the negatively charged carboxylic groups and the

hydrophilic side chains placed along the backbone in a specific molecular configuration. The mechanism of

action is based on the hypothesis that the polymers are adsorbed onto the cement particles and leave a

greater free surface exposed to water for hydration while maintaining the dispersion effect (Figure 1). This

effect leads to a faster activation of the hydration as compared to other superplasticizers. This leads to early

evolution of heat and rapid strength development.

Furthermore, the adsorption of this new polymer affects mainly the unhydrated cement and very slightly

the hydration products. For this reason, the crystallization reaction is activated in advance and not delayed

by further adsorption of the superplasticizer molecules. The early development of the heat of hydration can

further activate or accelerate the hydration of the cement. Therefore, the energy usually furnished from an

external source (steam or electric heating) is internally activated by this new type of PCE molecule. In

order to reach the required development of strength with the specific cement type, the PCE superplasticizer

tests have to confirm the compatibility of the cement with the PCE. The compressive strengths

development for cements A, B and C are summarizes in the table below. All concrete batches were

prepared and cured at same temperature.

Table 1: Concrete strenght development with different admixtures and cement types

Cement Type A Cement Type B Cement Type C

Time 16 hr 18 hr 16 hr 18 hr 16 hr 18 hr

Standard

PCE

17,6 N/mm 21 N/mm 19,4 N/mm 27,9 N/mm 8,7 N/mm 14 N/mm

Glenium

ACE type

41,2 N/mm 45,9 N/mm 41,3 N/mm 47,6 N/mm 35,5 N/mm 40,7 N/mm

Figure 1: New generation of plasticizers leaving cement surface area available for hydration

Figure 1 New generation of plasticizers leaving cement surface area available for hydration


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Admixture systems have to be tailored to meet the individual needs of the precast producer. It can be used

for optimizing the heat curing cycle, increase production by reducing the curing time, elimination of heat

curing, elimination of vibration or a combination of any of these parameters.

Precast tunnel segments example:Railway link Bologna - Florence

The high speed railway link between Bologna and Florence is a twin shaft tunnel of 6000 m length each

made with a Tunnel Boring Machine (TBM). The final lining of the tunnel is with precast concrete

segments of 40 cm thickness and a length of 1, 50 m. Each ring, of 16, 40 m volume, is composed of 7

segment plus one base element that will support the rail track. The plant is a carousel type designed to

produce 126 segments corresponding to 18 rings, each day. To meet the specifications regarding cement

type and content, maximum curing temperature and minimum compressive strength at demoulding, a mix

with cement content of 380 kg/m of CEM IV/A 42.5R and ACE type superplasticiser was adopted. The

consistence class is S1 because of the mould configuration and curing chamber temperature, maintained by

the hydration of cement, is 50C. The strengths at the time of demoulding at 6 hrs are above 25 MPa. This

allows 3 elements to be produced each day with the same mould, thus obtaining increased productivity

with the right choose of mixdesign and admixtures.

Precast tunnel segments example:Tunnel lining segments in U.K. for the Channel Tunnel RailLink

Carousel casting method using concrete with a

cement/fly ash blend (310/110 kg/m3) and steel

fibres was employed. Glenium ACE 30 was used in

order to achieve a water cement ratio of 0,36 and a

slump of 60mm. The segments were cured at 35-

40C for six hours. The average compressive

strength was 70 MPa at 28 days. About 300 rings

were produced each week.

CONCRETE BEHAVIOR UNDER FIRE

Clients and designers are increasing the required design life of tunnels by using high quality, dense

concrete [2]. Due to there low permeability these type of concretes resists to severe environmental

exposure. On the other hand during a fire these concretes can be subject to spalling, resulting in a reduction

of the durability and service life of the structure.Despite the benefits of its non-combustibility and low thermal diffusivity, low permeable concretes will

have the tendency to spall at lower temperatures. Concrete suffers from two problems during a fire:

- Deterioration in mechanical properties (particularly above 300C)

- (Explosive) spalling

The spalling of concrete is unpredictable and a number of factors are influencing this phenomenon [3].

Fire load

First we have to consider the influence of the fire like:

- Heating rate: a fast temperature increase is resulting stresses and tensions in the concrete.

- Maximum temperature: in a tunnel fire typical temperatures of 1100C to 1400C can be

reached

- Duration of the fire


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Concrete Composition

If we consider the materials the following properties have an influence

- Permeability

The permeability is influenced by the cement type, water cement ratio and the use of fillers

like silica fume. With the new types of superplasticizers lower water cement ratio, even below0,35, are used resulting in concrete with a low permeability.

- Aggregate type and size

Different types of aggregates have different thermal expansion coefficients which lead to

stresses in the concrete while it is heated. Also the maximum size will influence the spalling

behavior.

Moisture content

Concrete has always some water inside which is physical bonded in the pores. Depending on

the environment the amount of pore water is fluctuating. If this pore water is heated the

pressure can easily reach 100MPa. Modeling is showing that there is a big influence on the

pressure between dry and wet concrete.

With the close pore model (Figure 2) estimations of the pressure can be calculated assuming anequilibrium between liquid and gas phase of the water in the pores.

With increase temperature the pressure in the pores will increase depending on the filling degree with

water (Figure 3).

Liquid water

Air + water gas

Liquid water

Air + water gas

Figure 2 Close Pore model

Figure 3 Pore pressure at different tempereatures and filling rates


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Structural properties

It does not to be highlighted that the geometry, compressive loading, supports and restrained expansion

will have an influence on the spalling behavior since they will induce additional stresses in the concrete

Application

We should not forget the way of casting which can

influence the spalling behavior as experienced in a test

done by Efectis the Netherlands (see figure 4).This test is

showing the difference in spalling behavior of the same

concrete during the same fire test. The panel was casted

horizontal and one plate was tested with casting side down

and the other one with mould side down. The one with the

mould side down was spalling more severe. This test is

illustrating that although concrete has the same

composition, spalling can be influenced by the way of

casting. Influences like moulds, vibration and stability ofthe mix should not be underestimated.

FIRE PROTECTION

To date, the criteria for passive fire protection has been in practice to determine a thickness of thermal

insulation to limit the interface temperature below a critical level. This interface critical temperature

limit criterion is insufficient to protect the concrete against spalling because the heating rate (i.e. rate of

temperature increase) has a greater influence upon the occurrence of spalling than the temperature level

itself. So another criterion should be considered, in replacement of, or in addition to the critical temperature

criterion, namely the critical heating rate criterion.

Current Status of Tunnel Fire Protection

As a consequence of several notable fires, including the latest ones in the Frejus road tunnel, South of

France and the last fire in the Channel tunnel last year, the European understanding of the problems

associated with the safety of tunnels in fires has improved dramatically. A number of research programs

have been started soon after the year 2000 [7], and are finalized their findings through the EU funded

SafeT project, which are translated into mandatory national and regional requirements under the EU

Directive platform that will be of considerable benefit to the tunnel operators and travelling public.Currently in Europe national requirements are adopted. Furthermore since 2005, recent refurbishment

projects of major road tunnels in Europe have required wholesale upgrade of the safety features in the

tunnel (emergency lighting, escape routes, warning systems, active fire protection systems etc). This is

clearly set to continue this year, and the coming years.

In other regions of the world the picture is less developed, except for Japan, Australia and Singapore which

are similar to Europe in terms of project driven specifications and requirements. North America interest in

the role of passive fire protection is increasing, particularly in part being due to the number of European

design teams working on tunnel contracts, coupled with established European contractors who are in joint

ventures with American companies.

Figure 4 Difference in spalling depth


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Structural Issues

As mentioned above, the better the quality of concrete, the worse it performs under fire. Designers are

asking more and more for high durable concrete in order to have a structure with a life time of more then

100 years. In order to achieve this high durability requirement, concretes are designed to have a lowpermeability. But this high durable concrete with a low permeability will have a higher risk of spalling.

This was dramatically evident with the Channel Tunnel fire in November 1996, with almost complete loss

in concrete lining section from a train fire.

When concrete tunnel linings are exposed to fire there are structural issues to be considered:

1. The concrete typically undergoes explosive spalling, and will continue to do so until there is no

concrete left, or the fire diminishes

2. The concrete is heated to high temperatures and loses structural strength

3. If the structure contains active steel reinforcement, then loss in tensile strength occurs at high

temperatures

4. Due to the temperature gradient and different expansion rate of the constituents of the concrete,

deformation cracks and fissure will appear in the concrete.

To demonstrate the structural loss in strength of concrete and reinforcement steel, see figure 5 (adapted

from ITA 2004 & Khoury 2005) [3,4]. Clearly, the role of a passive fire protection system is to ultimately

protect the concrete from all the issues described above. As can be seen from Figure , maintaining the

structural concrete below 300C in the event of hydrocarbon or cellulose fires prevents all negative

structural issues form occurring.

Finally, to conclude this brief insight, the rate of heating is also crucial, and has a dramatic effect on the

spalling mechanism. Thermal shock can cause quite spectacular explosive events, as the water vapour

generation and thermal expansion of aggregates in the exposed surface of the concrete can be rapid.

Fire loads in reality

Over the last years there have been a number of serious underground fire incidents in tunnels. These fires

have caused extensive loss of life and severe collateral loss to the infrastructure. Aside from the tragic loss

of life, there is also a financial effect to the local infrastructure and the loss of public confidence in the safeuse of tunnels.

250-300C generally concreteand steel start to lose strength

550C both concrete and steel

have lost 50% on their strength

20%

40%

60%

80%

100%

0%0 200 400 600 800 1000100 300 500 700 900

20%

40%

60%

80%

100%

0%0 200 400 600 800 1000100 300 500 700 900

Temperature C

%o

fInitialStrength

( houryet a l

( houryet a l

Need to

keep

structures

below

250C

Lowstrengthconcrete

Highstrengthconcrete

Figure 5 Effect of temperature on concrete and steel reinforcement


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During a fire the fire protection system has to provide a stable structure in order to:

o allow the users to safely evacuate,

o allow the rescue personnel to enter the scene,

o effectively perform their required duties and to limit damage to the tunnel,

o limit the effect on the surroundings caused by a collapse

Concrete has been used in civil works as a fire resistant material and if designed properly it can with stand

a fire for a long period. The design load in order to simulate the fire in civil works is based on the ISO834

curve.

In road tunnels the situation is complete different compared to civil works, due to the HGV (Heavy Good

Vehicles) entering the tunnels [6,10]. These HGV often transport combustible products, which can cause a

severe fire in case of an accident, meaning a higher fire load, higher maximum temperatures and a faster

heating rate. It is evident that concrete behaves different in these kinds of conditions.

Assessment methods are constantly being developed to demonstrate the ability of materials and fire

protection systems to prevent concrete spalling and steel and metal elements from heating and melting due

to rapid heating under fire exposure conditions and to mitigate both structural and economic consequences

of fire.In the past designers have been using different kind of time temperature curves in order to design a

safe tunnel, (see figure 6). These curves, compared to the ISO834, are reaching their maximumtemperature already after 5 to 10 minutes.

Part of the European funded programs on safety in tunnels was the investigation of HRR (Heat Release

Rates) during a real tunnel fire in order to provide designers appropriate and more realistic design curves.

In the frame of Swedish national and European research programs on tunnel safety, comprehensive large

scale fire tests have been conducted. One of a large real scale fire was the Runehammer test in Norway in

September 2003 in the abandoned road tunnel in south-western Norway.

The Swedish National Testing and Research Institute (SP) have carried out the tests in collaboration with

other UPTUN partners from TNO Building and Construction Research in the Netherlands and the

Norwegian Fire Research Laboratory (SINTEF/NBL). Four large-scale tests with different type of

combustible loads on semi-trailer where carried out. These loads were not registered as dangerous good or

flammable liquids but consisting of normal wooden pallets or plastic cups. The outcome was that some of

the design curves used until now underestimated the real HRR during these fires. It was higher than 200MW and the gas temperatures in the vicinity of the fire were registered above 1350C.

0

200

400

600

800

1000

1200

1400

0 30 60 90 120 150 180

Time (minutes)

Temp

erature(oC)

RWS HCM Modified Hydrocarbon HC Hydrocarbon Eurocode 1

ISO 834 RABT VIG-1

Figure 6 Different types of design curves


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As results of these tests, guidelines and directives are published and giving criteria which designers can use

for the fire protection of new built or existing tunnels. As an example the UPTUN WP2 is recommending

that the ISO834 can be used if there are no or only empty HGV passing in the tunnel. The maximum HRR

can be estimated on 5 50 MW. In case of HGV of course the fire loads can be much higher and will

generate a HRR of 50 250 MW. Depending on the amount of combustible materials, the HC or the RWS

curve is recommended.

PROTECTING STRUCTURAL CONCRETE FROM FIRE

Passive verses active systems

Quite often there is confusion about these terms in the tunneling industry, amongst other things! Active fire

protection systems include water sprinklers, water mists and foam deluge systems, all of which are

activated by early warning sensors in the event of a fire. The theory is they reduce the fire before it

becomes out of control. The majority of existing tunnels worldwide rely wholly on these active systems to

ensure tunnel fire safety. These are Boolean systems, in other words, they work, or they dont due to

mechanical or electrical failure. They also may have some serious negative effects such as mixing with

toxic fumes that are otherwise confined to the crown of the tunnel, and drawing them down to the level ofthe evacuating public.

Passive fire protection is designed to be installed as a shield to protect the structure from fire at any time.

They are not reliant on any initiation system as with active systems, and they always work. Passive systems

do not put the fire out; but are the last line of defence and maintain the stability of the tunnel structure to

allow the safe escape of the public and safe access of fire department crews. They maintain ventilation

systems that are separated from the traffic by internal concrete structures, and also protect against

catastrophic damage to third party property and life by preventing tunnels from collapsing.

Currently in Europe, both active and passive systems employed together are seen to be necessary for new

tunnels in the future. There are essentially three main types of passive fire protection for tunnels: spray

applied mortars, prefabricated boards and PP fibre modified concrete.

Sprayed mortars

These historically have been vermiculite-cement based products applied by hand spraying with the

technology being transferred to tunnel applications from the petrochemical industry. Vermiculite based

systems are relatively weak products (2.5MPa compressive strength) and may not offer adequate

mechanical properties in light of increasing client demands for more durable solutions where cyclic loading

resistance is required. Vermiculite systems need to be mechanically bonded to the tunnel structure with

stainless steel mesh.

It is vital for sprayed systems to have

adequate durability to resist both

physical and chemical attack during the

normal service life of the tunnel. Thenew development in fire protection

products are combining high durability

with excellent fire protection. These

products are typically based on light

weight concrete technology giving a

compressive strength of 15 MPa

minimum.

These products are designed for

application with the well know

shotcrete technology and the modern

methods of robotic spray application,

allowing application rates of between150 and 250m

2/hr depending on theFigure 7 Application with automated MEYCO Logica


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protection thickness required. The tolerance of applications is normally +/- 4mm, which cannot be achieved

by hand application methods at these rates. The thickness of spray applied thermal mortars is determined

by the size and duration of the anticipated fire.

The main disadvantage with sprayed systems is the resultant sprayed surface finish, as some clients require

a high level of reflectance, particularly for highly trafficked road tunnels. Float finishing and over paintingis possible, but labour intensive. Rail tunnel surface finish requirements are less onerous in general, and an

as sprayed finish is acceptable, making the use of sprayed fire protection mortars particularly viable.

Pre-fabricated boards

Pre-fabricated fire protection boards offer a clear advantage for box shaped tunnels where there are no

curved tunnel walls or complex geometries e.g. cut and cover and immersed tube tunnels as shown in

Figure 8. Furthermore, the surface finish of the board systems is appealing to clients. However, they are not

well suited to curved profile tunnels and are generally 1.5 to 2 times more expensive than sprayed systems,

which can prove cost prohibitive. Apart from their high cost, vehicle collision damage is often considered a

maintenance problem in road tunnels using pre-fabricated board protection systems.

Polypropylene Fibre Modified Concrete

In recent years, fibre manufacturers have promoted multi- and monofilament polypropylene fibres (32 to 18

micron diameter fibres Figure 8) to contractors and design teams, detailing that the addition of 1 to 3kg

of fibres added to the concrete mix gives an extremely economical solution to concrete fire protection.

Figure 8 Polypropylene anti spalling fibres

From testing, fibre modified concrete will exhibit less spalling, and in some cases no spalling whatsoever

[8]. One theory is that the melting of fibres at approximately 160C produces channels for escape of the

steam that allows water vapour inherent in the concrete matrix to escape without generating internal

pressure, thus inducing high permeability at the critical time required and thereby preventing explosive

spalling. Another theory claims that micro-cracking around the fibres contributes to steam reduction. For

specific design fires, the quantity of fibres required will alter accordingly then larger the design fire, then

greater the quantity of fibres required. As an example, for an ISO834 cellulose design fire, approximately

1kg/m3 of fibres are required, whereas for RWS hydrocarbon design fires, the quantity may increase to

approximately 3kg/m3 as indicated. Concrete mixes with high fibre contents tend to be difficult to pump

and place, and careful mix designs using admixture technology to overcome these problems is required.

Although the fibres offer an anti-spalling system, they do not protect the structural concrete from the

detrimental effects of high temperature nor do they protect any structural reinforcement at the heat exposed

concrete tunnel lining. Consequently, the use of fibre modified concrete should be considered carefully for

use in structurally reinforced concrete tunnel linings.


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APPLICATION CASES

During the last years, several existing were upgraded according to the latest requirements and directives.

Based on a risk assessment the level of protection was determined. In some cases the complete tunnel had

to be protected with a thermal barrier and in other cases just a small section of the total length needed an

upgrade with a thermal barrier

Sderledtunnel, Stockholm

Due to recent legislation from the European Union, main road tunnels in excess of 300m length need to be

fire protected if a fire can cause tunnel lining collapse, and subsequent damage of third party property. One

of the major Stockholm road tunnels, the Sderledstuneln lies beneath hotels and a school, and therefore

required passive fire protection. The structure of the tunnel comprises a prestressed reinforced concrete

beam roof.

The first phase of the fire protection application was required d during the short tunnel closure during June

and July 2005 to a 60m long stretch of tunnel, with a view to completing additional sections of the tunnel

in September and October 2005. The program to complete the rest of the tunnel involves applications over

a period of 5 years. The contractor preferred toapply the system by sprayed coating, and this

was required to have a design life of 100 years.

The anticipated fire rating of the concrete

structures is 2 hours under a RWS fire curve.

From the MEYCO Fireshield 1350 Design

Guide, a thickness of 60mm was required to

both protect the concrete integrity and also the

capacity of the pre-stressed reinforcement bars

of the concrete beams. The soffit sections

between the beams were designed with 35mm.

To provide a durable solution, the MEYCO

Fireshield 1350 was fully bonded to the

structural concrete roof of the tunnel, thereby

negating the need for steel mesh. To ensure

bonding, the surface of the structural concrete

was hydromilled to remove approximately 2 to

3mm of the cement pastes and reveal the aggregate structure of the concrete suitable for bonding a

coating of MEYCO Fireshield 1350. Mixing of the material was carried out in standard 6m3 truck mixers

that were fed with 1305kg big bags. Application of the thermal barrier was performed using the robotic

spray manipulator on a MEYCO Roadrunner Robojet

Alp Transit, Bodio section

AlpTransit Gotthard AG, a wholly owned subsidiary of the Swiss Federal Railways, is constructing a new

flat rail link. At the heart of the new transalpine rail route is the Gotthard Base Tunnel (GBT). The tunnel

is part of the Swiss AlpTransit project, With its planned length of around 57.1 km and a total of 153.5 km

of tunnels, shafts and passages, once finished, the Gotthard Base Tunnel will be the longest tunnel in the

world.[11]

The designers consortium of the Bodio, Faido and Sedrun Sections (total length about 38 km) of the

Gotthard Base Tunnel is the Engineering Joint-Venture Gotthard Base Tunnel South (Lombardi

Engineering Limited, CH / Amberg Engineering Limited, CH / Pyry Infra Limited, CH).

In 2003 the fire protection task force was founded by AlpTransit Gotthard AG with the following goals:

- Identification of fire scenarios for freight train fire and for passenger train fire.

- Elaboration of a damage and risk assessment (without protection) for the different fire scenarios.

-Assessment and recommendation of protective measures, provided both availability requirements

are fulfilled.

Figure 9: Application on pre-stressed beams


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The cut-and-cover section of Bodio started in 2000 and was completed two years later. It consists of two

bores each of 400 m in length and one cross-passage, which is situated about 260 m from the southern

portal. Following the investigations of the fire protection task force it was decided that to comply with

the individual safety criterion a fire protection layer on the existing tunnel lining was necessary on the

whole length of the cut-and-cover section of Bodio. This because in the event of a fire, it could not beexcluded that damage or collapse of one bore could cause damage to the other making it impossible to

evacuation users. A collapse of one of the bores could also lead to a severe damage er even collapse of the

existing train line on top of the tunnel since this tunnel section is situated in a unstable landslide.

Many fire protection systems were analyzed and rated for their technical and economical performance. A

cement based fire protection was choosen as the best solution for the cut-and-cover section of Bodio.

The following are the requirement on the passive fire protection layer:

- Fire protection of the existing tunnel lining according to the RABT/ZTV standard design fire

curve (90 minutes at 1200C and the following cooling phase of 110 minutes) with respect of the

following two conditions: temperature at the interface 400C, temperature at the reinforcement

250C.

- After an event the fire protection layer can be partially or completely replaced

-Good tensile bond strength with the existing concrete lining

- High frost and freeze-thaw resistance

- Dead load resistance and resistance against stresses caused by the train service. The assumed

amplitude of air pressure fluctuation is 10 kN/m2

- Resistance against variations in temperature between -10C and +40C and against fluctuations of

relative humidity between 20% and 100%.

- Resistance against cleaning by high pressurized water.

- Resistance against local perforations and against stresses induced by fixation of railway

infrastructures.

- Service life of 50 years.

Figure 10 Automated application on rough concrete surface withadditional meshUnder the prescribed circumstances and requirements the application of a layer of mortar MEYCO

Fireshield 1350 was chosen. The minimum thickness, 31 mm, was defined on the base of the fire

protection requirements. The fire protection layer was applied on the concrete lining in both tunnel

sections. Under consideration of the applying tolerance in layer thickness of4 mm a standard thickness of

35 mm was defined (the effective layer thickness is variable between 31 mm and 39 mm).


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To extend warranty of the high requirements in tensile bond strength of fire protection layer with

the existing lining a fully bond solution combined with stainless mesh reinforcement was chosen.

(Figure 10)

REFERENCES

1. Corradi, Khurana, Magarotto, Torresan : paper Zero energy system an innovative

approach for rationalized precast concrete

2. Shuttleworth, P. (2002). Technical Paper Fire protection of concrete tunnel linings.

Written communication based on Rail Link Engineering tests for Channel Tunnel rail

Link, UK.

3. A. Breunese, Efectis The Netherlands: Presentation Fire Protection workshop, MEYCO

Global Underground Construction, 2009

4. ITA (2004). Guidelines For Structural Fire Resistance For Road Tunnels. Working

Group 6 Report. Published by the International Tunnelling Association, 2004.

5. Khoury, G.A. (2003). EU Tunnel Fire Safety Action. Tunnels and Tunnelling

International. February 2005. pp 20-23.

6. Khoury, G.A. (2005). EU Tunnel Safety Update. Tunnels and Tunnelling

International. February 2005. pp 41-43.

7. Khoury, G.A. (2005). Personal written communications on SafeT findings and concrete

strength change on elevated temperatures research work undertaken by Imperial

College, London.

8. ADFIL UK. Ignis Passive Fire Protection System. Product brochure for monofilament

polypropylene fibres. Published by ADFIL UK Ltd.

9. Munich Re. (2003). Risk management for Tunnels. Published by the Munich Re

Group, Munich, Germany. Order No. 302-03083.

10.Haukur Ingason (2006) Paper Design fires in Tunnels, Safe & reliable tunnels

Lausanne 2006, SP Swedish National Testing and Research Institute11.C. Verani, A Ferrari: Fire protection for new and existing underground structures,

Tunnel magazine 7/2009

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