72156-2 Evacuation and Ventilation

KOTI Korea Transportation Institute

Metropolitan Express Railway Evacuation and ventilation

November 2009

KOTI Korea Transportation Institute

Seoul Metropolitan Express Railway Evacuation and ventilation

November 2009

COWI A/S

Parallelvej 2 DK-2800 Kongens Lyngby Denmark Tel +45 45 97 22 11 Fax +45 45 97 22 12 www.cowi.com

Document no. 72156-2

Version 1.0

Date of issue 2009-11-23

Prepared JK/MF

Checked PON

Approved PON

Seoul Metropolitan Express Railway, Evacuation and ventilation

P:\57050Z\188 (Korea deep railway tunnel)\Report Evac and Vent\72156-2 Evacuation and ventilation.docx

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Table of Contents

1 Introduction 3

2 Summary and conclusion 5

3 Basis - project description 8

4 Safety considerations, general 10

4.1 Qualitative risk analysis 10

4.2 Risk acceptance 11

4.3 International standards 11

4.4 Train fires 12

4.5 ALARP principle 15

5 Ventilation considerations - general 17

5.1 Tunnel ventilation system 17

6 Basic option 19

6.1 Description of the option 19

6.2 Tunnel ventilation 20

6.3 Safety consideration incl. evacuation 22

7 Option: Emergency corridor with frequent access 26




8 Option: Short distance between ventilation shafts 31






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9 Option: Dividing wall 37




10 Comparison 44

11 References 48



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1 Introduction SUNJIN is performing feasibility studies of the Seoul Metropolitan Express Railway. In relation to these studies SUNJIN has commissioned COWI to rec-ommend on evacuation facilities on the basis of information of the envisaged tunnel layout, train vehicle, expected size of fire etc. Furthermore SUNJUIN has commissioned COWI to recommend on the tunnel ventilation including distance between emergency shafts and size of ventilation.

The evacuation facilities and the tunnel ventilation are closely related. Hence, the present report provides the results of both studies.

The basis for the work carried out is described in section 3.

General considerations regarding safety including evacuation and regarding ventilation are presented in sections 4 and 5, respectively.

On the basis of these general considerations it seems relevant to consider mod-ifications to the present design by SUNJIN, which is referred to as the "Basic option". In this option the passengers will in an emergency escape to emergen-cy shelters below the tracks.

The modifications lead to the following alternative options:

• Emergency corridor with frequent access

This concept is based on the principle that passengers in an emergency sit-uation escape to a corridor (safe area) under the railway tracks. The corri-dor leads to emergency exit shafts. Via these emergency exit shafts it is possible to go to the ground surface.

• Short distance between ventilation shafts

In this concept it is assumed that there are sufficient exhaust ventilation shafts to make escape possible via the walkways at track level.

• Dividing wall

In this concept it is assumed that the two railway tracks are separated by a fire proof dividing wall. The dividing wall has emergency doors at close



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distance. This concept will require a larger tunnel diameter than in the oth-er options.

The basic option and the modifications are considered in sections 6, 7, 8 and 9, respectively covering: • A description of the option • Ventilation • Safety considerations including evacuation

A comparison of the options considered is provided in section 10.



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2 Summary and conclusion COWI has regarding safety and ventilation considered the “basic option” as well as some modified options for the Seoul Metropolitan Express Railway. The accident considered is a train on fire stopped in the tunnel. The conclusion is, that the concept is not so much governed by considerations of ventilation system capacity, as by considerations of safe passenger evacuation and safe access for the fire brigade.

The “basic option” with a two track tunnel has been considered. This option can in theory, with a distance of maximum 500 m between entrances to safe spaces in shelters, fulfill international standards. This concept is however de-pending on a satisfactory detailing of the access to the shelters and of the shel-ters themselves (they need to accommodate a lot of passengers and the width of the access seems to be limited to less than required in international standards).

In addition to the shelters we have considered a distance of 2500 m between shafts for fire brigade access (and evacuation of passengers not going to the shelters) and 1250 between ventilation shafts. This is deemed a satisfactory so-lution for fire brigade safety and safety of other trains in the tunnel even though the more shafts the better.

According to the information we have received, the passenger density in the system is very high. This means that evacuation time may be too long even though the width of the walkways in the tunnel fulfills normal standard re-quirements. The evacuation time should be studied using appropriate models such as EXODUS, as opposed to the very rough estimates that could be in-cluded in this report.

In order to suggest on some improvements to the basic concept we have consi-dered three modified options:

• Option: Emergency corridor with frequent access • Option: Short distance between ventilation shafts • Option: Dividing wall

Emergency corridor We think that the use of an emergency corridor below the tracks rather than shelters is a better solution, as it allows the passengers to evacuate completely from the tunnel rather than having so many passengers waiting in a relatively



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congested space during an emergency situation. By frequent access to the emergency corridor the evacuation time is reduced.

The concept is depending on a satisfactory detailing of the access to the emer-gency corridor. (The width of the access seems to be limited to less than re-quired in international standards).

Short distance between ventilation shafts The use of closely spaced ventilation exhaust shafts (500 m distance) rather than emergency exits relies on very accurate knowledge of the location of the train on fire. It is vulnerable to wrong operation or malfunction of the ventila-tion system in an emergency situation. Also it is noted that this option will for-mally not meet international standards, as walking past a ventilation exhaust shaft can hardly be considered to provide the same safety as walking into a shelter. Finally the access of the fire brigade in this option is more complex than in the other two options considered above.

The advantage of this option is that the passengers need not use the space be-low the tracks, which would require complicated design of stairs etc.

Dividing wall In general it can be said that two track tunnels are more difficult than single track tunnels to operate in a safe and fail-proof way that ensures that the smoke during a fire does not endanger passengers, fire brigade or other trains in the tunnel.

This means that we see the option with a dividing wall as an improvement, as it allows the tunnel to work as two single track tunnels with unidirectional traffic. Also this option has advantages regarding fire brigade access, which, due to the larger tunnel diameter, is possible in the space under the track and independent of the traffic tunnels.

The design of the fire brigades access from this space to the tracks will have to be further studied in order to finally establish whether this solution is feasible.

This tunnel option can be constructed without shafts between the stations. This means that the additional costs, due to the bigger tunnel diameter necessary in order to contain the dividing wall, will more or less be compensated by the sav-ings of having no shafts.

Conclusion The “basic option” can fulfill normal international standards provided that the shelters or emergency corridors and access to them can be designed satisfactory for this big number of train passengers. We think there is considerable uncer-tainty regarding this point. Furthermore the time required for safe evacuation may be too long.

The option with a diving wall is considered to be the best from a safety point of view. This option is therefore recommend if there are no or only insignificant additional costs involved compared to the other options. Even if the additional



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costs are larger, this option should be preferred, as long as the additional costs are not disproportionate with the value of the reduction in risk.

We hope that the description and evaluation of ventilation concept and evacua-tion facilities provided in this report for the "basic option" and three modified options will provide a valuable basis for the feasibility study for Seoul Metro-politan Express Railway.



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3 Basis - project description There are several proposals for the alignment of the Seoul Metropolitan Ex-press Railway. For the purpose of this report we have been looking at the alignment from Song-do (new development area at Incheon) to Cheong-ryang-ri (North of the Seoul City Centre), please see the illustration on the next page.

The information on the considered system has been received through drawings, sketches, questions and answers exchanged in e-mail correspondence with SUNJIN.

Alignment and stations

The planned express railway system is all underground and with underground stations. Distance between stations varies between 2.9 km and 9.3 km. The sta-tions are closest in the city centre and more distant around Incheon. On the Cheong-ryang-ri to Song-do express railway line, which is approximately 50 km long, there are 9 stations. The stations will be highest standard and equipped with platform screen doors.

The tunnels are typically located at a depth of 30 – 50 meters below ground sur-face.

Rolling stock

The trains for the express railway system are expected to be electrical trains with overhead catenary.

• 138 m long (6 carriages each 23 m long)

• Train cross section area 7.8 m2

• Speed 200 km/h

• Pressure tightness coefficient τ =15 sec corresponding to a train with ex-cellent sealing.

• Number of passengers in each train: 898 man (Entrainment rate: 100%) to 1,140 man (Entrainment rate: 150%)

• Design train fire 15 MW.



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4 Safety considerations, general

4.1 Qualitative risk analysis As part of the basis of the design of an underground railway system, the risk to the passengers shall be identified, such that appropriate precautions can be tak-en against these risks. A brief identification is carried out here, pointing on the following risks to the passengers of the Metropolitan Express Railway:

• Risks when moving or standing inside stations including station platforms

• Risks when moving to and from the trains on station platforms

• Risk in the trains not related to train accidents (e.g. stumbling when mov-ing in the train or falling as the train brakes)

• Risks related to train accidents including:

- Train collision

- Train derailment

- Train hitting obstacle on the track

- Train fire

- Train fire caused by other accidents

- Fire in tunnel and station installations

- Explosion in a train (sabotage)

- Collapse of structures

In general the risk is reduced to an acceptable level as follows:

• Prevention of the occurrence of the accidents



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• Mitigation of the accidents consequences including among others:

- Evacuation of the passengers

- Intervention by the fire brigade including rescue of passengers and fire fighting

For the design of evacuation and rescue facilities the fire accidents are of most concern, as the time aspects here are very important. These accidents will also be a major contribution to the overall risk of the train passengers. Hence train fires are the focus of this report.

Train fires following accidents can have even larger consequences than train fires not caused by such other accidents, as passengers may be injured in the initial accidents and therefore not able to escape from the fire. Furthermore in train collisions there will be two trains involved, such that number of passen-gers having to escape will be approximately doubled. However, it follows from the list of tunnel fires presented in Ref. /4/ that there are recorded very few of such fires (since 1980 only the derailment 13. Jan. 1982 in the Washington DC underground railway/metro; some more in the earlier records).

Hence only a fire in a single train, stopped in the tunnel between stations, is considered in this report. This accident is further discussed in section 4.3.

4.2 Risk acceptance An acceptable level of risk in an underground railway system may include the following elements:

• Design of the tunnel according to applicable codes and standards. Requirements from international standards related to evacuation and rescue are presented in section 4.3.

• Establishing of risk acceptance criteria and documentation that these are met by means of quantitative risk analysis. The general consideration of fire accidents in section 4.4 may be consi-dered as a first small step in this process.

• Risk reduction is implemented according to the ALARP principle, see sec-tion 4.5.

4.3 International standards A brief review of major international standards for railway tunnels has been carried out regarding requirements to escape routes and access of the fire bri-gade. The standards covered are:



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• The American NFPA 130 (Ref. /1/) • The Directive 2001/16/EC of the European Union (Ref. /2/) • The code 779-9 of UIC (the International Union of Railways, ref. /3/)

The results are shown in the table below. It is noted that if cross passages are provided, then it is not required also to have exits to open air. It is further noted that UIC 779-9 indicates that the requirements for width of access routes is only for single bore tunnels (one or two tracks). In UIC 779-9 it is indicated that the safety measures are to be seen as guidelines but not as strict rules.

Table 4-1 Requirements in international standards for railway tunnels

4.4 Train fires The risk from train fires is generally reduced by the following measures:

• Minimizing the amount of flammable material in the trains. As explained in section 3 it is understood that the maximum size of fire will be 15 MW.

• The trains will be equipped with fire extinguishers, such that minor fires inside the train may be extinguished. (Our assumption in accordance with current practice).

NFPA 130 2001/16/ EC

UIC 779-9

Width of walkways 0.76 0.75 0.7Paragraph 6.2.1.11 4.2.2.7 I-40

Height of walkways 2.25Paragraph 4.2.2.7

Distance between cross passages 244 500 500Paragraph 6.2.2.3 4.2.2.6.4 I-43

Distance between exits 762 1000 1000Paragraph 6.2.2.2 4.2.2.6.3 I-43

Width of escape doors 1.4Paragraph 4.2.2.2.6.3&4

Height of escape doors 2.0Paragraph 4.2.2.2.6.3&4

Width of cross passages 1.12 1.5 2.25Paragraph 6.2.2.3.2 4.2.2.2.6.4 I-46

Height of cross passages 2.1 2.25 2.25Paragraph 6.2.2.3.2 4.2.2.2.6.4 I-46

Width of escape stairs 1.2Paragraph I-44

Width of access routes 2.25 2.25Paragraph 4.2.2.11 I-45



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• Any train on fire will attempt to drive to the next station if at all possible, as the risk to the passengers will be much less, when the train is stopped here, than if the train should stop in the tunnel. (Our assumption in accor-dance with current practice).

• There will be fire detectors on the trains, such that a fire will be detected early. This will improve the possibilities of the train on fire reaching a sta-tion. (Our assumption in accordance with current practice).

In spite of these precautions, a train on fire may stop in the tunnel between sta-tions. This is the situation which is considered further in this report, as this ac-cident scenario will be governing for the safety design of the tunnels.

The critical issues in the event of such an accident are:

• The passengers shall be able to escape from the burning train to a safe lo-cation (self rescue of the passengers). Here the capacity of the evacuation routes and the distance to the safe location is of concern.

• Passengers of other trains in the same tunnel shall be protected against the smoke from the burning train, either by the train driving out of the tunnel or by the ventilation system ensuring fresh air to these other trains. A situa-tion where passengers from other trains than the burning train will have to evacuate in a smoke-filled tunnel should be avoided.

• The fire brigade has good access to the accident location, such that they can rescue passengers not able to escape and fight the fire.

Comments to the above points:

Passenger escape The adequacy of the means for passenger escape should be investigated as follows:

• The fire accidents scenario is established including the number of passen-gers in the train, the fire curve, how far the fire is developed, when the train stops, the time from train stop till evacuation of the passengers is es-tablished and the envisaged operation of the emergency ventilation.

• The smoke spread and resulting temperatures in the tunnel are established.

• The escape of the passengers is modeled using appropriate models such as EXODUS.

• Comparison of the above results to establish whether passengers will be able to reach safe areas before being seriously affected by smoke and/or high temperatures.

This work is part of the risk analysis work mentioned in section 4.2.



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Here a very rough and simplistic calculation of evacuation time has been car-ried out using the method prescribed in NFPA 130, Ref. /1/, for documenting the adequacy of escape routes from station platforms. In order to be able to use this method in the tunnel the following simplifications have been made:

• The escape from the train to the walkway along the train has not been con-sidered.

• The prescribed deduction of 300 mm sidewalls and 460 mm at open plat-form edges has not been taken into account, as this would reduce the width of the walkway to be used in the calculation to close to zero.

The numbers from NFPA used in the very rough calculation of evacuation time are:

• Capacity of walkway: 0.0819 persons per mm and minute

• Capacity of stairs: 0.0555 persons per mm and minute

• Travel speed at walkway: 38 m/minute. (This is a low value, which presumably reflects the reduced speed in a crowded situation).

• Travel speed at stairs: 15 m/min To be used for the horizontal length of the stairs

Other trains Trains on the same track as the train on fire:

• A train ahead of the burning train will continue to the next station

• A train behind the burning train will have to stop. It may drive backwards to the station from where it came, but reversing the train traffic may take some time. Possibly, the fire may burn down the catenary overhead line before this is done.

If the tunnel contains only a single track, then air flow will be in direction of the running trains and thus preventing smoke from reaching the train behind the burning train. This direction of the air flow will be maintained by the ventilation systems, such that the passengers can escape in smoke-free air, if it is not possible to drive the train back to the previous station.

In case of a tunnel with two tracks, as is the case here, there will be no dis-tinct airflow protecting a train behind the burning train. A longitudinal ventilation system is not suitable for protecting the train in this situation, as it may adversely affect trains in the other track on the opposite side of the fire. The train may be protected if smoke can be extracted at a location be-tween the burning train and the stopped train.



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Trains on the other track:

• A train, that has passed the burning train, will continue to the next station.

• For a train, that has not yet passed the burning train, may attempt to drive past the burning train, but this may be dangerous, as the fire may burn down the catenary overhead line, stopping the train close to the fire. If the passengers have already started evacuation from the burning train, driving past the burning train is not an option.

If the train instead is stopped, then it may drive back to the station from where it came, but as described above this may be prevented by the burn-ing down of the catenary overhead line. A stopped train may be protected if smoke can be extracted at a location between the burning train and the stopped train.

The access of the fire brigade in a railway tunnel may generally be by one of the following means:

• Through a station or emergency access shaft and then along the tunnel. Movement in the tunnel may be along an emergency walkway or along the tracks by means of a small trolley, which is located in a room at the sta-tions and in the bottom of the emergency shafts.

• Using an emergency train. Emergency trains located at each end of the line would not be able to drive to the scene of the accidents, due to the trains stopped in the system in an emergency. Having an emergency train located at a side track at each station would be a very costly option.

• Using dedicated vehicles driving in a space underneath the tracks. This option has to our knowledge not been used previously for railway tunnels, but it has been used for road tunnels. It is considered for the option with a dividing wall, see section 9.3.3.

4.5 ALARP principle The ALARP principle (As Low As Reasonably Practicable) was established in the UK for design of nuclear power plants, Ref. /5/. The principle is illustrated in Figure 4-1. At the top of the figure, above the risk acceptance criteria men-tioned in section 4.2, is the unacceptable region, where the risk shall be reduced regardless of the costs. In the bottom of the figure is the broad acceptable re-gion. Risks falling in this region need little attention, as indicated in the figure. In between is the ALARP region. Here additional safety measures shall be im-plemented unless the costs are disproportionate with the risk reduction achieved.

Access for the fire brigade



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Figure 4-1 ALARP principle

Risk is intolerable and cannot be justified even in extraordinary circumstances

Tolerable only if risk reduction is impracticable or if its cost is grossly in disproportion to the improvement gained

Tolerable if cost of reduction would exceed the improvements gained

No need for detailed studies. Check that risk maintains at this level

Unacceptable region

ALARP/ ALARA region:

Broadly acceptable region

Unacceptable Unacceptable regionregion

ALARP/ ALARP/ ALARA ALARA region: region:

Broadly Broadly acceptable acceptable regionregion

High riskHigh risk

Negligible riskNegligible risk



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5 Ventilation considerations - general The ventilation consists of the following systems:

Tunnel ventilation system, which has the following purpose:

• During normal as well as congested operation, to obtain acceptable envi-ronmental conditions for the passengers in the trains.

• In case of fire in the tunnel, to control the smoke either by longitudinal ventilation (tunnels with single track) or by local smoke extraction (tunnels with two tracks) in order to enable the passengers to escape and the fire brigade to approach the scene of the fire.

• During maintenance and repair works in the tunnel to ensure an acceptable working environment,

Pressurization systems, which have the following purpose:

• During fire accidents to ensure smoke-free escape routes via the escape corridor, the shelters and the stairs. In the option with dividing wall, to en-sure smoke-free corridor under the tracks for fire brigade approach to the scene of the fire.

5.1 Tunnel ventilation system

5.1.1 Environmental conditions In railway tunnels with single tracks the piston effect created by the trains will normally be sufficient to obtain acceptable environmental conditions in the tunnel.

Only during congested operation or trains stopped in the tunnel, it will be ne-cessary to supply fresh air to the tunnel.

In the "Basic option" trains are running in both directions in the same tunnel tube. This will influence the air movements and the accumulation of heat and creation of piston effects (air exchange in tunnel) to an extent that will require a thorough study. The train time schedule, the location and size of ventilation shafts, openings to stations etc. influence the piston effect. We suggest use of a



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1-dimensional simulation program, e.g. SES). Therefore it may be necessary, in this case, to supply fresh air both during nor-mal as well as congested operation.

5.1.2 Emergency conditions (Fire in the tunnel) In case of fire in the tunnel the ventilation system shall be able to control the smoke in order to ensure smoke-free escape routes for passenger evacuation.

In tunnels with one track, longitudinal ventilation is normally used to obtain the critical velocity in the tunnel tube and thereby prevent backlayering of smoke. As it is possible to have other trains trapped behind the burning train, the pre-ferred ventilation direction is in the train direction. This will make smoke-free escape routes behind the burning train.

In tunnels with two tracks ("Basic option"), longitudinal ventilation cannot be used, as there may be trains trapped both ahead of the burning train (in the oth-er track) and behind it. Therefore, a semi-transverse ventilation system, with extraction at certain points and supply from the one end of the tunnel section, shall be used.

5.1.3 Pressurization system The pressurization system is not used during normal conditions. Only during emergency conditions the escape corridor, the shelters and the stairs will be pressurized to supply fresh air and avoid smoke ingress during the evacuation.



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6 Basic option

6.1 Description of the option The cross section of the basic option is single tube tunnel with two railway tracks. The tunnel has an internal diameter of 11.060 m.

The tunnel is equipped with ventilation as described below. The jet fans are used as supplementary fans for the tunnel ventilation.

On each side of the two railway tracks there is a 0.8 m wide emergency walk-way.

Figure 6-1 Cross section of basic option

Jet fans

Ventilation of emergency shelter

Shelter

Utilities

Walkway Walkway



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In an emergency situation the trains can be evacuated via the emergency walk-way to the evacuation shaft. Furthermore under the tracks there are shelters which are accessible through emergency hatches located between the railway tracks.

The shelters can resist the design fire. They are equipped with a separate sys-tem for fresh air supply and they have signboards with instructions for eva-cuated passengers. Also they are equipped with intercom and cameras con-nected to the railway system control center, so the passengers will be able to communicate with the staff of the control center in an emergency situation.

The distance between big shafts, i.e. shafts with both stairs and ventilation is assumed to be 2500 m. This distance is chosen as a reasonable distance for fire brigade emergency access for the tunnel. In between the big shafts there are small ventilation shafts (5 m2 or around 3 m diameter). These shafts can be used for smoke exhaust to make sure that the route to and from big shafts, as far as possible, is free of smoke in an emergency situation. The exact location of the shafts can vary in order to accommodate the actual distance between sta-tions.

The main features of the basic option are summarized in the Table 10-1.

6.2 Tunnel ventilation The tunnel ventilation is divided in sections: from station to station. Only for one typical section the tunnel ventilation system is described in the text and shown in Figure 6-1.

6.2.1 Description of Tunnel ventilation system The system comprises the following components:

• At stations: - Reversible ventilation plant for supply/extraction. - Piston effect shafts.

• At shafts (2500 m from the station and 2500 m between shafts): - Ventilation plant for air supply to the tunnel. - Ventilation plant for air supply/pressurization of shelters and corridor. - Ventilation plant for pressurization of the staircase.

• At ventilation shafts (1250 m from stations and shafts): - Ventilation plant for extraction.

• In the tunnel: - Jet fans to be used as booster fans for the tunnel ventilation in particular cases.



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Figure 6-2 Basic option, ventilation principle

6.2.2 Operation of the tunnel ventilation Normal conditions During normal conditions it may be possible to create sufficient ventilation (Fresh air supply) by the piston effect via piston effect shafts and extraction shafts. In case the above recommended 1-dimensional simulation shows, that this will not be possible, it will be necessary to supply fresh air with the tunnel ventilation system. Some of the supply plants and some of the extraction plants may be used. How many and at which location shall be determined based upon new simulations.

During congested operation it will be necessary to supply fresh air to the tunnel from the supply plants next to the location of the stopped train. The polluted air can be extracted through the extraction shafts.

Emergency conditions (Fire in the tunnel) In case the burning train stops at station platform, the smoke will be extracted by the ventilation plant at the station.

If the burning train stops between two stations, the smoke will be extracted through the smoke exhaust shaft next to the burning train.

Fresh air can be supplied from emergency shafts or stations. See Figure 6-2.

1250 1250 1250 1250L

2500 2500

Smoke

exhaust

Shelte

Emergency

Exit

Station

Stopped trainEm

ergency Exit

Smoke

exhaust

Shelte

Shelter

Shelter

Shelter

Shelter

Jet FanFresh air supplySmoke exhaustSmoke exhaust

Escape route



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The ventilation plants for pressurization of shelters, corridor and staircases will be started when a fire occurs.

Because there are two tracks, there may be trains trapped in front of the burning train on the other track and behind it on the same track. Therefore longitudinal ventilation can not be used during the evacuation.

As shown in Figure 6-2 the trapped trains on both side of the fire site can be free of smoke. The fresh air supply from stations and emergency shafts create a flow with a velocity ≥ vCritical. The jet fans can be used to maintain the velocity.

After the evacuation, the Fire Brigade can change to longitudinal ventilation, to get smoke-free access to the fire site from the one side. The Ventilation plants shall therefore have the necessary capacity to maintain an air flow with critical velocity. During this operation, it may be necessary to use the jet fans.

6.3 Safety consideration incl. evacuation

6.3.1 Evacuation of passengers from the burning train The passengers will escape to the walkway immediately adjacent to the train. (Escape to the other side of the train and across the other track to the walkway on the other side of the tunnel is not considered here, as this would be difficult if the tunnel is not specifically designed for this).

The passengers may escape in both directions. However, it is likely that the passengers will not be able to walk past the fire. If the fire is in one end of the train, then all passengers will have to walk in one direction. On average the fire may be considered to be in the quarter point of the train, such that 3/4 of the passengers will have to walk in the same direction.

From the end of the train the passengers will walk on the walkway towards the nearest shelter.

The 0.8 m width of the walkway is in accordance with the international re-quirements, see Table 4-1.

We have not been informed on the distance between the shelters. It follows from Table 4-1 that according to UIC and European standards the distance be-tween cross passages should be about 500 m. Going into a shelter is compara-ble to going into a cross passage leading to an other tunnel tube. Hence a dis-tance between entrances to shelters of 500 m is assumed here.

In order to be able to accommodate all passengers from a train the shelter should be rather large. There should be more room per passenger in the shelter than in the train. As the width of the shelter seems to be only about 2.6 m (de-ducted from Figure 6-1), which is less than the width of the train, then the



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length of the shelter should be several times the length of the train. The layout of the shelter requires further consideration taking into account:

• How the passengers are to be accommodated in the shelter. Preferably the passengers should be seated, as they may have to remain in the shelter for several hours.

• How the passengers shall spread along the very long shelter from the access stairs.

• Location of communication means, supplies, toilets etc.

Considering the small width of the shelter, it may be difficult to establish a de-sign that will work in an emergency. E.g. the first passengers entering the shel-ter may stop immediately within the shelter, such that the following passengers will not be able to enter the shelter.

It follows from Figure 6-1 that the width of the staircases leading down to shel-ter is in the order of 0.8 m. This is less than the widths indicated in Table 4-1 (1.12 m width of cross passage indicated by NFPA 130, and 1.4 m width of es-cape door indicated by 2001/16/EC). However, with the present tunnel diame-ter it is hardly possible to make a wider staircase.

The evacuation capacity of a staircase of a certain width is less than the evacua-tion capacity of a walkway of the same width. Even though the passengers in-itially may only walk on one of the walkways away from the burning train they may later spread on both walkways. There should therefore be three stairs at each end of the shelter in order to provide a capacity corresponding to the two walkways. (According to NFPA 130, Ref. /1/, the capacity of a walkway is 0.0819 persons per mm and minute and the capacity of stairs 0.0555 persons per mm and minute).

The design of the entrances to the staircases need further considerations regard-ing how the lid down to the stairs will open and how handrails preventing the passengers from falling down into the staircase hole are arranged.

A rough calculation, using NFPA 130 as described in section 4.4, of time for the passengers to reach safety within the shelters gives the following results:

• The number of passengers in the train is assumed to be 898 (100 %)

• The number of passengers walking in one direction is 3/4·898 = 674

• The time for the passengers to walk past the end of train on one walkway is estimated at 674 / (0.0819 min-1 mm-1 · 0.8 m) = 10.3 min.

• The time to walk from the end of the train to the entrance to the shelter will be maximum 500 m will be 500 m / 38 m/min = 13.2 min.

• Time to walk down the stairs: 3 m / 15 m/min = 0.2 min.



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• The total time until the last passenger is within the shelter is thus 24 min.

The ventilation system will extract the smoke from the ventilation shaft nearest to the train. Hence, there will be a probability of 0.5 that the train is located such that the evacuation, described above of the 674 passengers, will be in a smoke-filled tunnel.

The estimated 24 minutes in the smoke-filled tunnel seems to be a high figure, considering that the fire may develop in the full 15 MW fire within the order of 15 minutes (general assumption stated in paragraph 2.2.1 of Ref. /2/), of which a few minutes may have passed before the train stops.

Hence, even though the 24 minutes are calculated using a very rough method, it seems as if the evacuation facilities will have to be improved. This could be done by increasing the internal diameter of the tunnel, such that the walkway becomes wider, which would also allow an increase of the width of the emer-gency shelter.

Another possibility will be to design the tunnel such that the passengers can also escape form the other side of the train and go to the walkway along the other side of the tunnel. However, this will to some extent conflict with the lo-cation between the tracks of the stairs to the emergency shelters.

The distance between entrances to the emergency shelters could also be re-duced, but this would lead to that there will be a continuous emergency shelter under the tracks, and then the option described in the next section may be bet-ter.

It is noted that to our knowledge the concept of having escape to the room be-low the railway track has not yet been used in any railway tunnel. The concept has been used in road tunnels, but using it in a railway tunnel may be more dif-ficult due to the large number of passengers that can be onboard a train, and the smaller dimensions of railway tunnels compared to road tunnels.

6.3.2 Protection of other trains in the tunnel With the envisaged ventilation concept there will at maximum be 1250 m (the maximum distance between the train and the nearest smoke exhaust) of tunnel filled with smoke.

Any train on the opposite track stopped here will be seriously endangered. Hence, the procedures in the event of a fire in a train would be to operate the trains on the other track, such that this situation is avoided.

The next train on the same track will presumably be further than 1250 m behind the burning train, such that it will be protected against the smoke from the burn-ing train. If this concept is chosen then this should be further investigated.



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It is noted that if the emergency exits and stations are also used for smoke ex-traction, then the maximum length of smoke-filled tunnel would be reduced to 1250 m / 2 = 625 m, but this would have adverse consequences for the ability of the fire brigade to intervene, see below.

6.3.3 Access for the fire brigade The fire brigade will go to the tunnel via the nearest emergency exit from where they can proceed towards the burning train in a tunnel that is nearly free of smoke, as the smoke is extracted from the smoke exhaust at the other side of the train. The fire brigade will at maximum have to travel 1250 m to the burn-ing train.

Only if the fire is exactly at the location of an emergency exit will the distance to be travelled be longer, i.e. the 2500 m from the next emergency exit.

It is noted that if the emergency exits and the stations were also used for smoke extraction, then the fire brigade would not be able to use the nearest emergency exit in half of the fire scenarios, such that the fire brigade in these scenarios would have to travel maximum 2500 m.



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7 Option: Emergency corridor with frequent access

7.1 Description of the option The cross section of this option is the same as the basic option, with the excep-tion that under the tracks, it is assumed that there is an emergency corridor in-stead of shelters.

The tunnel is equipped with ventilation as described below. The jet fans are used as supplementary fans for the tunnel ventilation.

In an emergency situation the trains can be evacuated via the emergency walk-way to the nearest hatch to the emergency corridor. The hatches for the emer-gency corridor are located between the railway tracks. Via the safety corridor the passengers can walk to the nearest emergency evacuation shaft.

The emergency corridor below the railway tracks can resist the design fire. It is equipped with a separate system for fresh air supply.

The location of big shafts with stairs and ventilation and small ventilation shafts is the same as for the basic option, please see section 6.1.

The main features of this option are summarized in the Table 10-1.



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Figure 7-1 Cross section of option with emergency corridor with frequent access

7.2 Tunnel ventilation The tunnel ventilation for this option is almost identical to the ventilation for the “basic option” with the exception that there are no shelters, but the corridor under the tracks will be used as escape corridor.

The tunnel ventilation is divided in sections: from station to station. Only for one typical section the tunnel ventilation system is described in the text and shown in Figure 7-1.



• At emergency shafts (2500 m from the station and 2500 m between shafts): - Ventilation plant for air supply to the tunnel.

Jet fans

Walkway Walkway

Emergency corridor

Utilities Ventilation of emergency corridor



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- Ventilation plant for air supply/pressurization of the escape corridor. - Ventilation plant for pressurization of the staircase.

• At ventilation shafts (1250 m from stations and shafts): - Ventilation plant for extraction.


Figure 7-2 Fire scenario, Option with emergency corridor

7.2.2 Operation of the tunnel ventilation Normal conditions During normal conditions it may be possible to create sufficient ventilation (Fresh air supply) by the piston effect via piston effect shafts and extraction shafts. In case the above recommended 1-dimensional simulation show, that this will not be possible, it will be necessary to supply fresh air with the tunnel ventilation system. Some of the supply plants and some of the extraction plants may be used. How many and at which location shall be determined based upon new simulations.

1250 1250 1250 1250L

2500 2500

Smoke

exhaust

Em

ergency E

xit

Station

50 50

Emergency

Exit

Smoke

exhaust

Emergencyhatches

Emergencyhatches


Escape route



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Emergency conditions (Fire in the tunnel) In case the burning train is stopped at station platform, the smoke will be ex-tracted by the ventilation plant at the station.

If the burning train stops between two stations the smoke will be extracted through the smoke exhaust shaft next to the burning train.


The ventilation plants for pressurization of escape corridor and staircases will be started when a fire occurs.


As shown in Figure 7-2, the trapped trains on both side of the fire site can be free of smoke. The fresh air supply from stations and emergency shafts create a flow with a velocity ≥ vCritical. The jet fans can be used to maintain the velocity.

After the evacuation, the Fire Brigade can change to longitudinal ventilation, to get smoke-free access to the fire site from the one side. The Ventilation plants shall therefore have the necessary capacity to maintain an air flow with critical velocity. During this operation, it may be necessary to use the jet fans.


7.3.1 Evacuation of passengers from the burning train The passengers will escape from the burning train in the same way as described in section 6.3.1 above, but instead of going to an emergency shelter below the tracks they will go to an emergency corridor below the tracks. In this emergen-cy corridor, they will proceed to the nearest emergency exit, which is maximum 1250 m away. The emergency exit shaft should be located beside the tunnel and there should be a connection directly from the emergency corridor to the emer-gency shaft.

The stairs down to the emergency corridor could be as shown in Figure 6-1. It is envisaged that the distance between these stairs is only 50 m.

Hence, the distance which the passengers will have to walk after having reached the end of the train will at maximum be 2 times 50 m (two staircases will have to be used, as one staircase will not provide the same capacity as one walkway). Hence, the length, which the last passenger will have to walk after



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having passed the end of the train, will be maximum 100 m as opposed to the maximum 500 m considered in section 6.3.1. This will take 2.6 minutes using the model of NFPA 130, and the total time until the last passenger is within the emergency corridor becomes 13 minutes as opposed to the 24 minutes in sec-tion 6.3.1.

This is still a long time considering that a very rough method has been used, and depending on the results of a proper evacuation analysis it may be required to increase the tunnel diameter in order to increase the width of the walkway.

As indicated in section 6.3.1 the width of the stairs leading down to the emer-gency corridor may be considered not to meet the requirements stated in Table 4-1.

As noted in section 6.3.1 the concept of having escape to the room below the railway track has to our knowledge not yet been used in any railway tunnel. The concept has been used in road tunnels, but using it in a railway tunnel may be more difficult due to the large number of passengers that can be onboard a train, and the smaller dimensions of railway tunnels compared to road tunnels.

7.3.2 Protection of other trains in the tunnel As in section 6.3.2.

7.3.3 Access for the fire brigade As in section 6.3.3.



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8 Option: Short distance between ventilation shafts

8.1 Description of the option The cross section of this option is the same as the basic option with the excep-tion that it is assumed that the only path of evacuation is via the emergency walkways.

The tunnel is equipped with many small ventilation shafts, around 3 m diame-ter. These ventilation shafts with relatively small diameter are assumed to be constructed using a shaft boring machine or raise boring.

As for the basic option and the option with emergency corridor, see section 6 and 7, it assumed that the distance between big shafts with stairs and ventilation is 2500 m. The distance between small ventilation shafts is 500 m. This dis-tance makes sure that the distance to a smoke-free area is the same as to cross passages as required from common international standards, see Table 4-1.

In an emergency situation the trains can be evacuated via the emergency walk-way to the nearest emergency exit shaft. The protection of the passengers dur-ing emergency evacuation relies on the use of intensive ventilation with ad-vanced control.




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Figure 8-1 Cross section of option with short distance between ventilation shafts

8.2 Tunnel ventilation The tunnel ventilation for this option is almost identical with the ventilation for the “basic option” with the exception that there is short distance between venti-lation shafts (500 m in stead of 1250 m) and that smoke extraction will normal-ly be from two exhaust shafts as opposed to one. With the short distance be-tween smoke exhaust the extent of the smoke plume will be reduced.

The tunnel ventilation is divided in sections: from station to station. Only for one typical section the tunnel ventilation system is described in the text and shown in Figure 8-1.



Jet fans

Walkway Walkway

No specific use



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• At emergency shafts (2500 m from the station and 2500 m between shafts): - Ventilation plant for air supply to the tunnel. - Ventilation plant for air supply/pressurization of the escape corridor. - Ventilation plant for pressurization of the staircase.

• At ventilation shafts (500 m from stations and shafts and 500 m between ventilation shafts): - Ventilation plant for extraction.


Figure 8-2 Fire scenario, Short distance between ventilation shafts

2500 2500

Em

ergency E

xit

Smoke exhaust

Station

500 500

Emergency

Exit


Escape route



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.

8.2.2 Operation of the tunnel ventilation Normal conditions During normal conditions it may be possible to create sufficient ventilation (Fresh air supply) by the piston effect via piston effect shafts and extraction shafts. In case the above recommended 1-dimensional simulation show, that this will not be possible, it will be necessary to supply fresh air with the tunnel ventilation system. Some of the supply plants and some of the extraction plants may be used. How many and at which location shall be determined based upon new simulations.


Emergency conditions (Fire in the tunnel) In case the burning train stops at station platform the smoke will be extracted by the ventilation plant at the station.

If the burning train stops between two stations the smoke will be extracted through the smoke exhaust shafts next to the burning train.


The ventilation plants for pressurization of escape corridor and staircases will be started when a fire occurs.


As shown in Figure 8-2, the trapped trains on both side of the fire site can be free of smoke. The fresh air supply from stations and emergency shafts create a flow with a velocity ≥ vCritical. The jet fans can be used to maintain the velocity.

After the evacuation, the Fire Brigade can change to longitudinal ventilation, to get smoke-free access to the fire site from the one side. The ventilation plants shall therefore have the necessary capacity to maintain an air flow with critical velocity. During this operation, it may be necessary to use the jet fans.


8.3.1 Evacuation of passengers from the burning train The passengers will escape from the burning train in the same way as described in section 6.3.1 above, but instead of going to an emergency shelter below the tracks they will continue on the walkway until the next emergency exit in their walking direction.



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The smoke will be extracted at the two ventilation shafts adjacent to the burn-ing train. Hence, the passengers escaping from the train will walk in a smoke-filled tunnel until they have passed the first ventilation shaft, and then the con-ditions on the walkway will be significantly improved, as the exhaust ventila-tion should be designed, such that very little smoke is spread to the other side of the ventilation shaft.

The 2500 m distance between emergency exits is clearly not in accordance with the requirements to such exits stated in Table 4-1. The 500 m distance between the ventilation shafts is in accordance with the requirements for distances be-tween cross passages from UIC and 2001/16/EC. However, the conditions on the other side of the ventilation shaft can hardly be considered to be as safe as in a cross passage, such that formally the requirements in the table cannot be considered to be met.

Most of the smoke will be extracted by the shaft that is closest to the fire. Hence, if the train is located such that the passengers will have to walk the maximum distance of 500 m to the nearest ventilation shaft, then they will walk in a tunnel that is nearly smoke-free. Hence, for comparison with the other op-tions, the situation where the fire is located with 250 m to both ventilation shafts, such that the passengers will be exposed to half of the smoke from the fire, is considered.

A rough calculation, using NFPA 130 as described in section 4.4, of time for the passengers to reach safety within the shelters gives the following results:

• The number of passengers walking in one direction is 674 as indicated in section 6.3.1.

• The time for the passengers to walk past the end of train on one walkway is estimated at 10.3 min. as indicated in section 6.3.1.

• The last passenger will have to walk 250 m - 103 m = 147 m from the end of the train to reach the ventilation shaft in accordance with the assumption on the location of the fire. (The 103 m is the distance from the fire to the end of the train). The time to walk this distance will be 147 m / 38 m/min = 3.9 min.

• The total time until the last passenger has walked past the ventilation shaft is thus 14 min.

This is still a long time considering that a very rough method has been used, and depending on the results of a proper evacuation analysis, it may be required to increase the tunnel diameter in order to increase the width of the walkway.

Another possibility will be to design the tunnel such that the passengers can also escape form the other side of the train and go to the walkway along the other side of the tunnel. However, this will conflict with the location between the tracks of the stairs to the emergency corridor.



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As opposed to the options considered in sections 6 and 7, this option does not include the concept of escape to a room below the track. Here, the critical issue is instead the design of the ventilation shafts, such that spread of smoke beyond the shafts used for smoke extraction is prevented. The reliability of the smoke extraction shall be very high as the safety of the escaping passengers relies on this system.

8.3.2 Protection of other trains in the tunnel With the envisaged ventilation concept there will be smoke in 500 m of the tunnel, which is less than the maximum 1250 m that may be smoke-filled in the options described in sections 6 and 7.

Any train on the opposite track stopped within the 500 m will be seriously en-dangered. Hence, the procedures in the event of a fire in a train would be to op-erate the trains on the other track, such that this situation is avoided.

The next train on the same track will presumably be further than 500 m behind the burning train, such that it will be protected against the smoke from the burn-ing train. If this concept is chosen then this should be further investigated.

8.3.3 Access for the fire brigade As long as there are still passengers within the 500 m zone between the two ventilation shafts used for extraction, the mode of operation cannot be changed. Hence, the fire brigade will have to walk in a partly smoke-filled tunnel in or-der to proceed towards the burning train before the passengers have escaped.

The fire brigade may go to the tunnel via the nearest emergency exit from where they will at maximum have to travel 1250 m to the burning train. If they know the exact position of the train they may use this information to select their direction of approach, selecting either a short distance with a relatively large amount of smoke or a longer distance with less smoke. Such choice may lead to selection of an emergency exit, which is more than 1250 m from the burning train.

If the fire is exactly at the location of an emergency exit, the distance to be tra-velled could be the 2500 m from the next emergency exit.

The fire brigade can change the operation of the ventilation plant, such that they can approach the fire in a nearly smoke-free tunnel, as explained in section 8.2.2, when it has been established that this change will not adversely affect the escaping passengers.



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9 Option: Dividing wall

9.1 Description of the option For this option it is assumed that there is a fire proof dividing wall between the two railway tracks. Due to the wall it will be necessary to increase the diameter of the tunnel by around 2 m. This means that the internal diameter will be around 13 m.

The wall between the two railway tracks will divide the tunnel into two sepa-rate half rooms, which will be independent regarding ventilation.

The dividing wall has closely spaced emergency doors. Through these doors the passengers can escape to the opposite tunnel, which will constitute a safe area in case of fire in one half of the tunnel.

As the tunnel diameter is larger for this option, there will be more available space below the railway tracks. This available space is so big, that it is possible to have special emergency vehicles here, that can be used for fire brigade access.

Because the opposite tunnel constitutes a safe space and because there is ample space for fire brigade access in the space below the tracks, there are no shafts between the railway stations.

The concept with a dividing wall corresponds to the concept for the Green Heart Railway Tunnel in The Netherlands. Please see the illustration below.

The spacing of the emergency doors is considered to be 150 m, which is the distance used for the Green Heart Tunnel. The width of the emergency walk-way will at minimum be the 0.8 m used for the other options, but the tunnel diameter described above should allow a walkway with a width of 1.5 m along each side of the dividing wall as in the Green Heart Tunnel, Ref. /6/.



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Figure 9-1 Cross section with dividing wall (Green Heart, Netherlands)


A variant of this option will be to include shafts for emergency exit and access as in the other options, if it is found that using the space below the tracks for access of the fire brigade is considered not to be feasible.

Figure 9-2 Cross section of option with dividing wall, principle (not to scale)

Jet fans

Walkway Walkway

Space for fire bri-gade access. Special vehicle

Dividing wall w. emergency doors

Ventilation of fire brigade access



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9.2 Tunnel ventilation This option is very different from the other options as a dividing wall between the two tracks is introduced.

With the tunnel divided into two tubes with a single track longitudinal ventila-tion can be used for environmental as well as for smoke ventilation. Therefore the ventilation shafts (smoke extraction) can be omitted.


• At stations: - Reversible tunnel ventilation plant for supply/extraction. - Ventilation plant for air supply/pressurization of the corridor (for fire brigade approach and maintenance). - Piston effect shafts.

• In the tunnel: - Jet fans with sufficient capacity to maintain an air velocity in each tunnel tube ≥ vCritical.

• As a variant of this option in case emergency shafts are necessary: Emergency shafts with: - Ventilation plant air supply to the tunnel. - Ventilation plant for pressurization of the staircase.



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Figure 9-3 Fire scenario, Option with dividing wall

9.2.2 Operation of the tunnel ventilation Normal conditions During normal conditions it will be possible to create sufficient ventilation (Fresh air supply) by the piston effect via piston effect shafts.

During congested operation it will be necessary to supply fresh air to the tunnel in the traffic direction from station to station (the push-pull principle).

Emergency conditions (Fire in the tunnel) In case the burning train stops at the station platform the smoke will be ex-tracted by the ventilation plant at the station.

If the burning train stops between two stations, the smoke will be pushed by the jet fans in the traffic direction to the next station and exhausted by the ventila-tion plant. The exhaust/supply grills can be located directly above the track at the platform or before/after the station.

E E EEEE E

Station

•Smoke extraction

Train stops

Jet FanFresh air supplySmoke exhaustEscape route

Emergency doorE



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Figure 9-4 Creating higher pressure in the safe tunnel than in the injured

As shown in Figure 9-3 trapped trains behind the burning train can be free of smoke. The jet fans create a flow with a velocity ≥ vCritical of fresh air supplied from stations and emergency shafts.

To avoid smoke ingress through the emergency doors during the evacuation it will be possible to create a slightly higher pressure in the safe tunnel than in the injured tube by operating the jet fans in a way so the smoke is sucked away in front of the train and the fresh air is blown through the safe tunnel tube. The principle is shown in Figure 9-4.


9.3.1 Evacuation of passengers from the burning train The passengers will escape from the burning train to the walkway along the dividing wall. They will then walk along the walkway to the nearest door through the dividing wall to the other track. Here they will walk towards the nearest station. However, as this can be a rather long distance, they should be picked up by one or more trains. These trains will be ordinary trains emptied for their passengers at the nearest station. They will of course have to drive very slowly, when approaching the part of the tunnel, where there are escaping passengers on the walkways.

The 150 m distance between doors in the dividing wall clearly meets the re-quirements regarding distance between cross passages stated in Table 4-1.

The most adverse situation will be a train with a fire exactly at the location of a door through the dividing wall, such that this door cannot be used.

Track II

Track I

1

Station

Station

Jet fans in operation(Stopped jet fans not shown) Burning train

Evacuation from tunnel tube withburning train to safe tunnel tube. Pressure in safe tunnel tube shall be slightly higher to prevent smoke ingress

Jet fans in operation(Stopped jet fans not shown)



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A rough calculation, using NFPA 130 as described in section 4.4, of time for the passengers to reach safety on the other side of the dividing wall gives the following results:

• The number of passengers walking in one direction is 674 as indicated in section 6.3.1.

• The time for the passengers to walk past the end of train on a 0.8 m wide walkway is estimated at 10.3 min. as indicated in section 6.3.1.

• The last passenger will have to walk 150 m - 103 m = 47 m from the end of the train to the door in the dividing wall. The time to walk this distance will be 47 m / 38 m/min = 1.2 min.

• The total time until the last passenger has passed the dividing wall is thus 12 min.

If the width of walkway is increased to 1.5 m then the time to walk past the end of the train will be reduced to 5.5 minutes and the total time until the last pas-senger has passed the diving wall is reduced to 7 minutes.

It is noted that this scenario, where the fire is exactly at a door in the dividing wall, is very unfortunate. With other locations of the fire the total time to reach safety will be reduced.

9.3.2 Protection of other trains in the tunnel All trains on the opposite track will be protected from the fire by the dividing wall.

For the trains on the same track as the burning train the following applies:

• The train in front of the burning train is driving past the next station.

• The trains behind the burning train will be protected by the longitudinal ventilation.

9.3.3 Access for the fire brigade The fire brigade is assumed to be using dedicated vehicles driving in the space underneath the tracks. Whether there should be one such vehicle located at each station, or fewer vehicles would be sufficient would require further study taking into account the location of the fire brigades along the railway.

The access stairs from the space under the tracks to the railway tubes should be located with short intervals, e.g. with same spacing as the doors in the dividing wall. These stairs will have to be further studied in order to finally establish whether this solution is feasible. The arrangement should be such that the fire



43

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brigade's use of the stairs will not seriously disturb the evacuation of the pas-sengers.

The fire brigade will approach the fire in the train from the upstream side pro-tected by the longitudinal ventilation.

It is noted that the concept of using the room below the railway track for trans-port of the fire brigade has to our knowledge not yet been used in any railway tunnel. The concept has been used in road tunnels, but using it in a railway tun-nel may be more difficult due to the smaller dimensions of railway tunnels compared to road tunnels. From the size of the tunnel considered here there should be sufficient space under the tracks, but whether there is sufficient space to arrange appropriate access stairs for the fire brigade has not yet been estab-lished.



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10 Comparison The main features of the options considered are indicated in Table 10-1.

In the basic option there is assumed to be smoke extraction to the nearest venti-lation shaft, which will be within 1250 m of the burning train. This implies that the location of the train shall be known.

With a maximum distance between entrances to the emergency shelters being 500 m, the roughly calculated evacuation time is estimated at maximum 24 mi-nutes (reference is made to section 4.4 regarding the very rough assumptions made). This seems to indicate that the evacuation facilities should be improved in this option.

Considering the small width of the emergency shelter, it may be difficult to es-tablish a design that will work in an emergency. E.g. the first passengers enter-ing the shelter may stop immediately within the shelter, such that the following passengers will not be able to enter the shelter.

The option "emergency corridor with frequent access" has the same ventilation concept as the basic concept. As there are doors to the emergency corridor be-low the tracks every 50 m, the roughly calculated maximum evacuation time is reduced to 13 minutes.

As the passengers entering the emergency corridor shall walk to the nearest emergency exit maximum 1250 m away it is less likely that the first passengers entering the corridor will block the access of following passengers than in the basic option.

In both the basic option and the option "emergency corridor with frequent access" the design of the entrances to the stairs need further consideration. It may be difficult to find a suitable solution.

It is noted that to our knowledge the concept of having escape to the room be-low the railway track has not yet been used in any railway tunnel. The concept has been used in road tunnels, but using it in a railway tunnel may be more dif-ficult due to the large number of passengers that can be onboard a train, and the smaller dimensions of railway tunnels compared to road tunnels.



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In both of the above options other trains will be protected against smoke from the fire except for maximum 1250 m of the tunnel.

The fire brigade will have to proceed at maximum 1250 m in a tunnel to reach the fire in both the above options. The ventilation system should ensure that the tunnel here is smoke-free.

Tunnel option 1 Basic option

2 Option:

Emergency cor-ridor with fre-quent access

3 Option:

Short distance between ventila-

tion shafts

4 Option:

Dividing wall

Overall Concept

One tunnel, two tracks Internal D 11.06m



One tunnel, two tracks separated by wall Internal D ~ 13 m

Shafts V: Ventilation E: Evacuation A: Fire brigade access

V every 1250 m E every 2500 m A every 2500 m



None

Emergency evacuation

Evacuation to emer-gency shafts or to shelters under the tracks.

Evacuation via safety corridor under the tracks. The evacua-tion corridor has access hatches every 50 m

Evacuation via nor-mal walkways at track level.

Evacuation safety is controlled with many vent shafts

Dividing wall between the tracks and emer-gency doors per 50m.

Evacuation to oppo-site half of the tunnel. Then evacuation with train.

Fire brigade access Access via stations and A shaft

Access via stations and A shaft

Access via stations and A shaft

Access with special emergency vehicle under the tracks

Ventilation concept

Jet fans

Fresh air to shelters

Smoke exhaust via V shaft

Jet fans

Fresh air to emer-gency corridor

Smoke exhaust via V shaft

Jet fans

Smoke exhaust via multiple small size V shafts

Jet fans

No smoke exhaust between stations

Table 10-1 Main features of tunnel investigated options

In the option "short distance between ventilations shafts” the passengers shall walk away from the fire to the nearest evacuation shaft maximum 2500 m away. As there are 500 m between smoke exhaust shafts and the smoke is ex-



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tracted at the exhaust shafts at both sides of the train, the passengers will only have to walk a limited distance in smoke. The rough calculation of maximum time for the passengers to reach a smoke-free part of the tunnel results in 14 minutes, i.e. the same order of magnitude as for the option "emergency corridor with frequent access".

The concept is however depending on a very accurate knowledge of the loca-tion of the tunnel fire in order for the system to function as intended. The weak point is this advanced detection system and the control systems which opens up for human errors in programming and operation of the system.

It is also noted that this option will formally not meet international require-ments, as walking past a ventilation shaft can hardly be considered to provide the same safety as walking into a cross passage.

Furthermore the access of the fire brigade to the burning train is more difficult than in the above two options as there will be smoke on both sides of the train. The operation of the ventilation system can be changed to provide access in a smoke-free tunnel, but such change cannot be done until it is certain that it will not adversely affect escaping passengers in the tunnel.

The advantage of this option is that the passengers need not use the space be-low the tracks requiring complicated design of access stairs etc.

All of the above options could be improved by providing facilities allowing the passengers also to leave the train on the side facing the other track and go to the opposite walkway. However, in the first two options this will conflict with the access stairs located between the tracks.

The option with dividing wall allows the passengers to escape to the opposite part of the tunnel. This solution results in the shortest time for passenger evacu-ation roughly estimated at maximum 12 or 7 minutes depending on whether the emergency walkway is 0.8 m wide as in the other options or 1.5 m wide, which it should be possible to include in this option due to the larger tunnel diameter. We consider this solution for the evacuation to be more reliable than the “basic option” and the “option with emergency corridor”, which require careful con-sideration of the detailed solution for access hatches for the shelter or corridor.

Regarding fire brigade access the option with dividing wall will, due to the larger tunnel diameter, allow a separate space under the tracks which can be used for access with special vehicles. The design of the fire brigades access from this space to the tracks will have to be further studied in order to finally establish whether this solution is feasible. The arrangement should be such that the fire brigade's use of the stairs will not seriously disturb the evacuation of the passengers.

Regarding operation of the ventilation, the dividing of the tunnel allows a more robust solution which is easy to control, as there is only one option for the di-rection of the smoke ventilation.



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The main disadvantage of this option is the additional costs due to the increased diameter. However, this may be more or less balanced by the savings as no shafts are needed.

The option with a diving wall is considered to be the best from a safety point of view. This option is therefore recommend if there are no or only insignificant additional costs involved compared to the other options. Even if the additional costs are larger, this option should be preferred, as long as the additional costs are not disproportionate with the value of the reduction in risk, cf. the descrip-tion of the ALARP principle in section 4.5.



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11 References /1/ NFPA 130. Standard for Fixed Guideway Transit and Passenger Rail Sys-

tems. 2010 Edition.

/2/ Directive 2001/16/EC - Interoperability of the trans-European conventional rail system. Aspect: 'Safety in railway tunnels'. Published in the Official Journal of European Union 7.3.2008 under the heading "Commission decision of 20 December 2007 concerning the tech-nical specification of interoperability relating to 'safety in railway tunnels' in the trans-European conventional and high-speed rail system. (2008/163/EC)"

/3/ International Union of Railways: UIC code 779-9. Safety in railway tun-nels. 1st edition, August 2003.

/4/ COWI: Metropolitan Express Railway. Report on records of tunnel fire accidents. Doc. No. 72156-1, 2009-11-20.

/5/ Health & Safety Executive, UK: The tolerability of risk from nuclear pow-er stations. 1988, revised 1992. ISBN 0 11 886368 1.

/6/ Homepage of HSL Zuid: http://www.hslzuid.nl/hsl/uk/lijn/Safety/Safety_in_tunnels/Safety_of_Groene_Hart_tunnel/index.jsp

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72156-2 Evacuation and Ventilation

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