Concept adopted for long railway tunnels in Croatia Marko Vajdi , mag.ing.aedif. Tanja Mikuli , mag.ing.aedif. Darko Šari , mag.ing.aedif. mr.sc. Stjepan Kralj, dipl.ing.gra . Institut IGH, d.d., Hrvatska

Abstract After almost two decades marked by domination of road infrastructure projects, the new investment cycle has been initiated in order to revitalize currently dilapidated and noncompetitive rail infrastructure. The National Railway Infrastructure Program, adopted in 2008, defines plan for the construction, modernization and maintenance of railway infrastructure in order to make the current railway network more modern, safer, more efficient and commercially attractive. In keeping with the objectives set in the Program, the preparation of design documentation was initiated for a number of large-scale infrastructure projects in the scope of which the construction of new tunnel structures is also envisaged. New tunnel structures are to be built along existing railway corridors to make railways compliant with European technical & technological standards and regulations, and to take into account geographical features of the terrain. A number of tunnel structures are situated along the high-efficiency railway line "National Border (Botovo) - Zagreb - Rijeka". The most interesting ones are: Kapela 1, 9,273.87 m in length Kapela 2, 14,386 m in length In addition, the new Bibinje Tunnel, 3,000 m in length, is to be built along the railway line M606 Knin - Zadar. Vast experience gathered in the design of numerous road tunnels has successfully been transferred and used in the design of railway tunnels, while other necessary knowledge and state-of-the-art information has been obtained from foreign railway authorities and through consultation of relevant literature. Parameters significant for selecting the tunnel concept and cross-section (safety, technical & economic analyses), and the method used for solving safety issues (evacuation, ventilation, and fire detection) in accordance with the tunnel concept selected, are presented in the paper.

Povzetek Po skoraj dveh desetletjih, ki jih je zaznamovalo prevladovanje cestnih infrastrukturnih projektov, se je za el novi naložbeni cikel za ponovno oživitev zanemarjene in nekonkuren ne železniške infrastrukture. Nacionalni program železniške infrastrukture, sprejet leta 2008, opredeljuje na rt za gradnjo, posodobitev in vzdrževanje železniške infrastrukture za doseganje sodobnejšega, varnejšega, u inkovitejšega in poslovno privla nejšega obstoje ega železniškega omrežja. Za doseganje ciljev, postavljenih v programu, se je za ela priprava projektne dokumentacije za ve velikih infrastrukturnih projektov, v okviru katerih je predvidena tudi gradnja konstrukcij v novih predorih. Nove konstrukcije v predorih je treba graditi vzdolž obstoje ih železnišVajdi , M., Mikuli , T., Šari , D., Kralj, S.: Mode, sprejet za dolge železniške predore na Hrvaškem

Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

kih koridorjev, da se železnice uskladijo z evropskimi tehni nimi in tehnološkimi standardi ter predpisi in se upoštevajo geografske zna ilnosti terena. Ve konstrukcij v predorih je umeš enih na železniški progi visoke zmogljivosti „Državna meja (Botovo) - Zagreb - Rijeka“. Najzanimivejši so: Kapela 1, dolžina 9.273,87 m Kapela 2, dolžina 14.386 m Poleg tega je treba zgraditi tudi novi predor Bibinje v dolžini 3.000 m na železniški progi M606 Knin - Zadar. Pri projektiranju železniških predorov je bilo uspešno prenesenih in uporabljenih veliko izkušenj, pridobljenih pri projektiranju številnih cestnih predorov, drugo potrebno znanje in najsodobnejše informacije pa so bile pridobljene od tujih železniških uprav in ustrezne literature. Prispevek predstavlja parametre, pomembne za izbiro zasnove in pre nega preseka predorov (varnost, tehni no-ekonomske analize), ter metode, uporabljene za reševanje varnostnih vprašanj (evakuacija, prezra evanje, odkrivanje požarov) v skladu z izbrano zasnovo predorov.

~∗~∗~∗~ 1 Introduction Railways throughout Europe are facing a period of development and several tunnel projects are undertaken. The experience with the safety and design of such projects has shown that the most important decision is related to the selection of tunnel configuration for long railway tunnels. The selection of the appropriate tunnel configuration is based on decision criteria such as operability, safety and costs. If a single track system is in question, we have two possible conceptual solutions: Single track tunnel with a parallel service tunnel, Single track tunnel with emergency exits. The second of the two above mentioned concepts is applied on the railway bypass of the Bibinje community, i.e. the Tunnel Bibinje. In the case of double track tunnel the basic tunnel configurations are: One double track tunnel with a service tunnel; Two single track tunnels with a service tunnel; Three single track tunnels (in case of huge traffic volume); Two single track tunnels without a service tunnel. The last configuration has been selected in the recent tunnel projects as a compromise between safety and costs, [7].

2 Applied concepts of other tunnels on the single track lines – „Bibinje” Tunnel Relocation of the existing line is planned for the part of the single track line M606 between Knin and Zadar, to a location outside the inhabited part of Bibinje. Due to the demanding technical elements of the line and the relief complexity of terrain, the railway bypass of Bibinje includes construction of a new 3000 m long railway tunnel. Since this is a single track line, planned for mixed traffic, but mostly freight trains, the tunnel shall be constructed as a single tube tunnel with a single track and additional emergency exists, in order to provide adequate safety for tunnel users in case of emergency situations (fire or other accidents) in the tunnel. Additional emergency exits will be in the form of a service tunnel and a vertical shaft. The service tunnel shall be constructed 915 meters away from the entrance portal, i.e. 938 meters to the next evacuation exit (vertical shaft). This i sin accordance with the provisions of Directive 2008/163/EC (item 4.2.2.9.) and technical interoperability specifications relevant for „safety in railway tunnels“ (item 4.2.2.6.3.) which proposes exits at every 1000m as a minimum. The service tunnel location is determined by the conditions that the tunnel is as short as possible and easy to connect with the traffic

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

network. Longitudinal grade of the service tunnel is 12%. Clearance is 360 cm wide and 350 cm high, which enable a free passage for a typical emergency vehicle equipped with all required equipment. This solution, i.e. position of the service tunnel near the portals, gives one more point of approach to the tunnel tube by means of emergency vehicles. In order to satisfy the requirement of maximum allowed distance between emergency exits (1000 meters) the vertical shaft is to be approached from the second service tunnel which runs parallel with the main tunnel tube for app. 147 meters length, which is connected with the two emergency exits

through the main tunnel tube. It shall be equipped with equipment at the level of shelters, which includes lighting, signal lights for emergency evacuation, communication equipment, approaches for emergency teams etc. Location of the vertical shaft is to be at the position with the thinnest overburden over the tunnel tube, in order to optimize the construction of the shaft itself, at he same time shortening the emergency evacuation path. Since the vertical shaft is also to serve as tunnel ventilation, shorter vertical shaft decreases energy occurring during tunnel ventilation.

Figure 1. Vertical shaft [11]

Layout dimensions of the shaft are 10,6×8,4 meters. The ventilation shaft, elevator shaft and staircase, i.e. ramps min. clearance width 150 cm are planned to be within this emergency shaft, all in accordance with the valid standards for emergency evacuation paths. Evacuation from the service tunnel is planned by a staircase in the first stage, to gain height required for ventilation pipes to pass from the ventilation shaft into the main tunnel tube. After 3 staircase half-flights, evacuation is to continue by means of ramps grade 10%, thus every corner of the shaft has a landing, dimensions 150×150 cm.

3 Long tunnel concept applied on double track lines - Tunnels „Kapela 1“ and „Kapela 2“ Two following two concepts were considered in conceptual designs of subsection Skradnik – Ledenica: Double track tunnel with two parallel tracks in the same tunnel tube. Service tunnel, which is connected to the main tunnel tube by cross passages (Fig. 2), serves as a safe area for evacuation. Two parallel single-track tunnels that consist of two parallel tunnel tubes each with one track, and cross passages separated by fire doors, (Fig. 3).

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

Figure 2. Double-track tunnel tube with the connection to the service tunnel, [3]

Figure 3. Two parallel single-track tunnel tubes connected by a cross passage, [3]

From the safety point of view, it has generally been argued that twin tube tunnels are safer than single tube tunnels, and that new tunnels should therefore be built according to the parallel twin tube concept. In case of an accident in one tunnel tube, the other serves as a safe area for evacuation. Main tunnel tubes are connected by cross passages spaced at every 500 m. The cross connection allows the evacuation of train passengers from the affected tunnel tube to the safe tube, as well as rescue service access to the accident site. Although tunnels are statistically safer than the rest of the railway network, the public aversion to fire accidents in tunnels can justify more extensive safety measures than would be required on the basis of the estimated number of fatalities alone, [1]. Double track in single tube tunnels generally have large cross section areas (80-115 m2) with big air volumes under the tunnel roof, which will normally give good smoke stratification during the first phases near the fire. The natural ventilation direction in the tunnel is relatively unpredictable if there are several trains running in different directions. Normally there will be more than one train in the tunnel and if immediate evacuation from a train in the tunnel is necessary, it is important to regard any possible traffic on the other track, [6]. Double track tunnel is preferable from the economic point of view. However, the construction of a double track tunnel of

greater length would also entail the construction of a service tunnel. Since service tunnels have smaller dimensions, their construction becomes technologically demanding. In terms of construction technology by NATM method, it is more acceptable to construct two parallel tunnels with larger cross sections, where communication between initial cut points is achieved by excavating cross passages, which largely simplifies and reduces the cost of works. After safety, technical and economic analyses were completed, it was established that the concept with two single-track tunnel tubes, regardless of its shortcomings, is the best solution for long tunnels (such as Kapela 1 and Kapela 2). This design concept with two tunnel tubes allows uninterrupted maintenance of one tunnel tube, while the other is in operation.

4 Selection of tunnel cross section The cross section of the Bibinje Tunnel was chosen for the design speed of Vmax = 100 km/h and was constructed in accordance with the clearance defined by the Bylaw on technical requirements for safety of railway traffic which all railway lines must satisfy. The clearance of the chosen cross section of the single track tunnel is 44m2. Designed cross section allows all required equipment to be mounted within the tunnel profile at the

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

same time ensuring the demanding emergency evacuation path. (Fig. 4).

Figure 4. Normal cross section of Tunnel „Bibinje”, [11]

Tunnel cross section on the railway line from State Border (Botovo) – Zagreb – Rijeka was selected for design speed of V = 200 km/h (+/- 25%). Tunnel cross section meets the clearance requirements defined by the Ordinance on Technical Requirements for Railway Traffic Safety (Official Gazette of the Republic of Croatia No 128/08) as well as the requirements defined by the Austrian guidelines for railway tunnel design RVE 02.00.01 (proposal, 28 November 2006). The designed cross section allows for the accommodation of necessary equipment within the profile, it meets the criteria for pressure comfort, and ensures the required evacuation possibilities. An aerodynamic study was carried out for the selected cross section, which confirmed the selection. The main objective of the study was to carry out numerical simulations in order to evaluate: The pressure forces acting on the tunnel structure and the installed mechanical equipment; The comfort of the passengers due to pressure fluctuations; The traction power requirements. The occurrence of the minimum pressure during a single train passage is associated with the train leaving the tunnel and is located near the train exit portal. The maximum positive and negative deviations from normal pressure for the run of a single high speed train are +2.7/-2.7 kPa, whereas for the run of the single freight train they are +4.0/-2.9 kPa.

For single runs of high speed, fast passenger and regional trains the medical criterion for pressure changes is satisfied (max 10kPa during tunnel passage without accounting for train sealing). Considering the installed power available on the train it is possible to reach a speed of 200 km/h with the high speed train and 160 km/h for the regional train even with the gradient of 0.8%. The maximum traction power of 14.4 MW is required for the train passages in the tunnel with the constant inclination of 0.8% for the freight train and of 10.4 MW for the high speed train. The required traction power of 14.4 MW exceeds the available power on the freight train. The operational speed of 140 km/h of the freight train can not be achieved. For the occurring air velocities in the tunnel of approx. 42 m/s the dynamic pressure is in the magnitude of approx. 2.5 kPa, [8]. The clear opening of the selected cross section of single-track tunnels amounts to 49.5 m2. Area of excavation for the tunnel with invert is 73.74 m2, and 66.40 m2 for the tunnel without invert (Fig. 5.).

Figure 5. Cross section of a single tube tunnel with necessary equipment, [4]

5 Selection of track structure in the tunnel Track structure inside the tunnels shall be a ballastless track (like RHEDA 2000® system or similar), (Fig. 6.). The first application of ballastless tracks was the installation of a slab track in tunnels. The already present solid tunnel bottom slab as well as the requirement of a low construction height of track provides best conditions for using ballastless tracks on newly built railway lines. In general, all construction types of ballastless track used on earthwork

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

structures can be realized in tunnels. Here, hydraulically bound support layers are not necessary. Concrete layers are applied with reduced thickness directly on the tunnel base. Especially the concrete layer with a normal thickness of 30 cm may be reduced to 15 cm for use in tunnels, directly on the tunnel substructure slab.

Figure 6. Suggested system RHEDA 2000®

The climatic conditions in tunnels are advantageous for ballastless track types with concrete slabs. The temperature in the tunnel is quite homogeneous, except the areas of about 100 m next to the tunnel portals. Thus, the crack distributing reinforcement of the concrete slab could be reduced or even omitted, [5]. Ballastless tracks provide a high level of track stability, which allows for the possibility of silent running of trains and high comfort journey. Maintenance needs are decreased significantly, which largely contributes to the reduction of costs during life cycle, and better usability. The principal function of the permanent way is to ensure vertical and horizontal stability of the track grate, and the dynamic load of rolling stock and stresses caused by temperature changes in the rails act on it. Due to stiff substructure in tunnels, the degradation of the ballast track is accelerated, and the grains become worn and crushed fast at the contact zone with the concrete base, under the impact of traffic load. In this way, the unevenness of track geometry is increased, and at the same time the empty space between larger particles of ballast becomes filled with small particles which causes drainage problems (mudding of the ballast) and this will require frequent maintenance.

Increased ballast degradation on a stiff substructure is explained by the following assumptions in literature, [9]: A stiff substructure limits the extent to which the rails distribute the load, so that higher loadings result directly under the sleepers on a quasi-static basis. At increased speeds, greater particle velocity in the ballast layer is experienced; velocity of vertical movement at the underside of the sleeper is doubled as the train speed increases from V = 160 km/h to 250 km/h. This effect is reduced with greater elasticity in the track structure. Harmonic excitation, for example as a result of secondary bending between the rail supports locations, is reduced with increasing elasticity of the track structure. For the above mentioned reasons, and due to the fact that ballast maintenance inside the tunnel is much more difficult and complex, it was found that the simplest solution is to use ballastless tracks in tunnels. Asphalt or concrete base course may be placed directly on tunnel base, and its thickness may be reduced, on the condition that corresponding calculations are proven, as compared to the thickness of layers of the track structure outside the tunnel, [9].

Figure 7. Prefabricated slabs

Figure 8. Fire fighting vehicles [2]

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

One of Investor's requirements was the implementation of road intervention vehicles in tunnels. In order to satisfy this requirement, the design provides for the placement of prefabricated slabs that will fill the area between rails to the plane of track gauge, and thus enable undisturbed passage of road vehicles inside the tunnel. Prefabricated slabs (Fig. 7.), according to the patented solution of track manufacturer, shall meet the following requirements: bearing capacity – relevant intervention vehicle (Fig. 8); they shall enable drainage from the top surface into a planned drain channel; they shall be fixed in such a way to prevent lifting due to negative pressure.

6 Ventilation It has to be stressed here that there are no generally accepted standards or a consensus regarding the role, or the chosen type of ventilation in railway tunnels Namely, railway tunnels are, as a rule, much safer that road tunnels because of the nature of the ongoing traffic. Therefore the safety and fire protection area where ventilation plays a major role was not of the primary interest until now. Because of the integrity of railway traffic, it has to be said that the general measures of safety enhancement in railway traffic directly influenced the increase of safety level and fire protection in the tunnels themselves. Road tunnel ventilation, where specific requirements are set for regular operation and operation in fire incidents, differ from railway tunnels where ventilation systems are primarily connected to fire incidents. During a fire incident, the railway tunnel ventilation must operate safely and efficiently in smoke propagation, it must ensure optimal conditions for evacuation of passengers, approach and action of emergency teams. The priority in design and realization of the system is the protection of lives, followed by protection of goods and the structure itself. As a rule, the ventilation system is a part of the system and equipment which decreases the effects of fire in the tunnel. As such the ventilation system must be in synergy with all other available safety and protection measures. Due to the lack of national regulations that specifically covers the subject field of ventilation in railway tunnels, preparation of

this part of design documents mostly depends on the EU regulations (Technical Specifications for Interoperability (TSI) – Safety in Railway Tunnels 2008/163/EC), as well as on technical manuals of the top organization in the filed of railway traffic - UIC, which is some areas give detailed information regarding design development and which are not contrary to TSI. The above mentioned regulations however defined only the general criteria, from the aspect of safety and fire protection, without giving concrete numerical data for the forthcoming design stages, e.g. general aerodynamics and thermal dynamics. The ventilation system operation strategy for the „Bibinje“ Tunnel, in normal operation conditions, does not foresee ventilation operation. The tunnel is self ventilated by the “piston” effect of the passing composition. In case the train stops inside the tunnel, in order to keep the CO level less than 100 ppm in the tunnel (the railway will not be electric at the beginning, but will use diesel engines), a ventilation system is designed consisting of fans placed in the vertical shaft. Depending on the position of the trained in the tunnel, during a fire incident, the fans are turned on to the suction or the pressure operation mode. The ventilation system can also operate to reach the required longitudinal flow, reduce the air temperature inside the tunnel and remove the dissipated heat generated by the train itself, but this is not its primary function. The tunnel microclimate is monitored by means of instruments from the remote control center, and when the instruments react to increased temperature levels, the ventilation system is turned automatically on. Based on the implemented multi-criteria analysis of parameters influencing the choice of ventilation in the Tunnels „Kapela1“ and „Kapela2“, a system of longitudinal reversible ventilation was proposed, with impulse fans, equidistant inside the tunnel tubes, laterally above the traffic surfaces. According to the present level of knowledge, this is the most acceptable technical and economic design solution, with a satisfactory level of safety and fire protection. Operation strategy of the proposed ventilation system is these tunnels are designed in the same way as in tunnel „Bibinje“.

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Vajdi , M., Mikuli , T., Šari , D., Kralj, S.: Concept adopted for long railway tunnels in Croatia

7 Strategies of intervention in case of emergency situations Since it is planned that all interventions in emergency situations, in case of accidents in the tunnel, shall be carried out by road vehicles, the concept of fire protection and construction solutions are based on this requirement. Portals and exists from the service tunnels have emergency rescue points which are directly connected to the existing road network by means of asphalt approach roads. All these rescue points have a surface are of minimum 500 m2, equipped with water supply, electrical power supply and telecommunication equippment, all in accordance with the „Technical specifications for interoperability“ relating to safety in railway tunnels (item 4.2.2.12.). The fire fighting intervention strategy for tunnels is based on intervention outside the tunnel, which means that in case of accidents with a resulting fire, the train shall be pulled outside the tunnel area, where the evacuation of passengers and fire extinguishing shall take place. However, in case an intervention is required inside the tunnel and the train can not be pulled outside the tunnel area, the operation surfaces shall be established in any of the tunnel parts in the immediate vicinity of the fire from which the fire extinguishing can take place.

8 Conclusion Based on the conducted technological, technical, safety and economic analyses for the selected method of tunnel construction according to NATM principles in the anticipated rock material, the concept of single tube, single track tunnels with additional evacuation exits, and the concept of two parallel single-track tunnels were chosen as the best solution. Furthermore, in selection of particular technical concepts of the tunnel, primarily routing through tunnels and the choice of the permanent way, the optimization of operational costs of tunnels was taken

into consideration as well. The selected tunnel concept meets all safety criteria related to tunnel users in case of accidents. Moreover, the selected cross section satisfies the aerodynamic requirements for standard rolling stock of high performance railways.

References Zuber P.: Compared safety features for rail tunnels, Safe & Reliable Tunnels. Innovative European Achievements, First International Symposium, Prague 2004. Sommerlechner C., Valo R., Neumann C..: Emergency exercises in Austrian railway tunnels, 3rd International Conference „Tunnel Safety and Ventilation“ 2006, Graz Institut IGH: Idejno rješenje tunela željezni ke pruge visoke u inkovitosti Državna granica (Botova) – Zagreb – Rijeka, Zagreb, 2008./ Preliminary concept of high performance railway line State Border (Botovo) –ZagrebRijeka, Zagreb, 2008 Institut IGH: Idejni projekt tunela željezni ke pruge visoke u inkovitosti Državna granica (Botova) – Zagreb – Rijeka, poddionica Skradnik – Ledenica/ Preliminary design of high performance railway line State Border (Botovo) –Zagreb-Rijeka, subsection Skradnik –Ledenica, Zagreb, 2008. Fruehauf W., Jungwirth J., Scholz M., Stoiberer H.: „Slab track systems on engineering structures – A holistic design approach“, RTR Special – The German High Speed Rail System, March 2008, str. 78-88 Anderson T., Paaske Borre J.: Safety in railway tunnels and selection of tunnel concept, ESReDA 23rd Seminar, 2002, Delft University Diamantidis D.: Risk acceptance criteria for long railway tunnels: a need for periodic review, PSAM 6 International Conference San Juan Puerto Rico, 2002. Nyfeler S., Reinke P.: Aerodynamic studies of the high performance railway line between Zagreb and Rijeka, HBI Haerter Consulting Engineers, 2009. RTR Special: Slab track, Eurailpress, Hamburg, 2006. Slab track, the commercial case: A scoping study, Britpave by Ove Arup & Partners Ltd,2003 Institut IGH: Idejni projekt tunela Bibinje/ Preliminary design of the tunnel Bibinje, 2009.

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