In 1836 the 4.5 kilometer long Tollwitz-Dürrenberger Feldbahn was opened on a track width of 585 mm with the first 133 m long railway tunnel in Germany. The Oberauer Tunnel , the first full- line railway tunnel in Germany, was built between 1837 and 1839 on the Leipzig – Dresden line . The Paneriai railway tunnel and the Kaunas railway tunnel in Lithuania were built between 1859 and 1862 . A large number of railway tunnels were built in Germany between 1860 and 1880. Of the more than 900 rail tunnels in Germany today, almost two thirds date from this time. The early tunnels were built according to the building regulations of the state railways , which were very different in content. As a rule, tunnels were only laid out where the geology ensured that the mountains would last longer. The tunneling technology of that time, the main safety element of which was the wooden sheeting, did not allow tunnels near the surface or tunnels in weathered rock. Conversely, a base vault was therefore not necessary at that time .
On September 1, 1988, the then German Federal Railroad abolished the previously prescribed warning whistle in front of tunnels. After numerous exemption regulations had previously existed (especially in the S-Bahn area), it would have been necessary to signal the respective regulation, the benefits of which would have been disproportionate to their costs.
The cross-sectional areas of rail tunnels tended to increase in the course of technical development: For example, in the age of steam locomotives, a standard cross-section of 46 m² was provided for double-track railway tunnels in Germany; the high-speed lines of the DB, which are laid out for 300 km / h, have a standard cross-section of 92 m². All tunnels planned for mixed traffic since 1998 have two parallel, single-track tubes. In Switzerland, the 15 km long Gotthard tunnel (line speed 125 km / h) was satisfied with 38 m², but increased the area for the Hauenstein base tunnel (v max 140 km / h) to 48 m², for the Heitersberg tunnel (v max according to aerodynamic criteria : 170 km / h) on 58 m² and in the tunnels of the Bahn 2000 project (v max 200 km / h) on about 70 m².
In the course of the new lines , more and more tunnels have been built in Germany since the late 1970s. A total of 87 tunnels with a total length of around 150 km were built for the high-speed lines Hanover – Würzburg and Mannheim – Stuttgart, which went into operation in 1991 . On the high-speed route Cologne – Rhine / Main , which was opened in 2002 , as a pure passenger route, gradients of up to 40 (instead of the previous 12.5) per thousand could be achieved. With 30 tunnels with a length of 47 km, the proportion of tunnels in the total route fell from 38% to 27%. The new Nuremberg – Ingolstadt line , designed for passenger and fast (light) freight traffic, has nine tubes, a total of 27 km long, and a tunnel share of around one third. On the Nuremberg – Erfurt high-speed line, which was released in 2018, the proportion of tunnels and bridges in the section between Ebensfeld and Erfurt is over 50%, the new Erfurt – Leipzig / Halle line released in 2017 also has numerous long tunnels and the Wendlingen – Ulm line that is currently under construction continues over 50% tunnel new records.
In the area of the Deutsche Bundesbahn , the regulation for railway tunnels (printed matter 853) developed by the Bundesbahn-Zentralamt Minden and published for the first time in 1962 regulates the principles of planning, building and maintaining tunnels. It was updated several times, especially in the course of the construction of the first German new lines in the 1980s.
For the construction of new railway tunnels in Germany today, the tunnel guideline ( EBA guideline: Requirements of fire and disaster protection for the construction and operation of railway tunnels ) of the Federal Railway Authority is decisive. This not only regulates the requirements for the construction of such tunnels, but also provides specifications for its operation.
In 2003, Deutsche Bahn announced a program to increase safety for 22 tubes in the old network and all 49 tunnels over 1000 m in length on the two new lines opened in 1991. For around 150 million euros, additional accesses to the tunnel portals as well as new rescue areas at the portals, improved lighting and better marking of the escape routes were created . Dry pipes and additional emergency exits were requested by experts but not implemented . In Switzerland (as of 2004), more than 60 railway tunnels of more than 1000 m in length should be equipped with self-rescue facilities. Among other things, the establishment of approximately 60 cm wide escape routes and emergency lighting was planned.
At the end of 2019, Deutsche Bahn operated a total of 745 rail tunnels with a total length of 593 km; both with an increasing tendency. In 2011 there were 798 railway tunnels with a total length of 515 km.
Railway tunnels are examined for their stability and safety through regular assessments at fixed intervals.
The Wallers Ash tunnel collapse in 1842 was one of the first tunnel accidents in railway history.
Variants in terms of routing
Spur or head tunnels lead through a rock spur or head or the foothills of a mountain. They are mostly found in river valleys. In view of their normally moderate incline, many railway lines were laid through these valleys, but some of them often have large river loops . Then spur or head tunnels are required to straighten and shorten the route . Usually, spur tunnels are barely longer than 200 meters. Until it was blown up in 2010, the Felstortunnel near Etterzhausen was the shortest railway tunnel in Germany with a length of only 16 m, since then it has been the glass carrier tunnel III (18 m length) on the Black Forest Railway . As an unusually long spur tunnel, the Kaiser Wilhelm tunnel on the Moselle route reaches a length of 4203 m. The Elstertalbahn from Gera Süd to Weischlitz and the Nuremberg – Cheb line have a particularly large number of spur tunnels , where seven tunnels are passed through on the six-kilometer section between Vorra and Neuhaus .
Spur tunnels are also used if instabilities of the rock masses above are feared in the event of a rock spur being completely eroded. This is the case, for example, with the only 28-meter-long Viktoria Tunnel (after Queen Victoria ) on the Lötschberg south ramp.
On the SBB Basel – Biel line , nine particularly short spur tunnels follow each other between Roches and Moutier at short intervals. Here, too, the construction was motivated to maintain the stability of the penetrated rock outcrops.
A vertex tunnel is a tunnel that crosses a mountain below a mountain ridge . Characteristic are long ramps at both ends of the summit tunnel, which rise from the valleys along the mountain flanks to the height of the tunnel portals. The greater the height difference to be overcome on the ramp, the shorter the tunnel to cross the mountain. The oldest still used railway tunnel in Germany, the 691 m long Buschtunnel (1838), pierces a ridge in the south of Aachen after a 2 km long steep ramp with 27 ‰ .
A base tunnel leads in one line through a mountain, without steep access ramps from the valley floor . Since the route does not lead up the mountain flanks, a base tunnel is significantly longer than a top tunnel. The first base tunnels were built at the beginning of the 20th century. While the Simplon Tunnel, opened in 1905, due to the different topography of the northern and southern Alps, with one flat and one steep driveway each (and overburden in some cases more than 2000 meters), must still be described as a hybrid form between the apex and base tunnel according to the above definition In 1916, the 2.5 km long summit tunnel from 1858 was relieved by a real 8 km long base tunnel at Hauenstein in Switzerland . Further examples are the Apennine Base Tunnel , probably also the Furka Base Tunnel - which, however, begins in the Urserental at over 1,500 meters above sea level - and the Lötschberg Base Tunnel . Other base tunnels are the longest tunnel in the world on the Gotthard in Switzerland , which was cut through on October 15, 2010 (57 km, opening June 1, 2016) as well as the Brenner Base Tunnel , which is currently under construction, and the section under Mont-Cenis between France and Italy.
In contrast to tunnels, which overcome an existing obstacle underground, spiral tunnels help to overcome inclines in steep topography by artificially lengthening the route with loops or circular bends . If the terrain requires it, the curve of a hairpin or a roundabout lying on an incline is designed entirely or partially as a spiral tunnel.
Tunnels in which the route turns in the opposite direction of travel are referred to as turning tunnels or loop tunnels, while those with an angle of rotation of more than approximately 270 ° are known as screw tunnels, circular tunnels or spiral tunnels. Reversible tunnels only occur in connection with double or multiple loops .
See also: List of reverse rail tunnels
Underwater tunnels are used to cross bodies of water. Well-known examples are the Seikan tunnel with a length of 54 kilometers (23 of which are under the seabed), the 50 kilometers long Eurotunnel , which runs over 38 kilometers under the floor of the English Channel , the underground part of the Øresund connection , the tunnel under the Great Belt and the seven-kilometer crossing under the Severn Estuary between England and Wales.
With a length of 53.850 kilometers up to the breakthrough of the Gotthard base tunnel, the Seikan tunnel was the longest tunnel in the world.
In the rail-road tunnel, road traffic and railroad share the tunnel. In Ennepetal , both modes of transport use the Kruiner tunnel , in which the Ennepetalbahn crosses the Elberfeld – Dortmund railway line . The 89 m long structure was completed in 1882. Currently, the tunnel is only used by freight trains that stop in front of the entrance; their staff then switch on a signal system that blocks the passage to road vehicles.
Operational problems of longer tunnels
When operating long railway tunnels, various phenomena occur which are generally referred to as the tunnel problem . These are primarily caused by the limited space of the tunnel and the resulting restricted air volume, as well as its insufficient circulation. The greatest problems occur with thermal vehicles, i.e. steam locomotives and locomotives with internal combustion engines (e.g. diesel locomotives). Other problems arise in the rescue and evacuation of people and the use of life-saving equipment after accidents in rail operations.
The “tunnel problem” of the steam age
The temperature becomes a general problem, especially in tunnels with a thick mountain cover. Because geothermal energy means that the deeper the tunnel is underground, the warmer it is. As a result, the temperature in the tunnel can be much higher than outside the tunnel. In long base tunnels, the temperature can be over 40 ° C. The sharp change in temperature when passing through places high demands on the traction vehicles, especially in connection with the often high humidity, because the high ambient temperature makes it more difficult to dissipate the waste heat from the traction motors. This basic problem is further exacerbated by the fact that, due to the limited cross-section of the tunnel, there is no large amount of air available to absorb this heat. This can be a problem even at relatively low tunnel temperatures, especially with diesel locomotives in single-lane, steeply inclined tunnels, since their engines require a lot of cooling air under full load, i.e. they require a large cooling capacity. The problem is particularly acute when there are several motors in close succession on the train. Here the temperature of the intake air rises steeply from engine to engine. In the triple traction of the Krauss-Maffei ML 4000 C'C ' on the slopes of the Rocky Mountains , the intake air of the sixth engine measured temperatures of over 95 ° C.
Since only a limited amount of oxygen is available through the tunnel cross-section, this tends to decrease when thermal vehicles are used. The reduced oxygen content of the air has a direct impact on the combustion process, which in turn reduces the performance of the vehicles. In addition, staff and passengers can also be at risk from a lack of oxygen. For them, however, the carbon monoxide problem is the greater danger.
Due to the incomplete combustion in diesel engines, fuel can also get into the exhaust system, which ignites when you leave the tunnel due to the increased availability of oxygen. This problem with the fuel in the exhaust system occurred in the first six machines of the Krauss-Maffei ML 4000 C'C ' .
Risk of poisoning from carbon monoxide
This problem is partly directly related to the oxygen problem: the reduced oxygen content promotes incomplete combustion, which means that more carbon monoxide is produced instead of carbon dioxide. Since this is a poisonous gas, it can quickly become life-threatening. The problem most often occurs with steam locomotives and the wrong fuel choice. But even with diesel locomotives, the exhaust gases can contain too much carbon monoxide.
The accident on October 4, 1926 in the Rickentunnel can be traced back to this problem. Here a train got stuck in the tunnel, suffocating the train crew and part of the rescue team.
Vision problem, smoke problem
Especially with steam locomotives, the chimney in front of the driver's cab causes problems because it blows the harmful exhaust gases into the mostly open driver's cabs. This makes it difficult for the locomotive crew to see the tunnel route, especially the signals in the tunnel.
Promote natural ventilation and artificial ventilation
In some cases, the weather itself promotes improved ventilation of the tunnel, so in most Alpine tunnels there is a constant draft, which is caused by the different air pressure between the two tunnel portals. On the other hand, a tunnel that is perpendicular to the main weather direction and has an apex in the tunnel is almost not naturally ventilated.
In tunnels that rise evenly in one direction, the chimney effect supports natural tunnel ventilation. This effect is rather weak in the case of rail tunnels because of the flat incline.
Two single-lane tunnel tubes lying next to each other, which can only be used in one direction, ventilate better than a double-lane tunnel which can be used in both directions.
Exhaust chimneys can also be installed in tunnels with a weak cover. This was the normal practice for city tunnels during the steam age.
One solution to the tunnel problem is to artificially ventilate the tunnel with a fan. Due to the high temperature, ventilation may also be necessary in the initial phase of electrified tunnels.
Electric train conveyance
Most problems can be dealt with by introducing electric train conveyance. This usually also results in an increase in performance and is therefore often given priority despite the higher costs.
Because people in the hot, almost 20-kilometer-long Simplon Tunnel were concerned about getting a grip on the problems with steam operation, electric locomotives were used right from the start.
In America, the tunnels in Baltimore (Howard Street Tunnel) and New York (Park Avenue Tunnel and access roads to Pennsylvania Station ) were electrified. The Great Northern Railroad's Cascade Tunnel was electrified in 1909 and the Hoosac Tunnel in 1911.
In the case of steam locomotives, the arrangement of the driver's cab at the top of the locomotive in tunnels brought considerable advantages for the locomotive driver. The advantage of the cab-forward locomotives is bought at the expense of the disadvantages in terms of lighting and fuel transport.
The concept proved its worth with oil firing, but it was not cheap to operate. As a result, cab forwards could not spread widely and remained niche designs. On the South Adriatic Railway , the classes Gr670 and Gr671 had the largest number of coal-fired cab-forward locomotives in operation. The Southern Pacific Railroad , SP procured a large number of them with oil firing. The SP bought a total of 244 cab-forward locomotives, which were divided into classes AC-1 to AC-8 and AC-10 to AC-12.
Injection of cooling water into the exhaust gases
This technique is used in North America on rail lines with longer tunnels. Water is injected into the exhaust gas flow or into the exhaust air from the radiator of diesel locomotives in order to bind the thermal energy to the water droplets and dissipate it: one liter of water can absorb more than four times the amount of heat compared to one m³ of air.
Changed cooling air intake
The air inlets for the engine and radiator are usually located as high as possible to prevent foreign bodies and, above all, snow from being drawn in. But precisely this has more disadvantages than advantages in the tunnel, as the exhaust gases from the engines and exhaust air from the coolers also spread very quickly in the upper area and, in contrast to the open route, there is no fresh air in this area. For this reason, constructive changes are required for locomotives that run on routes with a high proportion of tunnels (example: the New Zealand class DX for operation through the Otira tunnel ). Most of these changes do not finally solve the problem of possible overheating due to the intake of hot and used tunnel air, but they can increase the driving time until the critical limit of overheating is reached, which can significantly increase the tunnel length that can be driven through without problems.
Another possibility is to arrange the fans of the cooler in such a way that a larger amount of air is brought through the cooler. This is because the fans for cooling the engine in diesel locomotives are usually located above the radiator and suck the air through it. In order to improve the effectiveness of the cooler, the fans were moved under the cooler and the air pressed through them. The Southern Pacific Railroad ordered such locomotives from 1973 with the series SD 45T-2 and SD 40T-2. These are known as "Tunnel Motors". This construction method is particularly useful if several short tunnels follow one another along a route.
Another possibility is the greatest possible spatial separation of the intake and exhaust air openings, which also suggests lowering the intake openings from the roof edge to the side walls. For this purpose, it is very important to determine the air currents along the vehicle in the tunnel, and especially the turbulence in the exhaust air. The effect is most effective if the cooling air is sucked in from an area into which no exhaust air can have reached yet.
Longer tunnels with only one newer type of tunnel are equipped with emergency exits . These emergency exits lead via ladders or stairs to outdoor rescue areas or, as with the Arlberg tunnel , to the parallel road tunnel . This gives rescue workers additional access so that people can be rescued and evacuated more quickly.
The railways operate fire-fighting and rescue trains to support rescue and recovery . These are usually equipped with equipment, medical and transport trolleys. The use of these rescue trains is trained in regular exercises with the rescue workers responsible on site.
In newer tunnels, systems are in place to switch off the overhead line in the event of an accident in the tunnel area and to be able to ground it. In some of the larger tunnels , radio systems for authorities , emergency lighting , telephones and fire-fighting water pipes are available.
Operational Problems of Long Tunnels: Present
Under certain circumstances, the significantly increased air resistance compared to open routes can also prove to be a problem. The air resistance in the tunnel is an extremely complex phenomenon, which is difficult to capture with computer models, as different processes interlock. On the one hand, the front of the train pushes a kind of “air cushion” in front of it in the direction of travel (piston effect). Other air packets tend to be "sucked" backwards along the train due to the pressure difference between the tip of the train (overpressure) and the end of the train (negative pressure). Both currents are subject to a more or less strong resistance , depending on whether laminar or turbulent flow patterns prevail. The resulting air resistance therefore depends on the length, cross-sectional area and surface properties of both the tunnel and the train. While the drag at high speed trains thanks to aerodynamic shaping up to relatively high speeds can be kept within tolerable limits, it can in goods and especially at Rolling Road trains on due labyrinthine surfaces very easy to strong vortices and - especially with long tunnels and even at moderately high speeds - correspondingly high air resistance. To overcome this, not only must a disproportionate amount of energy be expended; this must also be removed from the tunnel - in the form of heat.
If long tunnels are to be crossed at high speeds, other aerodynamic phenomena such as the sudden fluctuations in air pressure when a train enters the tunnel ( tunnel bang ) must be taken into account in addition to the transfer of energy .
- The Pfingstberg tunnel and the forest tunnel on the Mannheim – Stuttgart high-speed line were built primarily for environmental reasons (to avoid the separation effect of the railway line) and not to drive through a mountain. They have little overburden and were built in open construction pits that were covered over.
- In inner-city areas in particular, the construction of a new railway can often only be carried out underground, in the tunnel. This is especially true for underground and S-Bahn systems.
- The Weissenstein tunnel is sometimes used as the longest cinema in the world .
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