Air raid tunnels
An air-raid shelters , and tunnels bunker called, is an underground cavity in wartime the people as a shelter against air raids serves. The air raid shelter should not be confused with a cover ditch . Air raid tunnels were among the most bomb-proof bunkers of the Second World War . According to a study in the US Strategic Bombing Survey , air raid tunnels proved their worth because they withstood numerous direct bomb hits without injuring any of the bunker occupants.
Historical background
In 1935, the German Reich government passed the so-called Air Protection Act, expanded in 1937, which provided for the construction of air protection measures for suitable buildings. This was especially true for new buildings and was binding for all cities. Due to cost reasons and a lack of building materials , this law was implemented very slowly in practice. In October 1940, the Supreme Commander of the Wehrmacht issued an order for the construction of more air raid shelters for the civilian population. In 1943 there was hardly any building material available for new bunker systems in many cities, such as Berlin . The construction of air raid tunnels offered a good alternative here. In July 1943, an ordinance was issued that provided for the construction of air raid tunnels wherever it was possible due to the hydrological conditions . There were also regions, such as Graz , where the construction of air raid tunnels began relatively early, but further construction was delayed in the course of the war for cost reasons. There was also a lack of suitable specialists and suitable machines to advance the construction of the air raid tunnels. The further development of these protective tunnels was only reinforced again in the penultimate year of the war. In certain mining regions of the Ruhr area , old mining tunnels that were no longer required were also used as air raid protection tunnels.
Creation and structure
Basically there are two options for building air raid tunnels - either the creation of slope tunnels or the construction of deep tunnels. Slope tunnels are driven horizontally into the mountain by miners. Deep tunnels are excavated below the "normal" surface of the earth like mining tunnels . The construction of slope tunnels is less expensive than the construction of deep tunnels. Depending on the geology and local conditions, the tunnels were either built with a secure extension or unsecured. The German door frame was often used as an extension type for the extended tunnel . The secured tunnel sections were depending on local conditions, even with a masonry built of thick brick masonry. Where necessary, the air raid tunnels were built with a strong reinforced concrete wall . How and with what the tunnel was ultimately to be expanded, depended on the mountain pressure . According to the building regulations for air protection tunnels, the tunnels had to have a clear minimum width of 1.65 meters for single-row seating and a minimum clear width of 2.3 meters for double-row seating. The minimum usable clear height is 2.3 meters.
The tunnels had to be driven so deep below the surface of the earth that a protective layer of twelve meters of earth lay over the tunnel. In the case of slope tunnels that were excavated in rugged and solid rock , an overburden of six meters was considered sufficient. In practice, however, it turned out that for adequate protection against the effects of bombs it was necessary to maintain a minimum coverage of 15 meters. The respective air raid shelter had to have at least two entrances. There were tunnels with six entrances. In addition, some tunnels had several emergency exits through which one could get outside via stairs or a ramp. The tunnel entrances were bricked or made of reinforced concrete. The tunnel entrance was often followed by an angled access tunnel which, according to the building regulations, had to be bent at least three times in order to protect the bunker occupants from fragments of bombs. In addition, some of the tunnels were provided with gas-safe doors to protect the occupants from chemical warfare agents. Depending on the system, the tunnels had a length of a few tens of meters up to a hundred meters and more. The world's largest air raid shelter is the tunnel under Dortmund with a total length of 4.8 kilometers.
Interior, capacity and stay
There were vestibules and lounges in the air raid shelter. Depending on the design of the tunnel, the rooms were provided with one or two rows of opposite banks. The tunnel systems offered space for up to 100 people, depending on the size of the tunnel bunker. But there were also tunnel bunkers that were intended for over 1000 people. In the tunnel under Dortmund there was space for 80,000 to 100,000 people. The temperature in the air raid shelter was always ten degrees Celsius, and the cold tunnels were not heated. The people sat tightly packed in the tunnel bunkers. Four people had to share the space for each running meter of tunnel with two-row seating. So cramped, people often waited hours, sometimes even days, until the air raid was over. Due to the tightness in the tunnel, people warmed each other partly with their body heat, despite the lack of heating. The bunkers were provided with a ventilation system, which was usually provided with a main and a protective ventilation. In order to supply the technical systems with electrical energy, there was a machine room with the appropriate technology. But there were also tunnels that were equipped with makeshift ventilation shafts. Due to the large number of people in the bunker, the humidity in the tunnel increased. The tunnel bunkers were usually only equipped with very simple sanitary facilities. In addition to toilets, there were also some sinks. In order to be able to transport the wastewater out of the bunker in the event of a power failure, the wastewater lifting systems could also be operated by hand. Sometimes buckets were also used as toilets, or dry toilets were used in deep tunnels . In order to protect the tunnel from flooding in the event of a pipe burst , it was mandatory to equip the existing pipelines with gate valves. Additional collecting vessels had to be integrated into the lines.
Current condition
After the end of the war, the air raid tunnels were no longer needed and were left to their own devices, and many of the tunnels fell into disrepair. They offered bats a shelter. But there were also tunnel bunkers that were used for civilian purposes after the war. Some of the tunnels were used to grow mushrooms . There are also old tunnel bunkers that are used today for guided tours, such as part of the air raid shelter system on Heligoland that survived the blasting operation of 1947 . Other tunnel bunkers were later closed to the public due to mold growth. Over the years, various tunnel systems have lost their stability and have partially collapsed. In order to protect the population from damage caused by these collapsed tunnel systems, the systems have to be extensively examined, secured and filled with suitable materials such as concrete , dusk or electric flask.
Individual evidence
- ↑ a b c d e f g h i j k l m n Michael Foedrowitz: Bunker worlds, air raid systems in Northern Germany. 1st edition, Cristoph Links Verlag, Berlin 1998, ISBN 3-86153-155-0 .
- ↑ a b c d e Hauke Haubrock, Andreas O'Brien: The air raid shelter on the limestone hill. A former air raid shelter in Osnabrück, 4th edition, Verlag Books on Demand, Osnabrück 2012, ISBN 978-38-4481-154-4 .
- ↑ a b c d e Martin Rychlak, Stadt Salzgitter Specialist Service Order (Ed.): Former underground air raid tunnels in the area of the city of Salzgitter ( Memento from August 10, 2014 in the Internet Archive ) Final report, Salzgitter 2007, pp. 7–22.
- ^ A b Walter Brunner: Bombs on Graz: the Weissmann documentation. Leykam Verlag, Graz 1989, ISBN 3-7011-7201-3 .
- ^ A b Dietmar Arnold, Reiner Janick: Sirens and packed suitcases, everyday bunker life in Berlin. 1st edition, Cristoph Links Verlag, Berlin 2003, ISBN 3-86153-308-1 .
- ↑ Hochbunker Augustastraße 53/55. In: City of Witten, Planning Office. (Ed.): Open Monument Day, Witten 2013.
- ↑ a b c The world's largest air raid shelter is located under Dortmund . In: WAZ . November 5, 2013, p. 1 ( derwesten.de [accessed on January 2, 2016] Dortmund).
- ↑ a b Meyer-Hoissen: Structural air protection . In: THW (Hrsg.): Das Technische Hilfswerk, monthly magazine of the THW. No. 6, 2nd year, June 1955.
- ↑ a b c d e Contemporary witnesses cast in concrete. Bunker at Vieburger wood as a silent memorial to the Second World War. In: Carsten Frahm Verlag, Kiel local; The monthly city newspaper for the south of Kiel, Kiel January 2015, pp. 8–9.
- ↑ a b c d e f A bunker deep under the Wackenberg. In: PÄDSAK Wackenberger Echo; District newspaper for the Saarbrücken Wackenberg, Volume 31, No. 115/116, Saarbrücken 2007, pp. 24–26.
- ↑ The people dug themselves in . In: Kölner Stadtanzeiger . January 11, 2005 ( ksta.de [accessed January 2, 2016]).
Remarks
- ↑ However, only those injured who were damaged by the direct explosive effect of the bombs were taken into account in the evaluation. The United States Strategic Bombing Survey did not include personal injuries caused by poisoning by explosive gases from close hits in the area of the tunnel exits. (Source: Michael Foedrowitz: Bunkerwelten, air raids in Northern Germany. )