Bunker
A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs, artillery, or other attacks.
When a house is purpose-built with a bunker, the normal location is a reinforced below-ground bathroom with fiber-reinforced plastic shells.
Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and block radiation.
[2] The word possibly has a Scandinavian origin: Old Swedish bunke means "boards used to protect the cargo of a ship".
[4] In the First World War the belligerents built underground shelters, called dugouts in English, while the Germans used the term Bunker.
[7] The military sense of the word was imported into English during World War II, at first in reference to specifically German dug-outs; according to the Oxford English Dictionary, the sense of "military dug-out; a reinforced concrete shelter" is first recorded on 13 October 1939, in "A Nazi field gun hidden in a cemented 'bunker' on the Western front".
The walls of the 'Batterie Todt' gun installation in northern France were up to 3.5 metres (11 ft) thick,[11] and an underground bunker was constructed for the V-3 cannon.
They were built mainly by nations like Germany during World War II to protect important industries from aerial bombardment.
Industrial bunkers are also built for control rooms of dangerous activities, such as tests of rocket engines or explosive experiments.
[citation needed] To prevent the shelter from floating to the surface in high groundwater, some designs have a skirt held down with the overburden.
A specialized version of the munitions bunker called a Gravel Gertie is designed to contain radioactive debris from an explosive accident while assembling or disassembling nuclear warheads.
Most expedient blast shelters are civil engineering structures that contain large, buried tubes or pipes such as sewage or rapid transit tunnels.
Bunkers designed for large ground shocks must have sprung internal buildings to protect inhabitants from the walls and floors.
[18] Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and block radiation.
In bunkers inhabited for prolonged periods, large amounts of ventilation or air conditioning must be provided in order to prevent ill effects of heat.
In bunkers designed for war-time use, manually operated ventilators must be provided because supplies of electricity or gas are unreliable.
One form of expedient blast valve is worn flat rubber tire treads nailed or bolted to frames strong enough to resist the maximum overpressure.
Famous bunkers include the post-World War I Maginot Line on the French eastern border and Czechoslovak border fortifications mainly on the northern Czech border facing Germany (but to lesser extent all around), Fort Eben-Emael in Belgium, Alpine Wall on the north of Italy, World War II Führerbunker and in Italy, industrial Marnate's Bunker, the V-weapon installations in Germany (Mittelwerk) & France (La Coupole, and the Blockhaus d'Éperlecques) and the Cold War installations in the United States (Cheyenne Mountain Complex, Site R, and The Greenbrier), United Kingdom (Burlington), Sweden (Boden Fortress) and Canada (Diefenbunker).
