Bunker
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2008-07-11T15:31:05Z
The Anome
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fixing [[Category:Fortification]]
{{otheruses4|the military fortification}}
A military '''bunker''' is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks. They were used extensively in [[World War I]], [[World War II]], and the [[Cold War]] for weapons facilities, command & control centers, and stores (e.g., for [[Nuclear warfare|nuclear war]]).
[[Image:Albania bunkers.jpg|right|thumb|Bunkers in [[Albania]]<ref>''[http://www.washingtonpost.com/ac2/wp-dyn/A61698-2005Jan9?language=printer Albania's Chemical Cache Raises Fears About Others]'' - ''[[Washington Post]]'', Monday 10 January 2005, Page A01</ref>]]
{{externalimage|align=right|images=
[http://www.bunkerpictures.nl Atlantikwall]<br>
[http://www.bunkermuzeum.hu/index_en.html Bunker museums]<br>
[http://www.lonesentry.com/articles/fortifications/index.html Italy]<br>
[http://www.lonesentry.com/articles/fortifications/index.html Italy]<br>
[http://www.pillboxesuk.co.uk/ UK pillboxes]<br>
}}
{{wiktionarypar|bunker}}
<!--this should be a wikicategory, instead-->
{{sidebar|'''Articles for Bunker Types'''
*[[Air-raid shelter]]
*[[Blast shelter]]
*[[Flak tower]]
*[[Martello tower]]
*[[Observation post]]
}}
{{sidebar|'''Line-Type Bunker Systems'''
*[[Atlantic Wall]]
*[[GHQ Line]]
*[[Maginot Line]]
*[[Siegfried Line]]
*[[Taunton Stop Line]]
}}
==Types==
===Trench===
This type of bunker is a small concrete structure, partly dug into the ground, which is usually a part of a trench system. Such bunkers give the defending soldiers better protection than the open [[trench]] and also include top protection against aerial attack ([[grenade]]s, [[Mortar (weapon)|mortar]] [[Shell (projectile)|shell]]s). They also provide shelter against the weather.<ref>''[http://archives.queensu.ca/wwi/warfare.html An archival look at World War I]'' (from the [[Queen's University]] Archives, Kingston, Ontario, Canada. Accessed 2008-02-10.</ref>
The front bunker of a trench system usually includes [[machine gun]]s or mortars and forms a dominant shooting post. The rear bunkers are usually used as [[command post]]s or [[Tactical Operations Center]] ([[Tactical Operations Center|TOC]]), for storage and as field [[hospital]]s to attend to wounded soldiers.
===Pillbox===
Dug-in guard posts (with loopholes through which to fire guns) and made from concrete are also known as 'pillboxes'. The originally jocular name arose from their perceived similarity to the cylindrical boxes in which medical pills were once sold.<ref>''[http://www.pillbox-study-group.org.uk/whypillbox.htm Why Pillbox?]'' - Hellis, John; an article from the ''Loopholes'' journal with further references. Retrieved 2007-09-08.</ref> They are in effect a trench firing step hardened to protect against small-arms fire and grenades and raised to improve the field of fire.
[[Image:Pillbox.JPG|right|thumb|A WW2 type 22 Pillbox on the Norfolk coast of England]]
[[Image:1878222225.jpg|thumb|right|Inside the Chowder Bay Bunker near the [[Georges Head Battery]] on [[Sydney Harbour]].]]
Their use seems to have developed during the period of the [[World War I|First World War]] when [[defence in depth]] using the [[Machine Gun Corps]] was being perfected. However, most of those seen in Britain, having been left over from the [[British anti-invasion preparations of World War II|1940 invasion scare]], are designed for use by riflemen rather than for [[machine gun]]ners. The concrete nature of pillboxes means that they are a feature of prepared positions and their original use is likely to have been in the [[Hindenburg Line]]. This is likely to have been the time when they acquired their incongruous English name. The ''[[Oxford English Dictionary]]'''s earliest record of the use of the word ''pillbox'' in connection with a defensive post is from 13 September 1917, after the German withdrawal onto the Hindenburg Line.
Pillboxes are often [[Military camouflage|camouflaged]] in order to conceal their location and to maximize the element of surprise. They may be part of a trench system, form an interlocking line of defence with other pillboxes by providing covering fire to each other ([[defence in depth]]), or they may be placed to guard strategic structures such as bridges and jetties.
Many pillboxes were built before WWII in the [[Czech Republic]] in defence against the German invasion of Czechoslovakia. None of these were actually used in the end, since the German military met no resistance when invading the country because it was effectively forced to capitulate as a result of [[Munich Agreement|Allies annexing]] the country's border areas and handing them to Germany. The [[Japan|Japanese]] also made use of pillboxes in their fortifications of [[Battle of Iwo Jima|Iwo Jima]].
===Artillery===
Many artillery installations, especially for [[naval artillery]] have historically been protected by extensive bunker systems. These usually housed the crews serving the weapons, protected the ammunition against counter-battery fire, and in numerous examples also protected the guns themselves, though this was usually a trade-off reducing their fields of fire.
Since artillery bunkers were often constructed for very large guns in a pre-defined location and as part of a larger system of defenses (such as for a port town or a seacoast), they are amongst the largest individual pre-Cold War bunker types found. The walls of installations like the '[[Cross-Channel guns in the Second World War#German Guns|Batterie Todt]]' in northern France were up to 3.5 m thick, with the gun inside capable of reaching over the [[English Channel]] to the opposite coast.<ref>[http://www.batterietodt.com/ Accueil] (from the Muse du Mur de l'Atlantique d'Audinghen website, in French. Accessed 2008-02-10.)</ref>
{{sidebar|'''Mines & Caves converted to WWII Industrial Bunkers'''
*[[Ebensee]]
*[[Government bunker (Germany) |Lager Rebstock]]
*[[Mittelwerk]]
*[[Saint Leu d'Esserent]]
}}
===Industrial===
Typical industrial bunkers include mining sites, food storage areas, dumps for materials, data storage, and sometimes living quarters. They were built mainly by nations like Germany during World War II to protect important industries from [[bombing|aerial bombardment]]. Industrial bunkers are also built for control rooms of dangerous activities, e.g. tests of rocket engines or explosive experiments. They are also built in order to perform dangerous experiments in them or to store radioactive or explosive goods. Such bunkers also exist on non-military facilities.
===Personal===
When a house is purpose-built with a bunker, the normal location is a reinforced below-grade bathroom with large cabinets. One common design approach uses [[fiber-reinforced plastic]] shells. Compressive protection may be provided by inexpensive earth arching. The overburden is designed to shield from radiation. To prevent the shelter from floating to the surface in high groundwater, some designs have a skirt held-down with the overburden.<ref name=Kearny>{{cite web |last=Kearny |first=Cresson H |url=http://www.oism.org/nwss/ |format=html |accessdate=2008-06-19 |title=Nuclear War Survival Skills |year=1987 |isbn=094248701X |work= |publisher=Oak Ridge National Laboratory }} '''NOTE''': Kearny recommends stockpiling materials for a blast or [[fallout shelter]] and constructing it only if war appears very likely.</ref>
==Design==
===Blast protection===
Bunkers deflect the blast wave from nearby [[explosion]]s to prevent ear and internal injuries to people sheltering in the bunker. While frame buildings collapse from as little as 3 [[Pound-force per square inch|psi]] (0.2 [[Bar (unit)|bar]]) of [[overpressure]], bunkers are regularly constructed to survive several hundred psi (over 10 bar). This substantially decreases the likelihood that a [[bomb]] (other than a [[bunker buster]]) can harm the structure.
The basic plan is to provide a structure that is very strong in [[physical compression]]. The most common purpose-built structure is a buried, steel [[reinforced concrete]] [[Vault (architecture)|vault]] or [[arch]]. Most expedient (makeshift) blast shelters are civil engineering structures that contain large buried tubes or pipes such as sewage or rapid transit tunnels. Improvised purpose-built blast shelters normally use earthen arches or vaults. To form these, a narrow (1-2 metre) flexible tent of thin wood is placed in a deep trench (usually the apex is below grade), and then covered with cloth or plastic, and then covered with 1-2 meters of tamped earth.
A large ground shock can move the walls of a bunker several centimeters in a few milliseconds. Bunkers designed for large ground shocks must have sprung internal buildings, hammocks, or bean-bag chairs to protect inhabitants from the walls and floors.
===Nuclear protection===
Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the [[shock wave]] passes, and block [[radiation]]. Usually these features are easy to provide. The overburden ([[soil]]) and structure provide substantial radiation shielding, and the negative pressure is usually only 1/3 of the overpressure.
[[Image:PanoBunker.jpg|right|thumb|A German bunker in the Netherlands.]]
===General features===
The doors must be at least as strong as the walls. The usual design is a trap-door, to minimize the size and expense. To reduce the weight, the door is normally constructed of steel, with a fitted steel lintel and frame. Very thick wood also serves, and is more resistant to fire because it chars rather than melts. If the door is on the surface and will be exposed to the blast wave, the edge of the door is normally counter-sunk in the frame so that the blast wave or a reflection cannot lift the edge. A bunker should have two doors. Door shafts may double as ventilation shafts to reduce digging.
In bunkers inhabited for prolonged periods, large amounts of [[ventilation (architecture)|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 of the most efficient manual ventilator designs is the [[Kearny Air Pump]]. Ventilation openings in a bunker must be protected by [[blast valve]]s. A blast valve is closed by a shock wave, but otherwise remains open. One form of expedient blast valve is tire-treads nailed or bolted to frames strong enough to resist the maximum overpressure.
If a bunker is in a built-up area, it may have to include water-cooling or an immersion tub and breathing tubes to protect inhabitants from fire storms.
Bunkers must also protect the inhabitants from normal weather, including rain, summer heat and winter cold. A normal form of rainproofing is to place plastic film on the bunker's main structure before burying it. Thick (5-mil or 0.13 mm), inexpensive [[polyethylene]] film serves quite well, because the overburden protects it from degradation by wind and sunlight.
[[Image:Blavand Bunker.jpg|thumb|right|Beach bunker with improvised art in [[Blåvand]], [[Denmark]].]]
==Famous installations==
Famous bunkers include the post-World War I [[Maginot Line]] on the French eastern border, World War II [[Führerbunker]], the V-weapon installations in Germany ([[Mittelwerk]]) & France (e.g. [[La Coupole]], and [[Le Blockhaus]]) and the Cold War installations in the [[United States]] ([[Cheyenne Mountain]], [[Site R]], and [[The Greenbrier]]), United Kingdom ([[Burlington (UK)|Burlington]]), Canada ([[Diefenbunker]]), and Australia ([[Bankstown Bunker]]). The [[Soviet Union]] maintained huge bunkers (one of the secondary uses of the very deeply dug [[Moscow Subway]] system was as nuclear shelters), and in [[Albania]], [[Enver Hoxha]] dotted the country with hundreds of thousands of bunkers. [[Osama bin Laden]] at one time was also rumoured to be hiding in massive 'underground fortresses' in [[Tora Bora]], though these would only be natural features strengthened and extended to some degree.
{{commons|Bunker}}
==References & Notes==
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