Blast shelter
Encyclopedia
A blast shelter is a place where people can go to protect themselves from bomb
blasts. It differs from a fallout shelter
, in that its main purpose is to protect from shock wave
s and overpressure
, instead of from radioactive
precipitation
, as a fallout shelter does. It is also possible for a shelter to protect from both blast and fallout
.
.
There are above-ground, below-ground, dedicated, dual-purpose, and potential blast shelters. Dedicated blast shelters are built specifically for the purpose of blast protection (see bunker
). Dual-purpose blast shelters are existing structures with blast protective properties that have been modified to accommodate people seeking protection from blast. Potential blast shelters are existing structures or geological features exhibiting blast protective properties that have potential to be used for protection from blast.
Blast shelters deflect the blast wave from nearby explosions to prevent ear and internal injuries to people sheltering in the bunker. While frame buildings collapse from as little as 3 psi (20 kPa) of overpressure
, blast shelters are regularly constructed to survive several hundred psi. This substantially decreases the likelihood that a bomb can harm the structure.
The basic plan is to provide a structure that is very strong in compression. The actual strength specification must be done individually, based on the nature and probability of the threat. A typical specification for heavy civil defence shelter in Europe during the Cold war was an overhead explosion of a 500 kiloton weapon at the height of 500 meters. Such a weapon would be used to attack soft target
s (factories, administrative centres, communications) in the area.
Only the most heavy bedrock-shelters would stand a chance of surviving. However, in the countryside or in a suburb, the likely distance to the explosion is much larger, as it is improbable that anyone would waste an expensive nuclear device on such targets. The most common purpose-built structure is a steel-reinforced concrete vault
or arch
buried or located in the basement of a house.
Most expedient blast shelters are civil engineering structures that contain large buried tubes or pipes such as sewage or rapid transit tunnels. Even these, nonetheless, require several additions to serve properly: blast doors, air-filtration and ventilation equipment, secondary exits, and air-proofing.
Improvised purpose-built blast shelters normally use earthen arches or vaults. To form these, a narrow (1-2 metre-wide) flexible tent of thin wood is placed in a deep trench (usually the apex of the tent is below grade), and then covered with cloth or plastic, and then covered with 1–2 meters of tamped earth. Shelters of this type are approved field expedient blast shelters of both the U.S. and China. Entrances are constructed from thick wooden frames. Blast valves are to be constructed from tire-treads laid on thick wooden grids..
Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and prompt radiation. The overburden and structure provide substantial radiation shielding, and the negative pressure is usually only 1/3 of the overpressure.
The doors must be at least as strong as the walls. The usual design is a trap-door, to minimize the size and expense. In dual-purpose shelters, which have a secondary peace time use, the door may be normal. To reduce the weight, the door is normally constructed of steel, with a fitted steel lintel and frame welded to the steel-reinforcement of the concrete. The shelter should be located so that there is no combustible material directly outside it.
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. If possible, this should be avoided, and the door built so that it is sheltered from the blast wave by other structures. The most useful construction is to build the door behind a 90°-turn in a corridor that has an exit for the overpressure.
A bunker commonly has two doors, one of which is convenient, and in peace time use, and the other is strong. Naturally, the shelter must always have a secondary exit which can be used if the primary door is blocked by debris. Door shafts may double as ventilation shafts to reduce the digging, although this is unadvisable.
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. However, most civilian-built improvised shelters do not need these as their structure cannot stand a shock large enough to seriously damage the occupants.
Earth is an excellent insulator. In bunkers inhabited for prolonged periods, large amounts of ventilation or air-conditioning must be provided to prevent heat prostration. In bunkers designed for war-time use, manually-operated ventilators must be provided because supplies of electricity or gas are unreliable. The simplest form of effective fan to cool a shelter is a wide, heavy frame with flaps that swings in the shelter's doorway and can be swung from hinges on the ceiling.
The flaps open in one direction and close in the other, pumping air. (This is a Kearny Air Pump
, or KAP, named after the inventor Cresson Kearny
.) Kearney asserts, based on field testing, that air filtration is not normally needed in a nuclear shelter. He asserts that fallout is either large enough to fall to the ground, or so fine that it will not settle and thus has little bulk to emit radiation. However, if possible, shelters of should have air-filtration to stop chemical, biological and nuclear impurities which may abound after an explosion.
Ventilation openings in a bunker must be protected by blast valves. A blast valve is closed by a shock wave, but otherwise remains open. If the bunker is in a built-up area, it may include water-cooling or an immersion tub and breathing tubes to protect inhabitants from fire storms. In these cases, the secondary exit is also most useful.
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 125 µm), inexpensive polyethylene
film serves quite well, because the overburden protects it from degradation by wind and sunlight. Naturally, a buried or basement-situated reinforced-concrete shelter usually has the normal appearance of a building.
When a house is purpose-built with a blast shelter, the normal location is a reinforced below-grade bathroom with large cabinets. In apartment houses, the shelter may double as storage space, as long as it can be swiftly emptied for its primary use. A shelter can easily be added in a new basement construction by taking an existing corner and adding two poured walls and a ceiling. This also works well as a wine or root cellar.
Some vendors provide true blast shelters engineered to provide good protection to individual families at modest cost. 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. A properly designed, properly installed home shelter does not become a sinkhole in the lawn. In Switzerland
, which requires shelters for private apartment blocks and large private houses, the lightest shelters are constructed of stainless steel.
During World War II
, people in London
and Moscow
survived bombing during the German
Blitz
by taking refuge in the subways
, e.g., the London underground
. In the second half of the 20th century, subways in eastern Europe
and USSR were constructed as blast shelters.
General:
Bomb
A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
blasts. It differs from a fallout shelter
Fallout shelter
A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War....
, in that its main purpose is to protect from shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
s and overpressure
Overpressure
The term Overpressure is applied to a pressure difference, relative to a "normal" or "ambient" pressure, in various circumstances:* In engineering: the pressure difference over the wall thickness of a pressure vessel...
, instead of from radioactive
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
, as a fallout shelter does. It is also possible for a shelter to protect from both blast and fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
.
Types of blast shelters
Blast shelters are a vital form of protection from nuclear attack and are employed in civil defenseCivil defense
Civil defense, civil defence or civil protection is an effort to protect the citizens of a state from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery...
.
There are above-ground, below-ground, dedicated, dual-purpose, and potential blast shelters. Dedicated blast shelters are built specifically for the purpose of blast protection (see bunker
Bunker
A military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...
). Dual-purpose blast shelters are existing structures with blast protective properties that have been modified to accommodate people seeking protection from blast. Potential blast shelters are existing structures or geological features exhibiting blast protective properties that have potential to be used for protection from blast.
Design of blast shelters
Overpressure
The term Overpressure is applied to a pressure difference, relative to a "normal" or "ambient" pressure, in various circumstances:* In engineering: the pressure difference over the wall thickness of a pressure vessel...
, blast shelters are regularly constructed to survive several hundred psi. This substantially decreases the likelihood that a bomb can harm the structure.
The basic plan is to provide a structure that is very strong in compression. The actual strength specification must be done individually, based on the nature and probability of the threat. A typical specification for heavy civil defence shelter in Europe during the Cold war was an overhead explosion of a 500 kiloton weapon at the height of 500 meters. Such a weapon would be used to attack soft target
Soft target
Soft target is a military term referring to unarmored/undefended targets needing to be destroyed. For example, a soft target would be an automobile, a house, or assembly of people while a hard target could be a main battle tank or a well defended installation...
s (factories, administrative centres, communications) in the area.
Only the most heavy bedrock-shelters would stand a chance of surviving. However, in the countryside or in a suburb, the likely distance to the explosion is much larger, as it is improbable that anyone would waste an expensive nuclear device on such targets. The most common purpose-built structure is a steel-reinforced concrete vault
Vault (architecture)
A Vault is an architectural term for an arched form used to provide a space with a ceiling or roof. The parts of a vault exert lateral thrust that require a counter resistance. When vaults are built underground, the ground gives all the resistance required...
or arch
Arch
An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...
buried or located in the basement of a house.
Most expedient blast shelters are civil engineering structures that contain large buried tubes or pipes such as sewage or rapid transit tunnels. Even these, nonetheless, require several additions to serve properly: blast doors, air-filtration and ventilation equipment, secondary exits, and air-proofing.
Improvised purpose-built blast shelters normally use earthen arches or vaults. To form these, a narrow (1-2 metre-wide) flexible tent of thin wood is placed in a deep trench (usually the apex of the tent is below grade), and then covered with cloth or plastic, and then covered with 1–2 meters of tamped earth. Shelters of this type are approved field expedient blast shelters of both the U.S. and China. Entrances are constructed from thick wooden frames. Blast valves are to be constructed from tire-treads laid on thick wooden grids..
Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and prompt radiation. The overburden and structure provide substantial radiation shielding, and the negative pressure is usually only 1/3 of the overpressure.
The doors must be at least as strong as the walls. The usual design is a trap-door, to minimize the size and expense. In dual-purpose shelters, which have a secondary peace time use, the door may be normal. To reduce the weight, the door is normally constructed of steel, with a fitted steel lintel and frame welded to the steel-reinforcement of the concrete. The shelter should be located so that there is no combustible material directly outside it.
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. If possible, this should be avoided, and the door built so that it is sheltered from the blast wave by other structures. The most useful construction is to build the door behind a 90°-turn in a corridor that has an exit for the overpressure.
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. However, most civilian-built improvised shelters do not need these as their structure cannot stand a shock large enough to seriously damage the occupants.
Earth is an excellent insulator. In bunkers inhabited for prolonged periods, large amounts of ventilation or air-conditioning must be provided to prevent heat prostration. In bunkers designed for war-time use, manually-operated ventilators must be provided because supplies of electricity or gas are unreliable. The simplest form of effective fan to cool a shelter is a wide, heavy frame with flaps that swings in the shelter's doorway and can be swung from hinges on the ceiling.
The flaps open in one direction and close in the other, pumping air. (This is a Kearny Air Pump
Kearny Air Pump
The Kearny Air Pump is an expedient air pump used to ventilate a shelter. The design is such that a person with normal mechanical skills can construct and operate one. It is usually human powered and employed during a time of crisis...
, or KAP, named after the inventor Cresson Kearny
Cresson Kearny
Cresson Henry Kearny wrote several survival related books based primarily on research performed at Oak Ridge National Laboratory.-Career:Kearny attended Texas Military Institute in the 1930s, where he became the commanding officer of the cadet corps, a champion runner and rifle shot, and...
.) Kearney asserts, based on field testing, that air filtration is not normally needed in a nuclear shelter. He asserts that fallout is either large enough to fall to the ground, or so fine that it will not settle and thus has little bulk to emit radiation. However, if possible, shelters of should have air-filtration to stop chemical, biological and nuclear impurities which may abound after an explosion.
Ventilation openings in a bunker must be protected by blast valves. A blast valve is closed by a shock wave, but otherwise remains open. If the bunker is in a built-up area, it may include water-cooling or an immersion tub and breathing tubes to protect inhabitants from fire storms. In these cases, the secondary exit is also most useful.
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 125 µm), inexpensive polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
film serves quite well, because the overburden protects it from degradation by wind and sunlight. Naturally, a buried or basement-situated reinforced-concrete shelter usually has the normal appearance of a building.
When a house is purpose-built with a blast shelter, the normal location is a reinforced below-grade bathroom with large cabinets. In apartment houses, the shelter may double as storage space, as long as it can be swiftly emptied for its primary use. A shelter can easily be added in a new basement construction by taking an existing corner and adding two poured walls and a ceiling. This also works well as a wine or root cellar.
Some vendors provide true blast shelters engineered to provide good protection to individual families at modest cost. 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. A properly designed, properly installed home shelter does not become a sinkhole in the lawn. In Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, which requires shelters for private apartment blocks and large private houses, the lightest shelters are constructed of stainless steel.
Subways as blast shelters
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, people in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
and Moscow
Moscow
Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...
survived bombing during the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
Blitz
The Blitz
The Blitz was the sustained strategic bombing of Britain by Nazi Germany between 7 September 1940 and 10 May 1941, during the Second World War. The city of London was bombed by the Luftwaffe for 76 consecutive nights and many towns and cities across the country followed...
by taking refuge in the subways
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...
, e.g., the London underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...
. In the second half of the 20th century, subways in eastern Europe
Eastern Europe
Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
and USSR were constructed as blast shelters.
See also
- Air raid shelter
- Autonomous buildingAutonomous buildingAn autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid, gas grid, municipal water systems, sewage treatment systems, storm drains, communication services, and in some cases, public roads.Advocates of...
- BunkerBunkerA military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...
- Civil defenseCivil defenseCivil defense, civil defence or civil protection is an effort to protect the citizens of a state from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery...
- Collective protectionCollective protectionCollective protection is used for group protection of personnel in a nuclear, biological or chemical event, .Collective protection is an important aspect of fixed site defense....
- Continuity of governmentContinuity of governmentContinuity of government is the principle of establishing defined procedures that allow a government to continue its essential operations in case of nuclear war or other catastrophic event....
- Fallout shelterFallout shelterA fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War....
- Homeland securityHomeland securityHomeland security is an umbrella term for security efforts to protect states against terrorist activity. Specifically, is a concerted national effort to prevent terrorist attacks within the U.S., reduce America’s vulnerability to terrorism, and minimize the damage and recover from attacks that do...
- Launch control center (ICBM)Launch control center (ICBM)A launch control center , in the United States, is the main control facility for intercontinental ballistic missiles . A launch control center monitors and controls missile launch facilities. From a launch control center, the missile combat crew can monitor the complex, launch the missile, or relax...
- Nuclear warfareNuclear warfareNuclear warfare, or atomic warfare, is a military conflict or political strategy in which nuclear weaponry is detonated on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage...
- Radiation hardeningRadiation hardeningRadiation hardening is a method of designing and testing electronic components and systems to make them resistant to damage or malfunctions caused by ionizing radiation , such as would be encountered in outer space, high-altitude flight, around nuclear reactors, particle accelerators, or during...
- Nuclear War Survival SkillsNuclear war survival skillsNuclear War Survival Skills or NWSS by Cresson Kearny is a civil defense manual. It contains information gleaned from research performed at Oak Ridge National Laboratory during the Cold War, as well as from Kearny's extensive jungle living and international travels.The book aims to provide a...
General:
- SurvivabilitySurvivabilitySurvivability is the ability to remain alive or continue to exist. The term has more specific meaning in certain contexts.-Engineering:In engineering, survivability is the quantified ability of a system, subsystem, equipment, process, or procedure to continue to function during and after a natural...
- Earth shelteringEarth shelteringEarth sheltering is the architectural practice of using earth against building walls for external thermal mass, to reduce heat loss, and to easily maintain a steady indoor air temperature...
- Emergency preparedness
- Retreat (survivalism)Retreat (survivalism)A retreat is a place of refuge for those in the survivalist subculture or movement. Retreats are also sometimes called Bug-Out Locations...
- SurvivalismSurvivalismSurvivalism is a movement of individuals or groups who are actively preparing for future possible disruptions in local, regional, national, or international social or political order...
- Underground cityUnderground cityAn Underground city is a series of linked subterranean spaces that may provide a defensive refuge; a place for living, working or shopping; a transit system; mausolea; wine or storage cellars; cisterns or drainage channels; or several of these. The term may also refer to a network of tunnels that...
External links
- Much of this article summarizes the information on blast shelters at the Oregon Institute of Science and Medicine This website offers the entire online version of "Nuclear War Survival Skills" with full graphics and web navigation, created with the permission of the author Cresson Kearny. This manual has proven technical info on expedient blast shelters, shelter habitation, and assorted shelter system needs that can be created from common household items. OISM also offers free downloads of other civil defense and shelter information as well.