Explosion: shock wave actions and damaging factors. General characteristics of explosions and their damaging factors What does an explosion mean in

Public catering enterprises use and process combustible and explosive raw materials in various states of aggregation (essences, organic acids, fats, oils, flour, powdered sugar, etc.). In addition, the production is equipped with vessels and apparatus operating under excessive pressure, including refrigeration units, the refrigerant of which, as a rule, is an explosive gas or ammonia. For heating, drying, frying, cooking, baking, thermal equipment operating on a thermal manifestation is used. electric current, gas, liquid and solid fuels. Based on the properties of circulating substances, the nature of technological processes, food production is classified as explosive and fire hazardous.

Explosion called the rapid release of energy associated with a sudden change in the state of matter, accompanied by the destruction of the environment and the propagation of a shock or explosive wave in it, the transition of the initial energy into the energy of the movement of matter.

During an explosion, pressures of tens and hundreds of thousands of atmospheres develop, and the speed of the explosive is measured in kilometers per second.

Explosives- these are compounds or mixtures capable of rapid, self-propagating chemical transformation with the formation of gases and the release of a significant amount of heat. Such a transformation, having arisen at some point under the influence of an appropriate impulse (heating, mechanical shock, explosion of another explosive), spreads at high speed to the entire mass of the explosive.

The rapid formation of significant volumes of gases and their heating to high temperatures (1800 ... 3800 ° C) due to the heat of reaction explain the cause of the occurrence at the explosion site high pressure.

In contrast to the combustion of conventional fuel, the explosion reaction proceeds without the participation of atmospheric oxygen and, due to the high speeds of the process, makes it possible to obtain enormous powers in a small volume. For example, 1 kg of coal requires about 11 m 3 of air, and approximately 9300 W of heat is released. An explosion of 1 kg of hexogen occupying a volume of 0.00065 m 3 occurs in a hundred-thousandth of a second and is accompanied by the release of 1580 W of heat.

In some cases, the initial energy from the very beginning is the thermal energy of the compressed gases. At some point, due to the removal or weakening of bonds, gases can expand and an explosion will occur. An explosion of cylinders with compressed gases can be attributed to this kind of explosion. Explosions of steam boilers are related to this type of explosions. However, the initial energy of compressed gases in them is only a part of the energy of the explosion; An essential role here is played by the presence of a superheated liquid, which can quickly evaporate when the pressure is reduced.

The causes and nature of the explosion may be different.

chain theory the occurrence of a gas explosion determines the conditions under which chain reactions occur. Chain reactions are chemical reactions in which active substances (free radicals) appear. Free radicals, unlike molecules, have free unsaturated valences, which leads to their easy interaction with the original molecules. When a free radical interacts with a molecule, one of the valence bonds of the latter breaks and, thus, a new free radical is formed as a result of the reaction. This radical, in turn, readily reacts with another parent molecule, re-forming a free radical. As a result, by repeating these cycles, an avalanche-like increase in the number of active explosive centers occurs.

Thermal energy proceeds from the conditions of violation of thermal equilibrium, in which the heat input due to the reaction becomes greater than the heat transfer. The heating that occurs in the system additionally affects the reaction. As a result, a progressive increase in the reaction rate occurs, leading under certain conditions to an explosion. When exposed to heat, an explosion of high power and relatively slow combustion can form.

Explosion on impact is associated with the action of local microscopic heating, which is especially strong due to the presence of very high pressure upon impact. Local heating covers a huge number of molecules and, under certain conditions, leads to an explosion.

The compression and movement of the environment (air, water, soil) arising from the explosion are transmitted to more and more distant layers. A special kind of perturbation propagates in the medium - a shock, or explosive, wave. When this wave arrives at any point in space, the density, temperature and pressure increase abruptly and the substance of the medium begins to move in the direction of wave propagation. The speed of propagation of a strong shock wave, as a rule, significantly exceeds the speed of sound. As it propagates, this speed decreases, and eventually the shock wave turns into an ordinary sound wave.

Near the source of the explosion, the speed of air movement can reach thousands of meters per second, and the kinetic energy of the moving air is equal to 50% of the total energy of the shock wave.

When a shock wave propagates not in an inert medium, but, for example, in an explosive, it can cause its rapid chemical transformation, which propagates through the substance at the speed of a wave, supports the shock wave and does not allow it to fade. This phenomenon is called detonation, and the shock wave that contributes to the rapid reaction is called the detonation wave.

As a rule, any explosion causes fires. Combustion is a complex physical and chemical process of interaction between a combustible substance and an oxidizing agent. Oxidants in the combustion process can be oxygen, chlorine, bromine and some other substances, such as nitric acid, berthollet salt and sodium peroxide. A common oxidizing agent in combustion processes is oxygen in the air. The oxidation reaction can self-accelerate under certain conditions. This process of self-acceleration of the oxidation reaction with its transition to combustion is called self-ignition. The conditions for the occurrence and course of combustion in this case are the presence of a combustible substance, atmospheric oxygen and an ignition source. A combustible substance and oxygen are reacting substances and constitute a combustible system, and an ignition source causes a combustion reaction in it.

Combustible systems can be chemically homogeneous and heterogeneous. Chemically homogeneous systems include systems in which the combustible substance and air are evenly mixed with each other, for example, mixtures of combustible gases, vapors or dusts with air.

Chemically heterogeneous systems include systems in which a combustible substance and air have interfaces, for example, solid combustible materials and liquids, jets of combustible gases and vapors entering the air. At. In the combustion of chemically inhomogeneous combustible systems, air oxygen continuously diffuses through the combustion products to the combustible substance and then reacts with it.

The heat released in the combustion zone is perceived by the combustion products, as a result of which they are heated to a high temperature, which is called the combustion temperature.

Kinetic combustion, i.e., the combustion of a chemically homogeneous combustible mixture of gases, vapors or dust with air, proceeds differently. If the combustible mixture comes at a certain speed from the burner, then it burns with a steady flame. The combustion of the same mixture that has filled a closed volume can cause a chemical explosion.

Kinetic combustion is possible only at a certain ratio of gas, vapors, dust and air. The minimum and maximum concentrations of combustible substances in the air that can ignite are called the lower and upper concentration limits of ignition (explosion).

All mixtures whose concentrations are between the flammable limits are called explosive and flammable.

Mixtures whose concentrations are below the lower and above the upper flammability limits are not capable of burning in closed volumes and are considered safe. However, mixtures whose concentration is above the upper limit of ignition, when leaving a closed volume of air, are capable of burning with a diffusion flame, that is, they behave like vapors and gases that are not mixed with air.

Flammable concentration limits are not constant and depend on a number of factors. The power of the ignition source, the admixture of inert gases and vapors, the temperature and pressure of the combustible mixture have a great influence on the change in the ignition limits.

An increase in the power of the ignition source leads to an expansion of the ignition (explosion) area with a decrease in the lower limit and an increase in the upper limit of ignition.

When non-combustible gases are introduced into the explosive mixture, a sharp decrease in the upper flammability limit and a slight change in the lower limit occur. The ignition area is reduced and at a certain concentration of non-combustible gases, the mixture ceases to ignite.

With an increase in the initial temperature of the explosive mixture, its ignition gap expands, while the lower limit decreases, and the upper one increases.

When the pressure of the combustible mixture decreases below normal, the ignition area decreases. At low pressure, the mixture becomes safe.

At the lower ignition limit of the mixture, the amount of heat generated is insignificant and therefore the pressure during the explosion does not exceed 0.30 ... 0.35 MPa. With an increase in the concentration of a combustible substance, the explosion pressure increases. It is 1.2 MPa for most mixtures.

With a further increase in the concentration of a combustible substance, the explosion pressure decreases and at the upper ignition limit becomes the same as at the lower one.

The explosive properties of mixtures of vapors with air do not differ from the properties of mixtures of combustible gases with air. The concentration of saturated vapors of a liquid is in a certain relationship with its temperature. These temperatures are called the temperature limits of ignition (explosion).

upper temperature limit called the highest temperature of the liquid at which a mixture of saturated vapors with air is formed, which is still capable of igniting, however, above this temperature, the resulting vapors mixed with air in a closed volume cannot ignite.

lower temperature limit called the lowest temperature of a liquid at which a mixture of saturated vapors with air is formed, capable of igniting when an ignition source is brought to it. At a lower liquid temperature, the mixture of vapors with air is not capable of igniting.

The lower temperature limit of ignition of liquids is otherwise called the flash point, which is taken as the basis for classifying liquids according to their degree of fire hazard. So, liquids with a flash point up to 45 ° C are called flammable, and above 45 ° C - combustible.

At food enterprises, many technological processes are accompanied by the release of fine organic dust (flour, powdered sugar, starch, etc.), which, at a certain concentration, forms an explosive dust-air mixture.

Dust can be in two states: suspended in the air (aerosol) and settled on walls, ceilings, structural parts of equipment, etc. (aerogel).

Airgel is characterized by an autoignition temperature that differs little from the autoignition temperature of a solid.

The autoignition temperature of an aerosol is always much higher than that of an airgel, and even exceeds the autoignition temperature of vapors and gases. This is explained by the fact that the concentration of a combustible substance per unit volume of an aerosol is hundreds of times less than that of an airgel; therefore, the rate of heat release can exceed the rate of heat transfer only at a significantly high temperature.

In table. the self-ignition temperatures of airgel and aerosol of some dusts are given.

As with gas mixtures, ignition and flame propagation throughout the aerosol volume occur only if its concentration is above the lower ignition limit.

As for the upper flammability limits of aerosols, they are so high that in most cases they are practically unattainable. For example, the concentration of the upper flammable limit of sugar dust is 13500 g/m 3 .

The auto-ignition temperature of combustible substances is varied. For some, it exceeds 500 ° C, for others it is within the limits of the environment, which on average can be taken as 0 ... 50 ° C.

For example, yellow phosphorus at a temperature of 15°C self-heated and ignited. Substances capable of self-ignition without heating present a great fire hazard and are called spontaneously igniting, and the process of their self-heating to the stage of combustion is defined by the term spontaneous combustion. Self-igniting substances are divided into three groups:

substances that ignite spontaneously from exposure to air (vegetable oils, animal fats, brown and black coals, iron sulfides, yellow phosphorus, etc.);

substances that ignite spontaneously from exposure to water (potassium, sodium, calcium carbide, alkali metal carbides, calcium and sodium phosphorous, quicklime, etc.);

substances that ignite spontaneously when mixed with each other (acetylene, hydrogen, methane and ethylene mixed with chlorine; potassium permanganate mixed with glycerin or ethylene glycol; turpentine in chlorine, etc.).

A great explosion and fire hazard at food enterprises is a mixture of organic dust with air.

According to the fire hazard, all dusts, depending on their properties, are divided into explosive in the aerosol state and fire hazardous in the airgel state.

The first class of explosiveness includes dust with a lower flammability (explosive) limit of up to 15 g/m 3 . This class includes dust of sulfur, rosin, powdered sugar, etc.

The second class includes explosive dust with a lower flammability (explosive) limit of 16 ... 65 g / m 3. This group includes dust of starch, flour, lignin, etc.

Dusts in the airgel state are also divided into two classes according to fire hazard: the first class is the most flammable with a self-ignition temperature of up to 250 ° C (for example, tobacco dust - 205 ° C, grain dust - 250 ° C); the second class - flammable with a self-ignition temperature above 250 ° C (for example, sawdust - 275 ° C).

General information about the explosion

An explosion is a fast-flowing process of physical and chemical transformations of substances, accompanied by the release of a significant amount of energy in a limited volume, as a result of which a shock wave is formed and propagates, which has a shock mechanical effect on surrounding objects.

CHARACTERISTIC FEATURES OF THE EXPLOSION:

High rate of chemical transformation of explosives;
a large number of gaseous explosion products;
strong sound effect (rumble, loud sound, noise, strong bang);
powerful crushing action.

Depending on the environment in which explosions occur, they are underground, ground, air, underwater and surface.

The scale of the consequences of explosions depends on their power and the environment in which they occur. The radii of the affected zones during explosions can reach up to several kilometers.

There are three blast zones.

3she I- zone of action of the detonation wave. It is characterized by an intense crushing action, as a result of which the structures are destroyed into separate fragments, flying away at high speeds from the center of the explosion.

Zone II- the area of ​​action of the products of the explosion. In it, the complete destruction of buildings and structures occurs under the action of expanding explosion products. At the outer boundary of this zone, the resulting shock wave separates from the explosion products and moves independently from the center of the explosion. Having exhausted their energy, the products of the explosion, having expanded to a density corresponding to atmospheric pressure, no longer produce destructive effects.

Zone III- zone of action of an air shock wave - includes three subzones: III a - strong destruction, III b - medium destruction, III c - weak destruction. At the outer boundary of zone 111, the shock wave degenerates into a sound wave, which is still audible at considerable distances.

EXPLOSION EFFECTS ON BUILDINGS, STRUCTURES, EQUIPMENT .

Buildings and structures of large sizes with light load-bearing structures, which rise significantly above the earth's surface, are subjected to the greatest destruction by explosion products and a shock wave. Underground and underground structures with rigid structures have significant resistance to destruction.

Damage is divided into full, strong, medium and weak.

Complete destruction. Ceilings in buildings and structures collapsed and all the main load-bearing structures were destroyed. Recovery is not possible. Equipment, means of mechanization and other equipment are not subject to restoration. In utility and energy networks, there are breaks in cables, destruction of sections of pipelines, supports of overhead power lines, etc.

Strong destruction. There are significant deformations of load-bearing structures in buildings and structures, most of the ceilings and walls are destroyed. Restoration is possible, but impractical, as it practically boils down to new construction using some of the surviving structures. The equipment and mechanisms are mostly destroyed and deformed.

In communal and energy networks, there are breaks and deformations in certain sections of underground networks, deformations of overhead power lines and communications, breaks in technological pipelines.

Medium destruction. In buildings and structures, it was mainly not load-bearing, but secondary structures (light walls, partitions, roofs, windows, doors) that were destroyed. Possible cracks in the outer walls and falls in some places. Ceilings and cellars are not destroyed, part of the structures is suitable for operation. In utility and energy networks, destruction and deformation of elements are significant, which can be eliminated by major repairs.

Weak destruction. Part of the internal partitions, windows and doors were destroyed in buildings and structures. The equipment has significant deformations. There are minor damages and breakdowns of structural elements in utility and energy networks.

General information about the fire

FIRE AND ITS BEGINNING .

A fire is an uncontrolled burning that causes material damage, harm to the life and health of citizens, the interests of society and the state.

Essence of burning was discovered in 1756 by the great Russian scientist M. V. Lomonosov. By his experiments, he proved that combustion is a chemical reaction of the combination of a combustible substance with oxygen in the air. Therefore, in order for the combustion process to proceed, the following are necessary conditions:

The presence of a combustible substance (in addition to combustible substances used in production processes and combustible materials used in the interior of residential and public buildings, a significant amount of combustible substances and combustible materials is contained in building structures);
the presence of an oxidizing agent (usually, oxygen in the air is an oxidizing agent during combustion of substances; in addition to it, chemical compounds containing oxygen in the composition of molecules can be oxidizing agents: nitrates, perchlorates, nitric acid, nitrogen oxides and chemical elements: fluorine, bromine, chlorine);
the presence of an ignition source (open flame candles, matches, lighters, fires or sparks).

It follows that the fire can be stopped if one of the first two conditions is excluded from the combustion zone.

The possibility of fires in buildings and structures, and in particular the spread of fire in them, depends on what parts, structures and materials they are made of, what are their sizes and layout. As can be seen from Scheme 2, substances and materials are divided into flammability groups:

On non-combustible substances, unable to burn;
for slow-burning substances capable of burning under the influence of an ignition source, but unable to burn independently after its removal;
for combustible substances capable of burning after the ignition source is removed:
a) hardly flammable, capable of igniting only under the influence of a powerful ignition source;
b) flammable, capable of igniting from short-term exposure to low-energy ignition sources (flames, sparks).

Explosion - common physical phenomenon which played a significant role in the fate of mankind. It can destroy and kill, as well as be useful, protecting a person from threats such as flooding and asteroid attack. Explosions differ in nature, but in the nature of the process they are always destructive. This strength is their main distinguishing feature.

The word "explosion" is familiar to everyone. However, the question of what an explosion is can only be answered on the basis of what this word is used for. Physically, an explosion is a process of extremely rapid release of energy and gases in a relatively small volume of space.

The rapid expansion (thermal or mechanical) of a gas or other substance, such as when a grenade explodes, creates a shock wave (high pressure zone) that can be destructive.

In biology, an explosion means a rapid and large-scale biological process (for example, an explosion in numbers, an explosion in speciation). Thus, the answer to the question of what an explosion is depends on the subject of study. However, as a rule, it is precisely the classic explosion that is meant by it, which will be discussed further.

Classification of explosions

Explosions can have a different nature, power. Occur in various environments (including vacuum). According to the nature of occurrence, explosions can be divided into:

• physical (explosion of a burst balloon, etc.);
• chemical (for example, an explosion of TNT);
• nuclear and thermonuclear explosions.

Chemical explosions can occur in solid, liquid or gaseous substances, as well as air suspensions. The main ones in such explosions are redox reactions of the exothermic type, or exothermic decomposition reactions. An example of a chemical explosion is a grenade explosion.

Physical explosions occur when the tightness of containers with liquefied gas and other substances under pressure is breached. They can also be caused by thermal expansion of liquids or gases in the composition of a solid body, followed by a violation of the integrity of the crystal structure, which leads to a sharp destruction of the object and the appearance of an explosion effect.

Explosion power

The power of explosions can be different: from the usual loud pop due to a burst balloon or an exploded firecracker to giant cosmic explosions of supernovae.

The intensity of the explosion depends on the amount of energy released and the rate of its release. When evaluating the energy of a chemical explosion, such an indicator as the amount of heat released is used. The amount of energy in a physical explosion is determined by the amount of kinetic energy of the adiabatic expansion of vapors and gases.

man-made explosions

At an industrial enterprise, explosive objects are not uncommon, and therefore such types of explosions as air, ground and internal (inside a technical structure) can occur there. In coal mining, methane explosions are not uncommon, which is especially typical for deep coal mines, where, for this reason, there is a lack of ventilation. Moreover, different coal seams have different methane content, and therefore the level of explosive danger in the mines is different. Methane explosions are a big problem for the deep mines of Donbass, which requires increased control and monitoring of its content in the mine air.

Explosive objects are containers with liquefied gas or steam under pressure. Also military warehouses, containers with ammonium nitrate and many other objects.

The consequences of an explosion at work can be unpredictable, including tragic ones, among which the possible release of chemicals occupies a leading position.

The use of explosions

The explosion effect has long been used by mankind for various purposes, which can be divided into peaceful and military. In the first case, we are talking about the creation of directed explosions for the destruction of buildings to be demolished, ice jams on rivers, in the extraction of minerals, in construction. Thanks to them, the labor costs necessary for the implementation of the tasks set are significantly reduced.

An explosive is a chemical mixture that, under the influence of certain, easily achieved conditions, enters into a violent chemical reaction, leading to the rapid release of energy and a large amount of gas. By its nature, the explosion of such a substance is similar to combustion, only it proceeds at a tremendous speed.

External influences that can provoke an explosion are as follows:

• mechanical impacts (for example, impact);
• a chemical component associated with the addition of other components to the explosive that provoke the start of an explosive reaction;
• temperature effects (heating of the explosive or sparks on it);
• detonation from a nearby explosion.

The degree of response to external influences

The degree of reaction of an explosive to any of the influences is exclusively individual. So, some types of gunpowder ignite easily when heated, but remain inert under the influence of chemical and mechanical influences. TNT explodes from the detonation of other explosives, and it is not very sensitive to other factors. Mercury fulminate is undermined by all kinds of impacts, and some explosives can even explode spontaneously, making such compounds very dangerous and unsuitable for use.

How does an explosive detonate?

Different explosives explode in slightly different ways. For example, gunpowder is characterized by a rapid ignition reaction with the release of energy over a relatively long period of time. Therefore, it is used in military affairs to give speed to cartridges and projectiles without breaking their shells.

In another type of explosion (detonation), the explosive reaction propagates through the substance at supersonic speed, and it is also the cause. This leads to the fact that energy is released in a very short period of time and at a tremendous speed, so the metal capsules are torn apart from the inside. This type of explosion is typical for such dangerous explosives as RDX, TNT, ammonite, etc.

Explosive types

Features of sensitivity to external influences and indicators of explosive power make it possible to divide explosives into 3 main groups: propelling, initiating and blasting. Throwing powders include various types of gunpowder. This group includes low-power explosive mixtures for firecrackers and fireworks. In military affairs, they are used for the manufacture of lighting and signal rockets, as a source of energy for cartridges and shells.

A feature of initiating explosives is sensitivity to external factors. At the same time, they have low explosive power and heat dissipation. Therefore, they are used as a detonator for blasting and propellant explosives. They are carefully packaged to prevent self-destruction.

High explosives have the highest explosive power. They are used as fillings for bombs, shells, mines, rockets, etc. The most dangerous of them are hexogen, tetryl, and PETN. Less powerful explosives are TNT and plastid. Among the least powerful is ammonium nitrate. Brisant substances with high explosive power are also more sensitive to external influences, which makes them even more dangerous. Therefore, they are used in combination with less powerful or other components that lead to a decrease in sensitivity.

Explosive parameters

In accordance with the volumes and rate of energy and gas release, all explosives are evaluated according to such parameters as brisance and explosiveness. Brisatness characterizes the rate of energy release, which directly affects the destructive ability of the explosive.

Explosiveness determines the magnitude of the release of gases and energy, and hence the amount of work produced during the explosion.

In both parameters, hexogen is the leader, which is the most dangerous explosive.

So, we tried to answer the question of what an explosion is. And also considered the main types of explosions and methods of classification of explosives. We hope that after reading this article, you have got a general idea of ​​what an explosion is.

physical explosion - caused by a change in the physical state of matter. chemical explosion- is caused by the rapid chemical transformation of substances, in which the potential chemical energy is converted into thermal and kinetic energy of expanding explosion products. Emergency, this is an explosion that occurred as a result of a violation of production technology, errors of maintenance personnel, or errors made during the design.

Explosive "medical environment" - is a part of the room in which an explosive atmosphere can occur in small concentrations and only for a short time due to the use of medical gases, anesthetics, skin cleansers or disinfectants.

The main damaging factors in an explosion are an air shock wave, fragmentation fields, propelling effects of surrounding objects, a thermal factor (high temperature and flame), exposure to toxic products of explosion and combustion, and a psychogenic factor.

Explosive injury occurs when the impact of an explosion on people in a confined space or in an open area, as a rule, is characterized by open and closed wounds, injuries, contusion, hemorrhages, including in the internal organs of a person, ruptures of the eardrums, bone fractures, skin burns and respiratory tract, asphyxiation or poisoning, post-traumatic stress disorder.

Explosions at industrial enterprises: deformation, destruction of technological equipment, power systems and transport lines, collapse of structures and fragments of premises, leakage of toxic compounds and poisonous substances. Explosive technological lines:

Grain elevators: dust,

Mills: flour,

Chemical plants: hydrocarbons, oxidizers. In addition to oxygen, oxygen-containing compounds (perchlorate, saltpeter, gunpowder, thermite), individual chemical elements (phosphorus, bromine) are oxidizing agents.

Filling stations and oil refineries: vapors and aerosols of hydrocarbons.

The distance of damage on the example of the explosion of a tanker is 5 tons. Baiker U. 1995) I. Thermal damage from the impact of a fireball: - up to 45 m. Incompatible with life, - up to 95 m. Burns of the III degree. - up to 145 m. Burns of II degree. - up to 150 m. Burns I st. - up to 240 m. Burns of the retina. II. Mechanical damage by a shock wave: - up to 55 m. Incompatible with life, - up to 95 m. Head injury, barotrauma of the lungs and gastrointestinal tract, - up to 140 m. Rupture of eardrums.

The blast shock wave can cause great loss of life and destruction of structures. The size of the affected areas depends on the power of the explosion. The extent to which secondary measures are used depends on the likelihood of a dangerous explosive atmosphere occurring. Hazardous areas are divided into different zones according to the time- and local-dependent probability of the presence of a dangerous explosive atmosphere.

Zone 0. An area in which there is a permanent, frequent or long-term dangerous explosive environment and where a dangerous concentration of dust, aerosols or vapors can be formed. Such as mills, dryers, mixers, silos, production facilities using fuel, product pipelines, supply pipes, etc.

Zone 1. The area in which, due to the concentration of combustible vapors, aerosols, swirling, deposited dust, an accidental occurrence of a dangerous explosive atmosphere can be expected. Close proximity to loading hatches; at the sites of filling or unloading equipment; in areas with fragile equipment or lines made of glass, ceramics, etc.;

Zone 2. An area where a dangerous explosive atmosphere can be expected, but very rarely and for a short time.

Dust explosion risk assessment

In the immediate vicinity of devices containing dust from which it can leak, settle and accumulate in dangerous concentrations (mills). In the case of a dust explosion with a low concentration in the medium, the head compression wave of the explosion can cause a vortex motion of the deposited dust, which gives a high concentration of combustible material. The risk of explosion of a dust mixture is much less than that of a gas, steam or mist. Zones of accidents during volumetric explosions can cover large areas. Accident on a gas pipeline in Bashkiria (June 1989) Q2 km. Dead-871, wounded 339 people. The problem of saving people after an explosion and a fire was that almost all emergency medical equipment burned out in a flame, and about improvised means in such cases, victims and rescuers are almost forgotten.

The main criteria determining the magnitude of sanitary losses are: the type of explosive device, the power of the explosion, the location of the explosion and the time of day. Depending on the number and localization of damage can be isolated, multiple and combined. According to the severity of injuries: light, moderate, severe and extremely severe. Table 4.1. the degree of damage to people depending on the magnitude of excess pressure is presented.

Upon contact with an explosive device, explosive destruction of the outer parts of the body or destruction (detachment) of limb segments occurs. The wound process in this case has a number of features: - Acute massive blood loss and shock; - Contusions of the lungs and heart; - Traumatic endotoxicosis; - The combined nature of the impact of damaging factors.

Explodes within 0.0001 seconds releasing 1.470 calories of heat and approx. 700 liters of gas. Cm. Explosives.

Explosion, the process of releasing a large amount of energy into limited amount for a short period of time. As a result of vacuum, the substance that fills the volume in which energy is released turns into a highly heated gas with very high pressure. This gas acts with great force on the environment, causing it to move. An explosion in a solid medium is accompanied by its destruction and crushing.

The movement generated by the explosion, in which there is a sharp increase in pressure, density and temperature of the medium, is called blast wave. The blast wave front propagates through the medium at high speed, as a result of which the area covered by the movement expands rapidly. The occurrence of a blast wave is a characteristic consequence of V. in various media. If there is no medium, that is, an explosion occurs in a vacuum, the energy of V. passes into the kinetic energy of V. products flying in all directions at high speed. By means of an explosive wave (or V. products flying in a vacuum), V. produces a mechanical effect on objects located on at various distances from location B. As the distance from the explosion site, the mechanical effect of the blast wave weakens. The distances at which blast waves create the same impact force at V. of different energies increase in proportion to the cube root of the energy of V. Proportionally to the same value, the time interval for the impact of the blast wave increases.

Various types of explosions differ in the physical nature of the energy source and the way it is released. Typical examples of explosives are explosions of chemical explosives. Explosives have the ability for rapid chemical decomposition, in which the energy of intermolecular bonds is released in the form of heat. Explosives are characterized by an increase in the rate of chemical decomposition with increasing temperature. At a relatively low temperature, chemical decomposition proceeds very slowly, so that the explosive may not undergo a noticeable change in its state for a long time. In this case, between the explosive and environment thermal equilibrium is established, in which continuously released small amounts of heat are removed outside the substance through heat conduction. If conditions are created under which the released heat does not have time to be removed outside the explosive, then due to an increase in temperature, a self-accelerating process of chemical decomposition develops, which is called thermal decomposition. Due to the fact that heat is removed through the outer surface of the explosive, and its release occurs in the entire volume of the substance, thermal equilibrium can also be disturbed with an increase in the total mass of the explosive. This circumstance is taken into account when storing explosives.

Another process for the implementation of the explosion is possible, in which the chemical transformation propagates through the explosive successively from layer to layer in the form of a wave. The leading edge of such a wave moving at high speed is shock wave- a sharp (jump-like) transition of a substance from its initial state to a state with very high pressure and temperature. The explosive material, compressed by the shock wave, is in a state in which chemical decomposition proceeds very quickly. As a result, the region in which the energy is released is concentrated in a thin layer adjacent to the surface of the shock wave. The release of energy ensures that the high pressure in the shock wave is maintained at a constant level. The process of chemical transformation of an explosive, which is introduced by a shock wave and is accompanied by a rapid release of energy, is called detonation. Detonation waves propagate through the explosive at a very high speed, always exceeding the speed of sound in the original substance. For example, detonation wave velocities in solid explosives are several km/sec. A ton of solid explosive can be converted in this way into a dense gas with very high pressure in 10 -4 seconds. The pressure in the resulting gases reaches several hundred thousand atmospheres. The effect of a chemical explosive explosion can be enhanced in a specific direction by the application of specially shaped explosive charges (see below). Cumulative effect).

Explosions associated with more fundamental transformations of substances include nuclear explosions. In a nuclear explosion, the transformation of atomic nuclei of the initial substance into the nuclei of other elements occurs, which is accompanied by the release of the binding energy of elementary particles (protons and neutrons) that make up the atomic nucleus. Nuclear war is based on the ability of certain isotopes of the heavy elements of uranium or plutonium to undergo fission, in which the nuclei of the original substance decay to form nuclei of lighter elements. In the fission of all the nuclei contained in 50 g of uranium or plutonium, the same amount of energy is released as in the detonation of 1000 tons of trinitrotoluene. This comparison shows that a nuclear transformation is capable of producing V. of enormous force. The fission of the nucleus of an atom of uranium or plutonium can occur as a result of the capture of one neutron by the nucleus. It is essential that as a result of fission several new neutrons are produced, each of which can cause the fission of other nuclei. As a result, the number of divisions will increase very quickly (according to the law of geometric progression). If we assume that with each fission event the number of neutrons capable of causing the fission of other nuclei doubles, then in less than 90 fission events such a number of neutrons is formed that is sufficient to fission the nuclei contained in 100 kg of uranium or plutonium. The time required for the division of this amount of matter will be ~10 -6 sec. Such a self-accelerating process is called a chain reaction (cf. Nuclear chain reactions). In reality, not all neutrons produced in fission cause the fission of other nuclei. If the total amount of fissile matter is small, then most of the neutrons will escape the matter without causing fission. A fissile substance always has a small amount of free neutrons, however, a chain reaction develops only when the number of newly formed neutrons exceeds the number of neutrons that do not produce fission. Such conditions are created when the mass of the fissile material exceeds the so-called critical mass. V. occurs when separate parts of the fissile material (the mass of each part is less than the critical one) are quickly combined into a single whole with a total mass that exceeds the critical mass, or during strong compression, which reduces the surface area of ​​​​the substance and thereby reduces the number of neutrons escaping. To create such conditions, V. is usually used as a chemical explosive.

There is another type of nuclear reaction - the reaction of the fusion of light nuclei, accompanied by the release of a large amount of energy. The repulsive forces of the same electric charges (all nuclei have a positive electric charge) prevent the fusion reaction from proceeding, therefore, for an effective nuclear transformation of this type, the nuclei must have high energy. Such conditions can be created by heating substances to very high temperatures. In this regard, the fusion process, which proceeds at high temperature, is called thermonuclear reaction. During the fusion of deuterium nuclei (an isotope of hydrogen ²H), almost 3 times more energy is released than during the fission of the same mass of uranium. The temperature required for fusion is reached in a nuclear explosion of uranium or plutonium. Thus, if a fissile substance and isotopes of hydrogen are placed in the same device, a fusion reaction can be carried out, the result of which will be a V. of enormous force. In addition to a powerful blast wave, a nuclear explosion is accompanied by intense emission of light and penetrating radiation (see Fig. Damaging factors of a nuclear explosion).

In the types of explosions described above, the released energy was initially contained in the form of molecular or nuclear bond energy in matter. There are wind turbines in which the released energy is supplied from an external source. An example of such a voltage is a powerful electric discharge in any medium. Electrical energy in the discharge gap is released in the form of heat, turning the medium into an ionized gas with high pressure and temperature. A similar phenomenon occurs when a powerful electric current flows through a metal conductor, if the current strength is sufficient to quickly turn the metal conductor into steam. The phenomenon of V. also occurs when a substance is exposed to focused laser radiation (see. Laser). As one of the types of explosion, one can consider the process of rapid release of energy, which occurs as a result of the sudden destruction of the shell that held the high-pressure gas (for example, the explosion of a cylinder with compressed gas). V. can occur during the collision of solid bodies moving towards each other at high speed. On collision kinetic energy bodies are transformed into heat as a result of the propagation of a powerful shock wave through the substance that occurs at the moment of collision. The velocities of the relative approach of solid bodies, necessary for the substance to completely turn into vapor as a result of a collision, are measured in tens of kilometers per second, and the pressures developing in this case amount to millions of atmospheres.

Many different phenomena occur in nature, which are accompanied by V. Powerful electrical discharges in the atmosphere during a thunderstorm (lightning), sudden volcanic eruption, large meteorites are examples various kinds B. As a result of a fall Tunguska meteorite() V. occurred, equivalent in terms of the amount of energy released V. ~ 10 7 tons of trinitrotoluene. Apparently, even more energy was released as a result of the explosion of the Krakatoa volcano ().

Huge explosions are chromospheric flares in the sun. The energy released during such flashes reaches ~10 17 J (for comparison, we point out that at V. 10 6 tons of trinitrotoluene, an energy equal to 4.2·10 15 J would be released).

The nature of giant explosions occurring in outer space are flares new stars. During flashes, apparently within a few hours, an energy of 10 38 -10 39 J is released. Such energy is emitted by the Sun in 10-100 thousand years. Finally, even more gigantic V., going far beyond the limits of human imagination, are flashes supernovae, at which the released energy reaches ~ 10 43 J, and V. in the nuclei of a number of galaxies, the energy estimate of which leads to ~ 10 50 J.

Explosions of chemical explosives are used as one of the main means of destruction. Nuclear explosions have enormous destructive power. Explosion of one nuclear bomb can be equivalent in energy to V. tens of million tons of chemical explosive.

Explosions have found wide peaceful application in scientific research and in industry. V. allowed to achieve significant progress in the study of the properties of gases, liquids and solids at high pressures and temperatures (see. High pressure). The study of explosions plays an important role in the development of the physics of nonequilibrium processes, which studies the phenomena of mass, momentum and energy transfer in various media, mechanisms phase transitions substances, kinetics chemical reactions etc. Under the influence of V., such states of substances can be achieved that are inaccessible with other methods of research. Powerful compression of the channel of an electric discharge by means of a explosive chemical explosive makes it possible to obtain, within a short period of time, magnetic fields of enormous intensity [up to 1.1 Ga/m (up to 14 million Oe), see Fig. A magnetic field. The intense emission of light during the V. of a chemical explosive in a gas can be used to excite an optical quantum generator (laser). Under the action of high pressure, which is created during the detonation of an explosive, explosive stamping, explosive welding and explosive hardening of metals are carried out.

The experimental study of explosives consists in measuring the velocities of propagation of explosive waves and the velocities of the movement of matter, measuring rapidly changing pressure, the distributions of density, intensity, and spectral composition of electromagnetic and other types of radiation emitted during explosives. These data make it possible to obtain information about the speed of various processes, accompanying V., and determine the total amount of released energy. The pressure and density of matter in a shock wave are connected by certain relationships with the velocity of the shock wave and the velocity of the matter. This circumstance makes it possible, for example, to calculate pressures and densities on the basis of velocity measurements in cases where their direct measurement is inaccessible for some reason. To measure the main parameters that characterize the state and speed of movement of the medium, various sensors are used that convert a certain type of impact into an electrical signal, which is recorded using oscilloscope or other recording device. Modern electronic equipment makes it possible to register phenomena occurring during time intervals of ~ 10 -11 sec. Measurements of the intensity and spectral composition of light radiation using special photocells And spectrographs serve as a source of information about the temperature of a substance. High-speed photography, which can be carried out at a speed of up to 10 9 frames per second, is widely used for recording the phenomena that accompany shooting.

In laboratory studies of shock waves in gases, a special device is often used - a shock tube (see Fig. Aerodynamic tube). A shock wave in such a pipe is created as a result of the rapid destruction of the membrane separating the high-pressure and low-pressure gases (this process can be regarded as the simplest type of blowing). When studying waves in shock tubes, interferometers and penumbral optical devices are effectively used, the operation of which is based on a change in the refractive index of a gas due to a change in its density.

Explosive waves propagating over long distances from their place of origin serve as a source of information about the structure of the atmosphere and the inner layers of the Earth. Waves at very large distances from the place of V. are recorded by highly sensitive equipment, which makes it possible to record pressure fluctuations in the air up to 10 -6 atmospheres (0.1 n / m²) or soil movements ~ 10 -9 m.

Literature:

• Sadovsky M.A., Mechanical action of air shock waves of an explosion according to experimental data, in the collection: Physics of the explosion, No. 1, M., 1952;
• Baum F. A., Stanyukovich K. P. and Shekhter B. I., Fizika vzryva, M., 1959;
• Andreev K. K. and Belyaev A. F., Theory of explosives, M., 1960:
• Pokrovsky G. I., Explosion, M., 1964;
• Lyakhov G. M., Fundamentals of explosion dynamics in soils and liquid media, M., 1964;
• Dokuchaev M. M., Rodionov V. N., Romashov A. N., Ejection explosion, M., 1963:
• Cole R., Underwater explosions, trans. from English, M., 1950;
• Underground nuclear explosions, trans. from English, M., 1962;
• Action of nuclear weapons, trans. from English, M., 1960;
• Gorbatsky V. G., Space explosions, M., 1967;
• Dubovik A.S., Photographic registration of fast processes, M., 1964.

K. E. Gubkin.