Explosions occurring in production lead to the destruction of buildings, structures, equipment and injury. Therefore, it is important to know in advance that an explosion can lead to what kind of destruction. In the explosion of gas-air media, the area of \u200b\u200bdestruction is considered the area with the boundary is determined by the R radius, the center of which is the technological unit under consideration of the object or the epicenter of the explosion. The boundaries of each zone are characterized by excess pressure values \u200b\u200bat the front of the shock wave Δ R and, respectively, a dimensionless coefficient TO, characterizing the impact of the shock wave of an explosion to the object. Classes of zones of possible destruction when explosion of clouds of fuel and air mixture indoors and coefficients TO Depending on the excessive pressure of the AP, presented in Table. 4.4. This table is used to find the size of the zones of possible destruction from the explosive wave, and, knowing the characteristic of the damage zone, one can determine the excess pressure in the explosive wave and the mass of the explosive, participated in the explosion.
Table 4.4.
The level of possible destruction with explosive conversion of the clouds of the fuel-air mixture
|
destruction |
Overpressure Δ. P, KPA |
coefficient TO |
destruction |
Characteristics of the lesion zone |
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|
Destruction and collapse of all elements of buildings and structures, including basements, percentage of survival of people: For administrative household buildings and |
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conventional management buildings - 30%; For production buildings and conventional designs - 0% |
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|
The destruction of parts of the walls and overlaps of the upper floors, the formation of cracks in the walls, the deformation of the overlaps of the lower floors. It is possible to limited the use of basements that have been preserved after clearing the inputs. People survival percentage: For administratively household buildings and buildings of the management of ordinary execution - 85%; For production buildings and constructions of ordinary performance - 2%. |
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Destruction is mainly secondary elements (roofs, partitions and door fills). Overlapping, as a rule, do not collapse. Part of the premises are suitable for use after clearing the debris and repair. The percentage of people survival: for administratively household buildings and buildings of the regular execution management - 94%. |
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Destruction of window and door fills and partitions. Basements and lower floors are fully saved and suitable for temporary use after cleaning garbage and bookmark openings. People survival percentage: For administratively household buildings and buildings of the management of the usual performance - 98%; For production buildings and constructions of ordinary performance - 90%. |
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glass destruction fill out |
Destruction of glass fillings. The percentage of survivors is 100%. |
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Radius R, M, zones of possible lesions in general, can be determined by formulas: when M.< 5000 kg
at m\u003e 5000 kg
where M - Mass of the vapor environment involved in the explosion, kg
To - A dimensionless coefficient characterizing the effect of an explosion to the object and is determined by table. 4.4;
M. T - Troityl Equivalent of the explosion, kg, calculated by formula (4.2) ... (4.4).
In terms of the damage caused by the explosive wave of destruction using Table. 4.4 You can calculate the mass of explosive in Ttrotil equivalent, which participated in the explosion. Or, on the contrary, knowing the mass of explosive in a TNT equivalent, which can participate in the explosion, you can calculate the size of each zone with a certain characteristic of the lesion.
EXAMPLE .
Determine the maximum distance from the center of the explosion of the vapor of isobutyl alcohol in the manufacturing workshop, in which a person will temporarily lose his hearing. The mass of alcohol, exploded, is M \u003d 10 kg. Temporary hearing loss in person is observed at an overpressure of the shock wave
Decision .
1. Calculate in formula (4.3), taking into account formula (4.1), the Trotyl equivalent of an explosion in the air of the vapor of isobutyl alcohol, kg,
where is it:
For the isobutyl alcohol of the heat of combustion q n \u003d 36743 kJ / kg (reference value);
The proportion of the above mass of the vapor-gas substances involved in the explosion for production premises Adopted, on table. 4.1, equal to 0.3.
2. Since the mass of the vapor-gas mixture does not exceed 5000 kg, the calculation of the radius of the zone, where a person is temporarily lost with an explosion, one can determine by formula (4.6). In this case, the dimensionless coefficient K, characterizing the effect of the wave of an explosion to the object, is adopted in accordance with the value of overpressure in the shock wave of DR<2 кПа и табл. 4.4, равным 56. Тогда радиус зоны, м, составит:
Output.When a person is found in the zone of a possible explosion with a radius of the defeat of 27.2 m, there is a high probability of temporary loss of hearing. In the explosion there will be destruction of glass filling of window openings and minor damage to the equipment.
The characteristic features of the explosions of TVS are:
The emergence of different types of explosions: detonation, delaning or combined;
In the explosions, 5 zones of lesion are formed: a brisk (detonation), the actions of the explosion (fiery ball), the actions of the shock wave, thermal lesion and toxic smoke;
The dependence of the power of the explosion from the parameters of the medium in which the explosion occurs (temperature, wind speed, developmental density, terrain);
To implement a combined or detonation explosion for a fuel assembly, a prerequisite is a prerequisite for the creation of a product concentration in the air within the lower and upper concentration limit.
Delable - explosive burning with subsonic speed.
Detonation - The process of explosive transformation of a substance with supersonic speed.
Calculation of radii zones of lesion ( R.) and overpressure in the front of the shock wave (D R f) when the explosion is made according to the following formulas:
1. Brusan zone (detonation zone):
where M is the mass of fuel assembly in the tank (kg). A 50% capacity of the tank capacity for single storage and 90% is taken as a group storage.
For a brisk zone D R F \u003d 1750 kPa.
2. Zone of combustion products (fiery ball zone):
Zone radius:
(2)
Excessive pressure at the front of the shock wave is calculated:
(3)
For the rest of the zones, their radii are calculated according to the following formula:
. (4)
3. Skip Wave Action Area:
Weak destruction - damage or destruction of roofs and window and doorways. Damage - 10 ... 15% of the cost of buildings.
Middle destruction - The destruction of roofs, windows, partitions, attic floors, upper floors. Damage - 30 ... 40%.
Strong destruction - The destruction of the supporting structures and overlaps. Damage - 50%. Repair is inappropriate.
Full destruction - collapse of buildings.
The thermal impulse (KJ / m 2) is determined by the formula:
where I. - the intensity of thermal radiation explosion of fuel assembly at a distance R., kj / m 2 × with
, (6)
where Q. 0 - Specific fire heat, KJ / m 2 × C; F. - angular coefficient characterizing the mutual location of the source of burning and object
(7)
T. - Air transparency
(8)
t. SV - the duration of the existence of the fiery ball (C)
(9)
This is a simplified and fair objective technique, considered in the works. Based on the analysis and generalization of the materials of accidents with the explosion of the DHW in the focus of the lesion (explosion) in the open area (atmosphere), two zones are distinguished: detonation (detonation wave); distribution (actions) of the shock wave (HC).
Conditional (calculated) The radius of the detonation zone (detonation wave) R 0 is determined by the empirical formula:
r 0 \u003d 18.5 · (2.5),
where k is a coefficient characterizing the volume of gases or vapor substances passing into an explosive mixture. Its values \u200b\u200bin the calculations are taken k \u003d 0.4-0.6. In some methods, the value of the coefficient k is taken depending on the product storage method: k \u003d 1 - for tanks with gaseous substance;
k \u003d 0.6 - for gases liquefied under pressure;
k \u003d 0.1 - for gases liquefied with cooling (stored in isothermal containers);
k \u003d 0.05 - with emergency spills of flammable liquids;
- the amount of substance spilled out of the depressive tank (storage);
8.5 is an empirical coefficient that allows you to take into account various conditions for the occurrence of the explosion (characteristics of the DHW, the state of the atmosphere, the form of the cloud, the power of the source of ignition, the place of its initiation, etc.).
Outside the detonation zone, the excess pressure of the shock wave (ΔP f) is sharply reduced to atmospheric. In literature sources, certain dependences are proposed for calculating the maximum values \u200b\u200bof ΔP F in the detonation zone, taking into account the distance to the explosion site, for example, in the second method below.
In the same method, the calculations uses generalized data of overpressure changes (ΔP f) based on the distance expressed in the frail from the radius of the detonation zone (R 1 / R 0) and the maximum pressure (P max) in the detonation zone (Table 2). At the same time, P MAX for various DHW is located on Table 2 from reference books.
The distribution zone (actions) HC is usually divided into several (n) zones with radii:
· Death lesions or complete destruction (R 100) with overpressure at the ΔP ΔP \u003d 100 kPa (ΔP F\u003e 50 kPa);
· Strong and complete destruction, respectively, with ΔP f \u003d 30 kPa and ΔP F \u003d 50 kPa (R 50);
· Medium with ΔP f \u003d 20 kPa
· Weak with ΔP f \u003d 10 kPa (R 20)
· Safe zone with Δp f< <10 кПа, т.е. ΔР ф =6 -7 кПа (R 6, 7). * По международным нормам безопасным
· For a person is Δ p f \u003d 7 kPa.
Then, by defining P max (Table 2) for a given DHW, led to an accident from a container (storage), in Table. 3 With the received zones with ΔP f2 \u003d 100 kPa, ΔP f2 \u003d 50 kPa, ΔP f3 \u003d 20 kPa, R 6, 7 \u003d 7kpa find the ratio R 1 / R 0 and, therefore, radii (R n) of the received zones, knowing R 0 of (2.5)
and R n \u003d c n · r 0 (2.7),
where n is an indicator of a given zone adopted; C x \u003d. determined by Table 3.
By analogy with the characteristics of the areas of destruction, when exposed to air, nuclear explosions determine the size of hazardous zones, in which severe, possible (weak) destruction of residential and industrial buildings in the explosion areas of gas and steam-air mixtures of hydrocarbon gases and liquids occur. It should be said that taking into account the impulse nature of the exposure to loads from the HC, excessive pressure during the explosion of the DHW, causing severe destruction, will be about 1.5-1.7 times more than with a nuclear explosion, i.e. approximately ΔP F GWS CP ~ 50 kPa, and possible weak destruction - ΔP F GVS Sl \u003d 20 kPa.
Then the radii of the zone of strong (R c) and weak (R sl) of destruction:
R sl \u003d R 20 \u003d R 0 · C 20,
R c \u003d R 50 \u003d R 0 · C 50
The ratio R 50 / R 0 and R 20 / R 0 can be defined both by Table 3 and in Table 4. In tab. 4 shows the values \u200b\u200bof radii zones of strong (R c \u003d R 50) and weak (R Cl \u003d R 20) of destruction for the mass of the flowing DHW from the depressive tank (Q) - Q \u003d 1-10000 tons and maximum pressure values \u200b\u200bP max \u003d 500-2000 kp.
table 2
Physico-chemical and explosive properties of some substances and their DHW
7.3. Calculation of the characteristics of the explosion
The main afflicting effect of explosives is a shock wave. Therefore, to determine the impact of explosive, it is necessary to calculate excessive explosion pressure.
, (7.15)
where r - pressure on the front of the shock wave;
p 0. - Pressure of unmatched air - atmospheric pressure (101kpa).
Value D R. Depends on the type of explosive, the mass of the bleed charge, the distance from the center of the explosion and the nature of the underlying surface.
Calculation of excess pressureD R. It is carried out in two stages. At the first stage there is a reduced radius of the explosion zone by the formula
,
(7.16)
where R.- distance from the center of the explosion, m;
M. - weight of charge, kg;
TO - coefficient, taking into account the nature of the underlying surface;
T E. - Troityl equivalent of explosive.
In tab. 7.6 The values \u200b\u200bof the coefficient TO For different types of underlying materials.
Table 7.6.
The values \u200b\u200bof the coefficient TO For different materials
|
The material of the underlying surface |
Coefficient TO |
|
Metal |
1.00 |
|
Concrete |
0.95 |
|
Wood |
0.80 |
|
Priming |
0.60 |
The TNT equivalent, as shown above, is the ratio of the mass of the explosive to the mass of TNT, creating the same affecting effect. For T E. < 1 Explosive has a stronger destructive effect than Troil (one kilogram of explosive); for T E. \u003d 1 Explosive has the same destructive power, as well as TROTIL; for T E. \u003e 1 Explosive will produce a smaller destructive effect than Troil. In tab. 7.3 The values \u200b\u200bof the T-natil equivalent for industrial explosives were shown. In tab. 7.7 shows the values \u200b\u200bof the TNT equivalent for some combat explosives.
Table 7.7.
The value of TNT equivalent
for combat explosives
|
Explosive |
T E. |
|
Powder |
0.66 |
|
Ammonal |
0.99 |
|
TNT |
1.00 |
|
Tetril |
1.15 |
|
Hexogen |
1.30 |
|
TEN |
1.39 |
|
Titonal |
1.53 |
At the second stage, according to the calculated value of the reduced radius (7.16), the amount of overpressure is calculated D R.. Moreover, different formulas are used depending on the size. For values \u200b\u200b6.2, the calculation of excessive explosion is carried out by the formula:
, kPa. (7.17)
For values\u003e 6.2, the estimated formula for overpressure of the explosion has the form:
, kPa. (7.18)
Using the calculated values \u200b\u200bof excessive explosion pressure, it is possible to evaluate the destruction of the explosion produced. When evaluating the affecting effect of the explosive, four zones of the destruction of objects are distinguished, the characteristics of which are given in Table. 7.8.
Table 7.8.
Object destruction zones
with different values \u200b\u200bof excessive explosion
|
Zone of destruction |
D R., kpa |
|
Full destruction |
Over 50. |
|
Strong destruction |
30 ÷ 50. |
|
Middle destruction |
20 ÷ 30. |
|
Weak destruction |
10 ÷ 20. |
To assess the degree of destruction of buildings and structures at a particular explosion, you can use Table. 7.9, which presents the limit values \u200b\u200bof excessive explosion pressureD R.causing different degrees of destruction.
Table 7.9.
Values \u200b\u200bof maximum overpressure,
causeing various destruction of buildings and structures
|
D R., kpa |
Destruction |
D R., kpa |
Destruction |
D R., kpa |
Destruction |
|
0.5 ÷ 3.0 |
Partial destruction of glazing |
Destruction of partitions, window frames |
Destruction of brick and block walls |
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|
3 ÷ 7. |
Full destruction of glazing |
Destruction of overlaps |
Destruction of reinforced concrete structures |
Consider the procedure for calculating the excess explosion pressure on the following example.
It is required to determine the striking effect when exploding the charge of told a weighing 100 kg at a distance from the buildingR. \u003d 2 m on the outdoor ground.
First we define excessive explosion pressure D R. In the explosion of TNT in formula (7.16). Coefficient TO For open soil, we find the table. 7.6. It is 0.60. TROTIL EQUIVAL FOR TNT T E \u003d 1 (Table 7.7).