MANUAL OF NATO SAFETY PRINCIPLES FOR THE STORAGE OF MILITARY AMMUNITION AND EXPLOSIVES (May 2010)

AASTP-1

(Edition 1)

Section V - Ground Shock

2.5.4.1

General

Ground shock constitutes a grave danger to structures and their contents. In general, however, ground shock is

no critical parameter in the design of airblast and fragment resistant buildings.

Ground shock effects are very dependent on various charge configurations (e.g. sphere tangent to and above

ground surface, half-buried or hemispherical charges).

This paragraph describes the ground shock effects of surface and near-surface bursts.

Test detonations in the order of . . .

0.5 kg ≤ NEQ_TNT ≤ 500 000 kg

. . . have been evaluated and have supplied data for scaled distances.

0.2 ≤ z (m/kg^.1/3) ≤ 24

2.5.4.2

Phenomenology

General

Ground shock is a result of energy imparted to and propagating within the ground. Sources of energy may be

shocks due to explosions or mechanically produced shocks. In the event of an explosion, the shock loads

generated in the vicinity of the point of burst are transmitted directly through the ground as well as in-directly

by means of the airblast wave.

According to the manner of induction, two types of ground shocks are distinguished:

- DI-Ground Shock / Direct-Induced Ground Shock

- AI-Ground Shock / Airblast-Induced Ground Shock

Direct-Induced (DI) Ground Shock

The DI ground shock comprises the original, directly induced ground motions as well as those induced by

cratering. The latter are generally of longer duration and are the result of cratering explosion events. In general,

both phenomena are of longer duration than the AI ground shock. The shock waveform is usually sinusoidal.

Although the dominant motions are vertical, a DI ground shock may have strong horizontal components,

especially at close-in distances.

Airblast-Induced (AI) Ground Shock

The airbast wave compresses the ground surface and transfers the shock impulse to the adjacent medium.

Magnitude and duration of the shock impulse depend upon the progression of the blast wave and the

characteristics of the ground medium. In general, the induced ground motions are directed downwards. Starting

with maximum intensity at the ground surface the motions attenuate with depth. Discontinuities of the ground

material and stratifications, e.g. groundwater, rock layers, may change the attenuation process. In general,

however, the surface soil layer is the decisive factor.

Both types of shock act independently of each other. The decisive shock (motion) parameters - displacement,

velocity and acceleration of the soil particles - depend upon the super-position and the time of arrival of the

different shock waves. Primarily, this time is determined by the shock front velocity or the peak overpressure

of the airblast wave, respectively, by the seismic velocity, and the distance between the point of burst and the

exposed site.

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In the vicinity of the point of burst, the airblast shock front velocity is substantially higher than the seismic

velocity within the ground. Within this "superseismic region", the air-blast reaches the exposed site before

the DI ground shock wave. With increasing distance from the point of burst the velocity of the airblast wave

decreases and the DI ground shock wave finally catches up with and outruns the blast wave within the "out-

running region", resulting in the superposition of both shock waves. At greater distances, the two waves may

separate again, with the DI wave leading the AI wave.

2.5.4.3

Physical Fundamentals for Ground Shock Computation

General

Literature analyses show that, in fact, on the AI ground shock correlates quantitatively with the test results.

The acoustic impedance 'cp · rho' and the pore volume of the soil seem to be the important material

parameters in this context.

Formulations for the computation of DI ground shock parameters for three essential types of soil - dry soil,

saturated soil, and rock - are given in Table [5-14]. Generally, further subdivisioning does not result in

substantially greater accuracy.

AI Ground Shock

The AI ground shock can be determined by means of a one-dimensional wave propagation theory.

For surface structures with a response behavior unaffected by seismic wave reflected from soil layers, simple

empirical conditional equations will result.

The equations given in Table [5-12] provide reasonable estimates of the AI ground shock at the soil surface,

assuming a homogeneous soil structure for a distance corresponding to the wavelength of the blast wave.

For design purposes, the overall motions of structures with shallow foundations may be considered to be

similar to the motions described.

DI Ground Shock

For the determination of DI ground shock, empirical equations have been developed (-->> Table [5-14]),

which may be applied to TNT surface or near-surface bursts.

The equations are given for 3 selected types of soil . . .

. . . dry soil,

. . . saturated soil,

. . . rock.

2.5.4.4

Design Implications

General

The effects of ground shocks have to be considered in connection with safety and design requirements. There

are safety problems for or hazards to personnel, traffic routes, inhabited buildings, installations of ammunition

storage facilities and equipment. Therefore, the consideration of shock processes in the design is imperative.

The designing engineer certainly requires suitable basic design data, e.g. in the form of permissible limits of

motion parameters in the vicinity of the exposed site.

Personnel

Personnel is subjected to shock effects via the ground itself or the structure in which they are staying at the

time of an explosion. The human body will be exposed to accelerations and vibrating loads. The hazards to

personnel are: impact on hard surfaces or edges, distortion of limbs or possibility of being hit by objects which

have been accelerated as a result of the shock.

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Inhabited Buildings

Referenced sources derive the vulnerability levels of inhabited buildings and other unhardened inhabited

facilities from the motion parameters of the ground medium exposed to the ground shock load.

Magazines

When determining the permissible minimum distances between ammunition storage buildings such as

magazines and explosives workshops, the ground effect is an important factor. In general, the buildings

concerned are massive and solid structures with shallow foundations which must be capable of withstanding a

relatively high airblast as well as the impact of debris and fragments. The destruction of aboveground

ammunition storage facilities by a DI ground shock is thus quite improbable. The deeper a building extends

into the ground, though, the stronger is the effect of the DI ground shock.

Although at common inter-magazine distances small explosives quantities cause high accelerations of the soil

particles, there are practically no damages because of the slight soil displacements and the small quantity of

energy imparted.

In the case of large explosives quantities, the accelerations are relatively low, but high ground motion

velocities and large displacement may however constitute a substantial hazard to external connections and

joints of the building, which may be torn off. Usually, suitable design is an easy way to counteract that hazard.

For closely situated magazines, the AI ground shock is negligible.

(-->> Ref [4])

Equipment

In general, equipment and explosives located in ammunition storage facilities are highly vulnerable to shock

effects. Electric and electronic installations, in particular, have to be shock-hardened.

The shock is imparted either directly through the structure itself or indirectly by way of displacement (falling

down, impact etc.) of equipment.

The hazards described can be avoided by the following design measures:

Determination of the shock response spectrum (SRS) for the soil-structure interaction at a

specified shock loading.

Determination of the shock tolerance spectrum (STS) for essential pieces of equipment;

Performance of a shock analysis;

Installation of dynamically loadable mounting elements;

Installation of dampers and isolators with mathematically proven performance

characteristics;

Purposive shock tests for the determination of the specific shock effects.

Hazard limits: -->> Section VII

2.5.4.5

Design Procedure

For the protection of personnel and equipment against ground shock effects the design procedure described

below is recommended:

Determination of the relevant soil characteristics and detonation parameters;

Computation of the motion parameters of the ground using specified formulas;

(-->> Table [5-12], [5-14]; -->> Ref [1], [3])

Comparison of the maximum motion parameters to be encountered with the limits specified

in Section VII;

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Section VI - Cratering

2.5.5.1

General

This section describes the cratering process and the essential relevant parameters, depicts the spectrum of

effects and the hazard potential and specifies formulations for the determination of the decisive crater dimensions -

diameter, depth and volume.

In comparison with the other hazards resulting from an accidental explosion, cratering effects are usually of

minor importance. In certain situations, however, cratering may cause severe damage because of excavation, subsurface

disturbances or surface heaves. Under certain conditions, the propagation of detonation to an adjacent magazine is also

possible.

Hazards from crater ejecta and structural debris have to be taken into consideration, particularly for larger

quantities of stored ammunition and explosives.

These hazards are detailed in Section VII.

2.5.5.2

Phenomenology

A Crater is a hole in the ground resulting from mechanical displacement of the adjacent ground material in the

course of an explosion of demolition charges.

Primarily, a crater is defined by the following parameters:

(-->> Figure [5-12])

The "apparent crater" is the visible cavity left after an explosion and is defined by the "apparent radius" and the

"apparent depth".

The "true crater" is the entire cavity formed by an explosion part of which is being filled up again by the

fallback (fallen back ground material). The "true crater" is defined by the "true radius" and the "true depth".

The "rupture zone" is that region at the crater flanks, where the ground material remains in place, but its inner

structure is substantially disturbed by the forces of the explosion.

The "plastic zone" is the area adjacent to the "rupture zone" and is less disturbed than the latter.

The "upthrust zone" is the original ground above the rupture and plastic zones that has been permanently

elevated. The "upthrust zone" is usually covered by the crater ejecta.

The "Crater lips" is the material around the crater that lies above the original surface elevation and is formed

by upthrust and ejecta. The "Crater lips" may extend to widths of several crater radii.

2.5.5.3

Crater Computation

Decisive Parameters

The crater size depends mainly upon the following parameters:

Type of explosive;

Net Explosives Quantity (NEQ;

Depth of Burst (DOB) / Height of Burst (HOB)

Stratification and type of soil.

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Depth of Burst (DOB)

Figure 5-13 illustrates the variation in crater size and formation as a function of the DOB. Cratering is

described here from a classical context and no direct account is taken of the inefficiency associated with

accident explosions in most storage situations when compared with the standard, buried charge situation.

Accidental explosions which are large enough to form craters originate from concentrations of explosives in a

number of different configurations, typically:

On or just above the ground surface, e.g. in transport vehicles (-->> Figure 5-13a).

In deep-buried magazines where the explosions are less efficient in producing craters ad

ejecta than the standard buried charge from which most cratering data has been obtained (--

>> Figure 5-13b). The difference is mainly one of degree related to the free volume inside

the magazine and the mechanics of the crater formation and throw-out of ejecta / debris is

essentially the same.

Underground magazines where the depth of cover is such that no external crater is formed as

a result of an explosion (-->> Figure 5-13e).

For constant explosive quantity and type of explosive, crater size increases with depth of burst until the

maximum crater size is reached at the optimum DOB.

When the DOB is further increased, soil resistance exceeds the explosion energy; cratering is suppressed and

fallback of the crater ejecta increases, thus constantly reducing the visible crater size. Beyond a certain DOB,

there is no cratering at the surface any more.

Finally, complete confinement of the ground burst occurs. This results in surface heaves and soil disturbances

as well as in the forming of subsurface craters or camouflage craters.

Stratification and Type of Soil

Cratering is mainly determined by the type of soil, the stratification near the ground surface and the water

content of the soil.

Important relevant findings are:

Craters in sandy soil are smaller than those in clay soil. Other types of soil, such as clayey

sand, silt or loam, fall in between these two extremes.

Craters in moist or saturated soil are larger than in dry soil. This applies, in particular, to clay

soil.

Subsurface layers such as groundwater-saturated soil or rock may strongly influence the

crater size. This applies when the distance in depth to the layer concerned is less than 1.5 Ra

(Ra for layer free soil), and results in more shallow but wider craters. If the layer is

intersected by crater, the variation in size may be up to

50 % below or above the

corresponding undisturbed crater parameter (depth, radius). In cases where the groundwater

level lies approximately 2 m below the surface, a large explosion may form a crater with

twice the diameter of a crater in soil without groundwater.

In the case of saturated soil of relatively low density, there may be soil liquefaction effects

causing a slump of the crater walls. The resulting crater is very wide and shallow, with a

radius several times that of a normal crater. The liquefaction effects may endanger the

stability of structures at distances of 20 to 30 times the crater radius.

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Crater Dimensions

The results of many tests have been evaluated and prepared for practical use in the form of compensation

functions or design diagrams.

Figure [5-14] shows the "apparent crater" dimensions for three types of soil.

For the determination of the "true crater" sizes for all DOB less than the optimum DOB, the following rule

of thumb applies:

R_t ≈ 1.10 to 1.15 · R_a

(m)

eq [5-65]

D_t ≈ 0.16 · NEQ ^1/3 + DOB

(m)

eq [5-66]

On the case of a surface or air burst, the crater is "blown clear" so that the "true crater" is approximately the

same as the "apparent crater".

For DOB greater than the optimum, the diameter of the "true crater" corresponds largely to that for optimum

DOB, whereas the depth of the "true crater" increases with DOB.

The rupture zone extends to approximately 1.5 to 2 times the radius of the "true crater" and 1.3 to 2 times the

depth of the "true crater".

Generally, the plastic zone is twice as large as the rupture zone.

Ammunition Storage Facilities

For determining the decisive crater parameters for a major accidental explosion inside an aboveground storage

facility, the diagrams in Figure [5-14] to [5-19] or regression equations may be used.

It must be taken into account, though, that in the case of explosions inside structures the foundation or bottom

slab-depending upon the loading density - either prevents the forming of a typical crater (loading densities in

the order of 10 to 20 kg/m³ (-->> Ref [77]) or, at higher loading densities, more shallow craters with greater

diameters are formed.

The coupling factor "f_o" is used for converting the data of an underground storage facility completely filled

with explosives to that of a partially filled one. For the specified loading densities, the coupling factor is . . .

. . . τ

≈

1600 kg / m ³

--->> f_o

100%

1.0

. . . τ

≈

10 kg / m ³

--->> f_o

10%

0.1

Coupling factor 'f_o' :

-->> Figure [5-20]

Depending upon the loading density, the coupling factor reduces the ground shock, cratering and ejecta/debris

effects. The effective or calculated explosives quantity results from the following product:

NEQ_eff = f_o · NEQ_TNT

Crater Parameter Formulas

(1)

Symbols

R_a,R_t

(m)

radius of apparent/true crater

D_a, D_t

(m)

depth of apparent/true crater

V_a, V_t

(m ³)

volume of apparent/true crater

R_sl

(m)

fictitious crater radius for completely symmetrical explosive charge

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L_sl

(m)

crater length for oblong explosive charge *)

B_sl

(m)

crater width for oblong explosive charge *)

D_sl

(m)

crater depth

V_sl

(m)

volume of apparent crater

with bottom slab

a,f

apparent parameters; open surface burst without bottom slab

Here, " oblong explosive charge " means the usual distribution of explosives in an oblong

ammunition storage building.

(2)

Open Surface Burst Without Bottom Slab

According Ref [32] for sandy, gravely soil . . .

R_a,f

0.400 · NEQ ^0.333 (m)

D_a,f

0.200 · NEQ ^0.300 (m)

eq [5-67]

V_a,f

0.042 · NEQ 0.960 (m ³)

According to Ref [1], [2], [3] . . .

R_a,f

A · NEQ ^B (m)

eq [5-68]

D_a,f

A · NEQ ^B (m)

Basalt

Granite

Sandstone

high-strength

medium-strength

R_a,f

0.330

0.510

0.330

0.360

0.313

D_a,f

0.120

0.330

0.170

0.330

0.200

0.315

Sandstone

Gravelly Sand

Coarse Sand

slate

dry

R_a,f

0.760

0.294

0.590

0.294

0.570

0.294

D_a,f

0.320

0.294

0.200

0.294

0.220

0.294

Sand-Clay

Fine-Grained

Silt, Clay

coarse, dry

Wet Clay

saturated

R_a,f

0.400

0.333

0.510

0.333

0.830

0.333

D_a,f

0.190

0.333

0.260

0.333

0.500

0.333

According to Ref [1], [2] . . .

- Crater radius:

DOB / NEQ_TNT ^1/3

(m/kg) ^1/3

c₆ · x ⁶ + c₅ · x ⁵ + c₄ · x ⁴+ c₃ · x ³ + c₂ · x ² + c₁ · x + c₀

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Clay

Clayey Sand

Sand

wet

dry

wet

dry

wet

dry

c₆

- 0.9138

3.4296

1.5254

6.6138

5.3895

3.9615

c₅

4.5971

-14.1268

- 7.5848

-21.6824

-19.9765

-13.9722

c₄

- 9.6611

20.7724

13.5517

25.5991

25.9610

17.1007

c₃

10.6273

12.7799

-10.4240

-13.2913

-13.6946

- 8.7749

c₂

- 7.0956

1.1501

1.4237

1.5053

0.7827

0.3314

c₁

3.1878

2.2545

2.2503

1.7332

2.1788

1.7526

c₀

1.7470

1.1539

1.2592

0.9416

1.0426

0.8610

eq [5-69]

R_a,f =

· NEQ_{TNT 1 / 3}

(m)

Crater depth:

DOB / NEQ_TNT ^1/3

(m/kg) ^1/3

c₆ · x⁶ + c₅ · x ⁵ + c₄ · x ⁴+ c₃ · x ³ + c₂ · x ² + c₁ · x + c₀

Clay

Clayey Sand

Sand

wet

dry

wet

dry

wet

dry

c₆

0.0000

3.9156

0.0000

c₅

- 0.5074

- 0.5634

0.1109

-10.6347

- 1.7342

- 2.1635

c₄

1.8409

1.4661

- 0.5177

9.7514

4.6696

4.0866

c₃

- 2.0285

- 1.5432

0.7502

- 3.9218

4.6469

- 3.1802

c₂

- 0.3971

- 0.2424

- 1.4739

- 0.0049

0.8813

0.3980

c₁

1.4481

1.0880

1.3841

0.8711

0.9596

0.6974

c₀

0.5446

0.4125

0.4561

0.3016

0.3414

0.2616

R_a,f = C · NEQ_TNT ^1/3

(m)

eq [5-70]

(3)

Burst Inside a Detached Aboveground Magazine

According Ref [77], [32] . . .

R_s1 ≈ 1.5 · R_a,f

(m)

D_s1 ≈ 0.8 · D_a,f

(m)

eq [5-71]

V_s1 ≈ 1.5 · V_a,f

(m)³

with eq [5-67] . . .

R_s1 ≈ 0.600 · NEQ_{TNT 0.333}

(m)

D_s1 ≈ 0.160 · NEQ_{TNT 0.300}

(m)

eq [5-72]

V_s1 ≈ 0.063 · NEQ_{TNT 0.960}

(m) ³

(4)

Burst Inside an Earth-Covered Aboveground Magazine

For the derivation of universal crater parameters for earth-covered magazines only very few basic

data are available.

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Section VII - Thermal Radiation

2.5.6.1

General

Detonation of an explosive typically results in the production of a relatively short flash accompanied by high

thermal radiation.

Normally, the radiation from this short-lived flame constitutes a negligible hazard in comparison with blast and

projection effects. Propellants and pyrotechnic substances of Hazard Division 1.3 differ from detonating explosives of

Hazard Division 1.1 in that, unless heavily confined, their reaction does not result in the generation of high blast

pressures.

Although the energy per unit mass of these explosives is comparable, they differ in the duration of energy

release. The energy of detonating explosives is released within a time scale of a few milliseconds, whereas energy from

an unconfined propellant or a pyrotechnic substance is released over a period measured in seconds or longer. The

energy is released in the form of an intense, very hot flame. The potential hazard is due to thermal radiation and the

direct impingement of the flame.

As compared to blast and fragment/debris effects, there are only few studies on the effects of thermal radiation

available which offer quantifiable formulations.

Thus, the statements below are coarse, conservative guidelines for determining the decisive hazard parameters

of ammunition and explosives of Hazard Division 1.3 in the case of fire during storage and transport.

2.5.6.2

Fireball Computation

The development and the behavior of a fireball as well as the decisive parameters - dimensions, temperature,

and duration - are generally varying and strongly affected by the environment (e.g. wind, buildings, vegetation etc).

Therefore, the formulations below may only be used as rough estimates:

Burning of Propellant Powder in the Open

(-->> Ref [30])

(1)

Radius of Fireball

. . . Maximum radius of fireball few meters above the ground

R_{max, a}= 2.8 · NEQ^0.28 (m)

eq [5-74]

. . . Maximum radius at ground level

R_{max, s}= 0.45 · NEQ^0.44

(m)

eq [5-75]

(2)

Duration of Fireball

t_eff,50

= 0.93 · NEQ ^0.21 (s)

eq [5-76]

Note:

After ignition, the fireball expands and reaches a maximum within a period of about 2 seconds.

After several seconds of intense radiation, depending upon the quantity of propellant involved, the

fireball collapses. In general, the actual extinction of the visible flame occurs not until after thermal

radiation has decreased to comparative insignificance. The effective duration of thermal radiation

t_eff,50, thus is de-fined by the time required for the fireball to shrink to ≈ 50% of its maximum radius.

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Explosion of Explosives Inside an Earth-Covered Magazine

(-->> Ref [78]; -->> Figure [5-21])

(1)

Radius of Fireball

R_max≈ 1.9 · NEQ ^1/3 (m)

eq [5-77]

(2)

Temperature Inside Fireball

T ≈ 5000

(°C)

(3)

Maximum Duration

d_max ≈ 0.17 · NEQ ^1/3

eq [5-78]

Thermal Radiation Energy

The thermal radiant power of burning or exploding high explosives, propellants or liquids is difficult to

measure or determine otherwise. Thermal radiant power, fireball geometry and duration are strongly affected

by the type of packaging used, the direction and speed of the wind and the storage conditions.

Tests with bulk (unpacked) propellant powder (worst case) for an energy flux of . . .

q = 4 cal/cm² = 40 kcal/m² = 167 kWs/m²

. . . resulted in a formulation for the following limiting radius, at which the above value is reached . . .

R_max ≈ 1.0 · NEQ ^0.44 (m)

eq [5-79]

This value will generally not be exceeded.

Thermal Radiation Flux of Burning Propellant Powder

Thermal radiation flux of burning propellant powder is represented by the relationship below.

(-->> Ref [23])

q ≈ 19 · NEQ ^0.82 / R ² (kW/m ²)

eq [5-80]

where

NEQ

(kg)

quantity of propellant powder

(m)

distance from the radiation source

2.5.6.3

Barriers to Resist Thermal Radiation and Flame from Ammunition and Explosives of Hazard

Division 1.3

Normal construction materials such as steel, concrete or brick as well as earth-covered structures can be used

for the protection against thermal radiation and direct flame impingement.

Wooden or light metal doors and windows are structural weak points. Unless these doors/windows face away

from the external source of thermal radiation, they must be considered non-resistant or vulnerable. Windows are

diathermy and not resistant to direct flame impingement.

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Heavy metal covers and closures resist thermal radiation and flame impingement.

Closures must be sealed as to prevent the entry of flames.

2.5.6.4

Design and Construction of Storage Buildings for Ammunition and Explosives of Hazard Division

1.3

Storage buildings shall be constructed of non-combustible materials such as steel, concrete, brick or natural

stone. A standard earth cover may be considered as fireproof.

Buildings containing ammunition and explosives of Hazard Division 1.1 situated in the vicinity of storage

buildings containing Hazard Division 1.3 ammunition and explosives must be built of non-combustible materials.

Buildings for the storage of ammunition and explosives of Hazard Division 1.3 must not contain any exposed

components made of steel, iron, aluminum or aluminum alloy with magnesium content exceeding 1%.

The ceiling or roof should be made of concrete, reinforced concrete or steel plate and be designed as light as

possible (frangible cover).

Unless these requirements are met, flame jets ejected from openings (doors, windows) of the building have to

be expected that might ignite e.g. opposite buildings.

In the case of opposite building entrances, these should be offset by a minimum distance of one (1) fireball

diameter (eq [5-77]) or a barricade capable of stopping or deflecting a flame jet should be erected across the line of

sight to the adjacent building entrance.

Windows and/or wooden doors and other openings in unbarricaded storage buildings should be covered using

heavy steel plate backed up with thermal insulation material. The cover must be large enough to cover all combustible

structural components such as wooden frames.

Air vents and air shafts must be designed in such a way as to prevent the fireball, flame jet or burning debris

from entering the interior of the building.

If buildings for the storage of ammunition and explosives of Hazard Division 1.3 are equipped with a blow-out

wall (frangible cover), this weak wall must not face any stack or storage building, unless the distance is great enough to

prevent sympathetic detonation due to directed burning debris.

2.5.6.5

Hazards form Fire Involving Ammunition and Explosives of Hazard Division 1.3

Thermal radiation from the fireball produced by burning ammunition and explosives of Hazard Division 1.3 is

capable of causing injury to personnel and of communicating the fire to other buildings and explosives storage facilities.

This hazard may be substantially increased by even normal winds, which will deflect the upper parts of the fireball

away from the seat of fire. This may cause the thermal radiation source to be moved closer to the exposed site in the

order of one radius of the fireball.

Ammunition and explosives of Hazard Division 1.3 are normally packaged before storage or transport. A

typical storage arrangement would place the ammunition or explosives in buildings of different construction. The

confinement produced by even a weak building is sufficient to significantly affect the mode of burning of stacks of

propellant powder. The range of a directed high-energy jet of flame which may emerge through openings or frangible

covers will be much longer than the comparable flame radius of the unconfined explosive. Furthermore, direct

impingement of such a jet of flame will impart a greater heat dose to an exposed object than radiation from a fireball,

and may also eject burning stored items and other burning material.

In strong storage buildings a fire can lead to the buildup of high pressure generating effects comparable, after

all, with those of a detonating explosive, i.e. cratering, airblast and debris projection.

(-->> Ref [23])

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Section VIII - Damage Criteria / Hazard Limits

- Risk Assessment Guidelines -

2.5.7.1

Personnel

Airblast

Airblast caused by an explosion endangers personnel in different ways through:

The shock wave and the time-depending overpressure;

The debris from destroyed structures or accelerated objects;

The impact of the accelerated human body on obstacles or on the ground.

The body regions most endangered by airblast are:

The respiratory system with lungs and trachea;

Head;

Ears and ear-drums;

Spleen, liver, heart.

The extent of the injuries caused directly by airblast is strongly affected by:

The rate of pressure increase within the shock front;

The peak overpressure within the shock front;

The duration of the positive pressure phase.

Damage thresholds according to literature analyses:

(1)

Direct Airblast Effect

Type of

T_o

P_s

I_s

Ref

Injury / Position

Mpa

MPa-ms

2.00

[18]

0.90

[207]

100

0.25

> 1000

0.28

[207]

3.00

[18]

LETHALITY

1.20

100

0.35

> 1000

0.35

[207]

4.00

[18]

1.70

100

0.50

> 1000

0.50

[207]

-II-5-59-

Change 3

AASTP-1

(Edition 1)

(-->> Figure [5-24])

0.035

[74]

EARDRUM

0.044

[4]

0.086

-Temporary loss of

< 0.035

hearing

-Threshold inside a

> 0.017

shelter

0.1200

GASTROINTESTINAL

0.135

[74]

TRACT

0.250

(2)

Indirect Airblast Effect

(-->> Figure [5-25] and [5-26])

Type of

V_cr

Ref

Injury / Position

m/s

LETHALITY FOR IMPACT OF WHOLE BODY

3.0

ON HARD SURFACE (CONCRETE)

6.5

16.5

[144]

42.0

STANDING PERSON, STIFF-LEGGED

No Effect

2.4

Injury

3.0-3.6

[19]

Fracture

3.6-4.8

SITTING PERSON

No Effect

2.4

[19]

Injury

4.5-7.8

PUNCH against entire ABDOMINAL WALL

3.0

7.8

[19]

Injury

9.0

(-->> Figure [5-27]

SKULL INJURY; FRACTURED SKULL BASE

3.0

5.5

Blunt Impact

9.0

[4]

Edgewise Impact

< 3.0

-II-5-61-

Change 3

AASTP-1

(Edition 1)

Projections

- Fragments, Debris and Ejecta -

Because of the complexity of the process, the reliable determination of the ballistic parameters of projections

from accidental explosions is difficult. Basic data and information on structural debris and crater ejecta are

limited as compared to fragment data.

The hazards to the different regions of the human body - depending upon their respective sensitivity - are listed

below in descending order:

Head region

: fractured skull

Chest region

: fractured rip, pneumorrhagia, cardiac damage

Abdominal region : damage to liver, spleen

Limbs

: bone fracture and secondary damage

The unprotected area of a standing person is defined to be . . .

A_T = 0.56 m ²

The currently accepted limit values for hazards to persons due to projections are as follows:-

Mass density :

1 projection / 56 m ²

(1/600 ft ²)

Impact energy (E_kin = M · V ² / 2) : 80 Joule

(58 ft/lb_f)

With projections as described above, severe to lethal injuries have to be expected as a rule.

Table [5-15] lists discriminating limits for blunt impact injuries based on empirical tests with animals and

corps.

(-->> Ref [4], [19], [31], [206])

Table [5-15]

LETHALITY DUE TO IMPACT ENERGY

LETHALITY

IMPACT ENERGY / KINETIC ENERGY

(p in %)

(Joule)

HEAD

CHEST

ABDOMEN

LIMBS

105

155

140

240

140

200

380

100

230

280

620

200

850

2500

Note:

Figure [5-29] and [5-30] show lethality as a function of impact energy

Using the Walker-Duncan-method, formulas to calculate the probability of penetration of human and animal

skins by projectiles have been developed.

(-->> Ref [136], [137], [139], [144])

Probability of penetration of human skin:

P_i =

1 + e^{(-(A + B · In C))}

-II-5-62-

Change 3

AASTP-1

(Edition 1)

eq [5-81]

TARGET

Ref

Bare Skin

- 28.42

2.94

[144]

Bare Skin

- 27.35

2.81

[136]

Uniform, 2 Layers

-48.47

4.62

[159]

Uniform, 6 Layers

- 50.63

4.51

Constant C :

M_p · V_i2

C =

10 · A

M_p (kg) mass of projectile

V_i (m/s) impact velocity

A_f (m ²) projection area of projectile

Shock

The following shock loading threshold values for personnel are commonly accepted.

(-->> Ref [4], [144])

Table [5-16]

THRESHOLD FOR SHOCK LOADING ON PERSONNEL

DAMAGE

CRITICAL IMPACT

VELOCITY

V_i.cr (m/s)

Minor

3.0

Threshold

4.0

50% Skull Injury

5.5

100% Skull Injury

7.0

THREAT

ACCELERATION

a (g)

Loss of Balance

- nuclear, horizontal

0.5

- nuclear, vertical

1.0

CRITICAL OSCILLATION TOLERANCES FOR PERSONNEL

Acceleration (g)

Frequency (Hz)

< 10

10 - 20

20 - 40

> 40

Thermal Radiation

Burns may be classified in ascending order of severity as:

First degree burn : reddening and swelling of the affected skin region, pain, healing without

scarring;

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Change 3

AASTP-1

(Edition 1)

Second degree burn:

(a)

reddening, swelling, pain, blistering, healing without

scarring;

(b)

anemic skin / no coetaneous circulation/leatherlike white

necrosis, pain, blistering, scarring (necrosis = devitalized

tissue) ;

Third degree burn : total necrosis, destruction of skin to the point of charring, open flesh, no

pain.

The degree of burn is a function of the total dose of radiation energy received and of the radiant

power, i.e. the radiation energy received per unit of time.

(-->> Figure [5-31])

Table [5-17] ; Ref [89]

RADIANT ENERGY REQUIRED TO CAUSE FLASH BURNS

PERIOD

RADIATION ENERGY

DEGREE OF BURN

tw (s)

(kWs/m ²)

(cal/cm ²)

62.8

1.0

t_w < 1

125.6

3.0

188.4

4.5

125.6

3.0

t_w≈ 5

251.2

6.0

376.7

9.0

Source: AASTP - 1

Corr No 7

Ref [140] specifies the radiant power or radiation energy of burning fuel - as an equivalent of burning

propellants or pyrotechnic substances - required for causing the different degrees of burn on human bodies as

follows . . .

Table [5-18]

RADIATION INTENSITY q / t_w (kW · s / m ²

DEGREE OF BURN

PROBABILITY OF INCIDENT

(s)

50%

99%

1^st degree

38.5

68.8

122.7

2^nd degree

87.8

156.4

278.6

3rd degree

92.8

184.5

364.1

t_w = active duration of the radiation

2.5.7.2

Damage Criteria for Structures and Materials

Airblast

Damage to structures caused by conventional ammunition and explosives:

Table [5-19]

Symbols:

X occasional

C heavy damage

A minor damage

D destruction

B medium damage

Pressure: Pso [kPa]

-II-5-64-

Change 3

AASTP-1

(Edition 1)

DAMAGE CRITERIA FOR STRUCTURES / COMPONENTS DUE TO PRESSURE

OBJECT

glass, large window

0.2

glass, typical

1.1

3.5-7.0

window frame

0.5

window frame

10.6

door frame

10.6

door, window

6.0-9.0

plaster

3.5-7.0

tiles (roof)

3.0

5.3

0%-50%

dwelling house

3.0^*)

8.1^**)

36.6^**)

80.9^**)

wall, ceiling

14.1

partial

concrete wall, 0.3 m

14-21

plain

unreinforced build.

70.3

brick wall

56.3

70.3

brick wall, 20-30 cm

56.3

flexure

brick wall, 45 cm

91.4

steel building

9.1

14.0

17.6

21.1

wooden building

12.0

17.0

28.0

building, block

70.0

factory chimney

14.0

industrial building

28.0

administr. building

38.0

brick building

28.0

RC-structures

38.0

53.0

steel girder build.

31.6

63.3

cladding of build.

7.0

14.1

heavy bridge

492.3

steel truss bridge

63.3

coll.

motor vehicle

28.2

35.2

70.3

crushed

rail car

18.3

39.4

60.5

77.4

wooden utility pole

28.0

snapped

power mast

28.0

snapped

radio mast

14.0

snapped

oil storage tank

6.3

21.0

24.6

28.1

tree

21.1

175.8

90%

inhabitable

completely demolished

**)

uninhabitable

coll.

collapsed

Damage limits for brick buildings:

-->> Figure [5-32]

Projections

The impact of hard projections at relatively high velocities results in extremely high local load peaks at the

target (ES) with relatively short impulse duration. In general, hazards are presented due to the perforation or

punching of the affected structural component. Spalling involving high secondary projection velocities may

occur at the backside of the target. The hard projections often ricochet off the target and cause damage in the

vicinity. The extent of the damage depends upon the geometry and material properties of the target and has to

be analyzed in detail.

Figure [5-10] and [5-11] show approximate data for the thickness of unreinforced concrete slabs required in

the case of hard projection impact.

Normally, deformable projections transfer their entire kinetic energy to the target or break upon impact. The

longer shock pulse duration resulting from the deformation leads to a reduced peak load. As compared to the

impact of hard projections, the punching and perforation hazard to the target is substantially reduced. The

structural component affected is, however, subjected to a higher bending load.

-II-5-65-

Change 3

AASTP-1

(Edition 1)

Figure [5-10] shows approximate data for load peaks due to the impact of deformable projections (ejecta).

Shock

(1)

Inhabited Buildings

The damage threshold values below are recommended for inhabited buildings

Table [5-20]

DAMAGE THRESHOLD FOR DIRECT-INDUCED GROUND SHOCK / Ref[89]

DAMAGE

max. VELOCITY

SCALED DISTANCE

vertical/horizontal

V_max (m/s)

Z (m/kg ^1/3)

≤ 0.05

6.6

minor/medium

0.05

- 0.14

3.6

heavy

0.14

- 0.19

2.9

Note:

All the scaled distances above are shorter than the inhabited building quantity distance. They

are also within the airblast and projection hazard zones.

Table [5-21]

DAMAGE THRESHOLD for AIRBLAST-INDUCED GROUND SHOCK

( for -3- selected soils)

Ref [89]

DAMAGE

V_v/h,max

SCALED DISTANCE

Z (m/kg∧1/3)

(m/s)

soil -1-

soil -2-

soil -3-

≤ 0.05

5.7

3.4

2.9

Minor/medium

0.05

- 0.14

2.7

1.7

1.5

heavy

0.14

- 0.19

1.5

1.0

0.8

TYPE OF SOIL

DENSITY

SEISMIC VEOLOCITY

Rho

C_p

(kg/m ³)

(m/s)

Soil

1520

460

Saturated soil

2000

1520

Rock

2560

4000

For similar damage levels, the scaled distances for AI ground shock are shorter than those for DI

ground shock. Therefore, it is not likely for the AI ground shock to be used as a measure for the

determination of critical inhabited building quantity distances.

Other threshold values for comparison:

For buildings required to retain their useable condition, German Standard DIN 4150, Part 3,

specifies the following max. oscillating velocities resulting from a short shock load.

-II-5-66-

Change 3

AASTP-1

(Edition 1)

Table [5-22]

CRITICAL OSCILLATING VELOCITY

dwelling and business building

0.008 m/s

braced buildings with heavy components;

braced skeleton buildings

0.030 m/s

historical buildings/monuments

0.004 m/s

Ref [10] specifies the threshold values below for normal buildings in good condition:

Table [5-23]

CRITICAL OSCILLATING VELOCITY ON BASE Ref [10]

individual, minor damage

0.070 m/s

damage threshold

≈ 0.140 m/s

50% structural damage

≈ 0.180 m/s

(2)

Magazines

Ref [78] specifies the limiting criteria below for damage to or destruction of earth-covered

magazines:

Table [5-24]

CRITICAL SOIL PARTICLE VELOCITIES FOR AMMUNITION

STORAGE BUILDINGS

Ref [78]

QUANTITY OF STRUCTURE

max. VELOCITY of

soil particles

V (m/s)

no damage

< 0.2

rigid frame prefabricated

0.2

- 1.5

concrete buildings

heavy reinforced concrete magazines

3.0

(3)

Equipment

Shock tolerance limits -->> Ref [1], [3], [4] et al.

Some selected examples

Table [5-25]

SHOCK TOLERANCES FOR SELECTED EQUIPMENT

EQUIPMENT

DAMAGE

FREQUENCY

(g)

f_min

heavy

(Hz)

Heavy weight machinery

. engines, generators,

. transformers

M > 2000 kg

Medium weight machinery

120

. pumps, condensers,

-II-5-67-

Change 3

AASTP-1

(Edition 1)

SHOCK TOLERANCES FOR SELECTED EQUIPMENT

EQUIPMENT

DAMAGE

FREQUENCY

(g)

f_min

heavy

(Hz)

. air conditioners

M ≈ 500 - 2000 kg

Light Weight machinery

200

. small engines > 500 kg

Duct work, piping,

280

storage batteries

Electronic equipment,

relays, magnetic drum

units, racks of

communication equipment

a (g) acceleration ; fmin. (Hz) minimum natural frequency

Thermal Radiation

Thermal radiation can damage or destroy buildings. The damages range from scorching to complete burning of

structures. Heating of non-combustible materials may result in reduced strength and stiffness and thus in the

collapse of the building.

On principle, there are two (2) different damage classes resulting from thermal radiation.

(-->> Ref [140])

Class -1-

burning of a building or of essential structural components

collapse of a building or of essential structural components

Class -2-

heavy scorching of the building surface and deformation of non-

combustible structural components without collapse

For different materials, critical radiation flux values are specified. This critical intensity is defined as that value

which causes no ignition even after prolonged exposure.

Table [5-26]

CRITICAL RADIATION INTENSITY

kW / m ²

MATERIAL

CLASS -1-

CLASS -2-

Wood

Plastics

Glass

Steel

100

Hazardous radiation flux limits: -->> ref [21]

The estimated limits below may be used for determining the maximum acting thermal radiation flux q . . .

5 kW/m ²

breaking of windowpanes sensation of pain due to thermal radiation burn

10 kW/m²

occurrence of scorching possible ignition of combustible material

15 kW/m²

spontaneous ignition of material, e.g. wood

-II-5-68-

Change 3

AASTP-1

(Edition 1)

Sympathetic Detonation

(1)

General

As for the sympathetic detonation as a function of different detonation effects, only insufficient

quantitative limits are available. Several studies have attempted the formulation of such limits.

Airblast involving high peak overpressure, shock and the impact of projections may result in the

sympathetic detonation of high explosives. The individual tolerance thresholds of the high

explosives, however, are varying.

(2)

Airblast

Except for extremely high pressures, the majority of high explosives are insensitive to airblast

effects. In most cases, the sympathetic detonation is caused by secondary effects, such as the

projection of the high explosive against a hard impact surface.

(3)

Shock

The shock-induced motion of the storage building or the displacement of the explosive and the

resulting impact on a hard surface may lead to a sympathetic detonation.

Ref [78] specifies critical soil particle velocities. According to this reference, the propagation of

detonation will be 1.5 m/s for prefabricated, solid concrete structures and 3 m/s for heavy reinforced

concrete storage buildings.

(4)

Fragments

Because of their high kinetic energy, fragments can cause the sympathetic detonation of adjacent

ammunition components. Therefore, buildings or structural components should be designed

fragment-proof and open-storage stacks should be separated by the required quantity distances.

(-->> Ref [4])

Protective roofs and barricades are important means for preventing sympathetic detonation due to fragment

impact.

The limits below may be used as estimates for the impact energy and the critical impact impulse.

(-->> Ref [89])

Table [5-27]

CRITICAL PROPAGATION IMPACT PARAMETERS

IMPACT VELOCITY

ENERGY

IMPULSE

V_i (m/s)

E_kin (J)

(Ns)

≤ 50 m/s

----

100

≥ 50 m/s

2500

----

(5)

Craters

The radius of the crater to be expected should be used as the relevant assessment parameter. If the

acceptor magazine (ES) is located within the area defined by the radius of the crater, sympathetic

detonation has to be expected.

-II-5-69-

Change 3

AASTP-1

(Edition 1)

Section IX - References/PC Codes/Figures/Tables

2.5.8.1

References

[

TM 5-855-1 FUNDAMENTAL OF PROTECTIVE DESIGN

USAWES/CoE

U.S. Army Waterways Experiment Station

Vicksburg, Mississippi

USA

November

1986

[

TM 5-855-1 /FUNDAMENTAL OF PROTECTIVE DESIGN / Edition 1991, PC-Programm

Hyde,David,W

USAWESCoE /Department of the Army

Washington DC

USA

October

1989

[

PROTECTIVE CONSTRUCTION DESIGN MANUAL / ESL-TR-87-57 Final Report

Drake,J.L;Twisdale,R,A;Frank,W,C;Dass,C,E; et al

AFESC / Engineering & Services Laboratory

Tyndall AFB,FL

USA

November

1989

[

STRUCTURES TO RESIST THE EFFECTS OF ACCIDENTAL EXPLOSIONS / TM 5-1300

Department of the Army, the Navy and the Air Force

TM 5-1300, NAVFAC P-397, AFR 88-22

Washington DC

USA

November

1990

[

AIRBLAST PARAMETERS FROM TNT SPHERICAL AIR BURST AND HEMISPHERICAL

SURFACE BURST /ARBRL-TR-02555

Kingery,C,N; Bulmash,G

Ballistic Research Laboratory, ARBRL-TR-02555

Aberdeen ProvGr,MD

USA

April

1984

[

ENGINEERING DESIGN HANDBOOK - PRINCIPLES OF EXPLOSIVE BEHAVIOR

US Army Materiel Command, Headquarters

US Army Materiel Command, AMCP 706-180

Washington DC

USA

April

1972

[

STRUCTURAL DYNAMICS

Biggs,John,M

McGraw Hill, ISBN 07-005255-7

New York

USA

1964

[

DESIGN OF STRUCTURES TO RESIST NUCLEAR WEAPONS EFFECTS

ASCE

American Society of Civil Engineers ASCE No 42

USA

[

SCHWEDISCHES SCHUTZBAUHANDBUCH / FORTH 1

FORTF

Schwedische Schutzbauverwaltung /Fortifikationsförvaltningen, Forskningsbyran

Stockholm

Sweden

1987

[

10]

MILITÄRISCHE SPRENGTECHNIK - LEHRBUCH -

Autorenkollektiv

Militärverlag DDR

Berlin

Germany

1984

-II-5-71-

Change 3

AASTP-1

(Edition 1)

[

11]

JOINT MUNITIONS EFFECTIVENESS MANUAL - AIR TO SURFACE - TARGET

VULNERABILITY (U)

- BOOK 1 OF 2

US DOD -SECRET-

US Department of Defense

USA

1986

[

12]

STRUCTURAL DESIGN FOR DYNAMIC LOADS

Norris,C,H et al

McGraw-Hill

USA

1959

[

13]

DYNAMIC PROPERTIES OF RESIDENTAL STRUCTURES SUBJECTED TO BLAST LOADING

Dowding,C,H

Journal for the Hydraulic Division,ASCE, Vol 107, ST7

USA

1981

[

14]

PRINCIPLES AND PRACTICES FOR DESIGN OF HARDENED STRUCTURES

Newmark,N,M et al

US Department of Commerce, AB-295 408,

USA

1962

[

15]

DYNAMICS OF STRUCTURES

Clough,R,W;Penzien,J

McGraw-Hill

USA

1975

[

16]

APPROXIMATE FORMULATE FOR PERIOD OF VIBRATIONS OF BUILDING SYSTEMS

Adeli,H

Civil Engineering for Practising and Design Engineers, Vol 4

USA

1985

[

17]

THE DYNAMICS OF EXPLOSION AND ITS USE

Henrych,Josef

Technical University of Prague, Building Research Institute

New York

USA

1979

[

18]

HANDBUCH DER WAFFENWIRKUNGEN FÜR DIE BEMESSUNG VON SCHUTZBAUTEN

Schindler,G;Haerter,A

Arbeitsgruppe für den baulichen Zivilschutz

Bern

Switzerland

1964

[

19]

VAPENVERKAN FORTH 1 - SCHWEDISCHES HANDBUCH FÜR WAFFENWIRKUNGEN -

MOD Schweden

Schwedische Schutzbauverwaltung / MOD Schweden

Stockholm

Sweden

June

1973

[

20]

FEUERBALLMESSUNGEN UND FEUERBALLDAUER

Janser,P

Basler & Partner, Gruppe für Rüstungsdienste

Zürich

Switzerland

May

1981

[

21]

THERMAL RADIATION FLUX OF FIREWORKS

Harmanny,A

Prins Maurits Laboratorium, Report Nr T 1022 / 02/84

Den Haag

Netherlands

February

1984

-II-5-72-

Change 3

AASTP-1

(Edition 1)

[

22]

DESIGN AND SITING OF BUILDINGS TO RESIST EXPLOSIONS AND FIRE

Oyer Publishing Limited

London

United Kingdom

1980

[

23]

COMBUSTION OF GUN PROPELLANT IN IGLOO - THERMAL FLUX MEASUREMENTS

Allain,L

SNPE-Defense Espace-Direction de la Technologie et de la

Recherche;NT153/91/CRB-S/TS/NP

Vert-le-Petit

France

December

1991

[

24]

PROJECTILE PENETRATION IN SOIL AND ROCK. ANALYSIS FOR NON-NORMAL IMPACT. -

TECHREP SL-79-15 -

Bernard,R,S

USAEWES, VICKSBURG, MS

Vicksburg, MS

USA

1979

[

25]

DEPTH AND MOTION PREDICTION FOR EARTH PENETRATORS - TECHREP S-78-4 -

Bernard,R,S

USAEWES

Vicksbury,MS

USA

1978

[

26]

PENETRATION DEPTH OF CONCRETE FOR NONDEFORMABLE MISSILES.

Haldar,A;Miller,F,J

School of Civil Engineering, Georgia Institute of Technology

Atlanta

USA

1982

[

27]

ASSESSMENT OF EMPERICAL CONCRETE IMPACT FORMULAS.

Sliter,G

Journal of the Structural Division

USA

1980

[

28]

CRATERING BY EXPLOSIONS - A COMPENDIUM AND AN ANALYSIS

Rooke,A,D; Carnes,B,L; Davis,L,K

US Army Waterways Experiment Station, TR-N-74-1

Vicksburg,MS

USA

January

1974

[

29]

DIAL PACK : CRATER AND EJECTA

Rooke,A,D; Meyer; Conway

US Army Waterways Experiment Station, MP-N-72-9

Vicksburg,MS

USA

December

1972

[

30]

EXPLOSIVE EXCAVATION TECHNOLOGY

Johnson,S,M

US Army Engineer Nuclear Crater Group, NCG TR-Nr 21

USA

June

1971

[

31]

LETALITÄT VON PERSONEN INFOLGE KRATERAUSWUFS

Basler & Partner

Basler & Partner, B 3113-2,Grp Für RüDst

Zürich

Switzerland

October

1984

[

32]

GRÖSSE UND AUSWURFMASSEN VON KRATERN IN LOCKERGESTEIN BEI

OBERFLÄCHENDETONATIONEN

Basler & Hofmann

Baserl & Partner

Zürich

Switzerland

April

1979

-II-5-73-

Change 3

MANUAL OF NATO SAFETY PRINCIPLES FOR THE STORAGE OF MILITARY AMMUNITION AND EXPLOSIVES (May 2010) - page 11