U.S. DEPARTMENT OF COMMERCE Natioal TeChuical Infi oe Sunic

AD-A031 414

Blast Parameters from

Explosions in Model

Earth Covered Magazines Ballistic Research Labs Aberdeen Proving Ground Md

Sep 76

),D

MEMORANDUM REPORT NO. 2680 BLAST PARAMETERS F;ROM EXPLOSIONS IN MODEL EARTH COVERED MAGAZINES

C &

Charles N. Kingery George A. Coulter George T. Watson

September 1976

Approved ftr pblic tleas.; distr bution ,uitm ,d.

r -'

.

--

D

USA BAL USTIC RESEARCH LABORATORIES ABERDEEN PROVING GROUND, MARYLAND IP2SOOUCOID 3

NATIONAL TECHNICAL INFORMATION SERVICE U.S. DEPARTNIT OFCO1MMIM SP IIGFU.fl. VA. flf

---

Destroy this report when it is no longer needed. Do not return it to the originator.

~

SAcondary distribution of this report by originating or sponsoring activity is prohibited. Additional copies of this report may be obtained from the National Technical Information Service, U.S. Department of Comerce, Springfield, Virginia 221S1.

The -Findingsin this report are not to be construed as an official Department off the Army positien, unless so designated by other authorized docuets.

Unclassified SEURTYLAS:IF:ATION OF THIS PAGE (Whm Da

o.RCErcAAO

.. GorOTACESN

REPOT DOMNAMO

PAGE

U

R

BEFOE COPLT((FORM

BLAST PARAMETERS FROM EXPLOSIONS IN MODEL

I

Pinal

EARTH COVERED MAGAZINES_______________ 7AUTHOR(@)

S.

CONTRACT OP GRANT NUNUE~f*)

Charles N. Kingery George A. Coulter George T. Watson

CE-BRL-76- 1

PERFORMING ORGAIZATION NAME AND ADDRESS

S.

10.

PROGRAM ELEMENT. PROJECT. TASK( AREA A WORK UNIT NUMBERS

USA Ballistic Research Laboratory Aberdeen Proving Ground, Mbaryland

rUS

21005 12.

CONTROLLING OFFICE NAKE AND ADDRESS

II

Army Materiel Development & Readiness Command

II5001

Eisenhower Avenue

Alexandria, Virginia

REPORT DATE

September 1976 III. NUMBER OF PAGES

-

22304

14. MONITORING AGENCY NAME & ADORESS(Ul Efbewrt ion= ControllhV Office)

IS.

El

SECURITY CLASS. (of due .jpoft)

Unclassified 15.. DECL ASS1FICATION/OOWNGRADING SCHEDULE DISTRIBUTION STATEMENT (of AM&Awt)

It.

FRE

Approved for public release; distribution unlimited.

Tz-17.

DISTRIBUTION STATEMENT (o1 ile abeftsei inteee

In Block 2.It

-ffferent bee. RoPerl)

SUPPLEMENTARY NOTES

1S

This work was performed for and funded by the Department of Defense Explosave Safety Board. 19.

KEY WORDS (Cont-

ii en r.ere

side It naesw

Munition Magazines Scaled Model Tests Explosive Safety Blast Attenuation Free-Field Blast

Nsi 20

ABSTRACT (Cornleme en r

And ld"~Ify? by btOck nt~rnbe.)

Scaling Techniques Earth Cover

evere i

e

eyndiIbyok

e

(!j

c)

This report contains the results obtained from a series of high explosive tests designed to determine the blast parameters around a 1/50 scalle model

of an earth covered munition storage mnagazine.

The testq were conductedI

using hemi-cylindrical pentolite charges of scaled weights to simulate the effects of anI accidental explosion occurring in standard munition maga:ines when filled with 100,000, 300,000. aTJ 500,000 pounds of expiosivel;. rhe thickness of the earth cover was earied to determine the blast atenuation associated with double the standard earth cover thickness, the standard earth

DO JA

1473

EDITION OF I1NOV 6S IS ODSOLCE

Unclassified SECURITY CLASSIFICATION OP TIS PACE (Uhon Dore Enw..d

LInc lass ified SECUmTY CLASUOFICATIO

OF THIS PASEt1m brf

(ITEI 20 CONTINUED) cover and one-half the standard earth cover thickness relative to no earth cover. Excellent correlation was obtained with limited data from one fullsi:e storage maga:ine test.

i

"-

-

-.......

WM~ SON 0

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| /

,

i

No

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Unclassificd S1CUInT7 CLASSIFICATION OF ThIS PAGtEM eo Dor

Firefre)

A

TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS.......... ... .. .. .. .. .. .... LIST OF TABLES .. .......

9

........... ....

I. INTRODUCTION. ... ........... ........... 1 A. Background. ... ........... ......... 11 B. Objectives TH.

ZE EA.

... ....

.. .... .... ....

11

TEST PROCEDURE. .... .......... ......... 11 Model Magazine Design. .. ......... .. ....... 11 B. Test Charges........ . ..... . .

... .. .. .. . . ...

C.Test Instrjnmentation...... .... . .. . .. .. .. .. ... 1 1.

....

18

.......

18

Oscilloscope Recorder Systemft.. .......

2. Tape Recorder System .. .......

D. Test Layout............ . ... .. .. .. .. .. ... 1 E. Test Matrix .. ... ........... ........ 21 III.

RESULsS . .. .......

.......... ........ 22

A. The .8 Potmd (0.563 kg) Charge. ... .......... 23 23 1. Blast Parameters Along the 0 Deg~ree Line .. ..... 2.

Blast Parameters Along the 180 Degree Line

93.

B. I1. g

The 2.4 Pounid (1.088 kg) Charge ..

...

Blast Parpeters Along the 0 De;ree L.ine .. .Blast

.

.

28 .

.

28 28

.........

34

.....

Par.'2eters Along the 90 D!gree Line. .. ....

3. Blast Parameters Along the 180 Iligree Line FC.

....

Blast Parameters Along the 90 regree Line. ..

.

.

.

.

39 39

The 4.0 Pound (1.814 kg) Charge .. .. .......... 43 43 1. Blast Parameters Along the 0 Deg-ee Lire .. ..... .3 3. Blast Parameters Along the 10 Deree Line .. . . . 3.BatPrmtr

he10D'e

ln

3

ie....

5

TABLE OF CONTENTS (Continued) Page4 D. Comparison of Model and Full-Size Magazine Results

.

54

1. Blast Parameters Along the 0 Degree Lize . .. .. ...

54

.

.

2. Blast Parameters Along the 90 Degree Line .. .. .... 3. Blast Parameters Along the 180 Degree Line. .. . ... IV. SUMM4ARY AND CONCLUSIONS .. A.

The 0 Degree Line .. 1.

.. ..

. ....

.....

. ....

Peak Overpressure ..

..

.....

Peak Overpressure ..

..

REFE:RENCES .. .. .....

DISTRIBUTION LIST.

..

. ....

......

.....

..

.... .....

. ....

4

.....

........

2.Overpressure Impulse. ..

64 ....

....

..

.....

. ....

64 4

. ......

65

......

65 . ...

. .......

.....

5 5F

. ......

...........

Z Overpressure Impulse. .. .. L. The 180 Degree Line .. .. .... I.

. .....

8

. ...

65 66

67I

1

-i

LIST OF ILLUSTRATIONS Figure

Page ...

............

1. Standard Munition Storage Magazine ...

.......

2. l/SO Scaled Model Munition Storage Magazine

....

13

..

14

3. Internal Portion of the Model Magazine ............ 4. Model Magazine 1/50th Scale ....

...............

5. Model Magazine Instrumentation System ... 6. Model Magazine Field Layout ....

....

16

..

19

..........

...............

12

....

20

7. Pressure versus Distance Along the 0 Degree Line as aCharge Function for a 0.8 Pound f0.363 kg .... ........ of Earth Cover .........................

26

8. Impulse versus Distance Along the 0 Degree Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge ........ .............................

27

9. Pressure versus Distance Along the 90 Degree Line as

a Function of Earth Cover for a 0.8 Pound (0.363 rkg)

Ia

Charge ....... 10.

.......................

13.

....

30

Pressure versus Distance Along the 180 Degree Line as a Function of Earth ;over for a 0.8 Pound (0.363 kg) Charge

12.

................

.

Impulse versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge ...... .. ...................... ....

32

37

Impulse versus Distance Ahrg the 0 Degree Line as a Function of Earth Cover :or a 2.4 Pound (1.088 kg)

Charge ...... 15.

31

Pressure versus Distance Aliong the 0 Degree Line as a F-nction of Earth Cover for a 2.4 Pound (1.088 kg) Charge ....... .......................

14.

29

Impulse versus Dist2..ce Along the 90 Degree Line as Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge .......

11.

...........................

...

..

........................

38

Pressure versus Distance A ong the 90 Degree Line as

a Function of Earth Covei for a 2.4 Pound (1.088 kg) Charge ....... ........................... 5

40

LIST OF ILLUSTRATIONS (Continued) Figure 16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

Page Impulse versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge .......................

.41

Pressure versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge ...................

.42

Impulse versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge ...................

.

Pressure versus Distance Along the 0 Degree Line as a Function of Earth Cover for a 4.0 Pound (1.814 ....................... .... kg) Charge ......

47

Impulse versus Distance Along the 0 Degree Time as a Function of Earth Cover for a 4.0 Pound (1.814 ....................... kg) Charge .......

....

48

Pressure versus Distance Along the 90 Degree L.ine as a Function of Earth Cover for a 4.0 Pound (1.814 kg) Charge ...... ...................

....

49

Impulse versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 4.0 Pound (1.814 kg) CbargE ...... ... .......................

50

Pressure versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 4.0 Pound (1.814 kg) Charge .... ..... ..................

51

Impulse versus Distan:e Along the 180 Degree Line as a Function of Ea-th Cover for a 4.0 Pound (1.814 kg) Charge ..... .... ...................

52

Pressure versus Scale! Distance Along the 0 Degree Line from a Full-Si-e Magazine and a 1/S0 Scaled Model ...... ... ......................... ...

57

Scaled Impulse versw Scaled Distance Along the 0 Degree Time from a Full-Scale Magazine and a U5M0 Scaled Model ...................

27.

44

Pres~wre versus Scal. d Distance Along the 90 Degree Line from a Full-S ze Magazine and a 1/S0 Scaled Model ..... .... ......................... ...

6

59

60

LIST OF ILLUSTRATIONS (Continued) Page

Figure 28.

"I.

29.

30.

'I7

Scaled Impulse versus Scaled Distance Along the 90 Degree Line from a Full-Size Magazine and a 1/50 ...................... ... Scaled Model .......

61

Pressure versus Scaled Distance Along the 180 Degree Line from a Full-Size Magazine and a 1/50 ...................... ... Scaled Model .......

62

Scaled Impulse versus Scaled Distance Along the 180 Degree Line from a Full-Size Magazine and a ................... 1/50 Scaled Model ...... ...

63

LIST OF TABLES Table I. IT. III. IV. V. VI. VIla.

VIIb.

VIII. IX. X. XI. XII.

XIII.

t

I

!9

Page Charge Weights and Structure Volumes ....

15 ....

17

......................

21

.........................

22

Dimensions of the Model Charges ... Gage Station Locations ..... Test Matrix .........

...........

.............

Peak Overpressure from a 0.8 Pound (0.363 kg) Charge . Impulse from a 0.8 Pound (0.363 kg) Charge ....

.

........

24 25

Peak Overpressure and Impulse from 0.8 Pound (0.363 kg) Charge Scaled to 2.4 Pound (1.088 kg) Charge ........

3

Peak Overpressure and Impulse from a 4.0 Pound (1.814 kg) Charge Scaled to 2.4 Pound (1.088 kg) .......

34 .

35

........

36

Peak Overpressure fr m a 2.4 Pound (1.088 kg) Charge . Impulse from a 2.4 Pound (1.088 kg) Charge ....

Peak Overpressure from a 4 Pound (1.814 kg) Charge . Impulse from a 4 Pound (1.814 kg) Charge ....

..

45

.........

46

.

Scaled Blast Parameters - 0.8 Pound (0.363 kg) to 1.0 Pound (0.454 kg) - Standard Earth Cover . ......

55

Scaled Blast Parameters - 100,000 Pounds (45,359 kg) to 1.0 Peund (0.454 kg) ...... .. ................

56

Pn-

da

zl

I. A.

INTRODUCTION

Background

This report covers a general study sponsored by the Department of Defense Explosive Safety Board (DDESB) to establish the effect of earth cover on the blast parameters generated from accidental explosions in munition storage magazines. This kind of study would be prohibitively expensive to do with full-size magazines and large amounts of explosive, but in theory, the relative effects could be docunented using scaled models and high explosive charges. The Ballistic Research Laboratory (BRL) proposed to conduct a series of model tests and relate the results to effects that might be expected from full-size magazines. This proposal was accepted and funded by DDESB. B.

Objectives The primary objectives of the proposed tests were as follows:

I

1. Determine the blast parameters propagating along blast lines extending to the front, side, and rear of a 1/50 scale model magazipe with a standard earth cover. 2. Determine the effect on blast parameters when the earth cover was varied from no cover, to one-half the standard cover, and to double the standard cover.

I

3. Determine the effect on blast parameters when the amount of explosive stored in the magazine was varied.

II. TEST PROCEDURE The procedures used to meet the objectives were to, first design the model magazine, second design the high explosive charge weight and configuration, and third establish the instrtmentation and blast lines. A.

Nodel Magazine Design

The standard munition storage magazine being modeled for this series tests is shown in Figure 1. The overall width is 90 feet (27.43 metres) with a length of 95 feet (28.96 metres). The total volume of the earth cover for this size magazine is 58812 feet 3 (1665 M 3 ), while the interior volume is approximately 17,500 feet 3 (496 M 3 ). The 1/50 scaled model designed for this project is presented in Figure 2. All linear dimensions have been scaled by a factor of 50. This makes the volume of the earth cover for the model 0.47 feet3 (.0133 n 3 ) and the internal volme o. tile model is 0.14 feet 3 (.00396 M3). A photograph of the interior portion

of the model without the earth cover is shown in Figure 3. The odel 11

Precding Page hlaik

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134

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0

00

I

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144

A

magazine with earth cover is shown with the first two gage stations for each line in Figure 4. B. Test Charges The test charges were cast pentolite. The weight of the charges was based on the weight of the high explosive stored in a magazine of specified volume. The ratio of the charge weight to storage volume should be the same vhen scaling from the full size structure to a model structure.

V where W = Weight of munition explosive, V = Volume of Standard Magazine = Weight of model charge, and V1 =Volume of Model Magazine. The program was designed to simulate the blast from the accidental explosion of 500,000 pounds (226,800 kg), 300,000 pounds (136,080 kg), and 100,000 pounds (45,360 kg) of munition stored in a magazine having a volume of 17,500 feet 3 (496 M3). The model charge weights were determined as presented in Table I. The scaling factor for the model volume and the charge weights is 503 or 125,000. Table I. Charge Weights and Structure Volumes

lb

kg

fti

ma

lb

kg

4.0

1.814

0.14

.00396

500000

226800

17500

496

2.4

1.088

0.14

.00396

300000

136080

17500

496

0.8

.363

0.14

.00396

100000

45360

17500

496

M

ft

After the volume of the 1/50 scale model magazine was established, then the charge weights were detarmined and the configuration designed. There are data available on the airblast propagation from cylindrical charges (Reference 1) resting horizontally on the ground surface, with R. Reisier, L. GigZio-Tos, and C. Teel, "Air Blast Parcmeters from Pentoite Ojlinders Detonated on the Ground," BRL MR-2471, April 1.975. AD #BOO3BB3L.

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length to diameter cylindrical charge model magazine and face area the same

ratios of 3, 6, and 12. It was believed that a hemiwould best represent the storage configuration in a therefore the charges were designed with the end suras a cylindrical charge of L/D equal to 3.

Knowing the weight of the charge and assuming a density of pentolite of 103 lb/ft 3 (1.65 g/cm 3) the volume of the cylindrical charge can be calculated. When the volume of the charge (Vc) is known, then the other dimensions can be calculated. V c

wr

2L

c

for L/D = 3 L

herefore the radius r

= 6rc

for a cylindrical charge is r

I

(2)

c

rc=(~.)1/3 -

and the end area of the cylindrical is Ac = wr c 2

When Ac,

(3)

rc, and L for the cylindrical charge have been determined, then

the radius, rh, for the hemicylinder can be calculated. I

the hemicylinder must equal Ac, L to be the same. Therefore,

The area P% for

the area of the cylinder, for the length 12A\ 1/2 (4")

rh =!7

The dimensions of the model charge are listed in Table II. Table II. Dimensions of the Model Charges

Ih

Vh

Lh

rh

lb

kg

ft3

4.0 2.4

1.814 1.088

.0388 .0233

.00110 .00066

.763 .644

.229 .196

0.8

0.363

.0078

.00022

.447 .136

m

ft

a

Ah m

ftZ

mz

.1798 .1518

.0548 .0463

.0508 .0362

.0046 .0034

.1052

.0321

.0174

.0016

ft

theend charge placed in the theas point was When on the towardwasthe door and thismagazine was noted the of zeroinitiation degree line for the blast measurements. 17

C. Test Instrumentation The details of the complete instrumentation systems will be presented in this scction. The system includes 1) the pressure transducer, 2) the amplifier, and 3) the recorder. Because of the small charges used and the requirement for close-in documentation; i.e., high overpressures, two instrumPntation systems were utilized. 1. Oscilloscope Recorder System Three Tektronix 565 dual beam oscilloscopes were used to record the pressure versus time from six stations. Susquehanna Instruments Model ST-4 piezo gages with tourmaline sensors were the primary transducers used throughout the series of tests. The signal from the gage and source follower was fed directly into the oscilloscope where it was displayed on a video tube and photographed on a high contrast poloroid film. The analog display on the filni was converted into a digital fo-mat using a film reader and punching IBM! cards which were then processed through a computer. The digitized data was then tabulated and plotted. A block diagram of the oscilloscope recorder system is presented in Figure 5. 2. Tape Recorder System The tape recorder consisted of four basic units. The gages which have already been described, the power supply and voltage calibrator, the amplifier, and the FM recorder. The FM tape recorder used was a Honeywell 7600 having a frequency response of 80 kHz. Once the signal was recorded on the magnetic tape it was played back and recorded on a CEC-5-124 oscillograph for a quick look at the records. The analog signal on the magnetic tape was processed for an automatic dioital conversion and was then programmed through the computer for a digital output which was tabulated and plotted. The tape recorder system and other field instruments are shown in Figure 5. D. Test lUvout A requirement to meet the stated objectives is to measure the blast parameters at the current safe separation distances between storage maga:ines. Therefore, the blast lines, see Figure 6, were installed to measure overpressure and impulse in three principal directions in the near field. Stations to the front (0 degree line) should start at a scaled separation 1 ) and distance of 2 ft/lb 1/3 (.8 mikg 1/31/ extend out to about 10 ft/!b1 / 3 (4 m/kg /3). Stations to the rear (180 degree line) should start at and end at the same distances. The gage line extending from the side of the structure 90 degree line) should start at a scaled distance of 1.25ft/lb3 (.5 m/kg

n), d extend out to 50 ft

1/3 (20 m/kg3

The separation distance is measured from the internal wall of the steel arch for side to side separation distances and from the end wells for front and back separations rather than the center of the storage area. The gage station distances were measured from the geometric center of the flat side of the charge and therefore an adjusted distance of .26 feet (.079 m) was added to the separation listance on the 90 degree line 18

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_

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MODEL MAGAZINE FIELD LAYOUT ION~IZATION PROBE

J-2 DETONATOR

MGZN

I

IEZOELECTRIC GAGE aSOURCE FOLLOWER

FIELD SAFETY Box

300FT RG-518 COAX CABLES

I

TO INSTRUMENTION TRAI LER Figure 6.

I

Model Magazine Field Layout 20

_______4_

and .6 feet (.183 a) was added to the 180 and 0 degree lines. The station locations for the three charge weights are listed in Table III. Note that the distances remained the same for the uncovered tests and all earth covered tests. Table II. .8 lb

.363 kg

Station No.

0-i 0-2 0-3 0-4 0-5

*0-6

iT90-2

ft

Gage Station Locations

CHARGE WT. 1.088 kg 2.4 lb DISTANCE

x

ft

2.45 3.77 4.41 5.88

.750 1.15 1.34 1.79

3.28 4.41 5.88 8.16

8.16

2.49

12.0

90-s

1.42 2.46

90-3 90-4 90-5 90-6 90-7 90-8 90-9

3.77 4.67 6.68 9.10 13.3 23.2 41.7

180-1

2.46

180-2 180-3 180-4 180-5 *180-6

3.77 4.41 5.88 8.16 12.0

3.66

.433 .750

1.15 1.42 2.04 2.77 4.05 7.07 12.7 .750

1.15 1.34 1.79 2.49 3.66

a 1.00 1.34 1.79 2.49

12.0

3.66

18.0

5.49

1.93 3.28

.588 1.00

4.0 lb ft

3.77 4.41 5.88 8.16 12.0 18.0

2.24 3.77

1.814 kg a 1.15 1.34 1.79 2.49

I -

1

3.66 5.49

.683 1.1S

4.67 6.68 9.10 13.3 23.2 41.7 73.5

1.42 2.04 2.77 4.05 7.07 12.7 22.4

4.67 6.68 9.10 13.3 23.2 41.7 73.5

1.42 2.04 2.77 4.05 7.07 12.7 22.4

3.28

1.00

3.77

1.15

4.41 5.88 8.16 12.0 18.0

1.34 1.79 2.49 3.66 5.49

4.41 5.88 8.16 21.0 18.0

1.34 1.79 2.49 3.66 5.49

*Additional Station for the one-half of standard earth covered model tests. E. Test Matrix The test series was designed to meet the objectives with a minimum number of shots. Therefore, in establishing the base line for comparison only two cha-ge weights were fired in the "no earth cover" environment. The data from the 0.8 pound (0.363 kg) and 4.0 pound (1.814 kg) charges were used to predict the blast parameters for the 2.4 pound (1.088 kg) charge. The study of the blast attenuation from the one-half covered model was added to the series after the completion of the standard and 21

I

5

t 1

1 |

double cover.

The use of the dual-beau oscilliscopes was dropped in

favor of a second magnetic tape recorder. Therefore, a test shot was fired to repeat one of the conditions of the first series to check the change in instrumentation as well as a new lot of modeling sand used for simulating the earth cover. The repeat shot was with a standard ei.th cover -4del contairing a 0.8 pound (0.363 kg) explosive charge. The number of shots fired, the charge weights, and the test conditions are listed in Table IV.

Table If.

Test iatrix

MD

MH

No Cover-

_S t d Cover

Double Cover

One-Half Cover

Z

4

3

3

MN Charge 'eight_ lb kg

Ms

MH

0.8

0.363

2.4

1.088

4.0

1.814

3 3

3

3 3

3

-

will be used to denote the test firings with a bare charge -no cover

-

will denote a model test with the standard earth cover - 0.04 feet (0.012 m) covering the apex of the arch

-

will denote a model test with double the standard earth cover, 0.08 feet (0.024 a) covering the apex of the arch

-

will denote a model test with one-half the standard earth cover 0.02 feet (0.006 a) covering the apex of the arch.

III.

RESULTS

The results will be presented for the individual charge weights because each one represents a specific amount of explosive stored in a full size magazine. t-he volume of the model remains constant and therefore direct scaling from one charge weight to another should not be expected. The complete overpressure versus time was recorded at each gage station. The data presented in this report uill include th, peak overpressure and impulse in tabular and graphic form. With the exception of the standard cover and smallest charge, three shots were fired for each configuratior but average or mean values will be tabulated and plotted.

22

A.

The 0.8 Pound (0.363 kX) Charge

This charge was modeled to represent 100,000 pounds (4S,360 kg) of high explosive munition stored in a standard 60 foot magazine. The first series of shots was fired with the bare hemicylindrical charge placed with the flat side resting on the surface and the detonator end of the charge near the 0 degree blast line. The peak overpressure and impulse measured along the three blast lines are listed in Tables V and VI for the four conditions; i.e., uncovered, standard cover, double cover, and onehalf cover. i. Blast Parameters Along 0 Degree Line The average peak overpressure values rersus distance aeasured along the 0 degree blast line for the four conditions are listed in Table V and plotted in Figure 7. The peak overpressure along the zero degree blast line was expected to be higher when the charge was covered because the mass of earth around the other three sides of the structure tend to focus more of the blast energy out the front of the structure. The pressure value at the second station for the double cover test is based on only one datum point which is probably lower than it should be. There aopears to be little difference in the magnitude of the blast pressures along the 0 degree gage line between the standard and double covered magazine for this charge weight. The peak overpressures versus distance recorded for the half-covered model follow the same trend as the uncovered charge but with pressure enhancenent of approximately 40 percent. There is a pressure enhancement of approximately 100 percent for the standard and double covered model over the uncovered charge.

The positive pressure impulse measured under the same conditions as described in the preceeding paragraph are listed in Table VI. The values listed are aveiage values from three data points. The average values listed in the table are plotted in Figure 8. The same trend established for the peak overpressure is again shown in the Lmpulse, in that the impulse is higher when the earth cover is over the charge. The accuracy of impulse measured at the first station is very questionable for the uncovered condition and the datum point has not been plotted in Figure 8. A dashed line indicates the possible trend. There is an enhanceent of impulse recorded when the one-half standard earth cover model is placed over the charge. There is an increased impulse enhancement when the standard earth covered model is used. But when the double earth covered model configuration was used there appeared to be no further increase in the recorded impulse along the 0 degree line. The data fre: the standard and double models are represented with one curve in Figure 8. They show approximately the same enhancement (100 percent) as noted for the peak overpressure at the first three stations but the enhancement only about 30 percent at the last two staticm_,s. The one-half cover model data show approximately 40 percent enbmicement at the first three stations and less than 10 percent at the last two stations.

23

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2. Blast Parameters Along the 90 Degree Line Measured peak overpressure and impulse along the 90 degree blast line for the four test conditions are listed in Tables V and VI. A total of nine stations were -1.25 ft/lb 1/ 3 instrumented starting at a scaled separation distance of (.5 m/kg 1/5). The peak overpressure results listed in Table V for the 90 degree blast line are presented graphically in Figure 9. As the earth cover is increased, the blast attenuation is increased. It should also be noted that as the distance increases the peak overpressure attenuation decreases. The difference in the four average values of pressure measured at the last station is ±3 percent. The impulse versus distance measured along the 90 degree line for the four test configurations are listed in Table VI and plotted in Figure 10. Here the impulse measurements show a trend similar to the one established for the peak overpressure with the exception of the decrease in attenuation with distance. From the fifth station to the last station the percentage of attenuation remains approximately constant. The half-cover and standard covered models show approximately a 15 percent attenuation while the double earth covered model gives a 20 percent attenuation. 3. Blast Parameters Along the 180 Degree Line The 180 degree line was established to the rear of the structure. The peak overpressure measured along this line is listed in Table V. The values from Table V are plotted in Figure 11. There is a dramatic drop in the peak overpressure at the close-in positions when one-half standard earth cover model was tested and the results compared with an uncovered charge. The peak overpressures measured from the standard cover and double cover models show further reductions. Approximately a 10 percent pressure reduction is noted when going from the standard to the double cover magazine. The impulse measurements along the 180 degree line are listed it,Table VI and plotted in Figure 12. There is no measurable difference in the recorded impulse from the 0.8 pound (0.363 kg) charge detonated in the standard and double earth covered models. There is only a 10 percent greater value noted at the first three stations from the same charge weight detonated in a one-half standard earth cover model. B. The 2.4 Pound (1.088 kg) Charge There were six 2.4 pound (1.088 kg) charges fired. Three were detonated in the standard earth covered model magazine and three were detonated with one half of the standard earth cover in place. To establish a basis for comparing the effect of the earth covers versus no cover the results from the 0.8 pound (0.363 kg) and 4 pound (1.814 kg) charges fired without cover were scaled to a 2.4 pound (1.088 kg) equivalent. There were no tests conducted for the 2.4 pound (1.088 kg) charge detonated in a model magazine with double the standard earth cover. It was assumed that results from the 0.8 pound (0.363 kg) and 4 pound (1.814 kg) charges could be used to interpolate effects for the mid-range 28

X N - No Cover S-N - Half Standard Cover 0 sS 0-MD

71C

-

tadr oe Double Standard Cover

110;BIA$ a-

ac C-16

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40 ai

io

1.0

eo ._1.0

10 DISTANCE, FEET Figure 9. Pressure versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge 29

1003

II X 0 -

-No

Cover Half Standard Cover

0 - Ms - Standard Cover 0 - MD - Double Standard Cover

I×

I

~L.J

a--

LIN

I v 10-

BLAST

111I

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10 Figure 10. Impulse versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge

30

1000 X

X

-

MN

-

No Cover

0

-

M.

-

Half Standard Cover

0 - MS - Standard Cover *

- MD - Double Standard Cover

x

0×

:I

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10

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i0 DISTANCE, FEET

Figure 11. Pressure versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge 31

I

.00 x - M

- No Cover

0 - M4 H - Half Stendard Cover 0 - H

IS

- Standard Cover

0 - MD - Double Standard Cover

Xx

iA

-

-

1.0

I

II

1.0

II

~I 10

DISTANCE , FEET Figure 12.

Impulse versus Distance Along the 180 Degree

Line as a Function of Earth Cover for a 0.8 Pound (0.363 kg) Charge 32

~I

charge weight. The peak overpressure and impulse values listed in Tables V, VI, X, and XI for the uncovered charge condition have been scaled to 2.4 pound (1.088 kg) equivalent and are listed in Tables VIa and VIIb.

|

Table Vila. Peak Overpressure and Impulse from 0.8 Pound (0.363) Charge Scaled to 2.4 Pound (1.088 kg) Station No.

Distance feet metres

Pressure psi bars

0-1 0-2 0-3 0-4 0-5

3.SS 5.44 6.36 8.48 11.8

1.08 1.66 1.94 2.58 3.60

84.7 47.9 29.3 20.4 9.88

90-1 90-2 90-3 90-4

2.05 3.55 5.44 6.74

.625 1.08 1.66 2.05

9.36

90-S

832. 334. 101. 47.4

57.4 23.0 6.96 3.27

2.85

-

90-6 90-7 90-8 90-9

13.1 19.2 33.5 60.1

3.99 5.85 10.2 18.3

10.6 5.16 1.94 0.79

180-1 180-2 180-3 180-4 180-S

3.55 5.44 6.36 8.48 11.8

1.08 1.66 1.94 2.58 3.60

-

639. 312. 158. 33.4 10.0

.731 .356 .134 .054 44.1 21.5 10.9 2.65 .689

33

il

5.84 3.28 2.02 1.41 .681

Impulse psi-msec

I

bar-msec

37.2 15.1 11.8 12.8 9.96

2.56 1.04 .814 .882 .687

49.4 19.5 16.0 12.8

3.41

1.34 1.10 .882

-

8.94 6.20 3.75 2.31

.616 .427 .259 .159

39.0 29.6 15.7 8.65

2.69 2.04 1.08 .596

Table VIIb. Peak Overpressure and Impulse from a 4.0 Pound (1.14 kg) Charge Scaled to 2.4 Pound (1.088 kg) Station No.

Distance Feet

*

metres

0-1 0-2 0-3 0-4 0-5

3.18 3.72 4.96 6.88 10.1

.969 1.13 1.51 2.10 3.08

90-1 90-2

1.89 3.18

.576 .969

90-3 90-4 90-5 90-6 90-7 90-8 90-9

3.94 5.63 7.68 11.2 19.6 35.2 62.0

180-1 180-2 180-3 180-4 180-5

3.18 3.72 4.96 6.88 10.1

1.20 1.72 2.34 3.41 5.97 10.7 18.9 .969 1.13 1.51 2.10 3.08

Pressure

Impulse bar-msec

psi

bars

psi-zsec

175. 133. 72.6 28.6 12.1

12.1 9.17 5.01 1.97 .834

23.0 30.4 21.4 13.8 11.2

1.59 2.10 1.47 .951 .772

900. 483.

62.1 33.3

37.8 60.2

2.61 4.15

229. 67.5 37.6 15.2 4.40 1.91 0.52

15.8 4.65 2.59 1.05 .303 .132 .036

25.2 18.8 13.1 10.8 6.41 3.88 1.60

1.74 1.30 .903 .745 .442 .265 .110

659. 635. 467. 138. 21.8

42.1 43.8 32.2 9.51 1.50

62.2 39.1 35.1 24.6 lb.1

4.29 2.70 2.42 1.70 .696

1. Blast Parame- ers Along the 0 Degree Line The peak cverpressures and impulses measurcd along the 0 degree instrumentation line from the detonation of a 2.4 pound (1.088 kg) charge for the model magazine with a standard earth covcr and with a one-half standard earth cover are listed in Tables VIII and IX. The peak overpressure values listed are plotted in Figure 13 with peak overpressure as a function of distance for the three conditions. There was no significant difference in pressure measured between the standard earth cover model and the one-half standard earth cover along the 0 degree line. The peak overpressures were approximately 30 percent higher than those measured for the uncovered condition. The positive impulse values listed in Table VIIb for the uncovered condition and in Table IX for the standard and one-half earth cover model are presented in Figure 14. The positive impulse is plotted as a function of distance for the three conditions. There was no significant difference measured in the standard and one-half earth cover models. A comparison of the covered and uncovered condition indicate similar values close-in and beyond 8 feet (2.44 metres), but the values of impulse for the uncovered condition are lower than the covered condition over the mid-range distance. 34

Table VIII.

Station

Peak Overpressure from a 2.4 Found (1.088 kg) Charge Distance from Ground Zero

Std. Cover Peak Overpressure

One-Half Std. Cover Peak Overpressure psi

feet

metres

psi

0-1 0-2 0-3 0-4 0-5 0-6

3.28 4.4: S.88 8.16 12.0 18.0

1.00 1.34 1.79 2.49 3.66

178. 121. 72.0 28.5 13.3

90-1 90-2 90-3 90-4 90-s 90-6 90-7 90-8 90-9

1.43 3.28 4.67 6.68 9.10 13.3 23.2 41.7 73.5

180-1 180-2

3.28 4.41 S.88 8.16

180-3

180-4

180-5 180-6

12.0 18.0

.588

bar 12.3 8.34 4.96 1.96 .917

198. 123. 58.0 28.9 10.1 4.83

13.7 8.40 4.00 1.99 .696 .333

79.0 43.6 28.8 20.9 16.0 8.46 4.26 1.85 0.78

5.45 3.01 1.99 1.44 1.10

40.1 26.7

2.76 1.84

16.7

1.15

1.00 1.42 2.04' 2.77 4.05 7.07 12.7 22.4

63.4 39.8 25.8 15.1 12.3 8.04 3.85 1.81 0.76

4.37 2.74 1.78 1.04 .848

1.00 1.34

31.9 19.3

1.79

12.4

2.20 1.33 .855 .648

2.49

3.66

9.40 S.63

35

bar

.554

.265 .125 052

.388

11.3

6.58 3.76

.583

.294 .128 .054

.779 .44 .2S9

Table IX. Impulse from a 2.4 Pound (1.088 kg) Charge

Station

Distance fromZero Ground feet

Std. Cover Impulse

One-Half Std. Cover Impulse

metres

psi-asec

br-usec

psi-as

bar-ms

0-1 0-2 0-3 0-4 0-5 0-6

3.28 4.41 5.88 8.16 12.0 18.0

1.00 1.34 1.79 2.49 3.6b 5.49

25.8 31.9 21.5 14.9 9.13

1.78 2.20 1.48 1.03 .629

22.3 30.5 21.9 13.7 8.93 3.83

1.54 2.10

90-1 90-2 90-3 90-4 90-5 90-6 90-7 90-8 90-9

1.93 3.28 4.67 6.68 9.10 13.3 23.2 41.7 73.5

.588 1.00 1.42 2.04 2.77 4.05 7.07 12.7 22.4

16.4 14.5 13.2 10.1 11.3 9.0 5.29 3.42 1.93

.841 1.00 .910 .696 .779 .620 .365 .236 .133

19.5 16.4 14.7 12.9 12.2 8.79 6.19 3.68 2.05

1.24 1.13 1.01 .889 .841 .600 .427 .254 .141

180-1 180-2 180-3

3.28 4.41 5.88 8.16 12.0 18.0

1.00 1.34 1.79 2.49 3.66 5.49

10.6 8.4 8.26 7.69 6.80

.731 .579 .570 .530 .469

9.86 9.77 8.50 7.58 6.34 5.26

.680 .674 .586 .523 .437 .363

180-4

180-5 180-6

'1 36

1.51

.945 .616 .264

S-

MN - No Cover (Scaled from 4.0 Pound Charge)

a - MN - No Cover (Scaled from 0.8 Pound Charge)

o-

H

Half Standard Cover

0 - HS - Standard Cover

L b

!D!

_

xi

o

I

-

AA

1.01

\7

24od.0

kg010

Figure 13. Pressure versus Distance Along the 0 Degree Line as a Function of Earth Cover for a

!00

X

-

MN

-X - M

S0

-

M

0 - Ms

- No Cover (Scaled from 4.0 Pound Charge) -

No Cover (Scaled from 0.8 Pound Charge)

- Half Standard Cover -

Standard rover

,, 0J

DISTA AC

Figur_ 14.

impulse versus Distance

-C

ang the 0 Degrec

k)cagCover f~j. ~ Earth 2.ao~d Function of Line asa 38

2. Blast Para.eters Along the 90 Degree Lime The peak overp-essures and impulses predicted along the 90 degree instrurentationt line for the 2.4 pound (1.088 kg) charge in the uncovered condition, were based on scaled data meaesured frop the detonation of 0.8 pound t0.363 k-') Cnd 4.0 pound (1.814 kg) charges. These dat" are listed in Table-s- Me~ and M!b and plotted in Figures 15 and 16. The values of peak overpresbure as a functior of distance along the 90 degree line for the standard and one-half earth cover models are listed in Table VIII and p'otted in Figure 15. The attenuation of peak overpressure measured in going from a one-half earth cover riodel to the standard cover is approximately 20 percent at the first S statiois and 5 percent at the last 4 stations. There is an attenuation of peak overpressure by a factor of 10 at the first station between the covered and condition. This factor rapidly decreases with distance and becomes 1 at a distance of 17 feet (5.182 vietres). Beyond that distance the peak overpressure becomes greater for the covered charge than for the uncovered charge. 'hi: was not expe-ted and should have significant impact on the relative locations of zarth covered munition magazines and res Iential or inhabited structures.

iuncovered

The impult . versus distance for the 2.4 pound (1.088 !g) charge in the un.covered configuration was established by scaling the impulse versus distance measured fro; the .8 pound (.363 kg) and 4 pound (1.814 kg) charges to that weight. These values are listed in Table V1Ib and plotted in Figure 16. 'here is wide scatter of data points at the first two stations and therafoie a curve has not been drava, through those pnints. The impulse measurements for the standard and one-half covered magazine are listed in Table XI. !these values are pictted in Figure 16. 'he trend to be noted here is that asure! irwilse from the covered and uncovered charges converge at a vaie of 9 psl-s-sec (.62i bar-asec) at z distance of 13 feet (13 96 metres). There Is no significant differenc- in the -ata from the three conditions frc that oint on with the one value ifrom the 4 pound (1.814 kg) charges sp.pears low at a distance of 62 feet (18.9

Metes).

V

3. Blas: Parameters Alon.g the 180 Degree Line. The peak overpressure versus distance along the 180 degree line for the 2.4 pound (1.088 kg) charge uncovered was established from the 4alues recorded _rom the .8 pound (.363 kg) and 4 pound (1.81- kg) charges. Th-,e scaled w1ues are listed in Table VIa ard plotted in Figure 17. The scaled values show reasonable decay of peak overpressure versus dis.nce and is concluded to be representative of a 2.4 pound (1.088 kg) charge. ie peak overpressures versus distance eat,,red -fr.m tha 2.4 pound (1.088 kgj charge in a standaid aed one-half standard earth cover

magazine are listed in Table VIII. These val,_es afc plotted in Figure 17. Ther is a significant attenuation in peak overpressure to the rear of the structure e- the charge is fired in the covered magazine m.dels. Me at.tenuation becomes less uith increasing distance and it appears that

39

I 0L

X -

- Cover

(Scaled from 4.0 Pound) 100

A -MN NoCover (Scaled from 0.8 Pound') X

3 MH - Half Standard Cover 0 -. MS - Standard Cover

SLS

\I i00

__

,I , , '

_\

L 1I

T -

ii

k

1.0

10 DISTANCE, FEETA

Figure 15. Pressure versus Distance Along the 90 Degree Line as a Function of Earth Cover for a

o4 kg) Charge Pound (1.088 40

100

0 X -

N

-

No Cover (Scaled from 4.0 Pound Charge)

- MN - No Cover (Scaled from 0.8 Pound Charge) 1] - MH - HalfI Standard Cover

0 - MS - Standard Cover

CO

BLAST

II x --

U.'

-J

×f 1.0

1 0 DISTANCE, FEET Figure 16. Impulse versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge 41

100

×

0

No Cover (Scaled from 4.0 Pound)

-

MN

-

MN - No Cover (Scaled from 0.8 Pound)

-

MH - Half Standard Cover

0 - Ms

-

-

Standard Cover

_I

loI

100

a

CL.

LLII

IIl

_

T I

10o -i-i-I_ I I DISTANCE

I D

,

FEET

Figure 17. Pressure versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge 42

curves for the uncovered and one-half covered conditions will converge at greater distances. The attenuation of peak overpressure in going from one-half standard earth cover model to the standard earth cover is approximately 20 percent with slightly less at the greater distances. The impulse versus distance for the 2.4 pound (1.088 kg) charge uncovered, was established from the measurements made on the .8 pound (.363 kg) and 4 pound (1.814 kg) charges and scaled to 2.4 pounds (1.058 kg). These values are listed in Table VIIb and plotted in Figure i8. The value of impulse versus distance measured for the 2.4 pound (1.088 kg) charge detonated in the standard earth cover and one-half standard earth cover model magazines are listed in Table IX and plotted in Figure 18. questionable The impulsedatu.a plotted at based the first station for the uncovered charge is a point on only one measurement. There is a significant impulse atteiuation at the close-in stations when the explisive is covered. But there was no measurable attenuation between the im alse recorded for the two earth covered conditions. C. The 4.0 Pound (1.814 kg) Charge The 4.0 pound (1.814 kg) hemicylindrical charge was designed to represent 500,000 pounds (226,800 kg) of high explosive munition stored in a standard storage magazine. The charge was detonated with the flat side on the surface without cover, in model magazines with one-half standard earth cover, standard earth cover, and double earth cover. Three tests were ccnducted under each condition and the average values of peak overpressure and impulse along the three blast lines are listed in Tables X and XI. The mean values listed in Tables X and XI for the 0, 90, and 180 degree directions are plotted in Figures 19 through 24. 1. Blast Parameters Along the 0 Degree Line The peak overpressures listed in Table X along the 0 degree line for the four test conditions are presented in Figure 19. Here it is quite evident that the peak overpressures along the 0 degree line are higher for the three covered magazines than for the uncovered magazine. This increase is in the order of 50 percent for the one-half standard and standard earth cover model magazines. The increase in peak overpressure along the 0 degree line .'.r the double earth cover is an average of 80 percent over the uncovered high explosive.

iSimilar

Tne impulse measurements made along the degree line are listed in Table XI for the four test conditions and plotted as a function of distance in Figure 20. The trend established for the ii.pulse is not as well defined as that established for the peak overpressure measurements. The impulse measured from detonations in the one-half, single cover, and double cover magazine show only minor differences along the blast line. values were documented at the two close-in stations and the last station with significant differences measured at the third and fourth stations. A similar trend was noted on the 2.4 pound (1.088 kg) charge weight where the first and last stations have similar values with the covered magazine recording higher impulse values at the in-between stations. 43

x - MN - No Cover (Scaled from 4.0 Pound) - - MN - No Cover (Scaled from 0.8 Pound) _x

Half Standard Cover

0 - MS

-

Standard Cover

fA. IL--_

U,, IE

SW.

10 1.0 DISTANCE, FEET Figure 1.IplevruDitneAogthe 180 Degree Lieas a Function of Earth Cover for a 2.4 Pound (1.088 kg) Charge 44

I

S. >

Ir-co

0 ~.0.

U) 4.4 co 0

0

i '0

Go (

-

%oo-4

.

~

nC4. O(4-4

-iO-4-(%l n"C -4 -4 5..

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Figure 19. Fressure versus Distance Along the 0 Degree Line as a Function of Earth Cover for a

1.I47

4.0 Pound (1.814 kg) Charge

1100

100 X

- Mr,- No Cover

o3

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Half Standard Cover Standard Cover

-

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-

0

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Figure 20.

DISTANCE, FEET

I

Impulse versus Distance Along the 0 Degree 40Pound (1.814 kg) Charge 48

-

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x -~

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0-

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DISTANCE , FEET Figure 21. Pressure versus Distance Along the 90 Degree Line as a Function of Earth Cover for a 4.0 Pound (1.814 kg) Charge 49

100

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0 -

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0 - NS - Standard Cover 0-

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F-4

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DISTANiCE, Figure 22.

:

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impulse versus Distance Along the 90 Degree

Line as a Function of Earth Cover foy a "

4.0 Pound (1.814 kg) Charge

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x

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-10 DISTANCE JEElT 23. Pressure versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 40.0 Pound (1.814 kg) Charge

100

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Figure 24. Imrpulse versus Distance Along the 180 Degree Line as a Function of Earth Cover for a 4.0 Pound (1.814 kg) Charge

52

II

, .;-,,-.e ZY

Ea F-

Vpound

2. Blast Parameters Along the 90 Degree Line The peak overpressures measured along the 90 degree line are listed in Table X for the four test c,-nditions and plotted as peak overpressure versus distance in Figure 21. First, the charge is larger are three things to note in Figure 21. and therefore the earth cover will have less effect i-. attenuating the peak sured This can be seen at the first station where 900 psi (62 bars bars) measured on the uncovered condition has been reduced to 100 psi (6.89 bars) measured with the standard cover. On the .8 pound (.363 kg) the 900 psi (62 bars) pressure was attenuated to 48 psi (3.3 bars). A second point to note in that the change in cover thickness has less Most of the effect in blast attenuation with increase in charge weight. line fall within the 90 degree measured along values peak overpressure ±10 percent band. A third point to note is the crossover point where the peak overpressure is greater from the covered magazines than from the uncovered charge. The .8 pound (.363 kg) charge did not show a crossover but the peak-overpressure versus distance curves for the covered magazines became parallel with the one for uncovered. The 2.4 pound (1.088 kg) charge showed a crossover, but at 5 psi (.345 bars), and remained approximately 39 percent higher than the uncovered charge. For the 4 (1.814 kg) charge the crossover occurs at 9 psi (.620 bars) and then the pressure versus distance curves become almost parallel with the covered magazine data being approximately 40 percent higher than the uncovered condition with the exception of the last station where it is greater than 40 percent. The impulse measurements made along the 90 blast line for t:.e four test conditions are listed in Table XI and plotted in Figure 22. The impulse measured at the second station on the uncovered condition is of questionable validity and therefore the impulse versus distance curve is not drawn through it. The general shape of the impulse versus distance curve for the earth covered magazines are similar to the .8 pound (.363 kg) and 2.4 pound (1.088 kg) charges with the exception of the last two stations where uncovered and double earth models give similar values. The onehalf and standard earth cover models show the same trend as established for peak overpressare in that higher impulse values were measured on covered models than the uncovered condition at the greater distance.

3. Blast Parameters Along the 180 Degree Line

The peak overpressure

and impulse propagated along the 180 degree line is of prime interest because of the blast load developed on the door and headwall of an acceptor magazine when located at the rear of a donor magazine. The peak overpressures measured along the 180 degree blast line for the four conditions tested with a 4 pound (1.814 kg) charge are listed in Table X and plotted in Figure 23. All three covered magazines cause significant pressure attenuation at the close-in stations. The double earth cover

model attenuates the peak overpressure from 40 to 10 percent more than the standard earth cover model. The larger attenuation occurs at the first station. The standard earth cover model attenuates an average of 20 percent more than the one-half earth cover model. 53

-

-

-c-

The impulse values recorded to the rear of the structure (180 degree line) for the four test conditions are listed in Table XI and plotted in Figure 24 as function of distance for each test condition. It is of interest to note that although the peak overpressure along the 180 degree line decreased with distance the impulse remains almost constant over the first four stations, with a small decay occuring at the last two stations. There is less than a ±10 percent spread in the data points plotted for the three earth cover conditions with the exception of the second station with a dolble earth cover model. D. Comparison of Modei and Full-Scale Magazine Results When this experimental program was first proposed and designed it was the opinion of the authors that relative differences in the effects of earth cover on blast parameters could be obtained from the 1/50 scaled models if the charge weights to interior structure volume ratios were maintained. It was also the opinion of the authors that these relative differences could be applied to full-size munition magazines. It was Lived, but not as strongly anticipated, that direct correlation of results from Zne model tests and full-scale tests could be achieved. Results from a series of full-scale tests conducted during 1962 1963 are reported in Reference 2. In test six, of the series; a doner charge of 100,000 pounds (45,360 kg) in a standard 60 foot (18.29 m) storage magazine was detonated and the blast parameters to the front, side, ane -ear were measured This charge weight to structure volume ratio matches the 0.8 pound (0.363 kg) chaTge detonated in the 1/50th srale model magazine. Both the full scale and the 1/50th scale conditions have been scaled to a 1.0 pound (0.454 kg) charge at sea level and comparisons of blast parameters are made in the following sections. 1. Blast Parameters Aiong the 0 Degree Line The peak overpressure and impulse measured along the 0 degree line from the 0.8 pound (0.363 kg) charge have been scaled to 1.0 pound (0.454 kg) and listed in Table XII. The same blast parameters measured on the full-scale test 100,000 pounds (45,360 kg) have also been scaled to 1.0 pound (0.454 kg) and listed in Table XIII. The results of measured peak overpressure recorded from both scaled and full-size are plotted in Figure 25 as a function of scaled distance (R/W / 3 ) where R is the distance in feet from the charge that the measurement was made and W is the weight of the explosive in pounds. In Figure 25 it can be seen that excellent correlation was obtained between the model and full-scale results. The obvious low value of the full-scale test (Reference 2) at a scaled distance of 6.29 is a questionable datum point since the self-recording gage pre-initiated and recorded only a peak value.

r54

Table XII. Scaled Blast Parameters - 0.8 Pound (0.363 kg) to 1.0 Pound (0.454 kg) - Standard Earth Cover Station

Scaled

Scaled

Peak

No.

Distance

Distance

Overpressure

ft/lb 11 3

m/kg

0-1 0-2 0-3 0-4 0-5 0-6

2.65 4.06 4.75 6.33 8.79 12.9

90-1

1.53

90-2 9u-3

2.65 4.06

90-4 90-5 90-6 90-7 90-8 90-9 180-1 180-2 180-3 180-4 180-5 180-6

1 3

1.05 1.61 1.88 2.51 3.49 5.13 .607

psi

bar

Scaled Impulse psi-msec/lb1/3

ba.-msec/kg1 13

25.4 21.3 16.3 11.6 7.97 5.60

2.12 1.77 1.35 .970 .664 .466

179. 12.3 84.4 5.82 59.0 4.07 34.5 2.38 18.5 1.28 5.70 .393 45.2

3.12

1.05 1.61

29.6 1.

2.04 1218.19

5.03 7.20 9.80 14.3 25.0 44.9

1.99 2.86 3.88 5.68 9.91 17.8

14.0 10.4 7.0 4.23 1.73 0.78

.965 .717 .483 .292 .119 .054

2.b5 4.06 4.75 6.33 8.79 12.9

1.05 1.61 1.88 2.S1 3.49 5.13

22.2 13.6 12.0 8.73 5.93 3.24

1.53 .938 .827 .601 .409 .223

55

11.2

.933

8.72

.726 .682

6.46 6.57 5.28 3.88 2.48 1.51

.539 .548 .440 .323 .207 .125

5.82

.484 .475 .440 .385 .314 .242

5.71

5.28 4.63 3.77 2.91

I

Table XIII. Scaled Blast Parameters - 100,000 Pounds (45,359 kg) to 1.0 Pound (0.454 kg) Station No.

Scaled Distance ft/lb1

3

Scaled Distance

Peak Overpressure

1 /3 m/kgI

psi

bar

Scaled Impulse psi-msec/lbl/

3

bar-msec/kg1 /3

0-Nl 0-N2 0-N2A O-N3 O-N4 0-N5 O-N6

6.29 10.5 10.5 15.7 21.0 38.9 76.1

2.49 4.18 4.18 6.26 8.37 15.5 30.3

22.8 9.62 7.12 3.98 2.71 1.32 0.43

1.57 .663 .491 .274 .187 .091 .030

6.45 4.29 3.93 3.45 2.09 0.90

° .578 .384 .352 .309 .187 .081

90-Wl 90-W2 90-W2A 90-W3 90-W4 90-WS

6.29 10.5 10.5 15.7 21.0 38.9

2.49 4.18 4.18 6.26 8.37 15.5

8.39 5.95 6.12 4.04 2.43 0.99

.578 .410 .422 .279 .168 .068

5.45 5.54 3.15 1.59

.488 .496 .282 .142

6.29 10.S 15.7 21.0 38.9

2.49 4.18 6.26 8.37 15.5

11.1 5.09 2.69 1.94 0.60

.765 .351 .185 .134 .041

4.99 3.11 2.41 2.07 -

.447 .279 .216 .185

180-S1 180-S2 180-S3 180-S4 180-5

{5 5

0

-

0.8 Pound Scaled to 1.0 Pound

j_

Figure

~

10000 vrus Possr Scaled 0

aDereeLin ullSizeMagzin

fro

a:10ScldMoe1

I57

t1.0Aondh an

A

I 1/3 The scaled impulse values I/W where I is measured impulse from a charge weight of W pounds listed in Table XII and XIII are plotted in Figure 26 as a function of scaled distance. Here again the correlation of impulse measured to the front of the structures is excellent. 2. Blast Parameters Along the 90 Degree Blast Line The peak overpressures, scaled distances and scaled impulses recorded along the 90 degree blast line for both the model and full-size structure are listed in Tables XII and XIII. The peak overpressures are plotted as a function of scaled distance in Figure 27. The peak overpressure measured at a scaled distance of 6.29 on the full scale test (Reference 2) is low but here again only a peak value was obtained because the gage failed to run. There was also an acceptor magazine in place along side of the donor magazine which could have caused a decrease in the peak overpressure at that distance. The solid curve was developed from the results of the scaled model tests but it fits the scaled results fro7 the full size tests quite well. The scaled impulse and scaled distance along the 90 degree line for both nodel and full-size tests are listed in Tables XII and XIII and plotted in Figure 28. Here again it can be seen that using simple cube root scaling gives good correlation of impulse as well as peak overpressure. 3. Blast Parameters Along the 180 Degree Blast Line The blast parameters recorded to the rear (180 degrees) of the full size and model structure have been scnled to a 1 pound (.454 kg) charge equivalent and listed in Tables XII and XIII. The peak overpressures are plotted a! a function of scaled distance in Figure 29. The correlation of the two sets of data is excellent with the exception of the peak overpressure measured at the first station from the full-size test. In Figure 30 the scaled impulse is plotted as a fanction of scaled distance. It can be seen that there is good correlation between the two sets of data. IV. SUMARY AND CONCLUSIONS In summary, it can be stated that the results of this series of tests have established many trends and the effects of varying the earth cover on blast parameters to the front, side, and rear of the structure have been documented. Some specific conclusions on earth cover effects along the three blast lines are given in the following secri'ns. A. R. Sound, "Swmnary Report of Earth-Cbvered Steel-Arch Magazine Tests," NO1TS TP 3843, July 1965. 58

1O0

-

0

-

0.8 Pound Scaled to 1.0 Pound

-

100,000 Pounds Scaled to 1.0 Pound

I

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0.0-

L_

-01

0

1.0-

I1 1 j iji

o.A 1.0

11I1111 J0

100

SCALED DISTANCE, FT/LIS1 3

Figure 26. Scaled Impulse versus Scaled Distance Along the O Degree Time from a Full-Scale Magazine and a 1/50 Scaled Model 59

-i

-~,--4-

.-

///=-/----

-

0 A-

-

0.8 Pound Scaled to 1.0 Pound 100,000 Pounds Scaled to 1.0 Pound

I BLAST 10

-LI1LIIE

- "

t-

tO

1.0 SCALED

DISTANCE,

tOO0 FT/LI5S1 / 3

Figure 27. Pressure versus Scaled Distance Along the 90 Degree Line from a Full-Size .Magazine and a 1/SO Scaled Model 60

0 - 0.8 Pound Scaled to 1.0 Pound - 100,000 Pounds Scaled to 1.0 Pound

9A

-

I-.j~I

BLAST LINE

-I.

taJI

Ca

W

_)

0

_

SM/

ID0

11 SCALED DISTANCE, F/LBS

Figure 28. Scaled Impulse versus Scaled Distance Along the 90 Degree Line from a Full-Size Magazine and a 1/50 Scaled Model 61

100

!00

0 - 0.8 Pound Scaled to 1.0 Pound A - 100,000 Pounds Scaled to 1.0 Pound

II II

I

! II II

90

i

0 6

1.0

1

IC10

SCALED DISTANlCE, FT/18SS 1 Figure 29. Pressure versus Scaled Distance Along the 180 Degree Line from a Full-Size Magazine and a 1/SO Scaled Model 62

0

A I

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-

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