NBSIR 74-528 '''^)

DNA/NBS/Crane NAD Barrier Tests

R. T. Moore

Computer Systems Section

Computer Systems Engineering Division

Institute for Computer Sciences and

Technology

National Bureau of Standards

Washington, D. C. 20234

FILE COT

July 1974

Report for Period March 24- 29, 1974

Prepared for Defense Nuclear Agency

Washington, D. C. 20305

NBSIR 74-528

DNA/NBS/CRANE NAD BARRIER TESTS

R. T. Moore

Computer Systems Section

Computer Systems Engineering Division

Institute for Computer Sciences and

Technology

National Bureau of Standards

Washington, D. C. 20234

July 1974

Report for Period March 24 - 29, 1974

Prepared for Defense Nuclear Agency

Washington, D. C. 20305

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts. Director
CONTENTS

CONTENTS

ILLUSTRATIONS 1

1. INTRODUCTION 3

2. DNA/NBS /CRANE BARRIER TESTS 3

3. TESTS ON CONCRETE SLABS 4

Test 3L1 5

Test 4L1 7 Test 5E3 9

Test 6E2 11

4. TESTS ON A HIGH EXPLOSIVES MAGAZINE 15

Test 1421X1 17

Test 1421N2 21

Test 1421W3 25

5. CONCLUSIONS 31
ILLUSTRATIONS

3L1. Slab 3 - front; attack results after

16-round burst of 20 mm APT

3L1. Slab 3 - rear; attack results after

16-round burst of 20 mm APT

3L1. Slab 3, front view of completed

opening

4L1. Slab 4, front view of results of

17-round burst of 20 mm APT

4L1. Slab 4, rear view of results of

17-round burst of 20 mm APT

4L1. Slab 4, completed opening

4L1. Slab 4, impact marks from 40 mm HE

5E3. Slab 5, rear view after reinforcing

was exposed

6E2. Slab 6 , rear view showing small spall

6E2. Slab 6E2. Slab 6, front view

showing drilling pattern

6E2. Rear view of slab after second set

of holes had been spalled

6E2. Slab 6 after 44.45 minutes working

time

Typical ambient acoustical level inside

magazine

Typical ambient vibrational disturbances

1421X1. Interior view of grating

1421X1. Attacker being lowered through

ventilator shaft

1421X1. Acoustical disturbances produced

by burning bar

1421X1. Vibrational disturbances produced

by burning bar
19. 1421X1. Smoke from ventilator after burning grid

20. 1421N2. Acoustical disturbances produced inside

magazine by rotohammer

21. 1421N2. Vibrational disturbances from rotohammer

22. 1421N2. Acoustical disturbances produced by

spalling

.

23. 1421N2. Vibrational disturbances produced

by spalling

24. 1421N2. Completed opening

25. 1421W3. Acoustical disturbances produced

by clipper saw

26. 1421W3. Vibrational disturbances produced

by clipper saw.

27. 1421W3 . Acoustical disturbances produced

by battering ram

28. 1421W3. Acoustical disturbances from drilling

29. 1421W3. Vibrational disturbances from drilling

30. 1421W3. Interior grid work showing slight

bowing

31. 1421W3. Unruptured pipe grid hanging loose

from one side

2
DNA/NBS/CRANE NAD BARRIER TESTS

by

R. T. Moore

1. INTRODUCTION

In discharging its responsibilities for the safety and security of

special weapons, the Defense Nuclear Agency has sponsored a series of

investigations to develop estimates of the penetration resistance of

various barrier materials. In a number of instances these tests have

been conducted on specimen panels and slabs or simulated structures

which were specially constructed for the purpose of testing penetration

resistance. While this report describes the results of further tests

of this type, it also includes the results of tests on a high

explosives magazine of a type which might be employed for the storage

of special weapons.

2. DNA/NBS/CRANE NAD BARRIER TESTS

During the week of March 25, 197A, a series of barrier penetration

tests were conducted at the Crane Naval Ammunition Depot, Indiana.

The objectives of these tests were threefold:

(1) To obtain additional data on the penetration resistance

of four reinforced concrete slabs which had been the subjects

of an earlier test series conducted at the U. S. Army Corps

of Engineers, Construction Engineering Research Laboratory,

Champaign, Illinois in the fall of 1972.

(2) To obtain data on the resistance to penetration offered

by a typical high explosives magazine against attacks directed

against structural components other than the steel door, and

to collect samples of the acoustical, ultrasonic and

vibrational disturbances produced by these attacks.

(3) To develop preliminary estimates of the potential utility

of chemical deterrents to forced entry through the simulation

of pressurized grids of tubes or pipes which could be located

inside a protective barrier and arranged to release their

contents upon penetration.

3
3. TESTS ON CONCRETE SLABS

Concrete slabs numbered 3, 4, 5^^and 6 were specimens which had been

subjects of an earlier test series— . Each was made from reinforced

concrete eight inches thick. Slabs 3 and 5 were made with regular

concrete, while slabs 4 and 6 were made with fibrous concrete. Slabs

3 and 4 were reinforced with two layers of 6.35 mm (1/4") welded steel

mesh ((152.4 mm (6") mesh size)) and slabs 5 and 6 were reinforced with

number five bars on 127 mm (5") centers both ways.

During the earlier tests, each of the slabs had been subjected to one or more linear-shaped charges, sizes JA-4 or JA-5. These had

produced annular spalling on the outer face of the slab and some cracks

on the inner face, but had not been successful in making a complete

opening. Ninety-six square inch openings had been made in slabs 5 and

6 by other means, and drilling and burning bar tests had been conducted

on slabs 3 and 4.

At Crane NAD, the four slabs were positioned vertically on a firing

range and secured in position to short telephone poles on their downrange sides. It was planned to test slabs 3 and 4 using 20 mm

projectiles and to use conventional tooling to complete openings in areas damaged by the linear-shaped charges on the other two slabs.

Several single- or double-shot rounds of 20 mm M-95 series APT were

fired at slabs 3 and 4. These established that penetration was always

complete and accompanied by sizable spalling from the rear surface of

the slabs.

Ij Moore, R. T. , Penetration Tests of Reinforced Concrete Barriers,

NBSIR 73-101, December 1972.

4
Test 3L1

A relatively undamaged area was selected on slab 3 and

marked as a target area. Than a 16 round burst of 20 mm APT

was fired from a distance of approximately 150 m . Figure 1

shows the front and figure 2 shows the rear of the slab after

this burst. Damage was such that it required only five blows

with a sledgehammer to clear away the shattered concrete and

expose the reinforcing. This was cut with bolt cutters and in

only 0.44 minute working time an opening measuring 348 mm X

292 mm (13-1/2" X 11-1/2") was cleared as shown in figure 3.

Figure 1. 3L1. Slab 3 - front;

attack results after 16-round

burst of 20 mm APT

5
Figure 2. 3L1. Slab 3 - rear; attack results

after 16-round burst of 20 mm APT

Figure 3. 3L1. Slab 3, front view

of completed opening

6
Test 4L1

As in the preceding test, a target area was selected and

then a 17 round burst of the 20 mm APT was fired at this

target. Figures 4 and 5 show front and rear views of the

resulting damage. The fibrous concrete in this slab was more

difficult to clear away and 75 blows were required from a

Figure 4. 4L1. Slab 4, front view of results

of 17-round burst of 20 mm APT

Figure 5. 4 LI. Slab 4, rear view of results

of 17-round burst of 20 mm APT

7
4.5 kg (10- lb.) sledgehammer. These were followed by 15 cuts

with bolt cutters which produced an irregular shaped opening

of approximately 305 mm X 330 mm (12" X 13"). The total working time was 2.18 minutes. Figure 6 shows the finished opening.

Figure 6. 4L1. Slab 4, completed opening

A further unscheduled test was performed on slab 4.

Three rounds of 40 mm HE were launched from a distance of about

75 m against the face of the slab. These exploded on impact

leaving only the slight marks shown in figure 7.

8
Figure 7. 4L1. Slab 4, impact marks

from 40 mm HE

Test 5E3

In the earlier test series—^ on slab 5, a size JA-4

linear-shaped charge had produced a nominal 432 mm annulus

of spalling to a depth of about 40 mm. Using a rotohammer,

two 19.05 mm (3/4") holes were drilled to a depth of 88.9 mm

(2-3/4") from the deepest part of the top and bottom of the

annulus. These required 0.58 minute of working time.

\J Moore, R. T., Penetration Tests of Reinforced Concrete Barriers, ~ NBSIR 73-101, December 1972.

9
Then, using a bull-point punch and a 4.5 kg sledgehammer, the

bottoms of these holes were spalled out with 34 blows delivered

in 0.78 minute. This produced a spalled area on the rear surface of the slab that extended to the depth of the centered

reinforcing bars over an area approximately 864 mm (34") high

and 520 mm (20-1/2") wide. Then, 68 blows with the sledgehammer delivered in 1.05 minutes cleared away the remaining

concrete fully exposing the reinforcing as shown in figure 8 . Ten cuts with bolt cutters required 2.18 minutes and produced

a clear opening approximately 356 mm (14") in diameter. The

total working time was 4.60 minutes.

Figure 8. 5E3. Slab 5, rear view

after reinforcing was exposed

10
Test 6E2

On the fibrous concrete of slab 6, an attack similar to

test 5E3 was made, but with significantly different results.

First it was found that spalling could not be done until a hole had been drilled to within about 51 mm (2") of the rear surface of the slab. Then, the spall itself would invariably

be quite small, as shown in figure 9. As a result, it was necessary to drill holes along the bottom of the annulus at

intervals of about 127 mm (5") to a depth of 127 mm. These

were, in turn, spalled out and then a second series of holes

were drilled to a depth of 76 mm (3") around the annulus midway

between each of the first series of holes. This hole pattern

is shown in figure 10 , and figure 11 is a rear view of the slab

after these holes had been spalled.

Figure 9. 6E2. Slab 6, rear view

showing small spall

11
Figure 11. 6E2. Rear view of slab after

second set of holes had been spalled

12
Next, four more holes were drilled partially through the

slab near the center of the annulus . These were spalled and

then a direct sledgehammer attack eventually produced a small

central initial breakthrough. Using a combination of tapered

punches and direct sledgehammer attacks, the peripheral holes

were enlarged and spalled into the central breakthrough region

It required a total of 44.45 minutes of working time to make

the opening shown in figure 12. It is estimated that it would

have required at least two more minutes to cut the reinforcing

bars with bolt cutters.

Figure 12. 6E2. Slab 6 after 44.45

minutes working time

This attack took maximum advantage of the damage previously produced by the linear-shaped charge. It is estimated

that this damage reduced the required working time by about

10 to 15 minutes compared to that which might have been required

to make a similar opening in an undamaged slab of this

construction

.

13
Fibrous concrete has demonstrated a greater cost-effective

potential for use in highly penetration resistant barriers than

any other material which has been tested to date by this

2/, 3/, 4/ authoi^ — — .

Drilling Speed Tests

Sample holes were rotohammered in slab 5 to develop

additional information on drilling rate as a function

of drill size. The results are shown below:

Drill Size

19.05 mm (3/4")

22.23 mm (7/8")

31.75 mm (1-1/4")

38.10 mm (1-1/2")

Drilling Rate

2.28 sec. /mm (5.8 sec. /in.)

2.80 sec. /mm (7.1 sec. /in.)

4.00 sec. /mm (10.18 sec. /in.)

11.8 sec. /mm (30.0 sec. /in.)

From these data it appears that drilling rate is

inversely proportional to the volume of material removed

for drill sizes up to about 31.75 mm.

2/ Moore, R. T.; Acoustic, Ultrasonic and Vibrational Disturbances

Resulting from the Penetration of Conventional Structural Barriers.

NBS Report 10 682, January 1972.

3/ Moore, R. T., Penetration Tests on J-SIIDS Barriers. NBSIR 73-223,

June 1973.

h_/ Moore, R. T. , Barrier Penetration Tests, NBS Technical Note 837,

June 1974.

14
4. TESTS ON A HIGH EXPLOSIVES MAGAZINE

High explosives magazine No. 1421 was made available at Crane NAD as

a test site. This magazine is an earth-covered concrete structure having

an interior floor 23.77 m (78') long by 7.62 m (25') wide with an arched

roof that was 3.38 m (ll'l") high at the center. It had a straight

ventilator located in the center of the arch near the back of the magazine. The ventilator shaft was 38.1 cm (15") inside diameter and was protected on the bottom by a grating of 6.35 mm (1/4") diameter metal

bars spaced on 25.4 mm (1") centers, both ways, and with their ends

embedded in the concrete JDf the arch.

The instrumentation arrangement was essentially as described in

references 1, 3 and 4 and included two piezoelectric vibration transducers and a 6.35 mm (1/4") microphone.

Prior to the start of tests, the vibration transducers were attached

to the interior of the magazine at the center of the arch; one was located approximately 1 m forward of the ventilator opening and the

second was positioned approximately 3.2 m in back of the entrance door.

Due to the cool, moist conditions which prevailed, some difficulty was encountered in cementing the transducers in place, and extended use of an electric heat gun was necessary. Apparently these efforts were not

completely successful. At the end of the tests when the vibration

transducers were removed, it was found that neither was firmly attached

to the mountings. as a result, absolutely no confidence can be placed

in any of the observed vibrational data . Samples of the observations are included in this report but their validity is extremely doubtful.

The microphone was mounted on a small tripod and positioned inside

the magazine near the center of the floor plan. Its outputs, together

with those of the vibration transducers, could be selectively displayed

as the oscllloscoplc output of a real-time spectrum analyzer. This was operated with a 500 Hz bandwidth swept over the frequency range from

0 to 50 kHz at a rate of 5 kHz per 30 ms . The output was logarithmic in

amplitude, 10 dB per cm.

Sound pressure levels (SPL) were observed with a handheld meter using

a c-weighted filter network. These are reported as values of dBc,

together with the distance from the source of the disturbance.

The typical ambient, acoustical level inside the magazine is shown

in figure 13. The low frequency peaks around 70 dB were confirmed by SPL

readings and resulted from the diesel-powered generator which was used to

provide electric power at the test site. A recording of the ambient

vibrational disturbances is shown in figure 14.

15
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JXTSJrti j- 3sd3 "ioo:£

-i jsJ o i q

{8 8T6-'f

25 50

esLr b3b033xs bxjB ,33slq , FREQUENCY, kHz

:?or.r ;-3:ysvT a 3" to 'Via spsrfi v rrt^- ,- ~ -i aoxJBicriv sdj ,fi9/iw aJasi sri:J 3o bns sii- SA =^

s-iB Bffoiasv- Figure 13. Typical ambient acoustical level.

-.. luisdyob Ylsf.131:; inside magazine.

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mo It - £xt olmd3t'

•gill a u 1.

0.1

OOl

OOOl

0.0001 s

0.00001

31.9 n.s -SJalqf'-o':.

- ^otrbaasi:-

3 ill

25

FREQUENCY, kHz

Figure 14. Typical ambient

vibrational disturbances

16
Test 1421X1

The magazine ventilator was an obvious weak spot. The

ventilator shaft was large enough to easily admit the passage of

a man and was protected only by a rain cover which could be

easily lifted off and by the grating of metal bars at its bottom.

Since a battering ram, weighing approximately 113 kg (250 lbs.)> was available, it was dropped down the ventilator shaft in the

hope that it might knock the protective grating completely out

of the shaft. If this had occurred, a man-passable opening

would have been produced in less than 0.5 minute.

The battering ram broke through the grating bars and made

a hole only about half the required diameter(see fig. 15 ) , so the ventilator cover was replaced and the test was restarted

using an alternative approach.

Figure 15. Test 1421X1. Interior

view of grating

17
While the ventilator cover was again removed, a burning bar

was ignited. The oxygen-acetylene torch used for this was quite

small and ignition took 0.97 minute. Then the grating bars

were burned away around the interior periphery of the ventilator

shaft in 2.28 minutes working time, completing the opening in a total elapsed and working time of 3.25 minutes. Next, water

was sprayed down the shaft to cool the burned area and one of

the attack team put on air breathing apparatus in preparation

for descending into the magazine. The breathing apparatus was necessary because dense smoke filled the interior of the

magazine.

The breathing apparatus was jury-rigged. A belt was volunteered by one of the attack team and used to try to strap

the pressure regulator of the breathing apparatus in such a position that the semirigid air supply line would not kink the

hose between the regulator and breathing mask. When this had

been done, the intruder was lowered to the interior floor of

the magazine using belaying techniques as shown in figure 16.

The bottom was reached after 8.70 minutes of working time and

11 minutes elapsed time.

Figure 16. Test 1421X1. Attacker being

lowered through ventilator shaft

18
The jury-rigged breathing apparatus would not allow the

intruder to climb back up and out the ventilator shaft so the

magazine doors were opened to permit his exit.

Acoustical disturbances produced by the burning bar are shown in figure 17 and vibrational in figure 18. The latter were

from the transducer mounted 1 m from the shaft, and, as previously

noted, are of questionable validity.

0 ^ 25 50

FREQUENCY, kHz

Figure 18. 1421X1. Vibrational disturbances

produced by burning bar

19
edi \-7o11b iB^cBq:

After completion of test 1421X1, a grid work of plastic

pipes was placed across the interior of the ventilator shaft and

connected to a smoke generator. This was to simulate a proposed

chemical forced entry deterrent system. The magazine was again

closed and the pipe grids were cut with the burning bar. Smoke

/poured out of the ventilator, as shown in figure 19, and the

interior of the magazine was filled with dense smoke. When the

doors of the magazine were opened, it was several minutes before

there was sufficient visibility to even find the fans which had

been placed inside to facilitate forced ventilation and smoke

removal. After they had finally been located and turned on, it

took nearly half an hour to clear the magazine of smoke. It is

believed that unless an invader had been trained to perform his

mission in total darkness he could not have functioned in the

environment of a closed magazine filled with such dense smoke

even using breathing apparatus and portable lights.

Figure 19. Test 1421X1. Smoke from ventilator

B . , . . ; ; af ter burning grj.d ,

20
Test 1421N2

The site selected for this test was at the top of the

earth-covered arch, approximately 10 meters from the door of the

magazine.

A four-man attack team began shoveling away the moist,

grassy fill. It took approximately 175 shovels full and 4.02

minutes working time to clear an area approximately 0.5 m in

diameter on the membrane and extending out on one of the sloping

sides of the arch, enough to provide room to operate a sledgehammer. The earth fill over the arch ranged in depth from

0.79 m(31") to 0.91 m(36") and the top of the hole was approximately 1.0 m wide and 2.0m long. Shoveling produced SPL

of 70 to 86 dBc at a distance of approximately 3.0 m. No

disturbances above the ambient background were recorded from the

transducers inside the magazine.

21
Using a template developed during the course of prior test

series, a pattern of 14 holes was marked to outline a circular

target area approximately 30.5 cm (12") in diameter. The marked

locations were drilled 7.62 cm (3") deep with a 19.05 mm (3/4")

drill in 2.98 minutes. This produced SPL readings of 78 to

85 dBc at a distance of approximately 3.0 m on the outside and

acoustical disturbances as shown in figure 20 inside the magazine. Questionable data from a vibrational transducer located

6.1 m (20') from the attack point is shown in figure 21 . This

figure shows an uncharacteristic absence of high-frequency

components of vibration from the rotohammering

.

db

0 25 50

FREQUENCY, kHz

Figure 20. 1421N2. Acoustical disturbances produced inside magazine by rotohammer

FREQUENCY, kHz

Figure 21. 1421N2. Vibrational disturbances

from rotohammer

22
A bull-point punch was inserted in one of the drilled hole

and 1.62 minutes of working time was expended in an unsuccessfu

attempt to spall out the bottom of the hole. The sledgehammering produced sound pressure levels of 78 to 95 dBc on the outside of the magazine at a distance of 3.0m and 95 to 104 dBc

inside the magazine at a similar distance from the attack point

Spectra of the acoustical and questionable vibrational disturbances are shown in figures 22 and 23.

1 16 ^^^^^^^^^^^^^^^^^^^H

Figure 22.

100

25

FREQUENCY, kHz

1421N2. Acoustical disturbances

produced by spalling

50

9 1.0

FREOUENCY.kHz

Figure 23. 1421N2. Vibrational disturbances

produced by spalling

23
Failure to spall out the first hole suggested that the

thickness of the concrete arch might be greater than the six

inches shown on the drawings, so one of the holes was deepened to

12.7 cm (5") in 0.38 minute working time and this hole was spalled out in only 0.22 minute. The clocks were stopped and

the thickness of the concrete was measured and found to be

20.3 cm (8").

When the attack resumed, the holes were enlarged to 22.2 mm

(7/8") to provide better clearance for the bull-point punches as mud and concrete dust was getting back into the drilled holes.

Alternate holes were also deepened to 12.7 cm (5"). These

drilling activities took 3.13 minutes working time. The six

deep holes were then spalled out in 1.18 minutes working time

and 4.42 minutes additional working time was spent spalling out

the shallower holes. It was necessary to clean the debris out

of each hole with the rotohammer immediately before inserting the

bull-point punch.

After the spalling had been completed, the remaining shell

of concrete was knocked out in 3.25 minutes of direct attack with

a sledgehammer and the reinforcing wires were cut in 0.63 minute

using bolt cutters. The completed opening is shown in figure 24.

The total working time was 21.83 minutes and the elapsed time

23.12 minutes.

Figure 24. Test 1421N2. Completed opening

24
It is believed that this penetration time was significantly

lengthened by two factors. First, it was necessary to use two

models of rotohammers. The drill bits for the heavy duty (and

faster) model were not long enough for the required hole depths.

Thus, it was necessary to switch to the lighter (and slower)

model to finish out the holes. Secondly, the problem of debris

clogging the holes was not adequately anticipated. This

difficulty could have been avoided by simply reordering the

attack plan and spalling out each hole as soon as it was drilled

rather than doing all of the drilling prior to spalling. This

would have prevented the concrete dust and mud from getting back

into and clogging one hole while the next was being drilled.

In addition, at least two or three minutes were required to

accommodate features of the magazine which were not in accordance

with the design drawings. The thickness of both the over- burden and the concrete arch were greater than expected. Taking

all these factors into consideration, it is not unreasonable to

expect that a penetration time on the order of 15 minutes

working time could be realized.

Test 1421W3

The site selected for this test was on the top of the arch,

approximately 7.62 m (25') from the entrance of the magazine. A

grid-work of plastic piping was attached to the interior of the

arch and connected to a water pump to simulate a forced entry

deterrent system employing a liquid agent. Transducer locations

were unchanged.

As in the preceding test, the four-man attack team shoveled

away the overburden to provide a clear area on top of the arch

approximately 60.9 cm (2') wide and 121.8 cm (4') long. This

was somewhat larger than the hole made for test 1421W2 and

required 7.15 minutes working time and 233 shovels full of earth.

There appeared to be a crack in the exposed concrete

surface of the arch, so, on the off chance that it might go

through, the 113 kg (250 lb.) battering ram was dropped three

times from a height of about 76 cm (30"). No damage resulted.

A gasoline-powered clipper saw, equipped with a waterlubricated diamond blade, was then placed in the hole and two

parallel cuts were made. These were about 56 cm (22") long,

11.4 cm (4-1/2") deep and 20 cm (8") apart. These required 7.66

minutes working time and produced the acoustical disturbances

shown in figure 25 and the questionable vibrational disturbances

of figure 26.

25
0 25

FREQUENCY, kHz

.0

Figure 25. Test 1421W3. Acoustical disturbances

produced by clipper saw

FREQUENCY, kHz

Figure 26. Test 1421W3. Vibrational disturbances

produced by clipper saw

26
Then the battering ram was dropped 11 times in the area between the two cuts without useful results. The acoustical

disturbance produced by the ram is shown in figure 27. The

11 drops required 1.35 minutes working time.

25

FREQUENCY, kHz

50

Figure 27. Test 1421W3. Acoustical disturbances

produced by battering ram

27
Next, four holes 22.2 mm (7/8") in diameter were drilled to

a depth of 11.43 cm (4-1/2") in a row extending between the two

slits near their midpoint. This required 1.42 minutes and

produced the acoustical disturbances shown in figure 28 and the

questionable vibrational disturbances shown in figure 29.

106

96

db

76

56

O 25 50

FREQUENCY, kHz

Figure 28. Test 1421W3. Acoustical

disturbances from drilling

0 25 50

FREQUENCY, kHz

Figure 29. Test 1421W3. Vibrational

disturbances from drilling

28
The battering ram was then dropped 20 times on the weakened

area and again was ineffective. This required 1.50 minutes

working time. It was clear that additional drilling and spalling

would be necessary to complete this penetration, so a single

12.7 cm (5") deep hole and two 7.62 cm (3") deep holes were

drilled in a row at each end of the pair of slits. The drilling

was completed in 2.16 minutes working time. One of the deeper

holes was spalled out using a bull-point punch and sledgehammer

in 0.83 minute, but 0.85 minute later, while working on the next

hole, the handle of the last sledgehammer was broken. Testing

was suspended for the day with 22.92 minutes of working time.

The following day, the testing was resumed with a fresh

supply of sledgehammer handles. The 7.62 cm (3") deep holes

were extended to 12.7 cm (5") in depth and were spalled out in

3.95 minutes. On several occasions, punches came through the

concrete in positions which threatened to penetrate the pipe

grid vX)rk attached to the Interior of the arch but in each

instance the grid was merely bowed or deflected as shown in

figure 30.

Figure 30. Test 1421W3. Interior grid work

showing slight bowing

29
The ram was again dropped seven times without useful effects.

This took an additional 0.80 minute.

Next, three equally spaced holes were drilled along each of

the slits to a depth of 12.7 cm (5") • Each of these holes was spalled immediately after being drilled. The working time was

3.32 minutes.

Again the battering ram was dropped, and, on the tenth drop,

after a working time of 1.17 minutes, about half of the concrete

broke through. Then, 0,42 minute work with the sledgehammer

cleared an opening 20.3 cm (8") wide and 54.6 cm (21-1/2") long.

In the process, the pipe grid did not rupture but was torn loose

from its hangars on one side and hung vertically as shown in

figure 31. A final 0.57 minute of work with bolt cutters cleared

the remaining reinforcing wires, completing the opening in a total working time of 33.15 minutes.

Figure 31. Test 1421W3. Unruptured pipe grid

hanging loose from one side

30
After completion of the test, the pipe grid was reattached

under the opening and cut with bolt cutters. The pressurized

water flowed from the cut section into the interior of the

magazine but did not spray up or wet the attack team.

5. CONCLUSIONS

The penetration tests conducted on magazine 1421 required somewhat

greater working times than could be achieved by a skilled and well

rehearsed attack team using optimum penetration techniques. While no

tests were made of the magazine door, its vulnerability was judged to be

considerably greater than: that of the straight-through ventilator. It

could probably have been opened in less than a minute.

The isolated location of this magazine and the infrequency of

traffic in this portion of the Depot could be expected to greatly

facilitate the opportunity for covert penetration. Even with the

installation of intrusion detection sensors, it appears likely that the

travel times required to respond to an alarm would preclude the maintenance of a high level of security at this site.

The simulation of Chemical Forced Entry Deterrent Systems (FEDS) did

not provide conclusive results of their potential. They definitely show

promise, however, and further research, development, test and evaluation

of this concept is strongly recommended. There is little doubt that they

can add to the time required to penetrate and/or operate within a protected enclosure, such as a magazine, if by no other mechanism than

reducing visibility to virtually zero for a few minutes. Even with

protective clothing and breathing equipment, an intruder would not be

able to operate effectively within the magazine for this time interval.

They also offer an as yet unknown potential for an additional level of

intrusion detection in the event that conventional sensors were defeated

or disabled by a skilled attack team. This could come about through the

inclusion in the FEDS materials of some component which could be readily

detected at very low concentrations. Sensors surrounding the protected

area, but at an appreciable distance from it, might be responsive to the

release of the FEDS materials. This, together with knowledge of wind

conditions, might provide a vector to the target under attack, and/or to

the exit route taken by a successful penetration team. Such an array of sensors might be interconnected to a small computer which is also

integrated with both the conventional intrusion sensor systems and the

security communications systems to provide an enhanced level of security

for special ammunition storage sites. Further study and investigation

of this conceptual configuration is recommended.

31

NBS-l WA IREV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUIU.ICATION OR REPORT NO. NBSIR 74-528

2. Gov't Accession

No.

3. Recipient*s Accession No.

4. TITLE AND SUBTITLL DNA/NBS/CRANE NAD BARRIER TESTS

5. Publication Date July 1974

6. Performing Org.ini?ation Code 650.01

7. AUTHOR(S) „ „ „ R. T. Moore

8, Performing Organ. Report No. NBSIR 74-528

9. PERFORMING ORGANIZATION NAME AND ADDRESS NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Ta.sk/Work Unit No. Project 6509419

11. Contract/Grant No. lACRO DNA 74-408

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP}

Defense Nuclear Agency (DNA)

Washington, D. C. 20305

13. Type of Report & Period Covered Rgpo^t for

Per. March 24-29,1974

14, Sponsoring Agency Code DNA

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less tactual summary of most si^iiicant information. If document includes a significant bibliography or literature survey, mention it here.) In discharging its responsibilities for the safety and security of special weapons,

the Defense Nuclear Agency has sponsored a series of investigations to develop

estimates of the penetration resistance of various barrier materials. In a number of Instances these tests have been conducted on specimen panels and slabs or simulated structures which were specially constructed for the purpose of testing penetration

resistance. While this report describes the results of further tests of this type, it

also includes the results of tests on a high explosives magazine of a type which

might be employed for the storage of special weapons.

17. KEY WORDS (six. to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Barrier penetration; intrusion resistance; physical security.

18. AVAILABILITY \^ Unlimited

[X For Official Distribution. Do Not Release to NTIS

[

' Order From Sup. of Doc, U.S. Government Printing Offi Washinsron, D.C. 20402, Sf^ Ca-. N'o. Cn

O. Ji.T 1 r III .N.ition.il i'tciinicii Inicirmation Servici.' iN TlS) Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

'THIS PACE)

UNCLASSiriLU

21. NO. OF PAGES

33

22. Price

USCOMM.DC 2S042-PT*