14 -C749

31)^COMMONWEALTH OF AUSTRALIA

C.3

DEPARTMENT OF NATIONAL DEV

OF IOWA/Frec r e

DEC1PAOOPMENT

OFFtgE t 'BRAM'

BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

NON-LENDING COPY

NOT TO BE REMOVED

FROM LIBRARY

RECORDS 1,960 No. 130

NORTH BALWYN VIBRATION TESTS, VICTORIA 1960

by

P.J. Anthony

The information contained in this report has been obtained bythe Department of National Development, as part of the policyof the Commonwealth Government, to assist in the explorationand development of mineral resources. It may not be publishedin any form or used in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralResources, Geology and Geophysics.

RECORDS 1960 No. 130

NORTH BALWYN VIBRATION TESTS, VICTORIA 1960

by

P.J. Anthony

The information contained in this report has been obtained bythe Department of National Development, as part of the policyof the Commonwealth Government, to assist in the explorationand development of mineral resources. It may not be publishedin any form or used in a company prospectus or statement withoutthe permission in writing of the Director, Bureau of MineralResources, Geology and Geophysics.

CONTENTS

Page

ABSTRACT

1. INTRODUCTION

2. RESULTS

3.^CONCLUSIONS^

2

TABLE 1.

ILLUSTRATIONS

Figure 1^

Positions of recorder (G344-65)Figure 2

^Details of shot pattern (G344-65)

APPENDIXES

Appendix 1 References and extracts from authoritative publicationsconcerning safe vibration limits.

Appendix 2 Graph of safe vibration limits.

ABSTRACT

Vibrations of the ground resulting from explosives fired inthe course of trench excavations were recorded in the North Balwynarea for Prentice Bros. and Minson Pty. Ltd.

The measured vibrations are compared with thoseregarded as safe by various authorities.

1. INTRODUCTION

In response to an application by Prentice Bros. andMinson Pty. Ltd., who are digging a sewer trench at North Balwyn,the Bureau of Mineral Resources conducted vibration tests near thetrench. The tests were intended to measure the amplitude andfrequency of ground vibrations caused by the explosives used inexcavating the trench.

The vibrations were recorded with a SprengnetherPortable Blast and Vibration Seismograph. This instrument recordson a'photographic strip the vibrations in three mutually perpendiculardirections. The records show the ground displacement magnified 100times, with timing lines at intervals of 0.02 seconds.

1960.^The recordings were made by the author on 25th August

2. RESULTS

Records were taken with the seismograph at two differentpositions, which are shown on Fig. 1.^Fig. 2 shows details of theshot patterns from which vibrations were recorded.

Table 1 shows the magnitude of the three components ofground displacement (taken as half the peak—to—trough amplitude)corresponding to each of the positions of the seismograph. Theresultant amplitude is computed by taking the square root of thesum of the squares of the three components.

The shot pattern from which the Position 1 records weremade consisted of eight holes each loaded with 8 oz of AN60 gelignite.The pattern from which the Position 2 records were made consisted offive holes each loaded with 8 oz of AN60 gelignite.^In both casesmillisecond delay series 'detonators were used.

The largest amplitude component recorded was 0.00045 in.which occurred on the longitudinal component of the record taken inPosition 1. The recorded frequencies ranged from 50 to 80 c/s,the most commonly occumeing frequency being about 65 c/s (See Table 1).

The ground accelerations shown in Table 1 were calculatedfrom the formula

a = 4112f2 A/g

where a = acceleration of the ground in terms of gravity

f = frequency in cycles per second

A = amplitude in inches

g = acceleration due to gravity (=386 in./sec2)

The largest resultant amplitude and the largest groundacceleration were recorded at Position 1.^The displacement herewas 0.0007 in. and the frequency was about 67 c/s.

Extracts from different authorities recommending safeamplitudes of vibration and other criteria, are shown in Appendix 1.Appendix 2 is a graph of amplitude against frequency showing safevibration limits according to different authorities. The firstfive of these references would describe a resultant amplitude of0.0007 in. at 67 cis as a safe vibration.^Reference 6, however,shows that the U.S. Bureau of Mines would regard such a vibrationas unsafe for buildings.

2.

3. CONCLUSIONS

The ground vibrations at a distance of 70 feet from theexplosion would be regarded as safe by several quoted authorities,but would be unsafe according to the standards adopted by the U.S.Bureau of Mines.

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Geophysical Branoh Bureau of Mineral Resources, Geology and Geophysics,

0344-66^

__

—}

Trench in hardmud stone

Position 2Recorder^Brick patio of

residence

Recorder • Position 1Concrete pavement

POSITION OF RECORDER^ FIG. I

DETAILS OF SHOT PATTERNS^

FIG. 2

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/Shot holes

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milliseconds delay

firing sequence

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8ozs of AN 60^

8 ozs of AN 60gelignite per hole^ gelignite per hole

Shot Pattern Nol^

Shot Pattern NO2

6eophysica/ Brooch, Bureau of Mineral Resources, 6eology and GeoPhysics^G344-65Th Accompany Records /950, /Vo /30

APPENDIX I.

The following are references to and extracts fromregulations and authoritative publications in the United States andGreat Britain covering or recommending safe amplitudes of vibrationsthat may be applicable to buildings:

(Note:^f = frequency in cycles per seoond.

A = peak to trough amplitude, inches).

Reference 1.

State of New Jersey, U.S.A. Extract from rules andregulations governing Quarry Blasting and Related Operations.March 26, 1954.

"6.1.^Allowable Limits.^Allowable Limits of groundmotion and sound pressure contained in this sectionshall be considered neither to produce structuraldamage in any structure that has been reasonablywell constructed according to accepted engineeringpractice nor to constitute a nuisance to persons."

"6.3.^Frequency - amplitude relations. When groundfrequency and displacement characteristics inrelation to known quantities of detonated explosivesin primary blasts have been determined by approvedmeans of instrumentation to the satisfaction of theCommissioner, the allowable limits of the maximumamplitude of ground vibrations related to frequenciesof vibration shall be as indicated in the followingtable

Frequency of ground motion^Maximum amplitude of

^

in cycles per^second.^ground movement, ininches.

^

up to 10^not more than 0.0305

^

20^ 0.0153

^

30^ 0.0102

^

40^ 0.0076

^

50^ 0.0061

^

60^ 0.0051"

Reference 2.

Rules Concerning Blasting in Strip Mine Operations in theAnthracite Region, Pennsylvania, Act No. 472, June 27, 1947.

MSection 20.

..in no case shall the ground displacement be inexcess of 0.03 inches at any dwelling house,public building, school, church, commercial orinstitutional building."

2.

Reference 3.

Teichman9 G.A..and Westwater, R.

Blasting and Associated Vibration.

Engineering, April 12, 1955, PP. 460/465.

,"Becauee of the variation in the types of structureit has been recommended that they should belroadlyclassified into four groupsg

(a) structures of great value and frailty. Thiswill include certain ancient monuments, suchas churches and certain badly designed properties.

(b) Property, houses etc. closely congested.

(c) Isolated property.

(d) Civil engineering structures.

Taking suitable safety factors and after the sitehas been investigated by a vibrograph caution limitsare applied.^These limits usually are 0.0049 0.00890.0169 0.030 inches, respectively."

Reference 4.

Crandell, working on behalf of a United States Insurancesuggests fA as a suitable relationship and quotes -

Co. ,

^

"fA^0.745 as the damaging level

^

IA^0.527 as safe level."

Reference 5.

C. Morris - Vibrations due to blasting and their effect onbuilding structures.

The Engineer, Nov. 39 1950. pp. 394/395, 414/418.

"the limiting amplitude of 8.2 x 10-3 (0.0082) inchesgives a conservative estimate of the limiting amplitudefor conventional structures. The State of repairof the building does not seriously affect this estimate,as an old building technically less strong that a newone will have benefitted by a process of "bedding in"due to long-continued small movement."

Reference 6.

^Thoenen9 F.R. and^S.L. Windes9 1942.^Seismic Effects of QuarryBlasting.

United States Bureau of Mines Bull. 442.

^

" f2 A^10^Damage

^

f2 A^x: 1^Safe"

"Vibrations of very low amplitude and short duration were neglected,even though the accelerations may have been high, because theseconditions were noticeable in the records of many tests that didnot cause damage."