UNIVERSITY OF MINES AND TECHNOLOGY, TARKWA UMaT

BLASTING STANDARDS The Experience in Developing Countries

by

Prof. Newton Amegbey

Layout of Presentation

Introduction Scope of Study Modus Operandi and Data Analysis Brief theoretical background to Blast Vibration and

Airblast control

Blast Vibration and Airblast Levels Data from Mines Guidance levels Buildings at Mine site and Crack Monitoring Summary of Data

Safe Blast Design Recommendations

2

Introduction

Most developing countries have notestablished blasting standards for the local

conditions.

The practice for some years in Ghana forexample is that mining companies adopted

blasting standards used in their countries of

origin

The question is how successful have theseadopted standards been?

3

Introduction cont.

Ghanaian experience has it that thoughstandards are met, inhabitants of

neighbouring communities complain of

cracked structures from blasting

activities

Regulatory authorities commissioned ateam to look into this matter and this

presentation is an excerpt from the

study

4

Acknowledgements

5

EU Funding Minerals Commission

Chamber of Mines

University of Mines and Technology, Tarkwa

MAXAM company

Scope of the Assignment -TOR

6

To categorize the different kinds ofbuildings and other structures in Ghana

with particular reference to mining areas;

To determine the acceptable thresholdlevels of air blast and seismic vibrations;

and

To make appropriate recommendations forbest practice blasting operations in the

mining industry.

Modus Operandi

7

Desk study

Collected existing blast monitoring data, as wellas the operating standards used at various mine

sites

Blast monitoring data collected included: PPV levels and Air Blast levels (3 to 6yrs)

Distances from blasts to monitoring positions

Corporating charges or charge per delay

Meteorological conditions at the time of blast

Cracks in selected buildings were monitoredtogether with PPV levels

Data Analysis

8

Determine ranges, means and standarddeviations of PPV and airblast data;

Prevailing international standards weresubjected to various correction factors in order

to localise them;

Determine rock transmission factors (RTF) forvarious mining areas; and

Measured PPV and crack monitoring data wereused to establish levels at which no extension of

cracks beyond acceptable limits is expected for

common buildings at mine sites.

9Brief theoretical background

Blast Vibration Levels

10

Blast vibration waves travel through nonhomogeneous media

Empirical relationships are thereforepreferred

Empirical relationships used are based onthe fact that vibration level:

V W (Amount of explosives)

V 1/D (Distance from target structure), thus

V = k Wa /Db is a general equation, where k, a and b areconstants, and V is the peak particle velocity (PPV)

BLAST VIBRATION EQUATIONS

11

US Bureau of Mines (USBM): V=k(D/W )b

Ambraseys-Hendron (AMHEN): V=k(D/W1/3)-b

Gustaffsson: V=k(W/D1.5)

Langefors & Kihlstrom (LANKH): V=k(W/D3/2)b

Indian Standard (IS): V=k(W/D2/3)b

Ghosh-Daemen -

Modified USBM (GHDN1): V=k(D/W)be-D

Modified AMHEN (GHDN2): V= k(D/W1/3)-be-D

General equ. (GEN): V=kDa/Wb

Blast vibration equation suitable for

Ghana?

12

US Bureau of Mines: V=k(D/W )b

Gustaffsson: V=k(W/D1.5)

Ambraseys-Hendron: V=k(D/W)1/3

AIRBLAST

13

Airblast and noise levels arecontrolled when PPV levels are

within acceptable limits

Overcast conditions can increaseairblast and noise levels, hence

should be avoided

14

Vibration and Airblast levels

PPV and Air Blast Data Collected

15

Parameter Peak Particle Velocity (PPV) (mm/s)

Air Blast Level (dBL)

No. of Samples 8494 8560

Maximum 25.08 145.1

Minimum 0.002 12

Mean 0.76 104.93

Standard Deviation 1.06 11.70

Mean +Standard Deviation 1.82 116.63

Threshold PPV Levels for various

Countries

16

New Zealand- 5mm/s

Australia EPA - 5mm/s on 95% of occasion, not exceeding 10mm/s

ANZEC - 5mm/s on 95% of occasion

Hong Kong - 25mm/s for residential property

Germany 25mm/s

Swedish up to 100mm/s

Threshold PPV Levels by various Authorities

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Authority Threshold Level

U. S. Bureau of Mines (1971): 50 (12) mm/s

Edwards and Northward (1959): 50 mm/sCANNOT, Banner and Calder (1977): 50 mm/s

Dvorak: 10 - 30 mm/s

Swedish Standard SS 460 49 66 (1991):

70 mm/s (Granite, Gneiss, quartzite, etc.)

35 mm/s (Firm morain, shale stone, etc)

18 mm/s (Loose sand, gravels, clay, etc.)

Germany DIN 4150 (1975):

30 mm/s (Stable buildings)

8 mm/s (Residential Buildings)

4 mm/s (Historical monuments)

Rule of thump: 25 mm/s (1inch/sec)

PPV and Air Blast Thresholds adopted by

various Ghanaian Mines

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Peak Particle Velocity (PPV):

Minimum: 1.5 mm/s

Maximum: 6 mm/s

Air Blast:

Minimum: 115 dB(L)

Maximum: 126 dB(L)

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GUIDANCE LEVEL

Guidance Levels (1989, modified in 1991)

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Guidance level concept is used for establishingpermitted vibration levels or threshold valuesfor various types of blasting operations

Guidance levels are based on well-documentedcorrelation between PPV and induced damageto buildings founded on various types ofgeological formations

Guidance level (V) is given by: V=VoFkFdFt

Where, Vo = Uncorrected PPV

Fk = Construction quality factor, and Fk = FbxFm ,

Fb = Building factor, Fm = Construction material factor

Fd = Distance factor, and for distances over 350m, Fd = 0.22 forrock, 0.35 for morain and 0.50 for clay

Ft = Project time factor, (0.75-1.0) Ft = 1 for projects up to 1yr,and 0.75 for projects over 5yrs

Construction Quality Factor - FkFk=FbxFm

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Building Factor Fb

Type of building or construction FbHeavy Construction (Bridges, harbours etc.) 1.70Industrial and office buildings 1.20Standard living houses 1.00Sensitive buildings (museums etc.) 0.65Historical buildings in damaged conditions 0.50

Construction Material Factor Fm

Type of construction material FmReinforced concrete, steel or wood 1.20Not-reinforced concrete, brick or clinker 1.00Autoclave porous concrete 0.75Mexi-brick (artificial limestone brick) 0.65

PPV levels of some Countries and the

Ghanaian Equivalent

22

Authority PPV Standard

(mm/s)

Localised PPV

(mm/s)

USBM 12 2

Australia 10 1.6

Germany(Res.) 8 1.3

Hong Kong/RoT 25 4

Range of localised (Ghanaian) values: 1.3 to 4 mm/s

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Buildings at Mine site and

Crack Monitoring

Building Types in the Ghanaian

Mining Areas

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1. Buildings from raw earth

without treatment or additives:

Wattle and daub

Atakpame

Sun dried bricks or blocks

Building Types in the Ghanaian Mining

Areas cont.

25

2. Buildings from earth material

stabilized by compression or

compaction to increase density and

strength:

Compressed brick or block buildings

Landcrete block buildings

Sandcrete block buildings

Crack Monitoring

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Crack monitoring together with PPVand air blast monitoring were

undertaken at selected mine sites in

order to determine the actual impact

of blasting on structures

Four mining companies were selectedbased on their preparedness to host

the exercise

Crack Monitoring

Underlining Concepts

27

Cracks in buildings result from variouscauses

Blasting should be designed such that in theleast, whatever the initiating cause, they

do not extend existing cracks beyond

acceptable limits

Weakest buildings in the community are tobe the target Wattle and daub orAtakpame structures

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Crack on a Wattle and daub Building

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Monitoring of Crack , PPV and Airblast:

Measure with aprecision electronicvernier before andafter each blast, thedistance between twotiny pegs fixed acrossthe crack

Crack Monitoring Results -Summary

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y = -232.0x2 + 39.26x + 0.816R = 0.515

0

0.5

1

1.5

2

2.5

3

3.5

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

PP

V (m

m/s

)

Crack Extension (mm)

Zero Crack

Extension: 0.8mm/s

Max./Failure

PPV: 2.5mm/s

Yield PPV:1.6mm/s

Details

Summary of Data

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Item PPV mm/s Airblast dB(L)

Data from Mines 1.82 117

Adopted Standards in Use 1.5 6 115-126

Guidance Level Standards 1.3 - 4 -

Zero Crack Extension 0.8

Maximum/Failure PPV 2.5

Yield PPV 1.6

Recommended Ghanaian Standards: PPV: 2.0mm/s Airblast: 117dB(L)

32

Proposal for Safe Blast Design

Rock Transmission Factors (RTF)

33

For various mining areas across the

country RTF was determined based

on:

Gustaffson equation (K) and

USBM equation (k and b)

Rock Transmission Factors (RTF) for Various

Mine Sites

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Mine

*K values

**k **bMax. Min. Standard Deviation

Mean

Newmont 56.56 4.00 6.01 17.77 1.04 -0.0002

Chirano 36.04 7.96 6.95 19.29 1.57 -0.0174

Ghacem 42.20 42.20 N/A 42.20 N/A N/A

Golden Stars ResourcesWassa

N/A N/A N/A N/A N/A N/A

Golden Stars ResourcesBogoso

97.82 1.49 7.27 12.42 1.52 -0.00001

Golden Stars ResourcesPrestea

48.86 9.48 9.61 21.46 0.02 1.29

GoldfieldsTarkwa 135.69 6.70 15.34 29.79 3.58 -0.00009

Goldfields-Aboso 40.57 7.78 6.62 20.93 1.07 0.0042

Ghana Manganese Company

N/A N/A N/A N/A N/A N/A

AngloGold Ashanti Iduapriem

77.44 1.40 10.08 19.23 1.71 -0.08

*Gustaffssons K **USBM k and b

Recommendations

35

1. The standard for Peak Particle Velocity is

2mm/s and the standard for Airblast is

117dB(L)

2. More data on crack monitoring is required to

validate the proposed standards

3. The standards were based on wattle and daub

structures. Further studies to include

atakpame, sun dried bricks or blocks, thencompressed bricks or blocks, landcrete blocks

and sandcrete blocks is recommended

Recommendations - cont

36

4. Rock transmission factors (RTF) - Kvalues as well as the k and b valuesdetermined for various mines may be

used to design blasts to meet required

standards

5. More data required to validate the K aswell as the k and b values obtained

6. There was the need to include quarries in

further studies

37

Thanks for your attention

I am out of here