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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
17
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
18
Peak Particle Velocity (PPV):
Minimum: 1.5 mm/s
Maximum: 6 mm/s
Air Blast:
Minimum: 115 dB(L)
Maximum: 126 dB(L)
19
GUIDANCE LEVEL
Guidance Levels (1989, modified in 1991)
20
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
21
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
23
Buildings at Mine site and
Crack Monitoring
Building Types in the Ghanaian
Mining Areas
24
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
26
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
28
Crack on a Wattle and daub Building
29
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
30
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
31
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
34
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