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Blasting Competency ProgramB6. Environmental & HealthMay 2010
Monitoring at mine
indicates no
potential for claim
of blast damage
“Expert” assistsmine to blast again
& collects Fee
“ ”causingdamage
mining operation
& collects Fee
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So what went wrong?
! "#
Environmental and Health
! "
$
%&
' %
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Ground Vibrations
'
(
( )
% ) *
) $ )
+ ,
-. /!
)
) $-*
0)1 (
( "
Vibrations…
Intranet.mpg
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Vibrations
2 3 4
$
- 3
Surface
Inversion layerClouds
Airblast
Blast Site
Direct Waves
Reflected Waves
s ruc ure
Blasting Vibrations
Refracted Waves
Geology / Water Table
Change in rock properties
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Vibration Frequencies
!"
# $"
Ground motion depends on…
5 . .
/ .
5 6
-
' 4
7
5
5
5 &
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Summary of legal requirements
5
7 0-. 1
$-* )'(
Ground vibration damage summary
- USBMBased on observations to structures, coal mining environment RI 8507 (Siskind, 2000)
1000
m / s ) OSM (US)
USBM RI 8507 “Far”
10
100
w a b l e P a r t i c l e V e l o c i t y ( USBM RI 8507 “Near”
Cosmetic or threshold damage - theformation of hairline cracks or the growth ofexisting cracks in plaster, drywall surfaces or
mortar joints.
Threshold
Major
Minor Threshold damage
Minor damage
Major damage
1
10 100 1000
M a x i m u m A l
l
Blast Vibration Frequency (Hz)
Major or structural damage - damage tostructural elements of a building.
Minor damage - the formation of largecracks or loosening and falling of plaster on
drywall surfaces, or cracks throughbricks/concrete blocks.
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Damage control – USBM
Safe level blasting criteria from USBM RI 8507 and OSM derivative version (After Siskind, 2000)
1000
m / s ) OSM (US)
USBM RI 8507 “Far”
Lower frequencies
100
w a b l e P a r t i c l e V e l o c i t y (
“Far” – Drywall, gypsum board interiors
“Near” –Plaster finish, ‘Wattle’
USBM RI 8507 “Near”
means owervibration limits
1
10 100 1000
M a x i m
u m A
l l
Blast Vibration Frequency (Hz)
South African Guidelines (>50Hz)
Recommended Maximum Level
Heavily reinforced concrete structures 120
Property owned by the concern performingblasting operations where minor plastercracks are acceptable.
84
Commercial property in reasonable repairwhere public concern is not an importantconsideration.
25
Private property if public concern is to betaken into account or if blasting is conductedon a regular and frequent basis
10
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Suggested AEL controls for charge/delay when blasting adjacent to privateProperty – Quarries (PPV
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1. Sensor stands on level surface
Suitable on non-slip surfaces and where low vibration levels are
expected. (< 5 mm/s)
Sensor must always be orientated to the direction of the blast
Geophones
"
*
(
,4 4 8$;
"< += 5
* 0%1
“Flat” wave form(s)
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Sensor type- Accelerometer
=
-.
! 4
, > +=
/ 4
(
/
/
.. A kind of inverted pendulum
2. Attached to a spike that is driven into
soft soils
Sensor block
Pushed into soil
Fixing spikes
Poor coupling
Ground motion
This method is only suitable in “sticky, tight” soils and where low vibration
levels are expected. (+/- 5 to 12 mm/s)
Sensor must always be orientated to the direction of the blast
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2. a) Sand bagging
Large sand bag may assist where highervibration levels are expected. (< 15 mm/s)
,+20kg of fine material.
2. b) Burial
3x sensor height
Burial, excavation must be at least to a depth3x height of sensor and/or below the level
normally cultivated.
Spike sensor to bottom of holeand pack soil around and over sensor.
(+/- 15 to 20 mm/s)
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3. Bolting or gluing to the surface…
3. Bolting or gluing to the surface
Quick setting resin
Plate
Wing nuts and bar tosecure seismograph
Exposed, unfractured rock surface
Used for high PPVs on solid, unfractured surfaces.
Sensor must always be orientated to the direction of the blast
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4. Attached to a concrete block
Tri-axial detector
0.2 m
Soil surface Soil backfill
placed here
Cement cubeof side 0.2 m
array, Geophone etc
0.4 m
Used for high PPVs in soft or compacted soils.
Sensor must always be orientated to the direction of the blast
Permanent monitoring station (PPL)
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Mounting of Sensors
4Resonant Mount
V el o ci t y ( mm / s )
0
1
2
3
Non-Resonant mount
Actual
Not bondedadequately
PPV = 2.45 mm/s
0 400 800 1200 1600
Time (ms)
-1
-2
= .
Decoupled Geophone
5
10USBM R18507 and OSMRE
Scattered frequency plot
0.1
Irregular waveforms100502010521
Frequency (Hz) Tran Vert Long
0.05
0.2
0.5
V e l o c i t y ( i n / s
1
2
Trans
Vert
Long
0.0 1.0 2.0 3.0
.
0.0
0.0
0.0
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Kicked Geophone
Short, irregular wave forms
( i n / s )
1
2
5
10USBM R18507 and OSMRE
Scattered frequency plot
0.1
100502010521
Frequency (Hz) Tran Vert Long
0.05
0.2
0.5
V e l o c i t y
0.0 0.2
Factors in defining Safe Limits
5
5
5 4
5
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Complaints
?
05 1
05 < 1
07 @ < 1
07 & 7 1
+ A
1000
OSM (US)
USBM RI 8507 “Far”
m / s )
Human Perception
10
100
USBM RI 8507 “Near”
Intolerable
w a b l e P a r t i c l e V e l o c i t y (
1
1 10 100 1000
Disturbing
Perceptible M a x i m u m A l
l
Blast Vibration Frequency (Hz)
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Complaints
?
05 1
0( < &1
05 &1
0$ &1
' ,A
Building Response (Medearis 1976)
Localised excitation:
• Slamming doors
0.3
• Bumping walls
• Rattling windows
0.1
0.2
R e l a t i v e O c c u r r e n c e
Localised excitation
Field Study
Natural Frequency (Hz)
0 5 10 15
0
20
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Response of Structures to everydayactivities After Stagg (1984)
!
8; 8;
85B +;
>CDE6:
>FGEFH
EHFHIJFH
+
& DF> HFHE HF6
+ >JFH HFHE HF6
K EIFE HFG6 IF>
C6F6 HF:H >GFI
66FI HF66 GGFC
Grain Silo
3
2
18 tubes
3
Tri-axial100m
15m
1
2
Accelerometers
Void / Free FaceSpoil piles
BLASTVoid
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Building Response…
28.773Transverse velocity 100 m from structure
0.00 0.82 1.64 2.46 3.28 4.10 4.92 5.74 6.56 7.38 8.20-22.572
18.355Transverse velocity in ground near structure
0.00 0.82 1.64 2.46 3.28 4.10 4.92 5.74 6.56 7.38 8.20-19.596
0.00 0.82 1.64 2.46 3.28 4.10 4.92 5.74 6.56 7.38 8.20-10.914
10.914
Transverse velocity in structure
Building Response
0.354Fast Fourier analysis in ground, Transverse
1.28Fast Fourier analysis in structure, Transverse
0.122 5.683 11.244 16.805 22.366 27.927 33.488 39.049 44.610 50.171
0.236
0.118
0.00
0.122 5.683 11.244 16.805 22.366 27.927 33.488 39.049 44.610 50.171
0.64
0.96
0.32
0.00
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Goodbye silo’s
Comparison of different frequency based velocity
displacement control limits(From Dowding 1996)
1000
m / s )
OSM (US)
DIN (FRG)
100
w a b l e P a r t i c l e V e l o c i t y (
O
R
Based on “Damage”criteria
Special control - Dowding
Close-in Office
General urban
E
U
Office/Factory
Residence
O
R
U
E
1
1 10 100 1000
Blast Vibration Frequency (Hz)
M a x i m u m A l
l
German criteria based on “HumanPerception”
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Example - NG Decontamination- Site Characteristics
"# Esterpark
Edenvale
Lakeside
Thornhill
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NG Decontamination - Method
Old production area
Drain
6 to 9 kg Magnum Buster in plastic pipeabove drain position
Typical monitoring trace
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100
Site characteristics (a & b)
a – intercept with y axis
0.1
1
10
10 100 1000 P P V
b – gradient of the line
0.01
Scaled distance (m/kg1/2)
Background
b
E
Da=PPV
Data points
Typical trace - Frequency
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Minimising Vibrations
2
,
$
(3
2
7
Airblast and Flyrock
'
( $
%&
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NOISESudden, unwanted, irritating and/or disturbing sound
Definitions
AIRBLAST Includes noise but also those frequencies
which cannot be heard by the human ear
– Human ear, frequency 20 to 20 000 Hz
– Inaudible below 20 Hz
… but which can often be felt
Complaints
. F
$
F
! &<
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Basic Principles
GH += GH &+=
L GH +=
* 4
( '
* F 8+ $ B ;
Effects of weighted filtering on airblast records
(Siskind and Summers, 1974)
80
90
100
110
120
Linear
e ( d B )
010
-10-20-30
L
a) Weighed scales, Airblast vs. Hearing
c ) F o ur i er f r e q u en c y s p e
70
A m p l i t u
-40-50-60
-701 10 100 1000
Frequency (Hz)
Linear
C-weighting
80
90
100
110
120
S o u n d l e v e l ( d B )
70
b) Time histories
c t r a
200 400
Frequency (Hz)
600 800
70
80
90
100
110
120
C-weighting
A-weighting
A-weighting
Time (ms)
10
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Guidelines
• 100 db (0.002 kPa) - Barely noticeable
• -. -
• 128 db (0.050 kPa)
• 134 db (0.100 kPa)
• Rattling of loose windows/Doors/Ceiling panels
• Currently accepted by South African authorities as being areasonable level for public concern. (No more than 10% ofmeasurements should exceed this value.)
• Currently accepted by South African authorities that damage will not
• 170 db (6.3 kPa)
• Will break a well mounted window
.outside of the mining boundaries.)
• Good Highveld thunderstorm
• Poorly mounted pictures, rattling of objects onshelves/display units, potential for these to fall
Airblast sensor
0.3 to 1.0 m
If practical microphone should not be shielded from blast by buildings,
vehicles etc. If not possible, the horizontal distance of the microphone from
such object should be greater than the height of such object
Sensors must always be orientated to the direction of the blast
Near to geophone, with wind screen/sock/foam attached.0.3 to 1.0 m from ground level
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Measurement of Airblast
Mounding
2. Rock pressure pulse (RPP)
SourcesVideo 04 Video 05
Face Motion
Blast hole
1. Air pressure pulse (APP)
Ejection Profile
4. Stemming releasepulse (SRP)
Gas Profile
Blast hole
Video 07
rac ure one
3. Gas release pulse (GRP)
Blast holeVideo 06
Blast hole
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Stemming release pulse – “Flyrock”
SRPSRP
Mounding
2. Rock pressure pulse (RPP)
Sources
Face Motion
Blast hole
1. Air pressure pulse (APP)
Ejection Profile
4. Stemming releasepulse (SRP)
Gas Profile
Blast hole
rac ure one
3. Gas release pulse (GRP)
Blast hole
5. Initiating Systems, eg Detonating CordVideo 08 Video 09
Blast hole
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Weather effects - Normal
Low Airblast High Airblast
Source
Weather – Atmospheric conditions
Clouds
Low Airblast
Inversion layer
High Airblast
Source
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Topography or Surface layout(Increase Airblast by +5 db)
Quarry
Controls
M E
< < F
$ ' 8L GHHH ;
N :HO
N >H &
-
-
,
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Flyrock
Flyrock
E.wmv
(a) Excessive
Poorheave
.
(b) Goodbreakage anddisplacement
a r as anflyrock
(c) PoorfragmentationD1.wmv
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Flyrock
Flyrock
)%
$ &
$ = =
,& B
> >H
Equation 3 Flyrock hazard zone
( ) 670.dk35 = L
Where: Description Units
L Distance from blast Metres (m)
d Hole diameter Millimetres (mm)
k Powder factor kg/m3
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Flyrock, whilst there is always a potential for theunexpected!!!
Direction of movement
2L
Risk Zone
Blast Free face
Plan view, not to scale
Flyrock
* 8>DI:;
%& .
% 5
* – 5 8;
– + 8;
– 5 & 8;
> >H HHH HHH 8)& P;
%
= . F
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Flyrock
500
1000
T h r o w
d i s t a n c e ,
L ( m )
50
100
25051 127762513853 Hole diameter, d (mm)
Throw rock diameter, o (m)
0.001 0.01 0.1 1 1010
Flyrock, whilst there is always a potential for the
unexpected!!!
Direction of movement
2L
Blast
Risk Zone
Plan view, not to scale
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Blasting Fumes
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Blasting Fumes
! '
>& . . >HHH
% -.
% += -.
( + += $ %
Gases Produced by Blasting
% # & '((
)" ) * +,-
-. * +,-/ -
0 1 * 2 +,-
$-. 3 * 4-
65
6 3 /
, 4 4-/
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Toxic Gases
/ 2.
+
% < <
. /2G < @
(.
7
7 .
(.
Oxygen Positive/Negative
2.
5 . 8$/; .
5 2. /2. /G
2. /
7
(. .
+#7 ".
-
1 7, " ##.
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$% &
5&
Recommended