Blasting Environmental & Health

8/19/2019 Blasting Environmental & Health

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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


2/41

So what went wrong?

! "#

Environmental and Health

! "

$

%&

' %


3/41

Ground Vibrations

'

(

( )

% ) *

) $ )

+ ,

-. /!

)

) $-*

0)1 (

( "

Vibrations…

Intranet.mpg


4/41

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


5/41

Vibration Frequencies

!"

# $"

Ground motion depends on…

5 . .

/ .

5 6

-

' 4

7

5

5

5 &


6/41

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)


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


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


9/41

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)


10/41

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)



11/41

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)


12/41

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.



13/41

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.


Permanent monitoring station (PPL)


14/41


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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


16/41

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


17/41

Complaints

?

05 1

05 < 1

07 @ < 1

07 & 7 1

+ A

1000

OSM (US)


m / s )

Human Perception

10

100

USBM RI 8507 “Near”

Intolerable


1

1 10 100 1000

Disturbing

Perceptible M a x i m u m A l

l



18/41

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


19/41

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


20/412

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


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


M a x i m u m A l

l

German criteria based on “HumanPerception”


22/412

Example - NG Decontamination- Site Characteristics

"# Esterpark

Edenvale

Lakeside

Thornhill


23/412

NG Decontamination - Method

Old production area

Drain

6 to 9 kg Magnum Buster in plastic pipeabove drain position

Typical monitoring trace


24/412

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


25/41


26/412

Minimising Vibrations

2

,

$

(3

2

7

Airblast and Flyrock

'

( $

%&


27/412

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

! &<


28/412

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


29/412

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


30/413

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


31/413

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 &

-

-

,


34/413

Flyrock

Flyrock

E.wmv

(a) Excessive

Poorheave

.

(b) Goodbreakage anddisplacement

a r as anflyrock

(c) PoorfragmentationD1.wmv


35/413

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


36/413

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


37/413

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


38/413

Blasting Fumes


39/413

Blasting Fumes

! '

>& . . >HHH

% -.

% += -.

( + += $ %

Gases Produced by Blasting

% # & '((

)" ) * +,-

-. * +,-/ -

0 1 * 2 +,-

$-. 3 * 4-

65

6 3 /

, 4 4-/


40/414

Toxic Gases

/ 2.

+

% < <

. /2G < @

(.

7

7 .

(.

Oxygen Positive/Negative

2.

5 . 8$/; .

5 2. /2. /G

2. /

7

(. .

+#7 ".

-

1 7, " ##.


41/41

$% &

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Documents

Blasting Environmental & Health