03 Timing Precision ASIEX Workshop-C Cunningham

Blast Timing Precision When does it matter?

Explosive column

AQUARIUM

Claude Cunningham Blasting Investigations and Consultancy

Road Map       

Why the presentation? Blasting mechanics Timing Parameters Delay Limitations Minimum requirements Shock tube and ED characteristics Wrap-up…

October 202

Claude Cunningham: Blasting Investigations and Consultancy

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"hy the presentation# 

Involved with ED’s since 1993 

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

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Focussed on application, specs and expectations

General confusion over when and how timing precision can help Guidelines to help anticipate likely benefit of more precise timing But many good reasons to choose ED’s, other than precision

October 202


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%ey blasting results      

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Vibration amplitude and frequency Airblast amplitude and frequency Fragmentation size range Overbreak and depth of damage Movement direction and range Drilling/ Powder factor needed - cost and productivity All affected to some degree by timing…

October 202


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Blasting mechanisms governed by: 

Explosives characteristics 

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Ground reaction to detonation impulse 

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Energy, sensitivity, VoD Strength, rigidity, structure

Blast Layout   

Drilling pattern Free Faces Timing of holes…

October 202


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()plosive*Roc+ Interaction The initial ground conditions are FIXED They determine how the available energy is partitioned.

Shock phase: Plastic distension, Weakening of mass

Heave/Gas phase: Loosening of weakened mass, Expansion/ movement

Strong rock: 40 – 60% shock energy. Resists shock mechanisms

Weak rock: 60 – 90% shock energy. Absorbs shock mechanisms

• Less expansion of the hole • Greater transmission of strain waves • Greater displacement of burden.

• More expansion of the hole • Reduced transmission of strain waves • Reduced displacement of burden.

October 202


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Mechanisms in blasting        

Radial expansion/ compressive failure Transmission of strain waves Extension of microcracks weakens mass Tensile failure by reflected strain waves Tensile failure by gas expansion in cracks Displacement of burden rock Shear failure by displacement between holes Fragmentation by autogenous attrition

Hard rocks

Weak rocks

October 202


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Timing in.luence 

Ground condition and geometry determine if timing can influence hole interaction.  

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Holes too far apart cannot influence each other Fractured, weak ground limits benefits of precise timing

For holes that can influence each other, timing determines whether they interact well, badly, or not at all.  

Strong rock – strain interaction – quick timing Weak rock – gas interaction – slow timing…

October 202


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%ey needs o. timing 

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Sequencing:  holes firing in wrong sequence tend to be catastrophic to efficiency, effectiveness and safety. Interval:  given a critical interval, the physics of too-short or toolong will give sub-optimal outcome. Priority:  Timing that favours one outcome might degrade another outcome: e.g., movement vs fragmentation.

October 202


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ibration Control Weak rock, far off. Hard rock, close up Vibration Frequency vs Row Interval

100 90 80 z H y c n e u q e F g n i d n o p s e R

70 60 50 40 30 20 10 0

0

50

100

150

200

ms Interval

Frequency ~ 1000/dt

October 202


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1ragmentation * intervals Timing for Fragmentation in different rock types

Sound speed, m/s

100

Inter-row ~ 3 x Intra-row interval

90

80

70 l a v r e t n i

2000

60

3000

w o 50 r a r t n i 40 s m

4000 5000 6000

30

20

10

0 0

2

4

6

8

10

12

Burden m

October 202


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elay vs Interval: easy to con.use Blastholes

Scatter range on interval - 20% Interval 100ms 10 ms

15 ms

Delay Scatter 5% 200

90 – 110 ms

Interval determines Effect

400 TIME, ms Delay Scatter affects Interval

Delay determines Scatter

Scatter influences Effect

October 202

300

20 ms range


2

Basis o. Precision: 3ormal istribution Normal Distribution - 500 ms Shock Tube Delays, 7.5ms SD 6

477.5

485

492.5

500

507.5

515

522.5

5

4

t n e c r e P

3

34%

34%

2

1

2.1%

2.1%

13.8%

13.8%

0

7 7 9 8 1 8 3 8 5 8 7 8 9 9 1 9 3 9 5 9 7 9 9 0 1 0 3 0 5 0 7 0 9 1 1 1 3 1 5 1 7 1 9 2 1 2 3 7 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 5

Delay m s

1/20 shots fall outside 2σ Only 3/1000 shots fall outside this envelope October 202


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Real vs Modelled 4catter But we can only work with modelled stats

Actuals are not symmetrical 500ms Shock tube Delay Stats

Batches have different Means and SD’s

60%

50%

500ms Shock tube - Normal Distribution 45 40

40%

All 35 03-Feb 30 28-Feb n 25 i 06-Mar B

n o i t u b i r t s i

30%

D

03-Feb 28-Feb 6-Mar All

n i %20

20%

15

10%

10 5

0% 470

480

490

500

510

520

530

0 460

470

480

500

510

520

530

540

Delay ms (5ms bins)

5ms Delay Range

October 202

490


$

Timing 4catter 

Normal distribution  

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Range vs delay  

 

SD σ for Mean time Tm Range = + 6σ

Coefficient of Variance CoV = σ / Tm x 100%

Shock tube CoV 1.5% to 2% down hole ED CoV <0.1% (old systems only?)

October 202


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Pyrotechnic delay precision CoV, %

Standard deviation, ms

14 12

Main source of interval error

10 8 6 4 2 0 0

50

100

150

Surface delays October 202

200

250

300

350

400

450

500

Nominal delay, ms


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Ris+ o. .alling outside range: Co 5&6 and 26 Does it matter if 10% of the intervals are more than 13, or 17 ms out? Risk vs Range of Delay, SD varying 100.0

10% >17ms out e g n 10.0 a r e d i s t u o g n i l l a f f o k s i 1.0 R %

SD 7.5 SD = 10

10% >13ms out

0.1 0

October 202

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10

15

20

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Claude Cunningham: BlastingDelay Investigations ms outside Nominal and Consultancy

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35

,

4catter Ratio R 4 σ

Tm σ

= Standard deviation of timing e.g., 10 ms

6σ = Range of deviation 60 ms

Tw = Interval desired

Tw

e.g., 25 ms, < Range!

Rs = 6σ / Tw x 100% 60 / 25 = 204%

As Rs>100% control is lost  

October 202

non-sequential firing, inconsistent intervals


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(..ect o. R 4 on timing uni.ormity Mean CoV

498 0.9

497 1.8

494 1.3

AchievedInterval: Interval:120 25 ms 42 Achieved ms nominal nominal

100 100 200 50 s s s 50 m 100 m m

0 0 0 0 -500

October 202

0

20

40

60

80

100

120

140

160

20

40

60

80

100

120

140

160

20

40

RsRs 154% 91% Rs 32%

60

80

Rs Rs211% 126% Rs 44%

100

120

Rs Rs108% 64% Rs 22%

140


180 180

160

ED ED ED

180

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4o 7hat value o. R 4#   

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33% will ensure very steady breaking results. Anything more than 100% is “very irregular” In between, OK for weak ground or where focus is more on unit input cost than on quality of blast. Vibration control is most critical application: but weak ground loses frequency control anyway. Unplanned reversals = backbreak, vibration.

October 202


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"hat delays are needed#  

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Heavy, enduring debate with strong positions. ED’s have enabled delays never attainable before in production. Colliding shock waves theorists vs holistic realities doubters. Comparative trials very seldom done properly. By and large, try (a) effect of precision, (b) variation of delays. In weak rock, quick delays can work for reasons other than precision…

October 202


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Timing Precision: t7o systems Pyrotechnic

Shock tube: 500ms in-hole with pre-set sur!ce "el!#s Electronic

0 to $0000ms in-hole% in & ms pro'r!mm!ble steps

October 202


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4hoc+ Tube and (lectronic etonators 

All current ED’s are zero-based systems   

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Different delay for each det Increasing scatter with time Lag not an issue.

All opencast Shock tube systems are relaybased systems   

Same delay for down-hole dets Scatter constant Lag issues.

October 202


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( precision  

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Dependent on capacitor power and time Typically two influences  Fusehead jitter – constant ~ 0.1-2 ms SD  Delay circuit jitter – depends on delay <0.1%  For 1000 ms delay, SD ~ 1 ms, range ~ 6 ms.  Can be big if delay is say 10 000 ms. In general far better than shock tube  ST Range ~ 35 ms for 500 ms delay.  ED Range ~ 3 ms for 500 ms delay. But for very long delay, ED intervals can be worse than shock tube. And doubtful for inter/intra-millisecond apps.

October 202


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3ormal distribution timing curves Normal Distribution of 500ms Delay Detonators and Low Precision ED's

40 35

S/T SD, ms 7.5 ED1 SD, ms 1.1

30 25 y t i l i b a b o r P

20 15 10 5 0

470

480

490

500

510

520

530

Time ms

October 202


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8imits o. Precision Total Delay Range from ED and Shock Tube Systems 70 60 ) 50 s ' D S 6 ( 40 s m e 30 g n a R

Total ED ED circuit 0.10% SD ED fusehead 1 ms SD Shock tube 1.5% SD

20 10 0 0

1000

October 202

2000

3000

4000

5000

6000

7000

8000

9000


10000

2'

(..ect o. delay on Precision Effect of Delay on ED Precision. 40 35

As delay increases 30

Precision decreases

25

y t i l i b a 20 b o r P

15 10 5 0 0

1000

2000

3000

4000

5000

Delay ms October 202


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4ummary 

Weak and highly jointed rock masses dissipate shock energy. 

Less need for precision

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Strong, intact rock masses benefit from precision

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All rock masses are variable 

Extreme caution in modeling vibration, fragmentation

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Vital to test out effect of precision before changing delays

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Scatter ratio is key to grasping timing issues

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Timing precision is not the only criterion in choosing between ED’s and shock tube.

October 202


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The end 

Questions?

October 202


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03 Timing Precision ASIEX Workshop-C Cunningham

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