Study on Estimation of Re-entry Time After Blasting in Underground Mining PT Cibaliung Sumberdaya, Indonesia. As presented in Dec 4th, 2013 in CINEST International Symposium on Earth Science and Technology, Kyushu University, Fukuoka, Japan. Author: Sandro Hanaehan Sirait Nuhindro Priagung Widodo Mikha Simanjuntak

1. Sandro Hanaehan Sirait1, Nuhindro Priagung
Widodo1, Mikha Simanjuntak2
1Mining Engineering Department,
Institut Teknologi Bandung
2PT Cibaliung Sumberdaya
INDONESIA
International Symposium on Earth Science and
Technology (CINEST)
Kyushu University, Fukuoka, JAPAN 2013

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3. PREFACE
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4. Preface
1. Blasting in underground mine produces gas
that may harm worker’s health
2. Gas produced: CO, NOx, NO2, NH4
3. Time needed to dilute the gas until certain
level safe for worker are called
re-entry time
4. Mine ventilation system have significant role
in determining re-entry time
5. The issue: if the re-entry time is too short,
worker’s health would be endangered. If the
re-entry time is too long, it would reduce
mine productivity
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5. Locations
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6. Field experiment –
PT Cibaliung Sumberdaya (CSD)
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7. PT Cibaliung Sumberdaya
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8. BASIC THEORY
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9. Basic theory
Air in underground mine is flowing correspond to
advection-diffusion phenomena expressed in equation:
𝐶 𝑥, 𝑡 =
𝑉
2𝐴 𝜋𝐸𝑡
exp
−(𝑥 − 𝑢𝑡)2
4𝐸𝑡
• C (x,t) = concentration at position x and time t (cc)
• V = total substance in its original state (m3)
• A = cross-sectional area of the flow (m2)
• ū= average velocity (m/s)
• E = effective diffusion coefficient (m2/s) 9
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10. Basic theory – advection diffusion
concept
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11. FIELD EXPERIMENT
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12. Field Experiment - Flowchart
Record
CO gas
data from
blasting
CO gas
concentration
vs Time Curve
Matching Curve between
measurement data vs Advection
Diffusion Equation
Match
the
curve?
Yes
Estimate Re-
entry time using
E value
No
Change variable:
CO Volume, E,
and ū
START
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13. Field Experiment - Methodology
• Gas detector turned on and placed before blasting takes place, ie
when marking, drilling, or charging activity.
• Then, author must wait smoke clearing process in Lunchroom for
safety consideration
• After 30 minutes or the blasting smoke is cleared away, author
retrieve the instrument
• Import the measurements data to Microsoft Excel
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14. Field Experiment - Instrument
Gas Detector
• Using Riken Keiki GX-2003
• Import the data with
Software Data Logger
• Data Interval 10 seconds
• Data accuration 1ppm
• CO gas maximum value=
500ppm
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15. Field Experiment
• Gas detector is placed in a safe location from flyrock
and also from water seeping the walls
• Gas detector is hung on wiremesh or longstrap so that
it couldn’t easily fall
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16. PT CSD Ventilation Summary
• Using exhaust ventilation system
• Intake through Cikoneng portal
• Exhaust through :
• Cikoneng Shaft (Main fan 132kW)
• Cibitung Shaft (Main fan 132kW)
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PortalCikoneng
CikonengShaft CibitungShaft
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17. PT CSD Underground Mine Map
Data are taken at PT CSD in June 2013
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18. RESULTS AND
DISCUSSIONS
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19. PT CSD Simplified Mine Ventilation
Scheme
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20. CO Gas
Measurement
Scheme
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21. CO gas results – matching curve
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0
100
200
300
400
500
600
700
0 5 10 15 20
CO(ppm)
Time (minute)
50 meter 115 meter 165 meter
[1101 CBT-1]
CO Volume= 1,300,000 cc
ū=0.37 m/s; L/d= 11.2
E=7 m2/s
[1101 CBT-2]
CO Volume= 180,000 cc
ū=0.39 m/s; L/d= 25.7
E=10 m2/s
[1101 CBT-3]
CO Volume= 764,000 cc
ū=0.55 m/s; L/d= 36.8
E=15 m2/s
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22. Number of explosives by the
amount of CO gas graph
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0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 20 40 60 80 100
CO(l)
Explosives (kg)
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23. Summary
of
effective
diffusion
coefficient
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No
CO
Measurement
Station
ū
(m/s)
E
(m2/s)
Re L/d
1 1135 CKN-1 0.16 10.0 43983 11.2
2 1135 CKN-2 0.24 13.0 68954 22.3
3 1135 CKN-3 0.23 13.0 65265 73.7
4 1135 CKN-4 0.23 3.5 65265 90.4
5 1065 CKN-1 0.17 3.0 48239 6.7
6 1065 CKN-2 0.14 5.5 39726 12.3
7 1065 CKN-3 0.22 8.0 62427 22.3
8 1120 CKN-1 0.19 1.0 52496 4.5
9 1120 CKN-2 0.28 3.0 79453 63.6
10 1061 CBT-1 0.24 5.2 68102 13.4
11 1061 CBT-2 0.18 10.0 51077 39.1
12 1061 CBT-3 0.24 11.0 68102 49.1
13 1101 CBT-1 0.37 7.0 104991 11.2
14 1101 CBT-2 0.39 10.00 110666 25.7
15 1101 CBT-3 0.55 15.0 156068 36.8
16 DEC CBT-1 0.23 10.00 65265 8.9
17 DEC CBT-2 0.30 25.00 85128 17.9
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24. Graph E to L / d
L/d is length with
hydraulic diameter ratio
L/d can be a parameter
to estimate the E value
For health and safety
considerations, the
equation as reference
become
E* = 0.1595 (L/d) + 5.
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E = 0.1595 (L/d)
E* = 0.1595 (L/d) + 5
0
5
10
15
20
1 10 100
E(m2/s)
L/d
E vs L/d E E*
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25. Re-entry time estimation
• Using E*, E values are obtained 22.09 at Cikoneng
and 23.16 at Cibitung,
• Value of Cikoneng average speed is 0.21 m/s and
Cibitung 0.31 m/s
• Largest amount of CO gas 3,550,000 cc
• Using advection diffusion equations to estimate
the re-entry time in each area to reach the safety
limit (using 25 ppm to get Safety Factor=2) of CO
gas.
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26. Re-entry time estimation
• Cibitung needs 72 minutes and Cikoneng needs
118 minutes
270
50
100
150
200
250
300
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180
CO(ppm)
Time (Minute)
Cikoneng Cibitung
Vol CO= 3.550.000 cc
L/d= 107.1; ū=0.21 m/s
E= 22.09;
Time= 118 minutes
Vol CO= 3.550.000 cc
L/d= 113.8; ū=0.31 m/s
E= 23.16;
Time= 72 minutes
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27. CONCLUSION
REMARKS
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28. Conclusion Remarks
1. Measured CO gas curve is needed to evaluate gas
transportation in underground mine
2. In this study authors only consider CO gas and ignore the
presence of other gas that may be harmful to worker’s
health
3. In this study authors evaluate E to estimate re-entry time,
further research about this topic is still needed
4. Recommendation for advance study about this topic are to
conduct further experiments with numerical method to take
into account airways variation and consider several curves
representing variation of effective coefficient diffusion in
each lane.
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29. THANK YOU!
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ARIGATOU
GOZAIMASU!
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