Integration of blasting and communition processes

Integration of Blasting and Comminution Processes to
maximize productivity and minimize costs at Sabi Gold Mine
By
Kundai Murwira (R165645F)
Supervisor: Mr. Ndhlovu
2021
HMINE 523

 Sabi Gold Mine is a 100% owned subsidiary of
the Zimbabwe Mining Development
Corporation (ZMDC).
 It is located in the Mberengwa Greenstone
Belt that is 16 km from Zvishavane town.
 Sabi land spans 579 hectares north-east of
Sabi River.
Mine background

The mining department has been experiencing poor blast results
typified by oversized fragments (>250mm) from 8 level to 10 level
development and undersized fragments (<40mm) in 5 level production
stope. These oversized fragments are causing increased equipment
breakdowns as cocopans are seen toppling over due to impact of the big
rocks at draw points. They affect air loader and shovel productivity as
they lower the bucket and shovel fill factor through creating voids
resulting in underutilization of space. Increased secondary blasts at the
grizzle and boxes that damages, increase downtime and waste
explosives. They are also affecting the comminution steps as more
energy is used by crushers and the throughput gets lower due to
blockages and breakdowns.
Problem statement

On the other hand undersized fragments are a sign
of usage of excessive explosives and many
unnecessarily drilled holes for the rock type. It is
therefore important to optimize the blasting process
at the mine for it can reduce downtime, reduce costs
and increase production thereby maximizing profits.
Cont’d

Literature reviewed so far on the integration process is for other
mines that have different mineralogy to that of Sabi Gold Mine
which shows a gap in the study. This study largely benefits the
mine for it shows that higher production, minimized costs per
tonne treated and reduced downtime leading to greater profits
can be achieved through integrating blasting and mineral
processing . The study also add literature to the academic world
that can be used as reference for research purposes.
Significance of the study

 Integrating blasting and comminution by
fragmentation optimization to maximize
throughput, decrease total cost per tonne, and
reduce energy usage, thereby maximizing
profits at the Sabi Gold Mine.
Project aim

 To distinguish ore sources into rock structure and
strength domains that has identical fragmentation
properties.
 To investigate the possible causes of poor blast
results in these ore domains.
 To come up with methods to improve the blast
results.
 To implement the methods and assess the effect of
new fragments on downstream processes mentioned
in the problem statement.
Project Objectives

 This section highlights previous studies on the
causes of poor blast results, its impact on
downstream processes, prediction of
fragmentation and evaluation of the blasted
material.
 This helped the author to fulfil the some objectives
set in chapter 1 and structure the methodology
thereby solving the problem at Sabi Gold Mine.
Literature review

 Research paradigm
The study adopted mixed methods approach for it
guarantees an outstanding analytical practice.
 Research design
Methodology
Data
collection
Bench
marking
current
prac
Analysis of
current
prac
Blast
design
mod
Trial blasts
Analysis of
new
results

Data collection
 Intensive desktop study on literature
 Formal and informal interviews were conducted
Benchmarking current practices
 Underground visits,
 plant visits
Evaluation process through;
Riegl VZ1000 3D laser scanning, tramming time study,
grizzle blockage intervals, crusher utilisation and power
consumption.
Cont’d

Some of the blast design modifications
Cat-hole burn cut
Cont’d

 The number of total charged holes was increased from 23
to 24 per round.
 Replacing smaller diameter cartridges with ANFO in dev.
 Stemming material was changed to fine sand particles.
 A pattern template was designed.
 cartridges were reduced by 30% from 125 to 87 in
production stope.
This was followed by Trial blasts at 8 development ends and
1 production stope followed by the evaluation of downstream
processes
Cont’d

 Farwest ore body has poor competence because it
has too many joints and that structure does not
require a lot of energy to break and the Anglo reef
has fair competence meaning more energy is
needed.
Results and analysis

Causes of oversized fragments
 Burn cut pattern
 Poor stemming material
 Drill bit deterioration
 Lack of skilled labour
 Drilling inconsistences – these include hole
spacing, hole depth and hole deviation.
 Compressed air leakages
Causes of undersized fragments
 Overcharging
Cont’d

Parameters Old design New design
Pattern
Hole
spacing
Hole depth
Hole diameter
Drilled and charged
holes
Powder factor
Stemming material
Stemming
length
Staggered
1m
1.5m
30mm
25 holes
0.56 kg/m3(cartridges )
Sand
produced by drilling
20cm
Staggered
1m
1.5m
30mm
25 holes
0.40 kg/m3(cartridges)
sand
produced by drilling
20cm
Parameter Old design New design
Cut design
Hole spacing
Hole depth
Hole
diameter
Number of
charged holes
Powder factor
9 hole burn cut
Cut – 15cm, other holes
20cm
1.5m
30mm
23
3.10 kg/m3
Cat hole burn cut
Cut as designed, 20cm
the other holes
1.5m
30mm
24
1.35 kg/m3 (ANFO)

Prediction of fragmentation
 Production stope
 Development ends
Cont’d

Old practices
New practices
5 level Production stope
Name Number of
Measurement
s
% fines
(<40mm)
P50 (mm) P80 (mm) % oversize
(>250mm)
Farwest
stope
4 80 70 90 0.1
Name Number of
Measurement
s
% fines
(<40mm)
(>250mm)
Farwest
stope
4 25 85 100 0.1

Name Number of
Measuremen
ts
% fines
(<40mm)
(>250mm)
A
B
C
D
E
F
G
4
4
4
4
4
4
4
40.6
33.0
23.2
26.0
34.4
45.0
19.1
16.4
100
98
90
105
96
107
116
92
160
175
180
136
162
185
130
200
10
15
12
17
20
12
13
Old development end practices

Name Number of
Measureme
nts
% fines
(<40mm)
(>250mm)
A
B
C
D
E
F
G
H
average
4
4
4
4
4
4
4
4
41.6
30.0
21.2
24.0
32.4
47.0
23.1
26.4
30.7
90
88
80
100
86
97
111
82
91.75
130
140
130
126
132
125
120
113
127
2.0
1.5
1.2
4.0
0.0
2.3
1.3
4.0
2.0
New development end practices

With the new practices oversized fragments reduced
from 14.1% to 2% and undersize reduced from 80% to
25% in the production stope.
 Lashing – the time reduced from 5 hours to 3 hours
 Tramming – time to fill 8×1.5 tonne cocopans
improved from 15 plus minutes to 10 minutes. This
reduced downtime and damages of boxes
Analysis of results

 Grizzle blockages - No grizzle blockages where observed
during the tipping of ore produced by the new blasting
practices.
Plant utilisation - The crushing plant utilization increased
from 89% with the old practices to 98.8% with the new
practices. Also due to lesser blockages the crusher
throughput increased from 34t/h to 38t/h.
Jaw crusher power consumption - the work index changed
from 0.172kWh/t to 0.159kWh/t that is 8% decrease.
Cont’d

The aim of the project was achieved.
Costs were minimized by reduction of explosive usage,
lowering jaw crusher power consumption and reduced
breakdowns.
Throughput was maximized as they were little/no
blockages at the grizzle and jaw crusher and no tramming
break downs that they could reach their targets.
Time loss was also dealt with as the process with less
complications.
Conclusion

 Training – The implementation of the blast
design and proper charging is in the hands of
the blasting crew hence the mine needs to
provide constant training and special
education followed by experience.
 Motivation - Workers need motivation. This
can be in the form of monthly or yearly
awards to reward those that have been doing
their job well.
Recommendations

 Cut design - the mine should use cut designs
such as the cat-hole burn cut whose
effectiveness has been proven.
 Explosive type –the Anglo ore domain
structure needs low energy explosives to
prevent freezing so I recommend the use of
ANFO instead of emex cartridges
Cont’d

 Repair compressed air leakages – there are too
many air leakages at the mine that affect the
processes largely by prolonging drilling,
causing hole deviations and using more
energy as the compressors will generating air
that is wasted.
Cont’d

 REFERENCES
 Anon, 2013. Tunnels, Shaft and Development headings blast design. no city: REVEY Associates, Inc.
anon, n.d. Compare rocks. [Online]
Available at: www.rocks.comparenature.com
[Accessed 14 February 2021].
Bergmann, et al 1973. Model rock blasting: Effect of explosives properties and other variables on blasting
results.. 10 ed. s.l.:Int J. Rock Mech. Min. Sci. and Geomech Abstr.
Bergman, P., 2005. Optimisation of fragmentation and communition at Boliden MineraL, Aitik Operation,
Lulea: Lulea University.
C.L Jimeno, et al, 1995. Drilling and Blasting of Rock. s.l.:A.A. Balkema. Rotterdam. De Ramiro, Yvonne
Visser translated to English.
Creswell, W. J., 2013. Qualitative inquiry and research design: Choosing among five approaches (3rd ed.).
Washington, DC: SAGE.
Crosby, W., 2008. Lecture given to blasting personnel, s.l.: s.n.
Dlamini, G., 2008. Effects of large fragments [Interview] (4 december 2008).
F. I. Siddiqui, et al, 2009. Measurement of Size Distribution of Blasted Rock Using Digital Image
Processing. JKAU: Engineering science, 20(2), pp. 81-93.
Hustrulid, W., 1999. Blasting princiles for open pit mining. 1(A.A Balkema).
I. Onederra, et al, 2014. Measuring blast fragmentation at Esperanza mine using high-resolution. Mining
technology, 124(anon), pp. 34-36.
Komir, V. M., 1970-1979. Stemming. The Great Soviet encyclopidea. s.l.,
www.encyclopedia2.thefreedictionary.com.
Kristy-Ann, D., 2017. Achieving and sustaining productivity benefits through a miner to mill approach, s.l.:
www.ausimmbulletin.com.
Kurosh, T., 1997. Drillabilty prediction: Geological influences in hard rock drill and blast tunnelling.
International journal of earth science, 86(2), pp. 426-438

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