The Journal of Explosives Engineering - July/August 2022 - 32
Table 1. Cordless drilling test results.
Figure 1. Drilling a wedge cut to lower the floor in a cave passage.
Figure 2. A two-head micro-blaster system prepared for use.
Qualitative Findings
1. All forms of small-scale rock breaking work best in hard
rock that is free of major flaws. Both testing and interviews
with experts confirmed that soft or fractured rock
often requires more energy to split than competent rock.
This is true with feather and wedge breakage, detonating
cord pre-splitting, and 1.4S blasting.
2. With micro-blasting and 1.4S cartridges, a good gas seal
is critical to performance. The stemming material or tool
must be tightly-fitted in the hole. Holes should be drilled
perpendicular to any obvious cracks. Holes should be
cleaned of drill dust before loading, as the cartridges are
often a tight fit.
3. Detonating cord is extremely reliable at splitting even lowquality
rock. More explosive weight or a closer pattern of
holes may be required in fractured or soft rock, but it will
reliably split rock linearly or shatter small boulders under
almost any conditions.
4. Water is an efficient coupler of explosive energy. It's often
possible to achieve a rock split with lower-weight detonating
cord if water can be introduced into the hole.
32
5. Small-diameter drill bits (i.e. less than ¾ inch or 19 mm)
do not dissipate heat well and should be swapped out
frequently during drilling. In hot conditions, batteries and
drills may also overheat.
6. Battery consumption appears to scale linearly with hole
volume. Rock type can vary the energy requirement for a
give hole by up to a factor of 2.
7. SDS+ style drills should be used for holes < 19mm or ¾ "
and SDS Max systems should be used for larger holes.
SDS Max machines turn slower and deliver fewer blows
per minute. Small- diameter holes can actually be drilled
faster with the lighter SDS+ drill. Energy consumption per
volume of hole is similar between SDS+ and Max systems.
8. In all cases, rock with multiple free faces is much easier
to break. Free-standing boulders or flakes are easiest to
break while in-situ rock is the most difficult. Creating
relief through digging, drilling relief holes or making a
wedge cut is the key to removing embedded boulders or
bedrock.
9. 1.4S cartridges require accurate, straight drilling. Hole
depth must be at least 3 times the length of the cartridge
and holes should be situated to allow a predictable burThe
Journal of Explosives Engineering
July/August 2022
The Journal of Explosives Engineering - July/August 2022
Table of Contents for the Digital Edition of The Journal of Explosives Engineering - July/August 2022
From the Executive Director
Crack Displacement and Vibration Measurement of an Underground Portal
Product Spotlight
Industry News
Calendar of Events
Explosives, 100 Years Ago, More or Less
Chapter News
Blasting for Rescue Applications
29th Annual Photo Contest
Safety Talk
The Journal of Explosives Engineering - July/August 2022 - Intro
The Journal of Explosives Engineering - July/August 2022 - Cover1
The Journal of Explosives Engineering - July/August 2022 - Cover2
The Journal of Explosives Engineering - July/August 2022 - 1
The Journal of Explosives Engineering - July/August 2022 - 2
The Journal of Explosives Engineering - July/August 2022 - 3
The Journal of Explosives Engineering - July/August 2022 - From the Executive Director
The Journal of Explosives Engineering - July/August 2022 - 5
The Journal of Explosives Engineering - July/August 2022 - Crack Displacement and Vibration Measurement of an Underground Portal
The Journal of Explosives Engineering - July/August 2022 - 7
The Journal of Explosives Engineering - July/August 2022 - 8
The Journal of Explosives Engineering - July/August 2022 - 9
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The Journal of Explosives Engineering - July/August 2022 - 14
The Journal of Explosives Engineering - July/August 2022 - 15
The Journal of Explosives Engineering - July/August 2022 - Product Spotlight
The Journal of Explosives Engineering - July/August 2022 - 17
The Journal of Explosives Engineering - July/August 2022 - Industry News
The Journal of Explosives Engineering - July/August 2022 - 19
The Journal of Explosives Engineering - July/August 2022 - Calendar of Events
The Journal of Explosives Engineering - July/August 2022 - 21
The Journal of Explosives Engineering - July/August 2022 - Explosives, 100 Years Ago, More or Less
The Journal of Explosives Engineering - July/August 2022 - 23
The Journal of Explosives Engineering - July/August 2022 - 24
The Journal of Explosives Engineering - July/August 2022 - 25
The Journal of Explosives Engineering - July/August 2022 - Chapter News
The Journal of Explosives Engineering - July/August 2022 - 27
The Journal of Explosives Engineering - July/August 2022 - Blasting for Rescue Applications
The Journal of Explosives Engineering - July/August 2022 - 29
The Journal of Explosives Engineering - July/August 2022 - 30
The Journal of Explosives Engineering - July/August 2022 - 31
The Journal of Explosives Engineering - July/August 2022 - 32
The Journal of Explosives Engineering - July/August 2022 - 33
The Journal of Explosives Engineering - July/August 2022 - 34
The Journal of Explosives Engineering - July/August 2022 - 35
The Journal of Explosives Engineering - July/August 2022 - 29th Annual Photo Contest
The Journal of Explosives Engineering - July/August 2022 - 37
The Journal of Explosives Engineering - July/August 2022 - Safety Talk
The Journal of Explosives Engineering - July/August 2022 - 39
The Journal of Explosives Engineering - July/August 2022 - 40
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