The Journal of Explosives Engineering - July/August 2022 - 30

were utilized:
a. Each level of capability builds on the one prior. Higher
level capabilities leverage the existing investment in training
and equipment.
b. Almost all of the tools needed for each capability level
can be sourced from construction and mining suppliers
around the world.
c. The micro-blasting systems and 1.4S explosive cartridges
described are available from at least two manufacturers
and multiple distributors.
Training - A rescue team cannot commit to learning a new
skill without understanding the training commitment needed.
Based on our team's experience, the following principles were
developed:
a. Teams should first focus on proficiency at breaking and
moving small rocks. Since explosives fundamentally turn
very large rocks into smaller ones, small, close-quarters
rock breaking and removal is a foundational skill.
b. For a team to be proficient in a skill, it is recommended
that they not only train regularly on that particular skill
(i.e. mechanical breaking) but also seek out " awareness
level " training at the next higher level (i.e. micro-blasting
or commercial blasting).
c. Rock breaking should become an adjunct to other skills
the team already practices, such as bolting, mechanical
advantage systems or USAR skills.
Safety and Risk Management - Any new capability introduces
new risks. Since everyone involved in rescue operations
have to answer to some type of risk management, we have
included some general concepts to guide the rescuer:
a. In most cases, there is a rock-breaking option that is safe
to use even in direct proximity to a live subject.
b. The capabilities described can mean the difference between
life and death for a trapped subject. They may be
the only viable option for saving someone facing imminent
death due to hypothermia or crush injury.
c. The risk to rescuers can be reduced by modifying the rock
environment with explosives. Hazards such as rockfall and
squeezes can be greatly mitigated.
d. The class 1.4S cartridges and micro-blaster charges described
will not detonate unless confined inside rock.
They also produce a minimum of fumes and are safe to
use in non-ventilated areas.
Capability Level Model
We have developed a 4-tier model of team capability. The
levels defined below can be met within a single team or by
utilizing a composite team such as Search & Rescue (SAR), Fire/
USAR and private contractors working together.
A recommended set of equipment and techniques for each
level is outlined in appendix 2. They are designed to work
without access to utilities such as mains power or compressed
air.
These capability levels assume that a team undertaking
rock breaking is already proficient in some type of underground
or confined-space rescue. We do not consider other
non-explosive methods of rock breaking, such as the use of
expanding grout, as these are usually too slow for practical
rescue applications. Methods of hauling out the broken rock
30
are also outside the scope of this article.
Level 1: Can use mechanical rock breaking techniques
such as " feathers and wedges, " (Anon, 2021d) chisels, and
sledgehammers. Can crack and remove rock flakes or modify
openings with power and hand tools. Able to utilize technical
rescue techniques such as bolting and rope systems to move
rock. A level 1 team should also have awareness-level training
on micro-blasting.
Level 2: Adds proficiency with a commercial micro-blasting
system. This complements mechanical splitting and prying
techniques with the ability to break up boulders or rock
one (1) cubic yard/meter or less in size using 1-5 g explosive
charges. The team should have awareness-level training on
explosives and blasting and ideally, should have one person
working towards becoming a licensed blaster.
Level 3: Includes class 1.4 blasting with commercial cartridges
ranging in size from 5-120g net explosive weight
(NEW). A level 3 team has the ability to break multiple tons
of rock quickly and manage moderate air blast and flyrock
hazards. The team should have at least one licensed blaster
and all team members need support-level training on explosives
use. This capability may be in conjunction with a public
safety agency bomb squad or outside contractor who manages
product inventory and oversees the program.
Level 4: The team is fully integrated with a bomb squad or
blasting contractor. A level 4 team can utilize detonating cord,
shaped charges and other high explosives in conjunction with
level 1-3 techniques. A full level 4 team is capable of actually
mining 3 ft / 1m or more into unbroken rock, shattering blocks
over 3 cubic yards / meters in size safely and can operate in
difficult rock conditions. Multiple licensed blasters should be
able to deploy with the team. In addition, engineers, experienced
miners, or other professionals must be available for
help with technical issues.
Overview of Technologies
Micro Blasting is a small-scale rock-breaking process that
has become widely available in the last 20 years. The general
idea is that a small diameter hole is drilled, cartridges containing
nitrocellulose or similar propellant are inserted, and the
hole is stemmed up with a metal tool and fired. Rock is broken
via the hole pressurizing, causing it to fail in tension. No significant
shock wave is generated.
A variation on this, variously called " capping " or " Ticboum "
in Europe utilizes widely available .22-.27 caliber blank
cartridges made for nail guns that are fired with a slide hammer
or similar tool that can both stem the hole and strike the
cartridge's primer.
Commercial systems include a pneumatically-activated system
called the " EZ Break " that utilizes 5/16 " (8 mm) diameter
holes up to 18 inch " (45 cm) deep and an electrically-fired system
called the " Sierra Blaster " that uses 10 mm drill holes and
waterproof cartridges. The net explosive weight of a cartridge
for both systems is around 1g. Both systems can break up
and remove 1-3 cubic feet (.03-0.1m3
) of rock at a time and
typically do not require licensing nor magazines in most cases.
1.4 Cartidge Blasting is a process similar process to micro-blasting.The
products are larger and instead of a metal
stemming tool, a clay/sand/aggregate mixture is typically used
to seal up the hole.
The Journal of Explosives Engineering
July/August 2022
The Journal of Explosives Engineering - July/August 2022

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