Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
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MeCHanized BOlTing<br />
Mechanized bolting <strong>and</strong> screening<br />
utilization is the<br />
key<br />
In tunnelling operations, it is quite<br />
common to use the same equipment<br />
for all drilling requirements.<br />
These days, a single drill rig can<br />
accommodate drilling for face<br />
blasting, bolt holes, protection<br />
umbrellas, <strong>and</strong> drainage. As there<br />
are normally only one or two faces<br />
available for work before blasting<br />
<strong>and</strong> mucking, it is difficult to<br />
obtain high utilization for specialized<br />
equipment such as mechanized<br />
bolting rigs. By contrast, in<br />
underground mining, especially<br />
where a number of working areas<br />
are accessible using methods such<br />
as room <strong>and</strong> pillar, high utilization<br />
of specialized equipment can be<br />
expected. This is where mechanized<br />
bolting <strong>and</strong> screening is rapidly<br />
taking root, for speed, safety<br />
<strong>and</strong> consistency.<br />
Specializing for safety<br />
There was a time when underground<br />
mining <strong>and</strong> safety were terms not commonly<br />
referred to in the same sentence.<br />
However, times have changed, <strong>and</strong> today<br />
safety is given a place of prominence in<br />
the operational priorities of the mining<br />
industry.<br />
Freshly blasted openings leave considerable<br />
areas of loose rock, which must<br />
be removed to prevent fall-of-ground<br />
injuries. Improvements in drilling <strong>and</strong><br />
blasting techniques have helped to signi-<br />
ficantly reduce the amount of this loose<br />
rock. Scaling, which is the most hazardous<br />
part of the work cycle, is used to<br />
remove loose rock.<br />
Subsequent blasting might result in<br />
additional rock falls, especially in fractured<br />
ground conditions. Screening or<br />
shotcreting, as a means of retention of<br />
this loose rock, is often used in combination<br />
with rockbolting. Screening,<br />
which is a time-consuming operation,<br />
is common practice in Canada <strong>and</strong><br />
Australia. Since the 1960s <strong>and</strong> 1970s,<br />
considerable effort has been spent on<br />
Mechanized scaling with hydraulic hammer.<br />
mechanizing underground operational<br />
activities, including the rock excavation<br />
cycle. Within the drill-blast-mucking<br />
cycle repeated for each round, the drilling<br />
phase has become fully mechanized,<br />
with the advent of high productivity hydraulic<br />
drill jumbos.<br />
Similarly, blasting has become an ef-<br />
ficient process, thanks to the develop-<br />
ment of bulk charging trucks <strong>and</strong> easily<br />
configured detonation systems. After<br />
only a short delay to provide for adequate<br />
removal of dust <strong>and</strong> smoke by high<br />
capacity ventilation systems, the modern<br />
LHD rapidly cleans out the muck<br />
pile.<br />
These phases of the work cycle have<br />
been successfully mechanized, <strong>and</strong> modern<br />
equipment provides a safe operator<br />
environment.<br />
By contrast, the most hazardous ope-<br />
rations, such as scaling, bolting <strong>and</strong><br />
screening, have only enjoyed limited<br />
progress in terms of productivity improvements<br />
<strong>and</strong> degree of mechanization.<br />
The development of mechanized<br />
scaling <strong>and</strong> bolting rigs has been slower,<br />
mainly due to variations in safety rules<br />
<strong>and</strong> works procedure in specific rock<br />
conditions.<br />
To summarize, equipment manufac-<br />
turers have had difficulty in providing<br />
globally accepted solutions. Nevertheless,<br />
there is equipment available from Atlas<br />
Copco to meet most of the current dem<strong>and</strong>s<br />
of miners <strong>and</strong> tunnellers.<br />
Mechanization stages<br />
Various methods of mechanized bolting<br />
are available, <strong>and</strong> these can be listed<br />
under the following three headings.<br />
Manual drilling <strong>and</strong> bolting<br />
This method employs light h<strong>and</strong> held<br />
rock drills, scaling bars <strong>and</strong> bolt installation<br />
equipment, <strong>and</strong> was in widespread<br />
use until the advent of hydraulic<br />
drilling in the 1970s. Manual methods<br />
are still used in small drifts <strong>and</strong> tunnels,<br />
where drilling is performed with<br />
h<strong>and</strong>held pneumatic rock drills. The<br />
bolt holes are drilled with the same<br />
equipment, or with stopers. Bolts, with<br />
or without grouting, are installed manually<br />
with impact wrenches. To facilitate<br />
access to high roofs, service trucks or<br />
cars with elevated platforms are commonly<br />
used.<br />
Semi-mechanized drilling <strong>and</strong><br />
bolting<br />
The drilling is mechanized, using a hydraulic<br />
drill jumbo, followed by manual<br />
installation of the bolts by operators wor-<br />
king from a platform mounted on the<br />
underground mining methods 29