Mining_Methods_UnderGround_Mining - Mining and Blasting

Boxhole equipment.
Mine requirements
BOxHOle BOring aT el TenienTe
El Teniente tendered for the purchase of
two boxhole boring units to excavate
the draw bell slot holes for the panel ca-
ving operation. These units would also
be used to bore ventilation raises and
ore passes between the production and
the haulage level. The vertical draw bell
slots are generally 15 m-long and 692
mm-diameter. A total of 800 m, comprising
45-50 shafts, are bored annually.
Because drifts have not been deve-
loped on the production level, all venti-
lation raises and ore passes are bored
from the haulage level and upwards
using the boxhole boring technique. The
average length of the vertical and in-
clined ventilation raises is 25-50 m. The
inclined ore passes average 25 m-long,
but this varies up to 75 m-long. The total
annual requirement for 1.5 m-diameter
bored raises is 1,000 m.
Restrictions are placed on the machine
design by the size of the underground
sections. Work sites measure
3.6 x 3.6 m, and maximum transportation
dimensions are 2.5 m-wide x 2.5 mhigh
x 4.8 m-long. The machines must
either be self-propelled or transported
on rail, and have to have tramming and
directional lights, as well as a fire extinguisher
system. The mine electrical in-
stallations provide power at 575-4,000
V, 3-phases at 50 Hz, and 24-220 V, sin-
gle phase at 50 Hz. Each machine is de-
signed for three, or less, operators per
shift.
The operating environment is 2,300 m
above sea level, with teperatures from
+25 degrees C to 0 degrees C. Relative
humidity varies from 15% to 90% in
the mine, where acid water and occa-
sional blast vibrations may be experi-
enced. Both machines are operated 24
h/day, 7 days/week, with a maximum
machine utilization of 15-16 h/day.
evaluation period
An evaluation period of three months
was established to study the performance
capabilities of each machine. Target per-
formance criteria for the smaller slot
hole machine was set at 264 m bored
during the three month period, and 330
m for the larger boxhole machine.
This performance target was based
on a 24 h/day operation, with net av-
ailable operating time of 15-16 h. The
number of operating personnel required,
set-up and moving time, the rate of pe-
netration and machine availability were
all recorded during evaluation period.
Atlas Copco boxhole boring units
Robbins 34RH and 53RH were found
to meet the requirements of the up-hole
boring tender, and were selected by the
mine. Built on the experience of the
52R, the 53RH multi-purpose machine
has been developed since the early
1980s. The 34RH has been used as a
raiseboring and downreaming machine
for a similar period, and was first introduced
in the boxhole configuration in
1998. To accommodate the restricted
working space in the mine, the already
low-profile 34RH and 53RH had to be
redesigned to further decrease the working
height. Both machines are selfpropelled,
and equipped with efficient
muck collectors, remote-controlled pipe
handling and automatic data logging.
atlas Copco robbins 34rH
The Robbins 34RH is a low profile,
small diameter raise drill, designed for
applications such as slot raises, backfills
and narrow-vein mining. This multi-
purpose, lightweight raise drill can be
used for downreaming and upward
boxhole boring, as well as for conventional
raise boring.
The machine features a variable
speed hydraulic drive with a two stage
planetary gearbox, and hollow-centre
shaft to enable pilot-hole flushing. To
change boring methods, the Robbins
34RH is easily turned upside down, to
orient the drive head into either upward
or downward boring position.
The Robbins 34RH was already a
true low-profile raise drill. However, to
accommodate the restricted site dimensions,
and to allow room for a muckhandling
system on top of the machine,
the maximum working height had to
be lowered further. This was achieved
through the use of shorter high-thrust
telescopic cylinders, and by utilizing
750 mm-long by 254 mm-diameter drill
rods.
This reduced the working height of
the assembly to 3.6 m, including the
muck handling system.
The new muck handling arrange-
ment, which had been fitted on two ear-
lier Robbins 34RH machines commis-
sioned in 1998 and 1999, has been
further developed for efficient muck
collection in the boxhole boring mode.
The remote controlled and hydraulically
operated muck collector is fully
integrated into the derrick assembly, and
remains on the machine, even during
transportation.
92 underground mining methods