Mining_Methods_UnderGround_Mining - Mining and Blasting

Ore left in stope
Drawpoints
or chutes
STeeP Mining
Sublevel drifts are located within the
orebody, between the main levels, for
longhole drilling of blast patterns. The
drill pattern accurately specifies where
the blastholes are collared, and the depth
and angle of each hole.
VCR primary stoping.
Transport drift
Shrinkage stoping layout.
Crater
blasting
charges
Drill
overcut
Primary
stope no1
in production
Raise
Cross cut for loading
Drawpoints are located below the
stope to enable safe mucking by LHD
machines, which may tip into an adjacent
orepass, or into trucks or rail cars.
The trough-shaped stope bottom is ty-
pical, with loading drifts at regular
Loading draw
points
Primary stope no2
undercut and drilling
done
Timbered manway
(also ventilation)
intervals. Nowadays, the loading level
can be integrated with the undercut, and
mucking out performed by a remote
control LHD working in the open stope.
This will reduce the amount of drift
development in waste rock.
Sublevel stoping requires a straightforward
shape of stopes and ore boundaries,
within which only ore is drilled.
In larger orebodies, modules of ore may
be mined along strike, as primary and
secondary stopes.
Bighole stoping
Bighole stoping is an up-scaled variant
of sublevel open stoping, using longer,
larger-diameter DTH blastholes, ranging
from 140 to 165 mm. Blast patterns
are similar to SLOS, but with holes up
to 100 m-long. A pattern with 140 mm
blastholes will break a rock slice 4 m-
thick, with 6 m toe spacing. DTH drilling
is more accurate than tophammer
drilling, allowing the vertical spacing
between sublevels to be extended, from
40 m with SLOS mining, to 60 m with
bighole stoping. However, the risk of
damage to the rock structures has to be
taken into account by the mine planners,
as the larger holes contain more
explosives.
Shrinkage stoping
In shrinkage stoping, traditionally a
common mining method, ore is excavated
in horizontal slices, starting from the
stope bottom and advancing upwards.
Part of the blasted ore is left in the stope,
to serve as a working platform, and to
give support to the stope walls.
Blasting swells the ore by about 50%,
which means that a substantial amount
has to be left in the stope until mining
has reached the top section, following
which final extraction can take place.
Shrinkage stoping can be used for ore-
bodies with: steep dips; comparatively
stable ore and sidewall characteristics;
regular ore boundaries; and ore unaf-
fected by storage (some sulphide ores
oxidize, generating excessive heat).
The development consists of: haulage
drift and crosscuts for mucking at stope
bottom; establishment of drawpoints and
undercut; and a raise from the haulage
level passing through the undercut to the
34 underground mining methods