Introduction; Application of Cut-and-Fill (C & F) stoping; The activity cycle of the (C & F) method; Stages of the production cycle of the C & F method; Sequences of extracting ore bodies; Filling in C & F Method; About filling of stopes; Functions of filler; Types of fillers; Advantages and disadvantages of the C & F method
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A short series of lectures prepared for the Fourth year of Geology, Tanta University 2014- 2015 by Hassan Z. Harraz [email protected]This material is intended for use in lectures, presentations and as handouts to students, and is provided in Power point format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see [email protected]for contact details. Topic 6: Underground Mining Methods Cut-and-Fill stoping
This material is intended for use in lectures, presentations and as handouts to students, and is provided in Power point format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see [email protected] for contact details.
Stages of the production cycle of the C & F method
Sequences of extracting ore bodies
Filling in C & F Method
About filling of stopes
Functions of filler
Types of fillers
Advantages and disadvantages of the C & F method
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We will explore all of the above in Topic 6.
Introduction Method in which ore is removed at horizontal slices generally upwards. The ore is
drilled, blown up and removed from the stope. The resulting empty after the ore to be
removed, is filled with a filler ("backfill"). The filler serves as a support for the sides of the
stope, and as a platform for the devices when the next slice is mined.
It is a recommended method, for example, where iron ore and / or waste are slightly
relevant, which restricts the size of underground excavations and allows little time between
the removal and the deposition of the mineral filler.
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Application of Cut-and-Fill (C & F) stoping
The C & F method is required when: Ore Zones are irregular in shape and orientation.
Ore Is high grade and dilution control is critical.
The Need contacts between ore and waste are structurally critical
but not readily visible.
The Waste rock is weak.
Ore Zones are large, but Their rock quality is weak.
Localized Underground stability is required.
Surface Disturbance must be minimized.
The Value of the ore makes recovery of economically viable
support pillars.
The Reduction of surface waste storage is important.
The Need exists to advance the working platform for the upward
mining of the ore body.
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The C & F method In mining C & F generally upward (overhand)
advances; there is a least common variant - C & F underhand - where the feed is from the top down.
C & F advancing
bottom up
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overhand C & F
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a) drill-blast of a horizontal slice of ore, typically with three or four feet thick, removed the roof of the stope;
b) loading and transport of ore, mechanically removed from the stope for orepass, and then to a lower horizon of transportation;
c) removal of loose fragments ("cuttlefish") by the detonation and placement support / reinforcement ceiling;
d) filling the floor of the stope (backfilling) with a layer of composite material varied and equal in thickness ore disassembled ceiling.
The activity cycle of the C & F method involves the following steps:
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Stages of the production cycle of the C & F method :
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The workers perform all the activities of the production cycle in the newly opened roof of stope. So, for the method to be successful, one must control the behavior of the rock on the outskirts of the stope. This is done in several ways: by controlling the dismantling of the roof, using reinforcement / support for openings and using the stope backfill.
Use of roof
bolts in C & F
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Control ceiling by cable bolts :
Sequence of use :
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C & F method is versatile (there are
different configurations of extraction)
applied to bodies of different
geometries (shafts, inclined tabular or
massive deposits) can be divided into
separated by vertical pillars and
horizontal blocks.
Horizontal Pillar (i.e, Floor
pillar) separating stopes
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Sequences of extracting ore bodies ... View topic in 3.4.2 : Underground Mining Methods: engineering fundamentals
and international case studies. W.Hustrulid, R.Bullock, SME, 2001.
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C & F with overhand stopes separated by vertical pillars,
in this case made with backfill:
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C & F overhand with ramp and stope access
orepass located in the footwall:
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The method applies to deposits with dipping 35o to 90o, in
deep or shallow bodies. Stopes may have a width
ranging from 4 to 40 m. The filler allows to work in the
presence of enclosing a low resistance. The ore should,
however, have moderate resistance to high.
Thick body
being mined in
plan and in
section
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Different geometries of
openings in thick ore
bodies (seen in
section).
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Fig 1
Narrow body being mined: plan view (left) And
section (right).
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The C & F is a laborious method, requiring high value for the in situ ore. Some dilution
is expected, which occurs when the backfill is loaded with ore in the stope (usually
done by loading LHD's). Moreover, the method provides selectivity and flexibility,
allowing good control of ore contents and disposal in the stope, sterile material.
Also allows to follow irregular bodies during mining, due to the high degree of
selectivity of the drill-blast sequence
There are several benefits from an environmental standpoint, using the backfill. The
integrity of the host rocks allows less affect the hydrogeology of the mined area.
The possibility of subsidence at the surface is quite limited. Reduce the tailings
storage areas on the surface because they can be taken back to the stopes, as
backfill
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Variant of the C & F: Avoca method
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Filling in C & F Method
About filling of stopes:
filling is done during the production cycle (and not after complete
evacuation of the stope, as in SLS);
Hydraulic filling (water and sand particle size = hydraulic sand-fill) is the
most common, containing 60 to 70% solids and requiring deposition
techniques and special drain;
the filling with hydraulic sand-fill, the distribution for the stopes is done
by piping;
The stope is filled almost to the ceiling height;
backfill needs to be the strongest, is added to the cement mixture;
When the water is drained, a good base for moving mining equipment
while it is formed in the upper slice stope;
the backfill, traffic person is prevented for a few hours and the vehicle for
several days.
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Filler Models
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Filling
Functions of filler:
-preserve access to the stope;
avoid dilution of ore;
avoid subsidence on the surface;
serve as a working platform for workers in
mining the next horizontal slice;
The time of placing the backfill is critical because it
must take the original load was exerted on the ore.
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Types of fillers
Additional information on "backfill": read articles Underground Mining Methods: engineering fundamentals and international
case studies. W.Hustrulid, R.Bullock, SME, 2001, cap. 69.
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Types of fillers
1) Hydraulic fill (also
called slurry or sand fill)
3) Rock Fill
2) Paste fill
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Advantages of the method
It is a versatile method and can be adapted to the ore bodies from
any geometrical shape
Investments are moderated to implement the method
minimizes subsidence
High recovery and low dilution (selective method)
Waste can be taken to the basement, avoiding surface
contamination
Due to the high cost of mining, is only applicable in ores
of high value;
Requires hand labour intensive and more specialized;
The activity of filling complicates the production cycle,
causing reduction in production;
There are risks of instability in mass if the backfill is not
