cut and fill stoping
DESCRIPTION
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 methodTRANSCRIPT
A short series of lectures prepared for the
Fourth year of Geology, Tanta University
2014- 2015
by
Hassan Z. Harraz
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
Outline of Topic 6: 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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
2
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.
Prof. Dr. H.Z. Harraz Presentation Cut & Fill stoping
3
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.
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
4
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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
5
overhand C & F
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
6
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:
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
7
Stages of the production cycle of the C & F method :
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
8
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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
9
Control ceiling by cable bolts :
Sequence of use :
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
10
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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
11
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.
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
12
C & F with overhand stopes separated by vertical pillars,
in this case made with backfill:
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
13
C & F overhand with ramp and stope access
orepass located in the footwall:
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
14
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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
15
Different geometries of
openings in thick ore
bodies (seen in
section).
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
16
Fig 1
Narrow body being mined: plan view (left) And
section (right).
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
17
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
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
18
Variant of the C & F: Avoca method
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
19
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.
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
20
Filler Models
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
21
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.
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
22
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.
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
23
Types of fillers
1) Hydraulic fill (also
called slurry or sand fill)
3) Rock Fill
2) Paste fill
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
24
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
properly sized and applied.
Disadvantages
Prof. Dr. H.Z. Harraz Presentation
Cut & Fill stoping
25