Note: Descriptions are shown in the official language in which they were submitted.
23~
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Open ~it mininq
This invention relates to improvements in open pit
mining and adopts procedures that are especially suited to
the mining of tar sands. The invention is concerned with
improvements in the layout and method of operation of such
a mine.
In my prior Canadian patent No. 1,132,147 issued
September 21, 1982, there is disclosed a method of open
pit mining for tar sands ore that involves removing over-
burden and mining the ore longitudinally along at least
two strips to commence the formation of elongated cuts
that diverge from each other away from a common dump
station located adjacent an extraction plant. The strips
diverge frcm each other at an angle between about 45 and
about ~0, preferably around 60. The ore so mined is
hauled along each cut by a fleet of trucks to the dump
station. As mining continues each of the cuts is widened
laterally. This is done by removing overburden and
longitudinally mining ore from further strips adjacent and
parallel to the initial strips~ The result is to cause
each adjacent pair of the widened cuts to open to a track
that becomes common to the two cuts. This common track
extends to the dump station and acts as a route for hauling
ore to the dump station from both the cuts.
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This arrangement was designed to shorten the haulage
routes for the trucks travelling from the mining faces to
the dump station, in comparison with prior designs of open
pit mines.
The present invention represents an alternative scheme
which incorporates some of the features disclosed in my
earlier patent, but also provides some additional
improvements.
The very high capital cost and long lead time necessary
to put a "mega" sized tar sand project into operation,
suggest that a less capital intensive approach should be
sought. This lower capital approach may be accomplished by
using the scheme of my earlier patent with mobile equip-
ment, by developing the mine at a slow rate and expanding
by adding more mobile mining equipment in increments,
together with extra trains in the extraction and upgrading
plants. The lower capital objective can also be
accomplished by reducing the size of the sectors initially
mined with the same "common track" haulage pattern.
However, as the size of the sectors is reduced, the
length of the access ramps and other dimensional features
require some modification of the patented scheme. The
present invention will still involve mining a series of
benches from the surface to the base oÇ the ore at each
incremental advance of the mining faces from an initial
slot. However, the present invention differs from the
prior scheme in that the incremental advances are pie
shaped (by which I mean the shape of a segment of a pie,
i.e. essentially triangular) and take place in relatively
small modules. For greater efficiency and flexibility it
is ~referred to operate two modules simultaneously,
although one may (and usually will) begin before the other,
thus enabling the generation of revenue with a minimum of
initial capital expenditure.
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In addition, in the present invention haulage by truck
does not take place to the surface using a common track to
the dump. Instead, the ore is trucked from the mining face
on the bench to a collection point that is below surface
level, preferably intermediate in level between the surface
and the pit bottom. From this collection point the ore is
transported by a conveyor to the surface and to the
extraction plant dump. This combination of transporting
means (first trucks, then a conveyor) provides a combin-
ation of flexibility of operation and eCOnQmy of energy,
since it is cheaper to convey the ore to the surface by a
conveyor. While bringing the ore from the mining benches
to the conveyor feeder at the collection point may require
the trucks to do some lifting from levels below that of
the collection point, this lifting is much less in
vertical height than if the trucks were required to
elevate the ore all the way to the surface.
The advantage of this system is thus relatively short
haul by truck ~generally shorter than the patented scheme)
and minimal lifting in elevation of material by truck
(much less than in the patented scheme~. The lifting is
more efficiently handled by conveyor~ and ultimately (as
the mine expands by adding additional modules) ~airly long
distance transport is also handled by conveyor. On the
other hand, another advantage of the system, as compared
with the dragline and bucketwheel schemes currently in
use, is very short conveyors. Initially the conveyors
would be a small fraction of the length of those used in
the presently operating mines at Suncor and Syncrude in
Alberta. The capital costs, as well as the operating
costs, would thus be low in comparison. The modular
approach to expansion, which is largely responsible for
the lower initial costs, operates effectively and
efficiently with the present ore transportation scheme,
which would not be the case for large dragline and bucket
wheel systems such as are in use at the Suncor and
Syncrude projects.
4 ~ d2~
A scheme embodying the present invention is illustrated
by way of example in the accompanying drawings, in which:
Figure 1 is a plan view of an initial cut;
Figure 2 is an isometric view of Figure l;
Figures 3A and 3B extend into one another and
represent a section on A-A' in Figure l;
Figure 4 is a section on B-B' in Figure l;
Figure 5 is a plan view corresponding to Figure 1 but
at a later stage in the mining operation;
Figure 6 is an isometric view of Figure 5;
Figure 7 is a section on A-A' in Figure 5;
Figure 8 is a plan view of the mining operation at a
still later stage;
Figure 9 is an isometric view of Figure 8;
Figures lOA and lOB (with Figure 7) extend into each
other and represent a section on A-A' in Figure ~;
Figures llA and llB extend lnto each other and
represent a section on B-B' in Figure;
Figure 12 is a plan view of yet a further stage
20 illustrating the division of the mine into modules;
Figure 13 is an isometric view of Figure 12;
Figure 14 is a plan view of the mine showing further
modules;
Figure 15 is an isometric view of Figure 14; and
Figure 16 shows a completed layout diagrammatically.
Figures 1-4 illustrate an initial cut extending from
an extraction plant 10 which will include a dump station
(not separately shown). These views show the situation at
a stage when a sector of overburden (shown generally by
30 horizontal hatch lines) has been removed and mining of ore
has begun. At this stage, ore from the pit bottom 11 is
trucked up a ramp 12 to a hopper/breaker 13 ~or breaking
up the ore if necessary and loading it onto the foot of a
conveyor 14 which has a first upwardly inclined section
35 14a, followed by a flat section 14b at ground level and a
~2~3,q~
final, upwardly inclined section 14c extending into the
dump station portion of the extraction plant 10. The ore
will have been mined by conventional methods (not shown)
such as large power shovels.
Overburden stripping is continuing in an area 15 and
is just about to commence at a location 16, these regions
being connected to the pit by ramps 17 and 18 respectively.
Other ramps 19 to 23, some of which are constructed as
permanent roads, interconnect the various areas and
eventually lead up to the ground level including providing
access to additional, back-up hopper/breakers 24 situated
at ground level and feeding to a further section 14d of
the conveyor 14. The arrows on the ramps and roads
indicate the direction of upward incline (typically 8%)
1~ and the arrows on the conveyor sections indicate their
feeding direction. The arrows at the side of the cut in
Figures 1 and 2 indicate the direction of mining, as will
be more apparent from the next series of views (Figures
5-7) showing a somewhat later stage in the mining
2Q operation,
Figures 5 to 7 show development of the mine as a result
of continued widening of the cuto It will be noted that
the portions of the sides of the cut furthest from the
extraction plant 10 are widened more than the nearer
portions so that these sides continue to extend substant-
ially radially from the extraction plant 10, i.e. the cut
has begun to take on the general shape of a pie segment~
This result is achieved by continuing to strip overburden
at areas 30 and 31, as before, and to mine ore at various
3Q shovel faces 32 to 35. The hopper/breakers 13 and 24 are
unchanged as is the conveyor 14 and the general ramp and
road system. More permanent roads 36 and 37 have been
provided to facilitate the transportation of ore to the
hopper/breaker 13~ and a waste dump 38 for the stripped
overburden has been begun. In making the preliminary cut
- 6 -
(Figures 1-~) it had been necessary to haul the overburden
away to an external waste dump (not shown), but this is
now no longer necessary.
Eventually the mine will have developed to the status
shown in Figures ~-11, by which time the triangular shape
of the cut in plan view is clearly evident. The waste
dump 38 now has roads 39 and 40 on it for bringing the
stripped overburden to the dump. It also has a central
ramp 41 for conveying road construction material from a
limestone quarry ~2 assuming that such rock is available
below the level of the pit bottom. Otherwise the operation
continues essentially as already described, there now,
however, being additional permanent roads 43-45 constructed
to facilitate haulage. The roads 43 and 44 are for truck-
ing ore to the hopper/breaker 13 and the road 45 for
hauling reject to the dump. Overburden stripping continues
along the sides at 30 and 31, as before, and mining
continues at shovel faces 46, 47 and backhoe ~ace 48. In
additional to indicating up-grades, some of the arrows in
Figures 8 and 9 now represent travel directions and mining
directions.
It should be noted in comparing the three stages
illustrated so far (compare, for example, Figures 1, 5 and
8) that the cut has not only been continuously widened
towards a triangular form but simultaneously lengthened in
the direction away from the extraction plant. Eventually
the outwardly expanding sides will reach a position in
which they are substantially perpendicular to each other
and encompass the laterally projecting portion containing
the road 22. Thus completed, the area, which will now be
referred to as module 1, is an shown on the left hand side
of Figure 12 or 13, having the shape of an isosceles tri-
angle with its longest side 50 remote from the extraction
plant 10.
Figures 12 and 13 also show module 2 which will have
been started after module 1 began but before module 1 was
completed. Obviously, the particular sequence and overlap
of module construction can be varied to suit conditions on
the site and the capital and labour available. Frequently,
the preferred sequence will be to have some overlap between
module development while keeping them to some degree out of
phase. For example, Figures 12 and 13 show module 1
complete, module 2 nearly complete, module 3 started and
module 4 also started but somewhat behind module 3 in
development.
The further development of module 1 shown in Figures
12 and 13 includes an extension 14' of the conveyor 14 to
a hopper/breaker 13l located on the pit bottom along the
side 50, i.e. at the end of the basic cut remote from the
extraction plant 10. The conveyor extension 14' passes
under a road at 51 and on an overpass at 52. Numeral 53
designates a quarry below pit bottom level and 53' a site
for a future extension of such quarry. It will be noted
that the road 22 is common to ~he road systems of modules
1 and 2, which latter module does not yet include the
conveyor extension 14' but soon will. At present t~e early
stages of module 4 are supported by the road system of
module 2, while conveyance of material from module 3 will
be carried out principally by the extended and original
conveyors of module 1. Module 2 will not require any
equivalent to the back-up hopper/breakers 24 or conveyor
section 14d because of the common road 22 interconnecting
the modules.
The shape of modules 3 and 4 will necessarily differ
to some extent from that of their respective parent
modules 1 and 2. For example, the sides 54 and 55 of
module 3 will be rotated about a centre located
approximately in the vicinity of the hopper/breaker 13i as
this module is expanded, the angle between these sides
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-- 8
eventually reaching 180, in contrast to the final angle
between the sides of module 1, which is 90~ Hence module
2 eventually achie~es the shape of an isosceles triangle
but this time with the apex at the remote corner. This
arrangement will be best understood from Figures 14 and 15
which show modules 1, 2 and 3 complete, module 4 almost
complete and modules 5 and 6 in different stages of early
development. Another ma~or addition to the mine shown in
these latter ~igures is a trunk conveyor 56 and a parallel
road 57 extending from the extraction plant 10 along the
adjacent edges of modules 1 and 2 to a hopper/breaker 58
at the remote ends of such edges, namely at a new pivotal
centre from which modules 5 and 6 grow and expand.
Figure 16 shows diagrammatically an area of ground
(typically ~ km x 4km) in which a pattern of eight modules
1-8 have been mined in this way over a period of say thirty
years. Lines 60 and 61, i.e. the limits of modules 1 and
2, might typically be approximately the mining limits for
the first seven and a half year, and lines 62 and 63
(limits of modules 3 and 4) the mining limit for year 15,
although as already mentioned the left and right hand sides
of the mine will preferably not be mined exactly
simultaneously with each other. Lines 64 and 65 represent
the approximate 22 1/2 year limit and lines 66 and 67 the
30 year lirnit. The hopper/breakers 13 and 24 will be used
typically for about the first 7 1/2 years; then the hopper/
breakers 13' for a second 7 1/2 years. Conveyance to the
extraction plant 10 during the second 15 years will be
along the trunk conveyor 56 from hopper/breaker 58. The
arrows show the mining directions.
I~ desired this entire pattern can be repeated in the
region 68 below the extraction plant 10 as seen in Figure
16, either subsequently, simultaneously or partly
simultaneously.
232
g
Advantages of the mining scheme described and
illustrated are as follows:
1. The modular concept shortens conveying and
hauling distances.
2. Mining radially, i.e. in pie or fan shapes that
are expanded laterally, also shortens these
distances.
3. Locating the hopper/breakers below ground level
]imits the amount of lifting by trucks; it is
cheaper to lift by conveyor.
. The module repeat pattern allows use of a trunk
conveyor for servicing the later modules.
5. The modular concept also lends itself to a large
variety of configurations that can be adapted to
the shape of the ore body.
6. The geometry of the modules shortens haulage
routes and permits the sharing of roads between
modules; the distances for trucking waste are
reduced as well as the distances for hauling ore;
7. The o~lter limits of the first module form a
straight line that provides a desirable base for
the third module and so on.
8. Since it is usually necessary to construct roads
with rock when mining tar sands, the scheme
provides ready access to the pit bottom to form
quarries at convenient locations for the work
areas.
9. The direct dumping of overburden in the pit is
facilitatedO
10. The modular concept facilitates starting on a
small scale and mining even only a single module
economically, until capital for expansion is
available. There is no need for bucket wheel and
drag line equipment which is very expensive.
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11. The scheme is adapted to the use of relatively
less expensive equipment, namely, trucks, shovels
and backhoes.
12. Use of shovels permits selective mining, i.e.
picking off layers of good ore and centre re]ect,
avoiding contaminating good ore with bad ore and
reducing tailings and the handling thereof.
13. The modular concept also provides the alternative
of rapid expansion, since many modules can be
developed and mined simultaneously.
14. Multiple conveying with relatively short conveyors
to a single point, i.e~ a dump station at an
extraction plant, is efficient and reliable.
15. The modular concept further enables ~he initial
cut of each module to choose the area with the
best ore. The configuration need not in practice
be as symmetrically laid out as in the drawings,
but may be modified and adapted to the shape of
the ore body. An initial cut need not necessarily
be central to the shape of the final module.
16. This flexibility facilitates the omission of any
area with bad ore. Conventional mining layouts
have usually involved mining through a bad area
because to do otherwise would disrupt the entire
operation.
