STABILIZATION OF MINE TAILINGS DEPOSIT AREAS

STABILISATION DES DECHARGES DE RESIDUS DE MINERAIS

English Abstract

The invention is directed to a method of stabilizing
tailings deposits for mine tailings as well as to a method which
permits re-vegetation of those tailings deposits. Mine tailings
are generally finely divided, homogenous rock and other mineral
particles, which are unstable due to their fineness and particle
size. The invention provides a method of stabilizing the
tailings deposits by interspersing throughout the tailings
deposits a plurality of very large aggregate pieces which are
immensely larger than the particles of the tailings. The very
large aggregate pieces may very conveniently be used automotive
tires. The tires are generally placed in non-uniform layers
throughout the tailings deposits. It is convenient to place the
tires in the tailings deposits in a pile or pond as it is being
formed, but it is possible that they may be placed at least in
relatively accessible portions of the tailings pile or pond after
it is formed. The presence of the used automotive tires
throughout the tailings deposits provides a matrix through which
root systems of vegetation such as bushes, shrubs and trees may
gain purchase in the tailings deposit pile, so that the tailings
area may be re-vegetated by other than simply grass or weeds.
Re-vegetation of a tailings area ensures even greater stability
againsts slides or shifting, as well as maintaining the integrity
of the tailings area against dust blowing away from it in windy
conditions.

Claims

WHAT IS CLAIMED IS:
1. A method of stabilizing heaped tailings deposits so as to make said
heaped tailings deposits resistant to shifting, sliding, flow, or collapse
thereof, where the
particles of said tailings deposits substantially comprise finely divided,
homogenous rock
and other mineral particles; and where said heaped tailings deposits are
physically placed
on the ground; said method comprising the step of:
(a) randomly interspersing throughout said heaped tailings deposits
being stabilized a plurality of used automotive tires, where the used
automotive tires are
immensely larger than said tailings particles, and where said used automotive
tires have
substantially non-uniform peripheral surfaces that contact said tailings
particles when
said used automotive tires are placed in said heaped tailings deposits being
stabilized.
2. The method of claim 1, wherein said used automotive tires are placed in
non-uniform layers throughout said heaped tailings deposits.
3. The method of claim 2, wherein said layers of used automotive tires are
placed throughout said heaped tailings deposits as the heaped tailings
deposits are being
formed by additions thereto of further tailings particles.
4. The method of claim 2, wherein said used automotive tires are placed
substantially flat throughout said heaped tailings deposits.
5. The method of claim 4, wherein said heaped tailings deposits are piled on
the ground.

6. The method of any one of claims 1, 2, 3, or 4, wherein said heaped tailings
deposits are physically placed in pits or ponds formed in the ground.
7. The method of any one of claims 1 to 6, wherein after said heaped tailings
deposits have reached a predetermined size, said method further comprises the
step of:
(b) planting shrubs, bushes or trees on the upper surface of said
heaped tailings deposits, and watering the planted shrubs, bushes or trees so
as to
promote their growth.

Description

STABILIZATION OF MINE TAILINGS DEPOSIT ARE~A~S~~~8~ J
F ~D OF THE INVENTION:
This invention relates to a method for stabilizing tailings
deposits areas for mine tailings. The method provides a means of
disposing of used automotive tires safely and in an
environmentally benign manner, by essentially randomly dispersing
used automotive tires throughout the tailings deposit. The
invention is equally applicable to tailings deposits that may be
tailings piles or tailings ponds. The invention further provides
means for re-vegetation of the tailings deposit, where larger
plants than grass or weeds may be successfully grown to ensure
the stabilization the tailings deposit area.
BACKGROUND OF THE INVENTION:
Two environmentally hazardous or in any event unsightly
consequences of industrialization in today's civilization are
vast accumulations of used automotive tires and vast
accumulations of mine tailings. It is estimated that used
automotive tires are generated -- that is, disposed of as being
no longer required -- at the rate of one tire per person per year
in countries such as Canada and the United States. Mine tailings
deposits can, in certain regions such as that in the Sudbury area
of the Province of Ontario, Canada, cover many sguare miles,
Tailings deposits from mines are generally very finely
divided homogenous rock and other mineral particles. The
tailings deposits may very often have such fine mesh sizes as -
200 mesh, or even finer, which essentially makes the tailings
deposits huge volumes of unstable dust or powder. Very often,
mine tailings are deposited moist or as an aqueous slurry; when
they are dry or moist they may he piled on the ground, and when
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thFy are in the ~orm o~ an aqueous slurry they are deposited in
pits or panda that are ~ormed in the ground. In any case, the
tailings deposits are unsightly, and are incapable of supporting
any substantial vegetation growth other than grass or weeds.
Moreover, mine tailings deposits are extremely unstable due
to the fineness of the tailings particles, and the uniformity of
the tailings particles throughout the tailings deposit area.
This means that mine tailings piles may be subject to shifting or
to flow in circumstances such as earthquake or even heavy rain
storms, floods, and the like. If the mine tailings deposit
becomes dry, it may tend to be a source of finely divided dust
which may be suite abrasive, under windy conditions. Attempts to
stabilize the mine tailings areas have so .far failed, so much so
that vast areas in various mining regions throughout the world,
including especially mining regions of Canada and the United
States, have the general appearance of a lunar landscape.
The problem of used automotive tires, usually used
automobile tires although small truck tires and the like may also
particularly be included, is also one which is becoming
increasingly prominent and difficult to overcome, especially in
highly populated areas. It has been generally regarded that such
areas where used automobile tires are deposited are not
essentially environmentally hazardous, but are unsightly in the
extreme. However, dump areas where automotive tires are
accumulated have been known to catch on fire; and those fires can
be extremely costly to control and become environmentally
hazardous. Indeed, a fire which began at the beginning of
February 1990 near Hagersville, Ontario has created extreme
concern at all levels of government. Approximately 12 millicn
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tires may be involved; and it is now known that'~t
generated by the fire may essentially "crack" the rubber and
other materials of the tires to become liquid hydrocarbons --
essentailly crude oi7. -- with very high concentrations of toluene
or benzene which may soak down into the ground arid, indeed, enter
into ground water supplies.
It has been found, quite unexpectedly, that the problems of
the disposition of the two waste materials discussed above, mine
tailings on the one hand and used automotive tires on the other
hand, may essentially be overcome by combining the waste masses
into a single mass. This has the effect of the stabilizing the
tailings areas, whether they are tailings piles or tailings
ponds, and at the same time has the effect of disposing of used
automotive tires in an environmentally benign and aesthetically
acceptable manner. The further advantage is that the mine
tailings deposit areas may be re-vegetated with substantial
plantings of vegetation other than grass and weeds; and
particularly, that the mine tailings deposit areas may be re-
vegetated with shrubs, bushes, and trees. By incorporating the
used automotive tires into the tailings deposit areas, the risk
of fire and other pollution problems is minimized, the tailings
deposits are stabilized, and even the risk of dust blowing from
the tailings deposits is substantially reduced.
THS DRAWINGS:
The present invention is described in greater detail
hereafter, having regard to the single Figure of drawings which
shows a notional tailings pile having automotive tires
distributed throughout it and having re-vegetation placed on it.
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2D1088~
DESCRIPTION OF THE PREFERRED EMF30DIMENTS:
Essentially, the present invention takes into account the
fact that tailings deposits that require to be stabilized are
generally huge volumes of particles of tailings deposits where
the particles substantially comprise finely divided, homogenous
rock and other mineral particles. The finely divided rock and
other mineral particles are extremely fine, having a particle
size generally in the range of about -200 mesh or even finer.
The tailings deposits are physically placed on the ground or they
are placed in pits or ponds formed in the ground. The invention
provides for the step of interspersing throughout the tailings
deposit being stabilized a plurality of a very large aggregate
pieces, where the aggregate pieces are immensely ~~rger than the
tailings particles. Particularly, the invention contemplates
that the very large aggregate pieces have substantially non-
uniform peripheral surfaces which contact the tailings particles
when the very large aggregate pieces are placed in the tailings
deposit being stabilized.
Referring to the Figure, a pile of tailings deposits 10 is
shown placed on the ground 12. It is understood, of course, that
tailings deposit might be placed in a pit or pond formed in the
ground.
Interspersed throughout the tailings deposit pile 10 are a
plurality of very large aggregate pieces; and in the present
invention, it is contemplated that generally the very large
aggregate pieces are at least large portions of used automotive
tires. In its usual application, the invention contemplates that
the very large aggregate pieces are whole used automotive tires.
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Each of the very large aggregate piecea hay a :;u~svt~ana;f~y
n~ uniform peripheral surface, because of the nature of the tire
itself, which comprises a toroid which is in cross section a
generally U-shaped shell. In other. word:,, when the tire is
placed in the tailings deposit, the tailing particles surround
and intrude into the entire tire including the internal volume of
the tire where air would have been when the tire was in use on an
automobile or the like. However, when the tailing particles are
moist, or have been moistened as discussed hereafter, water may
collect in the bottom of the tires, especially when they are
placed flat -- that is, on their sides.
The present invention contemplates that the very large
aggregate pieces are placed in non-uniform layers throughout the
tailings deposits. It is meant by saying non-uniform layers that
the tires are randomly dispersed, but generally in a layer as
shown by the designations A, B, C, D, F, and F in the Figure.
The tires are not necessarily flat, although those contacting the
ground are more flat than others, but neither are they generally
placed in an upright position emulating their in use-position
during their active life.
In tailings piles that already exist, it may be possible for
a number of used automotive tires to be placed into the tailing
pile by driving or ramming them in, at least near the surface of
the tailings pile. Otherwise, when new tailings piles are being
created, it is contemplated that the used automotive tires would
be placed throughout the tailings deposits as it is being formed,
generally in non-uniform layers as discussed above.
The Figure shows a tree 16 having a root system 18, and a
bush or shrub 20 having root system 2~ in place and growing on

CA 02010885 2000-07-21
the tailings pile 10. Because of the presence of a plurality
of automotive tires 19 throughout the tailings pile, the root
systems 18 or 22 may find an anchor or purchase, so that the
root systems can be permitted to grow and thereby support a
tree, bush or shrub having substantial size. Moreover, when
the tailings deposit is moist or even placed as a slurry,
there may be a tendency for moisture to collect in the shells
of the used automotive tires 14, providing a source of
moisture for the root systems, and indeed providing a means
whereby the root systems may intertwine into the tires for
greater anchoring. By these means, vegetation other than
grass or weeds may be grown on the tailings pile 10. Indeed,
it is then possible for the tailings pile to be watered so as
to promote the vegetation growth, with the water collecting in
the used tires dispersed throughout the tailings deposit. By
this means, the tailings deposit is stabilized and is much
less likely to slide or collapse when it gets wet, or to lose
dust when it is dry and in windy conditions.
Moreover, it should be noted that by practicing the
present invention, the angle of repose of a tailings pile may
be increased. Thus, a higher pile -- and therefore greater
volume of tailings -- may be placed on the same area than was
previously possible.
The benefit to the environment of practising the present
invention should be clear from the above discussion.
Potentially harmful waste deposits may be utilized elsewhere,
and the unsightliness of waste deposit areas may be overcome.
The scope of the present invention is defined by the appended
claims.
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Representative Drawing