Note: Descriptions are shown in the official language in which they were submitted.
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A GROUTED FRICTION STABILISER
FIELD OF THE INVENTION
The present invention relates generally to devices used to anchor, secure
or stabilise earthen formations, such as the roof or side walls of an
underground
mine or tunnel. Devices of this type are usually referred to by many names
including rock stabiliser, rock-bolt, roof-bolt, friction stabiliser or split-
set bolt.
The present invention relates particularly to a stabiliser structure that
reduces known difficulties associated with such devices. Further, the present
invention provides a cartridge and method of installation of stabilisers that
reduces known difficulties associated with inserting filling material into
stabilisers
and installation of such filled devices.
BACKGROUND OF THE INVENTION
Stabilisers generally comprise an elongate tube of a substantially circular
cross-section with a channel or groove extending longitudinally along the
entire
length of the tube. Stabilisers are usually installed into a hole bored into
an
earthen formation requiring support with the hole being of a lesser diameter
as
compared with the outer diameter of the stabiliser body, During installation
of a
stabiliser into a hole, the tube is subject to radial compressive forces as a
result of
the interference fit between the tube and the surrounding rock or earthen
formation and the channel or groove allows the diameter of the tube to reduce
to
conform the diameter of the tube with that of the hole. Using this approach
ensures that there is at least some frictional engagement between the
stabiliser
body and the earthen formation. In practice, stabilisers are usually supplied
in a
range of diameters, each diameter having a recommended load carrying capacity.
The known installation procedure includes determining the diameter of the
tube associated with a recommended load carrying capacity, drilling a hole in
the
earthen formation, and forcing the tube into the hole using some form of
impact
tool.
In the instance of underground mines, stabilisers are typically about 2.4
meters long, and have an uncompressed diameter of approximately 47mm
although other diameters are also available. It is not always realised that
the
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actual diameter of the hole drilled into an earthen formation usually varies
along
the length of the hole. Figure 1 graphically illustrates this variance. The
hole
drilled has a nominal diameter of 45mm. It can be seen that the diameter of
the
hole varies from approximately 44 to 46 mm, and where the earthen formation is
not stable (not shown), the diameter may vary markedly due to rocks dislodging
from the side of the drilled hole. Assuming the hole is symmetrical (for the
purposes of discussion), if a 47mm stabiliser of the prior art is installed
into such a
hole (the nominal diameter of which is symbolised by the dotted line 2) the
stabiliser will be squeezed by the earthen wall of the hole at those parts
where
the diameter is less than 47mm, such as point 3. This will give relatively
good
frictional engagement between the earthen wall of the hole and the stabiliser,
and
thus enable the stabiliser to be loaded. However, the stabiliser will have
less
frictional contact with the hole wall at points where the diameter is larger
than 45
mm, such as point 4. At these points there is less loading ability provided by
the
stabiliser.
In the prior art, although a stabiliser having a diameter of 47mm has the
ability to be loaded approximately 4 tonnes per meter of embedment, this can
be
severely reduced where the bored hole does not enhance frictional engagement
between the stabiliser and the earthen formation over the full length of the
stabiliser as embedded.
When a hollow stabiliser is inserted into earthen material it tends to deform
and match the diameter of the bored hole in the earthen material. As the
stabiliser
is installed, narrow portions of the hole will cause the channel or groove to
close
at those portions. However, once a narrow portion of the hole is passed, the
channel or groove will tend to open again as the stabiliser body expands to
some
extent. In this respect, as the diameter of the hole varies along its length,
to some
extent the diameter of the stabiliser body will conform to the variations in
the hole
diameter.
It is known that by providing a grout internally to the stabiliser, after the
stabiliser is embedded into the hole, the support capacity of the stabiliser
is
increased to approximately 12-16 tonnes per meter of embedment. The grout,
once set, substantially reduces any subsequent radial deformation of the
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stabiliser which may occur as a result of the stabiliser being subject to
increased
forces by movement of surrounding material. Further, any load acting to
dislodge
or force the stabiliser out of the hole will be resisted as the load attempts
to force
larger diameter portions of the stabiliser body through narrower portions of
the
hole in which it is installed. Generally, grouting a friction stabiliser
substantially
increases the load carrying capacity of that stabiliser.
However, there are problems associated with the grouting of friction
stabilisers. It can be difficult to pump grout into a stabiliser such that the
grout
travels the entire length of the stabiliser. Often air is trapped inside the
stabiliser
which then inhibits the flow of grout. Also, stabilisers are often used to
stabilise
an underground mine roof. In such situations, the stabiliser is inserted into
the
earthen roof of the mine vertically. If a grout with relatively low viscosity
is
pumped into the stabiliser, it will tend to fall out of the stabiliser under
the action
of gravity prior to setting.
Further, when pumping grout into stabilisers, the pumping process usually
requires equipment that is relatively large and by necessity, the pumping
procedure is effected after the hole boring process for an area has been
completed and the drilling equipment removed from that area of the mine.
The two-step approach to installing and grouting friction stabilisers causes
delays. There is also a requirement for separate drilling and grouting crews.
The
two-step process is considered costly, cumbersome and time consuming.
Some examples of prior art stabilisers are illustrated, in cross section, in
Figures 2a, 2b, 2c and 2d.
US reissue patent Re 30,256 (Scott) discloses a stabiliser similar to that
illustrated in Figure 2a. The stabiliser consists of a tube with a slot
defined by
edges 5 and 6 which are separate prior to installation. During the
installation
process, in those parts of a hole which are narrower than the nominal diameter
of
the stabiliser, the edges 5 and 6 are forced together (as shown by arrow 7).
If
portions of the hole are very narrow, the edges 5 and 6 will butt together and
thus
restrict any further radial compression of the stabiliser. This would make
installation of the stabiliser very difficult or in some cases impossible. It
has also
been found in practice that the edges 5 and 6 and the inner and outer surface
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area are relatively exposed to water (from underground seepage) and over time
the stabiliser will tend to rust and fail.
US patent 4,012,913 (Scott) discloses a stabiliser similar to that illustrated
in Figure 2b. The stabiliser has offset edges 8 and 9 which are separated
prior to
installation. During the installation process, in the narrower parts of the
hole, the
edges 8 and 9 will be moved past each other as shown by arrow 10. However,
this deformation causes further problems after installation as with further
radial
compression, the external surface area of the stabiliser reduces thus
decreasing
the area over which the surrounding material has the ability to develop a
frictional
force to act upon the stabiliser. Radial compression of a stabiliser of this
type
subsequent to installation can result in premature dislodgement of the
stabiliser
which is unsafe.
If this type of stabiliser is installed in a roof section of an underground
mine, and sufficient load is applied to the stabiliser, say by a portion of
the roof
weakening and applying extra load to the stabiliser acting to dislodge the
stabiliser, then just as the stabiliser exhibits compression and expansion as
is it is
inserted into the hole, equally and conversely, the stabiliser can expand and
compress as it is forced out of a hole under the load of the mine roof
section. In
other words, the applied load may dislodge the stabiliser from the hole, with
the
stabiliser deforming in the direction of arrow 10 as the stabiliser is forced
out of
the hole and passes the narrower parts of the hole. As a result, it is
generally
considered that the effective bond strength due to friction between
surrounding
material and stabilisers of this type is relatively low.
A further problem with stabilisers of this type is a problem referred to as
`tangential gap'. Figure 2c illustrates this problem. Figure 2c is a
representation
of the part of Figure 2b "Compressed" marked "A". As previously mentioned, as
the stabiliser is installed in a hole, edges 8 and 9 are moved passed each
other.
However, proximate the edge 8, there is always a gap 10b (referred to as the
tangential gap) which is formed as a result of the stabiliser wall 9 moving
inwardly
of the stabiliser wall 8. The gap is formed between the stabiliser wall 9 and
the
hole wall 1 Oa. This gap reduces the overall frictional engagement of the
stabiliser
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with the earthen formation into which the stabiliser is installed as there is
no
frictional engagement along the portion of the stabiliser proximate the gap
10b.
US patent 5,297,900 (Witzand) discloses a stabiliser similar to that
illustrated in Figure 2d. The stabiliser has edges 12 and 13 that are
separated
5 prior to installation. The stabiliser has a `V' shaped portion extending
substantially along the entire length of the stabiliser. The `V' shaped
portion is
described as providing greater frictional resistance to movement between the
bolt
and the mine roof as compared with slotted stabilisers (as illustrated in
Figures 2a
and 2b). During the installation process, in those parts of a hole which are
narrower than the nominal diameter of the stabiliser, the edges 12 and 13 are
forced together (as shown by arrow 14). As occurs in the stabiliser of Figure
2a, if
portions of the hole are very narrow, the edges 12 and 13 will butt together
and
thus prevent any further circumferential deformation of the stabiliser. This
would
make installation of the stabiliser very difficult or in some instances
impossible. It
has been also found in practice that many parts of the `V' shape remain open
and
exposed to the earthen hole wall and are thus relatively exposed to water
(from
underground seepage) and over time the stabiliser will tend to rust and fail.
The `V' shaped portion, being internal to the stabiliser, is considered to
inhibit the flow of grout as it is pumped internally along the length of the
stabiliser. Further, it is difficult to insert grout externally along the
stabiliser
proximate the `V' shaped portion which is desirable in order to reduce the
likelihood of further radial compression of the stabiliser subsequent to
installation.
It is an object of the present invention to alleviate at least one of the
problems associated with the prior art.
Any discussion of documents, devices, acts or knowledge in this
specification is included to explain the context of the invention. It should
not be
taken as an admission that any of the material formed part of the prior art
base or
the common general knowledge in the relevant art on or before the priority
date of
the claims herein.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a stabiliser for stabilising
earth, rock or other structures, the stabiliser having a hollow elongate body
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portion including an opening extending substantially the entire length of the
body
portion and at least one closure member firmly affixed to the body portion on
one
side of the opening and aligned to substantially cover the opening of the body
portion in the vicinity of the closure member, the closure member being
configured to extend substantially parallel to an inner wall of the body
portion in
the vicinity of the opening.
The opening in the body portion should allow compression and
deformation of the stabiliser body portion when subject to a sufficient
compressive
force such as will generally occur during installation of the stabiliser into
a bored
hole in an earth or rock structure.
In a preferred embodiment, the stabiliser body portion is a substantially
cylindrical tube with a slot extending along the entire length of the tube,
the slot
being parallel to the longitudinal axis of the tube.
In another embodiment, the closure member is a sleeve segment of
substantially the same length of the stabiliser body and firmly affixed along
one of
the sleeves longitudinal edges to the inner wall of the stabiliser body such
that the
sleeve substantially covers the slot whilst allowing the slot to partially
close upon
application of a sufficient radial compressive force to the stabiliser body.
In this
embodiment, the sleeve segment is shaped to conform with the shape of the
internal wall of the stabiliser body and resides within the body portion. This
embodiment is particularly useful in instances where filler material is
inserted into
the stabiliser body before installation of the stabiliser into a bored hole.
Accordingly, in another aspect, the present invention provides a method of
installing a grouted friction stabiliser having a hollow elongate body portion
including an opening extending substantially the entire length of the body
portion
and at least one closure member firmly affixed to the body portion on one side
of
the opening end aligned to substantially cover the opening of the body portion
in
the vicinity of the closure member, the closure member being configured to
extend substantially parallel to an inner wall of the body portion in the
vicinity of
the opening, including the following steps:
a. drilling a hole in the region to be stabilised, the hole having a
smaller diameter than the diameter of the stabiliser to be installed;
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b. placing a filler substance internal of the stabiliser; and
c. inserting the stabiliser into the hole.
Conforming the shape of the closure member to the shape of the inner wall
of the stabiliser body in the vicinity of the opening has the added advantage
of the
closure member acting to guide the edges of the opening toward each other when
a compressive force is applied and as deformation of the stabiliser body
occurs.
In essence, it has been found that the closure member provides a means
by which, upon circumferential compression of the stabiliser, the surface area
of
the body portion in contact with the surrounding earthen material does not
decrease to the same extent as compared with some prior art arrangements. It
has also been found that the closure member provides a means by which filler
material is retained in the stabiliser when that filler material is inserted
into a
stabiliser prior to installation.
In another aspect, the present invention provides a cartridge for use in a
stabiliser, the cartridge containing filler material where the cartridge wall
includes
at least a portion of fluid permeable material and a closure member of
sufficiently
rigid material to substantially prevent the escape of filler material from the
cartridge during insertion into a hole when said cartridge is installed in a
stabiliser
said cartridge being shaped to substantially conform to the internal
dimensions of
a stabiliser body. There is preferably some clearance between the external
dimensions of the bag and the internal dimensions of stabiliser body to enable
relatively easy insertion of cartridges into stabiliser bodies.
Preferably, the filler material is grout that is activated by exposure to an
activating fluid such as water and immersing the bag in a reservoir of water
and
removal therefrom commences the setting process.
In another aspect, the present invention provides a method of installing a
grouted friction stabiliser having a hollow elongate body portion including an
opening extending substantially the entire length of the body portion and at
least
one closure memberfirmly affixed to the body portion on one side of the
opening
and aligned to substantially cover the opening of the body portion in the
vicinity of
the closure member, the closure member being configured to extend
substantially
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parallel to an inner wall of the body portion in the vicinity of the opening,
the
method including the following steps:
a. drilling a hole in a region to be stabilised, the hole having a smaller
diameter than the diameter of the stabiliser to be installed,
b. inserting filler material into the hollow elongate body portion to
substantially fill said body portion; and
c. inserting the stabiliser into the hole.
In another aspect, the present invention provides a method of installing a
grouted friction stabiliser having a hollow elongate body portion including an
opening extending substatnailly the entire length of the body portion, said
method
including the following steps:
a. drilling a hole in a region to be stabilised, the hole having a smaller
diameter than the diameter of the stabiliser to be installed;
b. inserting at least one cartridge according to the present invention
into the hollow elongate body portion; and
c. inserting the stabiliser into the hole.
Preferably, the cartridge is immersed in a reservoir of activating fluid prior
to placement of the cartridge into a stabiliser of the type according to the
present
invention. In another embodiment, the cartridge is placed into a stabiliser
according to the present invention to form a stabiliser assembly and the
assembly
is immersed in a reservoir of activating fluid prior to insertion of the
stabiliser
assembly into the hole.
It is particularly advantageous that the stabiliser assembly include a
stabiliser according to the present invention as the cartridge closure member
, substantially reduces the likelihood of cartridge filler material escaping
from the
cartridge or the cartridge becoming ensnared with material of the inner wall
of the
bored hole during installation of the stabiliser assembly.
In a preferred embodiment, the cartridge closure member is adhered to the
external surface of a cartridge. Installation of the cartridge according to
this
embodiment into a stabiliser body effects simultaneous installation of a
cartridge
and a closure member.
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Preferably, the cartridge closure member adhered to the external surface
of the cartridge is shaped to conform to the shape of the internal wall of the
stabiliser body in the vicinity of the opening. In the instance where the
opening is
a slot and the stabiliser is a substantially cylindrical tube, the closure
member is
preferably a sleeve segment which is adhered to the external surface of the
cartridge. Further, the sleeve segment preferably includes a protuberance on
its
surface for location within the slot (ie between the edges of the slot) of the
stabiliser body. The protuberance acts to retain the closure member in
position
covering the opening along the longitudinal surface of the stabiliser body
during
insertion of the stabiliser into a hole. Of course, the protuberance should
not
protrude beyond the external notional diameter of the stabiliser body portion
otherwise the protuberance would be likely to catch upon the wall of the hole
as
the stabiliser is installed.
In essence, the inventive method according to the present invention
provides a manner in which filler material and a stabiliser can be installed
into a
hole in a substantially one-step process. Preferably, the filler hardens and
provides resistance to subsequent radial compression of the installed
stabiliser.
In a still further aspect, the present invention provides a filler delivery
system adapted to install filler into a stabiliser, the delivery system
including:
a containing device adapted to contain a predetermined quantity of filler,
said filler, upon activation, hardening to a relatively incompressible state,
and
wherein
the containing device having a shape substantially elongate relative to its
cross-sectional area, the containing device being of a size such that it
contains
substantially the same amount of filler that would occupy the internal cavity
of an
installed stabiliser.
In essence, the filler material delivery system provides a relatively easy
means to install filler material into a stabiliser. By providing a means by
which
the filler material can be inserted into the stabiliser prior to installation
of the
stabiliser into the earthen formation, a number of the disadvantages of the
prior
art are overcome.
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In a further aspect, the present invention provides a stabiliser assembly
including:
a stabiliser for stabilising eart h, rock or other structures, the stabiliser
having an elongate body portion including an opening extending substantially
the
5 entire length of the body portion;
at least one closure member firmly affixed to the body portion on one side
of the opening and aligned to substantially cover the opening of the body
portion
in the vicinity of the closure member; and
a cartridge containing filler material wherein the cartridge wall includes at
10 least a portion of fluid permeable material, the cartridge being shaped to
substantially conform to the internal dimensions of the hollow interior of the
stabiliser body;
wherein the closure member substantially covering the opening of the body
portion significantly reduces the likelihood of a cartridge becoming ensnared
upon
the wall of a hole and the contents of the cartridge escaping from the
stabiliser
body in the vicinity of the closure member during insertion of the stabiliser
assembly into a hole.
In yet a further aspect, the present invention provides a stabiliser assembly
including:
a stabiliser for stabilising earth, rock or other structures, the stabiliser
having an elongate hollow body portion including an opening extending
substantially the entire length of the body portion;
a cartridge containing filler material wherein the cartridge wall includes at
least a portion of fluid permeable material and a closure member for impeding
the
escape of filler material from the assembly during insertion into a hole said
cartridge being aligned to cause said cartridge closure member to be in
substantial alignment with said stabiliser body opening
said cartridge being shaped to substantially conform with the internal
dimensions of the hollow interior of the stabiliser body.
In a preferred embodiment, the stabiliser assembly includes an end-ring
affixed to the stabiliser body at a region toward the end that is impacted for
the
purpose of inserting the stabiliser into a hole. In this embodiment, the end-
ring
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extends partially around the entire outer circumference of the stabiliser body
and
is affixed to the body by welding both sides of the ring in the region of
abutment
with the external surface of the stabiliser body.
In another embodiment, a plurality of end-rings are affixed to the stabiliser
body wherein each of the plurality of end-rings extend partially around the
entire
outer circumference of the stabiliser body and are affixed to the stabiliser
body by
welding both sides of each of the plurality of rings to the stabiliser body in
the
region of abutment of each ring with the external surface of the stabiliser
body. It
is particularly preferred that welded joints residing between end-rings abut
each
side of those end-rings.
Although end-rings need not fully extend around the entire circumference
of a stabiliser body portion, they preferably at least traverse that portion
of the
circumference of the stabiliser body portion that includes the opening.
Throughout this specification, in relation to the invention, the word `grout'
is
used to mean any substance capable of acting to reduce radial compression of a
stabiliser once the grout has been inserted into a stabiliser. Such substances
are
usually inserted into a stabiliser in a fluid form having been activated and
require
a period of time to enable the substance to `set' thereby transitioning to a
solid
form. Further, the word `stabiliser' is used to mean any form of earth
stabiliser,
rock stabiliser, tubular pin, anchoring device or a device which serves to
facilitate
stability of formations, such as an earthen, rock or man-made formations.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will now be described with
reference to the accompanying drawings, in which:
Figure 1 is a graph illustrating the possible variation of hole diameter along
the length of a bored hole in an earthen formation;
Figures 2(a), 2(b), 2(c) and 2(d) are cross sectional illustrations of
examples of prior art stabilisers;
Figure 3 is a perspective view of a stabiliser according to one embodiment
of the present invention;
Figures 4(a) and 4(b) are cross sectional views of stabilisers according to
embodiments of the present invention;
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Figures 4(c) and 4(d) are cross sectional and perspective views
respectively of a further embodiment of the present invention using a sleeve,
with
locating lugs;
Figures 5(a), 5(b), 5(c) and 5(d) illustrate, in cross section, alternative
stabilisers according to the present invention;
Figure 6 is a flowchart illustrating a method of installing a stabiliser
according to the present invention;
Figure 7 is a perspective view of a cartridge;
Figures 8(a) to 8(c) are further cross sectional views of alternative
embodiments of the present invention;
Figures 8(d) to 8(g) are various views of cartridge enclosures according to
the present invention;
Figures 9(a) and 9(b) are a cross sectional and perspective view
respectively of a particularly preferred embodiment of the present invention;
and
Figures 10(a) to 10(c) illustrate various embodiments of end-ring
arrangements for a stabiliser body.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to Figure 3, one embodiment of a stabiliser according to the
present invention is illustrated. The stabiliser has a generally elongate and
hollow
body 15, which is of a predetermined length. In underground mines, the
preferred
length of a stabiliser is approximately 2.4 metres.
In the embodiment illustrated, the body portion 15 has a generally
cylindrical shape as defined by the stabiliser wall 16. There is a `step' 21
and a
closure member in the form of an `overlapping' portion 17, which extends along
substantially the entire length of the body portion 15. The overlapping
portion 17
could extend over only a small part of the length of the body portion, or
extend
intermittently along the length of the body portion.
Figure 4(a) illustrates in greater clarity, in cross section, the overlapping
portion 17 of Figure 3. In addition, the stabiliser includes a first stop 18,
and a
second stop 19. It is these two stops which serve to prevent the body portion
of
the stabiliser according to the present invention being radially compressed
too far
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(ie beyond the point where the stabiliser loses its effective bond strength
with the
earthen formation into which it is installed (not shown)).
A closure member in the form of an overlapping portion 20 is shown. One
purpose of this overlapping portion 20 is to provide a means by which grout
(not
shown) inserted into the stabiliser is contained substantially within the
stabiliser.
It is preferred that the overlapping portion 20 also serves to guide the first
stop 18 and second stop 19 to abut each other in the event that the stabiliser
is
radially compressed to the extent that the first and second stops 18 and 19
meet.
The overlapping portion 20 may be fixed to the body portion 15 by, for
example welding, or other suitable means. The overlapping portion 20 may
alternatively be an integral part of the body portion 15. In this respect, a
substantially flat piece of material, typically steel, may be formed in the
shape of a
substantially hollow tube. Prior to forming a tube shape, the flat piece of
material
may have a `step' formed in the material such that upon forming a tube, the
material on one side of the step may form the overlapping portion 20.
Alternatively, the overlapping portion 20 may be coupled to the body
portion 15 via a step 21. The step 21 optionally serves as an additional
abutment
against which stop 19 can come to rest if the stabiliser of the present
invention is
significantly radially compressed.
Alternatively, with reference to Figure 4(b), the closure member may be
separate to the stabiliser body yet shaped to substantially conform with the
shape
of the stabiliser. Preferably, any separate closure member is provided with a
locating means to locate the closure member with the slot or opening along the
stabiliser body so that it does not move away from the opening during
installation.
An example of an embodiment with a separate closure member is detailed in
Figures 4(c) and 4(d).
In Figure 4(c), a sleeve segment 22 having a locating protuberance 23 is
positioned such that the protuberance 23 resides within the slot defined by
edges
24 and 25. The sleeve segment 22 substantially reduces, and ideally prevents,
grout escaping from the stabiliser 15 during installation of a stabiliser into
a hole
and whilst grout is setting within the stabiliser. In this regard, the sleeve
may be
made of a degradable material (if needed). The protuberances 23 are
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incorporated as necessary, to substantially prevent the sleeve segment 22 from
moving during installation of the stabiliser and whilst grout is setting to
prevent
unset grout escaping from the stabiliser. The protuberances should not
protrude
beyond the notional outer diameter of the stabiliser body portion through the
opening of the stabiliser. In one embodiment, the sleeve segment serves to
substantially prevent the longitudinal slot of the body portion 15 being
exposed.
The sleeve segment may also be made to incorporate a `groove' which
interlocks or fits with the step 21 of the stabiliser embodiment shown in
Figure
4(b).
The sleeve may have many embodiments but should be constructed such
that:
= The annular space between the sleeve segment and the inner
surface of the stabiliser is minimised;
= The cross section area of the sleeve segment is minimised;
The sleeve segment remains in contact with the inner surface of the
hollow body portion of the stabiliser; and
= The sleeve segment is shaped to conform to the inside of the
stabiliser's surface and substantially form a barrier across the slot or
opening in
the stabiliser body to prevent egress of grout from the inside of the
stabiliser
during installation of the stabiliser and during setting of the grout but not
necessarily the latter .
Figures 5a to 5d illustrate cross sectional views of alternative stabilisers
according to the present invention. The first stop 18, second stop 19, and
closure
member 20 is identified in each alternative embodiment.
Filler material may be inserted into a stabiliser body before the stabiliser
is
installed. Alternatively, grout may be encapsulated in a bag that is installed
into a
stabiliser body either before or after installation of the stabiliser into a
bored hole.
CARTRIDGES
In another aspect, the present invention provides an improved cartridge
that assists the installation of filler material into stabilisers. According
to this
aspect of the invention, grout or other filler substance, is preferably
encapsulated
in a porous container, such as a bag (refer Figure 7). The bag may be shaped
to
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substantially conform to the internal dimensions of a stabiliser body, but
preferably has external dimensions less than the internal dimensions of the
stabiliser to enable the cartridge to be relatively easily installed into the
stabiliser
body. Further, where the grout contained in a bag is activated by fluid, the
bag
5 preferably allows the ingress of such fluid for the purpose of activating
the grout.
Where the grout is activated by water, after drilling a hole, by inserting one
or
more wetted bags into a stabiliser, and then installing the stabiliser into an
earthen formation, the grout sets. A flowchart illustrating the steps of this
method
is represented in Figure 6.
10 In another embodiment, cartridges are placed into a stabiliser body prior
to
immersing the stabiliser body into a bath of activating fluid or by rupturing
an
internal frangible member thus releasing activating fluid. In this embodiment,
stabilisers are removed from the bath of fluid and immediately placed onto the
head of an impact tool for insertion into a bored hole.
15 In either embodiment of the method of installing stabilisers described
above, the two-step process known in the prior art is replaced with a one-step
process wherein fully grouted friction stabilisers are installed without the
requirement for any additional equipment as compared with the equipment
required to bore holes and install stabilisers. The only additional
requirement to
effect the improved method of installation is a supply of cartridges, a supply
of
activating fluid and a reservoir or bath to hold the activating fluid. None of
these
additional requirements involve a significant requirement for additional space
and
as such they are relatively easily to accommodate and do not significantly
affect
the operations of a drilling crew.
Of course, the improved method of installing grouted friction stabilisers has
many advantages including a substantial improvement in productivity and
efficiency of mine operations as a result of reducing the overall resources
required to install the devices. Similarly, the provision of a method that can
install
fully grouted stabilisers as part of a single process avoids the set-up time
and
capital expenditure usually required for additional pumping equipment.
Further, as
the load carrying capacity of a grouted friction stabiliser is superior to
that of a
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non-grouted stabiliser, to support any particular formation, fewer grouted
stabilisers will be required as compared with non-grouted stabilisers.
It is particularly advantageous to install cartridges into a stabiliser body
prior to insertion of the stabiliser into a bored hole in the earthen
formation
especially when the stabilisers are to be installed in the roof of a mine.
However,
when installing a stabiliser containing cartridges, exposure of the cartridges
through the slot or opening of the stabiliser body can cause the cartridge to
catch
on material forming the inner wall of a bored hole and prevent the cartridge
from
progressing through the bored hole with the stabiliser. In some instances,
where
a cartridge has become ensnared with material forming the inner wall of a
bored
hole, the stabiliser body has continued to travel through the hole (by the
action of
an impact tool acting on the head of the stabiliser) whilst the cartridge has
remained relatively stationary. This has caused stabilisers to be installed
without
cartridges extending along the full length of the stabiliser which is
undesirable.
As a result, it is preferable that the closure member of a stabiliser
according to the present invention, provide sufficient closure to prevent the
catching or ensnarement of cartridges on the inner wall of a bored hole. Of
course, in the instance of using a cartridge, the requirement for the closure
member to close the slot or opening of the stabiliser body is not as stringent
as
compared with the instance of pumping grout into a stabiliser before it is
installed.
The `cartridges' enable a relatively easy insertion of cementious material
into a stabiliser. In one embodiment, the cartridge has the following
properties:
= Inclusion of an outer water permeable bag or containing device that
is of sufficient strength that it will be not be easily ruptured during
handling or
during installation of the cartridge into the stabiliser. The bag may be made
of
fibrous material such as paper or dress makers "fusing", cloth or similar
material.
The bag is preferably permeable to enable the ingress of water to activate the
cementious material within the bag. The cementious material may `set' or
harden
in a relatively short period of time, such as in use within a mine in order to
accelerate the progress of the mine, or it may set or harden over a longer
period
of time. The contents of the bag will determine the `setting' time, as will
the
permeability of the bag.
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= The length of bag may be typically between 300mm and 600mm. In
one embodiment, the bag length is designed so that multiple bags fill the
stabiliser over its total length. It is thought that a number of relatively
smaller
bags are easier to handle and install into a stabiliser as compared with a
single
bag or a few relatively large bags. The length of the bag may vary. The length
suggested has been found to facilitate ease of handling in a mining
application.
= In the instance of a substantially cylindrical stabiliser body, the bag
diameter may be 2-3mm less than the inner stabiliser tube diameter. This
facilitates ease of installation of the bag into the stabiliser prior to or
shortly after
installation of the stabiliser.
= In one embodiment, the bag is filled with Portland cement and a
shrink resisting additive that will not allow linear shrinkage of more than
0.5%.
= In other embodiments, it may be advantageous to use a filler
material that swells upon contact with water, the material, after setting,
having a
relatively low shrinkage under stress.
= The filler material may contain one or more of a combination of the
following materials:
Plaster of Paris, epoxy resin, earthen materials, bituminous materials,
polyurethane foam, or other materials that exhibit desirable properties such
as
relatively high resistance to strain when subject to stresses.
To further assist the installation of cartridges into the body of a
stabiliser,
cartridges of the type depicted in Figure 7 may be enclosed within structures
of
the type depicted in Figures 8(d) to 8(g). In this respect, Figure 8(d)
comprises a
perforated tube, Figure 8(e) is a spiral structure shaped such that it may be
wrapped around a cartridge, Figure 8(f) is a structure similar to a document
binder
comprising a curved portion to which curled prongs are attached and Figure
8(g)
is a cylindrical tube with a slot along its longitudinal axis. The slot is
formed at an
angle to the bisection through the diameter of the tube such that one side of
the
cylinder will overlap the other when the cylinder is radially or
circumferentially
compressed beyond the stage where the slot becomes closed. Of course, Figures
8(d) to 8(g) are not an exhaustive representation of the structures that may
be
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used for containing cartridges within a stabiliser assembly according to the
present invention.
Whilst a permeable bag may be necessary to enable the ingress of an
activating fluid into the bag, permeable materials do not generally provide
substantial rigidity. Hence, the grout bags can be difficult to handle.
Enclosure of a cartridge within one of the structures depicted, improves the
ability to handle cartridges by substantially containing the bag within a
structure
that may display the desirable characteristics of rigidity whilst still
enabling the
grout bag to be exposed to fluid when either immersed or sprayed with fluid.
In
some embodiments, a portion of the structure enclosing the cartridge acts as
the
closure member of the stabiliser.
In a particularly preferred embodiment, a closure member is affixed to a
cartridge and forms an integral part of the cartridge such that installation
of a
cartridge into a stabiliser forms a stabiliser assembly including the
stabiliser body,
a cartridge residing within the stabiliser body and a closure member residing
internally within the stabiliser and aligned with the slot or opening of the
stabiliser
body.
A particularly preferred embodiment of the invention is illustrated in Figures
9(a) and 9(b) which provides a cross sectional and perspective view
respectively
of the preferred embodiment of the stabiliser assembly.
With reference to Figure 9(a), a stabiliser assembly 30 includes a
substantially cylindrical stabiliser body having a slot (defined by edges 27
and 28)
extending the entire length of the stabiliser body.
Included within the stabiliser body is a cartridge 32 that has a closure
member 34 affixed to the cartridge 32. The closure member 34 includes a
protuberance 36 that is located in the slot (ie between the edges 27 and 28).
When inserting the cartridge 32 into the stabiliser, alignment of the
protuberance
36 with the slot and sliding the cartridge into the stabiliser ensures that
the
closure member 34 is aligned with the slot and thus closes this opening of the
stabiliser until the stabiliser assembly is installed into a bored hole.
Figure 9(b) provides a perspective view of the stabiliser assembly 30. As
will be noted, the closure member 34 does not necessarily extend the entire
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length of the stabiliser body and may be segmented along the cartridge 32. The
precise dimensions of the closure member will vary depending upon the
characteristics of the material employed to form that member. However, the
requirement to sufficiently close the opening of a stabiliser body prior to
installation such that catching or ensnarement of a cartridge is avoided
remains
the objective of such a member.
In the preferred embodiment of Figure 9(a) and 9(b), the closure member
34 is formed from plastic materials and is affixed to cartridges either
mechanically
or with adhesive prior to insertion into a stabiliser body. After the adhesive
has
cured, the cartridge is installed into a stabiliser body thus simultaneously
effecting
installation of a cartridge and a closure member.
Of course, the closure member may be incorporated into the grout bag, be
bonded to the inside of the bag or alternatively form part of the bag itself.
Similarly, the closure member may be constructed in any one of a range of
shapes including those depicted in Figures 8(b) and 8(c) where the vertex of
the
"V" shaped closure member effectively forms a protuberance for the purpose of
locating the closure member with the opening of the stabiliser body.
When stabilising an earthen or rock formation, a plate is generally mounted
and secured on one end of a stabiliser prior to installation and the
stabiliser is
installed into the hole such that the plate is forced up against the surface
of the
earthen or rock formation. In instances where stabilisers are installed into
the roof
of a mine, the plate applies a distributed upward force to the surface of the
formation thereby reducing the likelihood of portions of the surface of the
formation separating and dropping away from the mine roof.
With reference to Figure 10(a), a stabiliser body portion 40 is detailed with
a plate 43 mounted on one end thereof. The plate is secured to the end of the
stabiliser body portion 40 by an end-ring 38. The end-ring 38 does not
completely
encircle the circumference of the stabiliser body portion 40 but at least
traverses
that portion of the circumference where the slot resides. In addition to the
end-
ring 38 acting to secure the plate 43, by traversing the portion of the
circumference that includes the slot the end-ring 38 also provides structural
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support to the end of the stabiliser and prevents the end of the stabiliser
from
splaying when struck by an impact tool during installation.
Once installed, a grouted friction stabiliser has an improved load carrying
capacity as compared with non-grouted stabilisers. As a result, a greater
force
5 acting downwardly upon the stabiliser body and the plate is be required to
dislodge a grouted stabiliser.
Previously, stabilisers with a lesser load carrying capacity have been
known to slip through the hole to a small extent when subject to increased
forces
acting to dislodge the stabiliser. An increased loading on a stabiliser may be
10 caused by various factors and is usually related to a change in the earthen
or
rock formation. For example, internal forces in a formation may act to force
an
outer slab of material to separate from the formation. In this instance, a
small
slippage of a stabiliser with respect to its hole can relieve the pressure
acting to
force the slab of material to separate.
15 However, with the improved load carrying capacity of a grouted friction
stabiliser the propensity for the stabiliser to slip is reduced and it has
been found
that the end-ring affixed to the end of the stabiliser body portion is more
likely to
fail and separate from the stabiliser when it is subjected to increased forces
acting
to dislodge the stabiliser. This is of course undesirable as failure of an end-
ring
20 fails to secure the plate and hence material may fall from the formation.
Accordingly, in a preferred embodiment of the invention, the end-ring 38 is
affixed to the stabiliser body portion 40 by welding the end-ring 38 to the
body
portion on both sides of the end-ring 38. As can be seen in Figure 10(a), the
end-
ring 38 is affixed to the body portion 40 by two weld joints 42 and 44.
In another embodiment detailed in Figure 10(b), the end-ring is in the form
of a sleeve 46 which is also affixed to the body portion 40 by two weld joints
48
and 50. In yet another embodiment detailed in Figure 10(c), the end-ring
arrangement includes two sleeves 52 and 54 both of which are affixed to the
body
portion 40 by weld joints 56, 58 and 60. In this particular embodiment, weld
joint
56 completely fills the gap between the sleeves 52 and 54.
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In each of the end-ring arrangements detailed in Figures 10(a), 10(b) and
10(c), the weld joints preferably extend around the entire abutment region
between the ring or sleeve and the body portion.
As the present invention may be embodied in several forms without
departing from the spirit of the essential characteristics of the invention,
it should
be understood that the above described embodiments are not to limit the
present
invention unless otherwise specified, but rather should be construed broadly
within the spirit and scope of the invention as defined in the appended
claims.
Various modifications and equivalent arrangements are intended to be included
within the spirit and scope of the invention and appended claims.
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