Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHODS FOR STABILISING ROCK
FIELD OF THE INVENTION
The present invention is directed to the field of rock stabilization,
particularly as applied to
mining activities. More specifically, the invention is directed to rock bolts
that are capable of
absorbing movement in rock strata.
BACKGROUND TO THE INVENTION
In mining and other activities requiring the excavation of rock, the problem
of stabilising a
rock face often presents. The act of excavating leads to disruption of the
rock face, leading
for the potential of dislodgement of rock from mine walls, ceilings and
shafts.
Rock bolts are well known contrivances, having been used for many years to
stabilize
excavations such as tunnels and cuts. When properly installed, the rock bolt
transfers load
from an unstable rock face, to a more stable adjacent rock mass.
The "Split Set" has been the industry standard rock bolt for many years. A
friction bolt is
inserted into a hole in the back and shoulders of the mine directly behind the
cutting face.
Despite being well used and cost effective, the Split Set has a number of
problems.
A problem presents in situations where mine strata are dynamic. The movement
in rock can
be due to the excavation itself or to seismic activity. Many rock bolts of the
prior art have no
give, and will become dislodged or fracture when rock strata shift.
Accordingly, the rock face
becomes unstable, and may collapse.
Underground mining is progressing to greater depths in many countries in the
world. Mining
at depths of around 3000 m is already common, with depths of 5000 m being
contemplated.
Even at shallower depths than these, damaging seismicity frequently occurs. In
some cases
this may be due to the fact that high horizontal stresses occur. Such
conditions are well
known in Western Australia, as well as other locations globally.
Seismicity can cause rockbursts which result in dynamic loading of rock
support elements.
Rockbursts manifest as the violent ejection of rock from any of the surfaces
of tunnels, and
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often in very localized areas. It has been observed that about a metre
thickness of rock may
be ejected, and that ejection velocities can be up to about 10 m/s.
Rockfalls are also typically seen in underground mining. These events have
lead to
fatalities, and also result in financial loss to mining companies. After a
rockfall, production
mining is ceased and a safety audit is carried out. It can take many weeks for
a mine return
to full production after clearing debris, securing the strata and conducting
safety inspections.
Another problem is that some types of rock bolt take a significant length of
time to set in
place, meaning that production time in a mine is lost. For example, where rock
bolts are
used to stabilise the roof of a mine bore hole it is not possible for workers
to work
underneath immediately.
Another problem is that some rock bolts require grouting before any
significant level of rock
stabilization is achieved. As mentioned earlier the grouting process adds to
the installation
time, but an added problem is the grouting step can sometimes be forgotten
completely.
A further problem is that some rock bolts require three or more teams of
workers to install
the bolt: at least a first team to drill the borehole, a second team to insert
the bolt, and a third
team to grout the bolt.
Yet a further problem is that a standard type of rock bolt having the ability
to deal with rock
movement is not available. On site, some modifications to rock bolts are made
in order to
cope with rock movement, however such modifications are ad hoc, and must
always be
overseen by an appropriately qualified engineer on a case-by-case basis.
It is generally desired by geotechnical engineers, shift supervisors, mine
managers, and
contractors for a one pass scheme to be available for use in deep mines, high
stress
environments and other complex situations.
It is an aspect of the present invention to overcome or ameliorate a problem
with the prior
art, or to provide an alternative to prior art rock bolts.
The discussion of documents, acts, materials, devices, articles and the like
is included in this
specification solely for the purpose of providing a context for the present
invention. It is not
suggested or represented that any or all of these matters formed part of the
prior art base or
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were common general knowledge in the field relevant to the present invention
as it existed
before the priority date of each claim of this application.
SUMMARY OF THE INVENTION
Reference throughout this specification to "one embodiment" or "an embodiment"
means
that a particular feature, structure or characteristic described in connection
with the
embodiment is included in at least one embodiment of the present invention.
Thus,
appearances of the phrases "in one embodiment" or "in an embodiment" in
various places
throughout this specification are not necessarily all referring to the same
embodiment, but
may. Furthermore, the particular features, structures or characteristics may
be combined in
any suitable manner, as would be apparent to one of ordinary skill in the art
from this
disclosure, in one or more embodiments.
Similarly it should be appreciated that the description of exemplary
embodiments of the
invention, various features of the invention are sometimes grouped together in
a single
embodiment, figure, or description thereof for the purpose of streamlining the
disclosure and
aiding in the understanding of one or more of the various inventive aspects.
This method of
disclosure, however, is not to be interpreted as reflecting an intention that
the claimed
invention requires more features than are expressly recited in each claim.
Rather, as the
following claims reflect, inventive aspects lie in less than all features of a
single foregoing
disclosed embodiment. Thus, the claims following the Detailed Description are
hereby
expressly incorporated into this Detailed Description, with each claim
standing on its own as
a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not
other features
included in other embodiments, combinations of features of different
embodiments are
meant to be within the scope of the invention, and from different embodiments,
as would be
understood by those in the art.
For example, in the claims appended to this description, any of the claimed
embodiments
can be used in any combination.
In the description provided herein, numerous specific details are set forth.
However, it iws
understood that embodiments of the invention may be practiced without these
specific
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details. In other instances, well-known methods, structures and techniques
have not been
shown in detail in order not to obscure an understanding of this description.
In the claims appended to this description and the description herein, any one
of the terms
"comprising", "comprised of" or "which comprises" is an open term that means
including at
least the elements/features that follow, but not excluding others. Thus, the
term comprising,
when used in the claims, should not be interpreted as being limitative to the
means or
elements or steps listed thereafter. For example, the scope of the expression
a method
comprising step A and step B should not be limited to methods consisting only
of methods A
and B. Any one of the terms "including" or "which includes" or "that includes"
as used herein
is also an open term that also means including at least the elements/features
that follow the
term, but not excluding others. Thus, "including" is synonymous with and means
"comprising".
In a first aspect, the present invention provides an apparatus for stabilising
a rock, the
apparatus comprising: a first component adapted to engage a first rock region,
a second
component adapted to engage a second rock region, and a yielding component,
wherein in
use the apparatus is inserted into a shaft in the rock, the shaft extending
through a first rock
region and a second rock region, the first component engages with the first
rock region, the
second component engages with the second rock region, the yielding component
allowing
movement of the first rock region with respect to the second rock region such
that the
apparatus is not disengaged from the rock.
Applicant proposes for the first time a rock stabilising apparatus that is
capable of providing
instantaneous stabilisation, but also stabilisation under conditions of rock
movement. This
arrangement is a significant advance in the art because a miner can start work
about a
newly stabilised rock immediately, and safely, even before the yielding
portion of the
apparatus has managed to cure properly. The increased productivity of mining
workers and
the speed with which the mining process proceeds is of clear economic
advantage and
safety benefit of a true one pass static and dynamic scheme.
Furthermore, it is advantageous in underground mining that a drilling and
bolting jumbo can
quickly and safely support the ground directly behind the face so the next
round of
production drilling and blasting can continue. Bolting is not a "value adding"
exercise in
mining so reducing the time devoted to the activity is clearly beneficial.
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By way of example the time taken to install a prior art Split Set, insert a
cable and grout it
effectively can be broken down to three passes and explained as follows:
Installation of Split Set 1 minute
Installation of cable into the Split Set 5 minutes, 30 seconds
Grouting the bolt 2 minutes
Thus, the total time to install a Split Set, Cable and grout the combination
is about 8 to 9
minutes
By comparison time taken to install a bolt of the present invention is around
the same time
as just installing a standard Split Set friction stabiliser (up to 60
seconds).
The time saved by using a bolt of the present invention is about 5 to 7
minutes per bolt, or a
minimum of 200 hours of installation time per month (assuming use of 2,000
bolts per
month).
In one embodiment, the first component is substantially tubular, and the
frictional
engagement is achieved partially or completely by direct contact of an outer
side of the first
component and the inner wall of the shaft. In an embodiment, the first
component is or
comprises a friction rock bolt.
As used herein, the term "friction rock bolt" is intended to mean any part of
the apparatus
that frictionally engages with the rock, or facilitates the frictional
engagement of the
apparatus with the rock. The simplest method of frictional engagement is where
an outer
dimension of the bolt is larger than the drilled bore hole into which it is
inserted. The bolt is
forced into the narrow bore hole (usually by hammering) and the bolt presses
firmly against
the bore hole walls.
Many types of friction bolts are known in the art with many being manufactured
from high
strength steel tubing, typically having a slot running along the entire
length. One end is
tapered for easy insertion into a borehole and the other has a welded ring
flange to hold the
bearing plate. With the bearing plate in place, the tube is driven into a
slightly smaller hole,
using the same standard percussion drill that made the hole. As the tube of
the rock bolt
slides into place, the full length of the slot narrows, causing radial
pressure to be exerted
against the rock over its full contact length. Due to its split shape, the
friction bolt engages
with the rock of the borehole wall over its complete length after
installation.
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Friction bolts having alternative mechanisms are also contemplated to be
amenable to the
present apparatus. For example, friction bolts that rely on the swelling of a
compound
injected inside the bolt may be useful. These bolts are placed into an
oversized borehole in
a compressed state, with the expansion of the compound forcing the walls of
the bolt against
that of the borehole.
Friction bolts may also engage with a borehole by way of an expansion shell.
The shell is
inserted into the borehole, and via a mechanical means is expanded outwardly
to engage
the borehole wall. Typically the shell is expanded by way of rotating a
threaded rod which
causes the outward extension of the two or more leaflets that make up the
shell.
Many commercially available friction bolts will be useful as the first
component, or part of the
first component in the context of the present apparatuses. Alternatively,
designs based on
commercially available friction bolts will be useful.
The Nardi Friction Rock Stabilizer (Nardi Rock Control, Europe) and Garford
Clover Friction
Rock Stabilizer (Garford Cable Bolts, Australia) are types of commercially
available bolt
useful in the context of the invention. Accordingly, in one embodiment the
friction rock
stabilizer is, or comprises, substantially a Nardi friction rock stabilizer or
functional part
thereof; or a Garford Clover Friction Rock Stabilizer or functional part
thereof.
The Nardi Stabilizer has shown some success in mines throughout Europe, with
tests
showing that it outperforms the industry standard by a minimum of 50% on
pullout tests.
The bolt has, only because of its construction, a high friction with the rock
in which the bolt is
installed without the need of additional bonding materials. This friction,
measured in kN. pull
out strength, ensures immediate ground support after installation. The
friction is the result of
the spring action of the special V-profile of the Nardi bolt that is pressed
into in a pre drilled
hole with a smaller diameter than the Nardi bolt.
The Nardi bolt is further advantageous in that installation is facilitated
given that it can be
driven into the borehole with the same equipment used as for drilling the
hole. It provides
direct ground support and very high friction due to the spring action by the
four memory
zones in the V-profile. Typical specifications for the Nardi Friction
Stabilizer follow:
Specifications HB-39
Type of steel : St-44-3 N, werkstof nr.1.0144,
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conform EN 10 025
Tensile strength steel min. 420 Mpa, typical 460 ¨ 480 Mpa
Yield strength steel >320 Mpa
Elongation bolt > 30%
Wall Thickness nominal 2,00 mm. +/- 10%
Breaking load : 130 - 140 kN
Bolt diameter : 39.3 +/- 3 mm.
Recommended hole diam 36.0 ¨ 38.0 mm
Bolt length : 0.9 ¨ 4.0 meter
Specifications HB-46
Type of steel : St-44-3 N, werkstof nr.1.0144,
conform EN 10 025
Tensile strength steel : min. 420 Mpa, typical 460 ¨ 480 Mpa
Yield strength steel : >320 Mpa
Elongation bolt > 30%
Wall Thickness =
nominal 2,15 mm. +/- 10%
Breaking load : 160 - 170 kN
Bolt diameter : 46.5 +/- 3 mm.
Recommended hole diam 43.0 ¨ 46.0 mm
Bolt length : 0.9 ¨ 6.0 meter
In one embodiment of the apparatus, the second component is adapted to
frictionally
engage the second rock region. The frictional engagement may be achieved
partially or
completely by direct contact between the second component and the inner wall
of the shaft.
In one embodiment the second component comprises an expansion means such that
the
frictional engagement is achieved partially or completely by direct contact
between the
expansion means and the inner wall of the shaft. As mentioned supra, a number
of
expansion means are known in the art.
In one embodiment, the frictional engagement is achieved partially or
completely by contact
between the second component and a bonding material, and contact between the
bonding
material and the inner wall of the shaft. As used herein, the term "bonding
material" is
intended to include any grout (cement or resin based), glue or similar
substance. Cement
based grouts are generally pumped into a borehole containing an apparatus of
the present
invention, while resin based grouts take the form of a two-part cartridge
which is inserted into
a drilled borehole before a bolt is installed. This method of resin grout is
activated by
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"spinning" (rotating) the bolt/tendon into the pre-inserted cartridge as the
bolt enters the
borehole enabling the two part catalyst-mastic to mix and become active.
In one embodiment the expansion means is a mechanical expansion shell,
optionally of the
type disclosed supra. The apparatus of the present invention comprises a
yielding
component. As used herein the term "yielding component" is intended to include
any
dedicated or non-dedicated part, region, area, or mechanism of the apparatus
that permits
movement of the apparatus without breakage, significant deformation, or
dislodgment of the
apparatus from the borehole. The yielding component may be operably linked to
the first
component or the second component or both first and second components. In some
embodiments the yielding component is attached to, or incorporated into the
first and/or
second components. The yielding component may in some embodiments also be the
first
and/or second components.
In one embodiment, the yielding component is adapted to allow movement under
seismic
conditions that can be encountered at depths of greater than 1000, 2000, 3000,
4000 or
5000 meters.
In one aspect, the yielding component is, or comprises, substantially a cable
bolt. These
bolts are usually composed of multiple-strand cable and are typically longer
than friction
bolts, and may be meters in length. The strands of the cable may be twisted
open to form
"bird cages" which act to mix and become interwoven in bonding materials such
as grouts
and resins. Some cable bolts include anchorage by way of an expansion shell,
as described
supra.
In a preferred embodiment, the yielding component is or comprises or is the
same or is
similar to that described in international patent application
PCT/AU2003/001667 (to
GARFORD PTY LTD; published as WO/2004/055327, the contents of which is herein
incorporated by reference).
The mechanism of the Garford dynamic cable bolt may be used as a yielding
component in
the context of the present apparatus. Accordingly, in a particularly preferred
embodiment
the yielding component is, or comprises, substantially a Gafford dynamic cable
bolt, or
functional portion thereof.
The Garford bolt incorporates a specially designed mechanical Dynamic device
which is
attached to the cable at a specified point depending on the yield requirement
of the bolt. The
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Dynamic device is anchored in the borehole using cement or resin grout. A
polyethylene
debonding sheath along the bolt length prevents bonding of the steel element
with the
cement or resin grout, enabling the bolt to be pulled through the Dynamic
Device repeatedly.
The Garford dynamic cable bolt may have one, more or all of the following
properties:
Mimimum Typical
15.2mm Seven Wire Compact Strand
Yield Force (kn) 212 285
Tensile Strenth (kn) 300 310
Mass Per Metre (kg) 1.176
Yielding Sleeve is Nitrocarburised.
In addition or alternative to the mechanical properties cited supra, the
Garford solid bolt may
have one, more or all of the following features:
= Static Yield Force Capacity 150kn (min) to 180kn (max).
= Dynamic Yield Force Capacity 80kn to 120kn.
= Various yield loads can be achieved by modifying the yielding mechanism.
= Ultimate Displacement Capacity 300mm (standard) - Larger capacity may be
specified.
= Ultimate force Capacity 250kn (25 tonne) at displacement capacity.
= Energy absorption Capacity at 300mm displacement 30kj - larger capacity
may be
specified.
= Dome Plate 150 x 150 x 8mm Dome Plate.
= Radius Barrel and 3 part Wedge.
= Standard equipment is used to for strand tensioning and barrel and wedge
installation.
The mechanism of the Gafford solid bolt may also be used as a yielding
component in the
context of the present apparatus. Accordingly, in a particularly preferred
embodiment the
yielding component is, or comprises, substantially a Garford solid bolt, or
functional portion
thereof. This bolt may be characterised as a yielding rock bolt arranged to be
inserted into a
hole in a rock surface, characterised by comprising a shaft formed of a solid
metal bar, the
shaft having a first end and a second end, the shaft having a relatively, wide
portion adjacent
the first end thereof and a relatively narrow portion adjacent the wide
portion, an anchor
member having a longitudinal bore mounted about the shaft at the relatively
narrow portion
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and adjacent the wide portion, the longitudinal bore having at least a portion
of lesser
dimension than the relatively wide portion.
The energy absorption ability of the dynamic solid bolt is achieved by
attaching a treated
dynamic device to the bolt. When the seismic event occurs the solid bolt is
able to be pulled
through the dynamic device hence enabling the bolt to absorb the energy and
remain intact.
The polyethylene sleeve acts as a debonding agent that allows the solid bolt
to slip through
the dynamic device. The dynamic device is mechanical therefore enabling
repeatability in
regard to the energy absorption process.
The Garford solid bolt may have one, more or all of the following mechanical
properties:
Minimum Typical
Core Diameter - Bar (mm) 21.45 21.7
Cross Sectional Area - Bar (mm2) 361 370
Yield Strength (MPa) 550 580
Yeild Force (kN) 199 215
Tensile Strength (MPa) 850 915
Tensile Force (kN) 307 339
Elongation (%) 12 16
Mass per metre - Bar (kg/m) 3.0
In addition or alternative to the mechanical properties cited supra, the
Garford solid bolt may
have one, more or all of the following dynamic properties:
Static Force Capacity 140kN
Dynamic Force Capacity 100kN
Displacement Capacity up to 500mm
Another type of yielding component that is contemplated to be useful is the
sliding
mechanism described in United States Patent No 7,955,034 (to MEIDL) which has
a sliding
control element having a sliding body cage having at least one recess for
receiving a sliding
body that is in contact with a lateral surface of an anchor bolt rod, wherein
each recess for
receiving the sliding body is disposed in the sliding body cage tangentially
relative to the
lateral surface of the anchor bolt rod, a lateral enveloping surface of each
recess projects by
a predefined dimension into a free cross section of the through-opening, and
each sliding
body fills the transverse cross section of the recess associated with it.
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As a further example, the yielding component may be the same or similar to the
yielding
tendon described in United States Patent No. 6,390,735 (to GAUDREAU et al).
Other
yielding designs are based on frictional pulling resistance mechanisms. For
example, tendon
threads may be designed to yield under stress, allowing a nut or clamp to move
with respect
to the tendon. Other deformable structures may be provided. See for example,
United States
Patent Nos. 3,967,455; 5,791,823; and 5,882,148.
Another type of yielding component is found in the COMRO Cone Bolt in 1992, a
groutable
tendon equipped with a cone anchor. For the Cone Bolt, energy dissipation is
achieved
when a wedge located downhole at the grouted end of the tendon plows through
the filling
material confined in the borehole, until the force on the face is no greater
than the residual
strength of the tendon-grout-rock hole system. The Cone Bolt can sustain slow
or rapid
convergence of tunnel walls.
It will be appreciated that the apparatus may be point anchored, or non-point
anchored. The
skilled person is enabled to select an appropriate apparatus for a given
application.
In one embodiment, the apparatus comprises grouting means. As used herein, the
term
"grouting means" is intended to include any physical or functional feature of
the apparatus
that allows or facilitates the ingress of a bonding material into and/or about
the apparatus.
The grouting means may comprise one of more of a grouting collar, a grouting
channel, and
a grouting breather tube.
Grouting methods may include the use of a pumpable cement grout or pumpable
resin, resin
or cement cartridges by which activation of the grout may use spinning of the
bolt being
installed or other methods.
In one embodiment, the apparatus comprises tensioning means. It may be
necessary to
pretension point anchored bolts in order for the bolt to take up static
loading and, in the case
of yielding cable bolts, to engage the dynamic component which may be put
under load to
improve function. Typically, cable bolts with dynamic capabilities are
tensioned but dynamic
solid bar bolts generally do not require tensioning for the dynamic component
to function
adequately (i.e. once rock joint separation or seismic rock movement has
occurred) due to
the fact that a corrosion attack can inhibit the ability of the yielding
device if there is slack in
the system. The tensioning means may comprise one or more of a tensioning
collar, a
threaded bolt, and a tensioning anchor means. In some embodiments of the
apparatus the
grouting collar also functions as the tensioning collar, and/or the tensioning
anchor means
also functions as the expansion means.
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In the preferred embodiment, the one-pass scheme does not require tensioning
post-
installation as the bolt will have been pre-tensioned during the manufacturing
process.
Preferably the apparatus is of a substantially unitary construction. In this
way, the apparatus
can be easily inserted (and optionally grouted and/or tensioned) by a single
team of workers,
and in some embodiments require only one pass to install. This saves manpower,
and
importantly time. A unitary apparatus also provides for reproducibility in
performance, as is
required in many mining applications.
By way of construction, the yielding component (e.g. bar or cable) of the bolt
may be
inserted inside the friction rock stabilizer so that the bar or cable runs
from the collar end of
the bolt, along the entire length of the friction stabilizer component and
continues past the
distal end of the friction bolt for a length sufficient to provide anchorage
into an adjacent
section of more stable rock (i.e. where there is less likely to be significant
joint separation).
The yielding component may be positioned at the distal end of the stranded
cable, or indeed
positioned elsewhere on the cable or bar.
Once the cable or bar has been installed inside the friction stabilizer
component, the distal
end of the friction bolt may be squeezed or crimped in order to join the
friction component
and yielding component. A small diameter tube may then be attached to the
distal end of
the bolt, positioned in the recessed or folded "V" portion of the friction
stabilizer bolt for a
desired length, running up past the end of the friction bolt and then attached
to the yielding
cable or yielding bar by a method such as tack welding, or by the use of ties.
The small
diameter tube acts as an air release mechanism during the grouting process,
which
essentially take airs from the top of the borehole and enables it to escape
past the incoming
grout and be expelled down through the exterior fold on the friction
stabilizer tube and out of
the borehole.
In a further aspect the present invention provides a method for stabilising a
rock, the method
comprising the step of inserting into a borehole pre-drilled into the rock an
apparatus as
described herein. Installation may be achieved using a drilling and bolting
jumbo with
standard attachments, preferably with no further equipment being required. To
the best of
the Applicant's knowledge, a grouted friction bolt with dynamic capabilities
has not been
installed in a single pass prior to the filing date of the present
specification. Prior art
methods require two or more discrete processes, with each discrete process
often being
performed by a separate worker, or separate teams of workers. In the present
method, the
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grouting process may be achieved relatively rapidly by a grouting coupling
being pressed or
clamped over the grouting/collar ring and then ably grouting at pressure
during another pass
of workers. It is contemplated that a standard jumbo with the correct driving
dolly will be able
to install the bolt successfully including the grouting step which may occur
in the same pass
as insertion of the bolt. In one embodiment the method comprises the step of
tensioning the
apparatus.
In another embodiment the method comprises the step of introducing a grouting
material
within or about the first component and/or the second component and/or
yielding
component.
In a further embodiment the method comprises drilling a shaft capable of
accepting an
apparatus as described herein.
In another embodiment of the method, the method is devoid of the step of
adding a yielding
component to the first component and/or second component
In a preferred embodiment, the apparatus is installed as a non-point anchored
scheme but
transfers to point anchored scheme as dynamic movement occurs.
PREFERRED EMBODIMENT OF THE INVENTION
The present invention will now be more fully described by the following non-
limiting
examples, and in which:
Fig 1 is a cut-away lateral view of a non-point anchored rock bolt.
Fig2. is a lateral view of a point anchored rock bolt which is capable of
being tensioned and
grouted.
Fig 3 is a cross-sectional view of the point anchored rock bolt of Fig 2,
showing detail of the
tensioning/grouting collar.
Fig. 4 is a perspective view of the grouting/tensioning component of the rock
bolt of Fig. 2.
Fig. 5 is a cut-away view of the rock bolt of Fig. 2, showing detail of the
grouting and
tensioning means.
Turning first to Fig 1 there is shown an apparatus according to the present
invention having
a first friction bolt component 2 having a V-profile resilient means 4, a
breather tube 6, a
flange 7 and a grouting collar 8. A stranded cable 10 runs through the lumen
of the friction
bolt component 2, and is attached (not shown) to a region about the grouting
collar 8. The
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distal end of stranded cable 10 is fitted with a yielding component 12 of the
type used in the
Garford cable bolt.
In use, the apparatus is inserted in a borehole drilled into a rock face. The
apparatus is
inserted upper end (with reference to the figure) first, and driven into the
borehole until the
flange 7 abuts the rock face. At this point, the friction bolt component 2 is
firmly engaged
with the wall of the borehole thereby supplying a certain level of
stabilisation. The resilient
means 4 provides a higher level of frictional engagement. This form of the
invention is non-
point anchored.
Subsequently, the apparatus may be grouted by introducing an appropriate
material via the
grouting collar 8 into the grouting channel 4. The grout displaces air via the
breather tube 6,
while extending into and about the apparatus.
Figs 2, 3, 4 and 5 show an apparatus adapted to be anchored to a point in the
rock to be
stabilized. This apparatus invention having a first friction bolt component 20
having a V-
profile resilient means 22, a breather tube 24, and a tensioning/grouting
collar 26. A
threaded solid bolt 28 runs through the lumen of the friction bolt component
20, and is
attached (not shown) to a region about the grouting collar 26. The distal end
of the threaded
solid bolt 28 is fitted with a yielding component 30 of the type utilized in
the Garford cable
bolt. The debonded portion of the bolt 28 is shown at 32. The distal end of
the bolt 28 is
fitted with a mechanical expansion shell 34 used to anchor the distal end of
the apparatus.
In use, the apparatus is driven into a borehole until the tensioning/grouting
collar 26 abuts
the rock face. At this point, the tensioning/grouting collar 26 may be rotated
such that the
threaded bolt 28 is urged toward the rock face, and drawing the mechanical
expansion shell
34 toward the rock face also. This results in expansion of the expansion shell
34 such that it
frictionally engages with the borehole wall, thereby acting as a point anchor.
Once the
required amount of tension is applied, the apparatus may be grouted via the
grouting collar
26, as described for the apparatus of Fig 1.
Figs 3 and 5 show greater detail of the tensioning means. It will be noted
that the tensioning
means has a barrel 36 which is capable of rotating by rotating the nut 37
within the friction
bolt component 20. The barrel 36 has a threaded sleeve 38 which rotates in
concert with
barrel, thereby acting to draw the threaded bolt 28 downward (by reference to
the figure).
The apertures 40 allow passage of grouting material through the barrel 36 and
into the
remainder of the apparatus, these being more clearly shown in Fig 4.
14
CA 02911526 2015-11-05
WO 2014/179828
PCT/AU2014/000496
It should be appreciated that in the above description of exemplary
embodiments of the
invention, various features of the invention are sometimes grouped together in
a single
embodiment, figure, or description thereof, for the purpose of streamlining
the disclosure and
aiding in the understanding of one or more of the various inventive aspects.
This method of
disclosure, however, is not to be interpreted as reflecting an intention that
the claimed
invention requires more features than are expressly recited in each claim.
Rather, as the
following claims reflect, inventive aspects lie in less than all features of a
single foregoing
disclosed embodiment. Thus, the claims following the Detailed Description are
hereby
expressly incorporated into this Detailed Description, with each claim
standing on its own as
a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not
other features
included in other embodiments, combinations of features of different
embodiments are
meant to be within the scope of the invention, and form different embodiments,
as would be
understood by those skilled in the art. For example, in the following claims,
any of the
claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth.
However, it is
understood that embodiments of the invention may be practiced without these
specific
details. In other instances, well-known methods, structures and techniques
have not been
shown in detail in order not to obscure an understanding of this description.
Thus, while there has been described what are believed to be the preferred
embodiments of
the invention, those skilled in the art will recognize that other and further
modifications may
be made thereto without departing from the spirit of the invention, and it is
intended to claim
all such changes and modifications as falling within the scope of the
invention. For example,
components and functionality may be added or deleted from diagrams and
operations may
be interchanged among functional blocks. Steps may be added or deleted to
methods
described within the scope of the present invention.
