Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02763987 2012-01-11
Rock bolt
DESCRIPTION
The present invention relates to a rock bolt according to independent claim 1.
In the fields of mining and tunnel construction, rock bolts are used to
prevent or
slow movement in the solid rock, or to secure solid rock against larger-area
flaking, thereby enabling operation without danger. In this case, two
functional
principles are known, and are also known in partial combination. In mechanical
systems, the bolt is anchored by means of a friction fit, wherein mechanical
rock
bolts generally also have an expansion sleeve and an expanding element. In the
case of chemical rock bolts, an axial conduit is connected to the substrate
and/or
the solid rock in a material connection by means of a curable mortar or an
artificial resin used as a fixing agent. The rock bolts in this case are
installed in
the solid rock with or without pretensioning. In contrast to applications in
tunnel
construction, rock bolts used in mining, e.g. in underground coal mining,
serve to
temporarily secure the rock. This is because, in general, the temporarily
secured
rock will be extracted in a later work phase, and the rock bolts will then
also be
removed from the rock.
In mining and tunnel construction, rock bolts are used which have an axial
conduit, the same being particularly designed as a hollow tube.
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2
In this case, the rock bolts consist of fiberglass reinforced plastic. The
plastic
reinforced with fiberglass only expands to a minimal degree when the axial
conduit is subjected to tensile forces in the rock, and also possesses low
resistance
to compression and to shearing forces. Due to the low expansion capacity of
the
axial conduit made of fiberglass-reinforced plastic, these rock bolts must be
used
in high quantities and placed closely together to prevent any movement of the
substrate and to reduce the shearing forces applied to each rock bolt. Due to
the
low resistance to compression and shearing of the material, a large fraction
of the
rock bolts having the axial conduit made of fiberglass reinforced plastic are
damaged and/or destroyed during the installation thereof due to the
compression
forces and/or shearing forces involved. In coal mining applications, such rock
bolts having axial conduits which are manufactured from fiberglass reinforced
plastic are used in the coal seam itself to secure the advancing section in
front of a
longwall section. These rock bolts are extracted together with the coal, but
then
cannot be removed from the coal, or can only be removed with very great
difficulty. Rock bolts having an axial conduit made of steel are generally not
used
to secure coal seams because they cannot be cut, and/or have sharp edges
following excavation of the coal. The rock bolts having an axial conduit made
of
steel cut up the conveyor belts or destroy other devices used in coal mining,
thereby leading to high costs and interruptions. Rock bolts used in coal
mining
which have an axial conduit made of fiberglass reinforced plastic cause
substantially no damage to conveyor belts or other devices in the mine during
excavation because they can be cut easily, and therefore can be easily broken
up
by the excavation equipment. However, these rock bolts posses insufficient
properties with respect to mechanical considerations of expansion, resistance
to
compression, and resistance to shearing. Rock bolts having axial conduits made
of steel pose the disadvantage that they cause damage to conveyor belts and
other
equipment of the mine during excavation of the coal.
WO 2007/059580 Al discloses a self-cutting rock bolt having a cutting head and
an axial conduit.
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The problem addressed by the present invention is that of providing a rock
bolt
which possesses sufficient capacity for expansion and tensile strength, and
can be
cut to enable simplified separation of the excavated pieces of the rock bolt.
This problem is addressed by a rock bolt, particularly for use in mining,
having an
axial conduit, an anchor nut, and a plate supported by said anchor nut, said
plate
being for the purpose of placement on the rock, wherein the axial conduit
consists
at least partially, and particularly entirely, of metal and plastic, and this
at least
one component of the axial conduit which consists of metal and plastic serves
to
receive tensile forces.
The axial conduit of the rock bolt therefore consists of metal, particularly
of steel,
and of plastic. As such, the axial conduit can undergo larger expansions in
the
axial dimension when tensile forces are applied thereto, such that the rock
bolt is
also by design a directional anchor. In this way, movements which occur in the
secured rock can be secured against in an improved manner. In addition, the
axial
conduit of the rock bolt can be easily broken up and/or separated by mining
machines in the mining applications, particularly in coal mining applications,
such that damage can be substantially prevented to the technical equipment of
the
mining operation.
The rock bolt particularly consists, in one inner segment of the axial
conduit, at
least partially, and particularly entirely, of metal and plastic.
In a further embodiment, the axial conduit has a front end and a rear end, and
the
inner segment is distanced from the front and the rear ends by a gap of at
least
5%, 10%, or 20% of the total length of the axial conduit. Therefore, the
design of
the rock bolt as consisting of metal and plastic preferably does not involve
the
region of the rock bolt in the proximity of the front and the rear ends.
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In a further embodiment, the rock bolt is constructed in multiple sections of
components consisting of plastic and metal. The at least one component of the
rock bolt made of plastic and the at least one component of the rock bolt made
of
metal are initially produced separately, and are connected to each other
during the
manufacture of the rock bolt.
One component made of metal and one component made of plastic are preferably
arranged in an alternating manner along the longitudinal dimension of the rock
bolt, and/or the rock bolt consisting of metal has no sheathing made of
plastic,
particularly on the inner segment, and the at least one component consisting
of
plastic is particularly not a sheathing of the at least one component
consisting of
metal.
In one variant, the plastic is reinforced plastic, particularly plastic
reinforced by
fiberglass, and the metal is steel.
The at least one plastic component consists advantageously of at least 50%,
70%,
or 90% plastic, and particularly is entirely plastic, and/or the at least one
component consists of at least 50%, 70%, or 90% metal, and particularly is
entirely metal.
In a further embodiment, the rock bolt consists of at least 50%, 70%, or 90%,
and
particularly consists entirely of, plastic in a first segment thereof,
particularly in
the inner segment as a cross-section which is perpendicular to the
longitudinal
axis of the rock bolt, and in a second segment, particularly in the inner
segment as
a cross-section which is perpendicular to the longitudinal axis of the rock
bolt, the
rock bolt consists of at least 50%, 70%, or 90%, and particularly consists
entirely
of, metal.
The components are particularly connected to each other by means of an inner
or
outer plastic sheath, and/or fibers of the reinforced plastic are arranged on
the
metal components. The fibers are particularly saturated with a matrix material
and
CA 02763987 2012-01-11
then cured, and the plastic component is connected to the metal component by
means of the fibers, and/or the inner diameter of one component corresponds
substantially to the outer diameter of another component, such that the other
component is arranged coaxially inside the component, and both components are
5 connected to each other by an adhesive bond, and/or one component has an
inner
threading and another component has an outer threading, such that both
components are screwed into each other via the inner and outer threadings,
and/or
the outer diameter of one component and the inner diameter of another
component, preferably sectionally, are substantially the same, and the other
component is partially slid over the component on an overlap region thereof,
and
then both components are connected to each other by a sheath which is pressed
onto the outside of the same, said sheath particularly consisting of metal,
e.g.
steel.
In a further embodiment, the axial conduit is designed as a hollow tube.
In a complementary variant, the axial tube encloses an interior space, and the
rock
bolt has a fixing agent arranged in the interior for the purpose of
establishing a
material, fixed connection of the axial conduit to the rock, a movable piston
arranged in the interior of the fixing agent and outside the axial conduit
when the
axial conduit is arranged in a bore hole in the rock, and at least one means
for
moving the piston. The rock bolt is therefore a chemical rock bolt.
In a further variant, a rear end of the axial conduit is closed by a cap, and
the axial
conduit and/or the cap have at least one opening for conveying the fixing
agent
out of the interior space enclosed by the axial conduit.
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In a further embodiment, a mixer is arranged between the fixing agent and the
at
least one opening for the purpose of mixing the fixing agent, particularly the
two
components thereof, prior to the fixing agent exiting the at least one
opening.
The rock bolt particularly has an expansion sleeve and an expansion element.
The
rock bolt is therefore a mechanical rock bolt.
Rock bolts are preferably also rock anchors.
In a complementary embodiment, the fixing agent, particularly an artificial
resin
or mortar, has two components, e.g. one adhesive component and one curing
component.
The two components are preferably each arranged in separate pouches. In this
case, any device which contains the two separate components is considered a
pouch. For example, a cartridge or a different type of container can be
contemplated.
In a further embodiment, the rock bolt has a drilling head, particularly in
the
region of the front end or on the front end of the axial conduit. The rock
bolt is
therefore a self-cutting rock bolt.
Embodiments of the invention are described in greater detail below with
reference
to the attached illustrations, wherein:
Fig. I shows a longitudinal section of a rock bolt which is inserted into a
bore
hole, wherein the fixing agent has not yet been inserted into the space
between the rock and the axial conduit,
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Fig. 2 shows a longitudinal section of the rock bolt in Fig. 1, wherein the
fixing
agent has been inserted into the space between the rock and the axial
conduit,
Fig. 3 shows a longitudinal section of an axial conduit of the rock bolt
according
to Fig. 1,
Fig. 4 shows a longitudinal section of a component of the axial conduit
according to Fig. 3, made of metal and plastic, having a connection
between the two components in a first embodiment,
Fig. 5 shows a longitudinal section of the components of the axial conduit
according to Fig. 3, made of metal and plastic, having the connection
between the two components in a second embodiment,
Fig. 6 shows a longitudinal section of the components of the axial conduit
according to Fig. 3, made of metal and plastic, having the connection
between the two components in a third embodiment,
Fig. 7 shows a longitudinal section of the components of the axial conduit
according to Fig. 3, made of metal and plastic, having the connection
between the two components in a fourth embodiment, and
Fig. 8 shows a longitudinal section of the components of the axial conduit
according to Fig. 3, made of metal and plastic, having the connection
between the two components in a fifth embodiment.
A rock bolt I designed as a directional anchor 2 is used in mining
applications for
the purpose of temporarily securing the rock in a gallery. The rock bolt I has
an
axial conduit 3 which encloses an interior space 4. The rock bolt 1 is a
chemical
rock bolt 1, meaning that the axial conduit 3 can be attached to the rock 28
in a
material connection by means of a fixing agent 5 arranged in the interior
space 4.
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For this purpose, a bore hole 29 is constructed in the rock 28, and the rock
bolt I
is then inserted into the bore hole 29. This process is portrayed in Fig. 1,
prior to
the fixing agent 5 being pressed out into a space between the axial conduit 3
and
the rock 28. In Fig. 2, the rock bolt I which is attached by a material
connection
to the rock 28 is illustrated. The fixing agent 5 in this case is an
artificial resin 6
which has an adhesive component 7 and a curing component 8. The adhesive
component 7 is contained in a first pouch 9, and the curing component 8 is
contained in a second pouch 10. Both pouches 9, 10 are contained in the
interior
space 4.
The interior space 4 has a hydraulic chamber 17 which is closed by a ring
piece
in the region of the outer, rear end 37 of the axial conduit 3. The ring piece
20
has a hydraulic bore hole 19. In addition, the hydraulic chamber 17 is bounded
by
a piston 11 in the region of a different, inner, front end 36. The inner,
front end 36
15 of the axial conduit 3 is closed by a cap 23 having an opening 24. The
fixing
agent 5 can flow out of the interior space 4 of the axial conduit 3 through
the
opening 24 and out into the space, particularly the annular space, between the
rock bolt 3 and the rock 28. In this case, a mixer 25 is arranged on the
opening 24,
and the fixing agent 5 must necessarily flow first from the two pouches 9, 10
20 through the mixer 25, due to the geometrical arrangement of the mixer 25 in
the
interior space 4, then the fixing agent 5 flows out through the opening 24. In
this
case, the mixer 25 has devices, by way of example a corresponding geometry,
such that the fixing agent 5 flows through the mixer 25 in a circuitous or
looping
manner, achieving a mixing of the adhesive component 7 and the curing
component 8 of the artificial resin 6 prior to the same flowing out through
the
opening 24.
An anchor nut 14 is screwed onto the outer threading 18 in the region of the
outer,
rear end 37 of the axial conduit 3, the same having an outer threading 18,
wherein
said anchor nut 14 has an inner threading and an anchor plate 15 lies on the
anchor nut 14. The anchor plate 15 in this case has a plate boring 13 with no
inner
threading, and the axial conduit 3 is arranged inside said plate boring 13. In
this
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way, pressure can be applied by the rock 28 according to the illustration in
Fig. 2
onto the anchor plate 15. This pressure is transmitted by the anchor plate 15
to the
anchor nut 14, and then from the anchor nut 14 to the axial conduit 3, such
that a
tensile force acts on the axial conduit 3. This tensile force is transmitted
to the
rock 28 by the axial conduit 3, in a material connection with the fixing agent
5 on
the outside of the axial conduit 3.
For the purpose of introducing the fixing agent 5 into the space between the
axial
conduit 3 and the rock 28, a piston 11 is moved inward, meaning that,
according
to the illustration in Fig. 1, the piston 11 moves upward. In this manner, the
first
and the second pouches 9, 10 are destroyed by the piston 11, such that the
adhesive component 7 and the curing component 8 move, and the fixing agent 5
is pressed through the mixer 25 and through the opening 24 into the space
between the axial conduit 4 and the rock 28 due to the shrinking volume of the
interior space 4 between the piston 11 and the cap 23, and the fixing agent 5
subsequently cures. For this purpose, a hydraulic fluid, e.g. water, is pumped
under high pressure into the hydraulic chamber 17 through the hydraulic bore
hole 19, thereby moving the piston 11. The hydraulic chamber 17 and the
hydraulic bore hole 19 are therefore a means 12 for moving the piston 11.
In Fig. 2, the fixing agent 5 is already fully extruded into the space between
the
axial conduit 3 and the rock 28, meaning that the axial conduit 3 is attached
to the
rock 28 in a material connection, particularly by means of adhesive bonding.
In
the state of installation illustrated in Fig. 2 in this case, the axial
conduit 3 is
substantially entirely arranged in the interior space 4, meaning that only a
small
fraction of the axial conduit 3, by way of example less than 10% or 5%, is
present
outside the interior space 4. In this way, when the rock bolt I is installed,
very
little space is required in the work space 30 in the mining gallery. In the
state of
the rock bolt illustrated in Fig. 2, the anchor plate 15 rests on the rock 28,
and can
therefore receive compression forces. In addition, shearing forces applied
perpendicular to a longitudinal axis 38 of the axial conduit 3 can also be
received
by the rock bolt 1, and the rock 28 can be additionally secured in this
manner.
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In Fig. 3, a part of the axial conduit 3 is illustrated in a longitudinal
section as a
hollow tube. The axial conduit 3 consists of components 26 made of metal,
particularly steel or a steel alloy, and components 27 made of plastic,
particularly
5 a plastic which is reinforced by fiberglass. In this case, these components
26, 27
made of metal and plastic are arranged in an alternating configuration along
the
direction of a longitudinal axis 38 of the axial conduit 3. In Fig. 3, the
type of
connection between the component 26, 27 is not illustrated. The fibers 32 of
the
fiberglass reinforced plastic of the components 27, said fibers 32 being not
10 illustrated, have fibers 32 which are oriented in the direction of the
longitudinal
axis 38 for the purpose of receiving tensile forces exerted on the axial
conduit 3,
and have fibers 32 which are oriented at an angle to the longitudinal axis 38,
by
way of example perpendicular thereto or at an angle of approximately 45 to
the
direction of the longitudinal axis 38. The latter fibers 32 constitute cross
fibers
and can receive torsional loads exerted on the axial conduit 3. The components
26
made of metal have a roughened surface 22 on the outer side thereof.
In Figs. 4 to 8, different embodiments of the connection of the components 26,
27
are illustrated. In the first embodiment, according to Fig. 4, a plastic
sheath 31 is
applied by means of injection molding to both the components 26 made of metal
and the components 27 made of plastic. In this way, both components 26, 27 are
connected to each other.
In the second embodiment, according to Fig. 5, fibers of the fiberglass
reinforced
plastic of the components 27 are applied to the outside of the components 26
made of metal. These fibers in this case are saturated with a matrix material,
for
example an artificial resin, and then cured. In this way, it is possible to
produce a
load-bearing connection to the component 26 made of metal, i.e. a steel
component.
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In this case, these fibers 32 are laid out as both longitudinal fibers and
cross
fibers.
In Fig. 6, a third embodiment of the connection between the components 26, 27
is
illustrated. The inner diameter of one component 26 corresponds in this case
substantially to an outer diameter of another component 27. This means that
the
inner and outer diameters in this case substantially comprise a difference of
less
than 10%, 5%, 2% or 1%. In this way, the component 27 as a plastic part can be
inserted coaxially into the component 26 as a steel part. By means of adhesive
bonding 33, both a material connection and a positive-fit connection can be
produced between the components 26, 27.
In the fourth embodiment illustrated in Fig. 7, the component 26 has an outer
threading, and the component 27 has an inner threading, both indicated as the
threading 34. In this way, the two threadings 34 can be screwed together,
thereby
producing a connection between the two components 26, 27.
In Fig. 8, a fifth embodiment of the connection between the components 26, 27
is
illustrated. The fibers 32, particularly the fibers laid out as longitudinal
and cross
fibers, are applied in this case to the outside of the component 26. These
fibers 32
applied to the outside of the component 26 are pressed or clamped to each
other
by means of a sheath 35, particularly a steel sheath 35. The sheath 35 is
therefore
pressed onto the fibers 32 or is designed with a conical shape and/or is
screwable,
for the purpose of generating a radial pressure between the fibers 32 and the
outer
side of the component 26 made of metal.
The axial conduit 3 therefore has, in alternating sequence, the steel parts 26
and/or
components 26 made of steel, and the plastic parts 27 and/or the components 27
made of plastic. After the rock bolt 1 is fixed in the bore hole 29 and/or on
the
rock 28, the tensile forces are received by the axial conduit 3.
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In this case, the components 26 made of metal, particularly of steel, have
high
expansion upon the exertion of tensile forces, such that a large overall
expansion
occurs in the axial conduit 3 when high tensile forces are exerted on the
same.
This happens because a substantial fraction of the axial conduit 3 consists of
the
components 26. In this case, the components 26 comprise at least 30%, 50%, or
70% of the total expansion of the axial conduit 3, preferably in the direction
of the
longitudinal axis 38. In this way, the rock bolt I is also a directional
anchor, and
as such has a sliding function such that small movements in the secured rock
28
can be received due to the length modification of the axial conduit 3 in the
form
of elongation. As such, movements of the rock 28 are permitted by the rock
bolt
1. In this way, it is possible to substantially prevent the axial conduit from
breaking unexpectedly.
The rock bolt 1 will be used substantially in mining, particularly coal
mining. In
the case of application in mining, the rock bolt 1 is used for the purpose of
temporarily securing the solid rock 28, and particularly coal. The coal is
excavated using a shearer or a coal plow. During this excavation, the rock
bolts 1
are also removed with the coal and/or in the rock 28, and can be broken up by
the
shearer or the coal plow, and thereby transported away, because the components
27 made of plastic can be easily separated by the shearer or the coal plow. In
this
way, following excavation, only small partial pieces of the axial conduit 3
appear,
and these can be easily transported by the conveyor system. Due to the
fraction of
metal also present in the components 26, the same can be easily separated by a
magnetic separator. Moreover, it is also possible to separate the bolt pieces
made
of metal from the coal in a wash plant, because the two materials have largely
different densities.
In a further, not illustrated, embodiment of the rock bolt, the rock bolt
substantially comprises only the axial conduit 3, the anchor nut 14, and the
anchor
plate 15. In this case, the axial conduit 3 is not designed as a hollow tube,
but
rather as a solid profile.
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When this rock bolt 1 is inserted into a bore hole 29, a fixing agent 5 is
first
inserted into the bore hole 29, and the axial conduit 3 is then inserted into
the bore
hole 29. In this manner, the fixing agent 5 is distributed in a space between
the
axial conduit 3 and the bore hole 29. In this case, the fixing agent 5 can
also have
been inserted into the bore hole 29 in at least one pouch 9, 10 prior to the
insertion of the axial conduit 3.
As a whole, the rock bolt I according to the invention involves substantial
advantages. Due to the use of metal, the axial conduit 3, having components
26,
27 made of metal and plastic, comprises a sufficiently high expansion in the
event
of tensile forces exerted on the same following the installation of the rock
bolt 1
into the bore hole 29, such that it is possible to substantially prevent an
unexpected break of the bolt. In addition, the axial conduit 3 can receive
large
compression forces exerted during the insertion of the same into the bore hole
29.
Both the components 26 made of metal and the components 27 made of plastic
have high resistance to compression, meaning that said components 26, 27 can
receive large compression forces exerted in the dimension of the longitudinal
axis
38. In the case of rock excavation 28, particularly of coal, the axial
conduits 3 can
be easily severed due to the exclusive use of components 27 made of plastic
along
the longitudinal dimension 38. In this way, it is possible to prevent damage
to the
excavation equipment in the mine.
