U.S. patent application number 12/809998 was filed with the patent office on 2011-03-24 for self drilling rock bolting.
This patent application is currently assigned to Alminco Pty Ltd.. Invention is credited to Di Pietro Ricardo.
Application Number | 20110070035 12/809998 |
Document ID | / |
Family ID | 40800557 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110070035 |
Kind Code |
A1 |
Ricardo; Di Pietro |
March 24, 2011 |
SELF DRILLING ROCK BOLTING
Abstract
The present invention relates to self drilling rock bolting. In
particular, the invention concerns both a drilling apparatus for
rock bolting, and a rock bolt for use with the drilling apparatus.
The drilling apparatus comprises within it a fluid injector having
an upper part that mates with a self-drilling rock bolt for boring
a hole. The injector includes three fluid inlets, three fluid
outlets in the upper part, and three fluid conduits extending from
respective inlets to respective outlets. The self drilling rock
bolt comprises an elongate body having a leading end with a cutting
tip, and around the tip a thread with a coarse pitch. The bolt also
has a trailing end with an integral collar for fluid connection to
a channel that extends axially through the body of the rock bolt to
the leading end. Above the collar is a thread with a fine pitch. In
other aspects the invention concerns a system comprising the
drilling apparatus in combination with a rock bolt and a method for
rock bolting using the system. The invention has application, but
not exclusively, to rock bolting to stabilise the roof and walls of
underground coal mines.
Inventors: |
Ricardo; Di Pietro;
(Tarrawanna, AU) |
Assignee: |
Alminco Pty Ltd.
Fairy Meadow, NSW
AU
|
Family ID: |
40800557 |
Appl. No.: |
12/809998 |
Filed: |
December 15, 2008 |
PCT Filed: |
December 15, 2008 |
PCT NO: |
PCT/AU08/01838 |
371 Date: |
December 2, 2010 |
Current U.S.
Class: |
405/259.5 |
Current CPC
Class: |
E21D 21/0053 20160101;
E21D 20/02 20130101; E21D 20/028 20130101 |
Class at
Publication: |
405/259.5 |
International
Class: |
E21D 21/00 20060101
E21D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2007 |
AU |
2007907063 |
Claims
1. A drilling apparatus for rock bolting with a self-drilling rock
bolt, comprising within it a fluid injector having an upper part
that mates with a self-drilling rock bolt inserted into the
drilling apparatus for boring a hole; wherein the injector includes
three fluid inlets, three fluid outlets in the upper part, and
three fluid conduits extending from respective inlets to respective
outlets.
2. A drilling apparatus according to claim 1 wherein, in use,
water, resin and catalyst are pumped through respective conduits at
selected times, and enter a channel in the rock bolt.
3. A drilling apparatus according to claim 1, further comprising a
pump to pump water to a first fluid inlet, and pumps to pump resin
and catalyst to second and third fluid inlets.
4. A drilling apparatus according to claim 3, wherein the pumps
operate to provide different resin and catalyst flow rates.
5. A drilling apparatus according to claim 3, wherein the pumps
provide precise differential control, to allow different resin
catalyst mix ratios for different bolting conditions.
6. A drilling apparatus according to claim 1, wherein the upper
part of the injector is insertable within a fixed collar of the
trailing end of the rock bolt to make a fluid tight mating between
them.
7. A self drilling rock bolt, comprising an elongate body having a
leading end with a cutting tip, and around the tip a thread with a
coarse pitch; the bolt also has a trailing end with an integral
collar for fluid connection to a channel that extends axially
through the body of the rock bolt to the leading end, and above the
collar a thread with a fine pitch.
8. A self drilling rock bolt according to claim 7, wherein, in use,
a nut is threaded onto the fine pitch and engaged with a drill
which operates to drive the nut along the fine pitch thread to abut
against the collar during boring.
9. A self drilling rock bolt according to claim 8, wherein after
boring, reversal of the drill drives the nut away from the
collar.
10. A self drilling rock bolt according to claim 7, wherein the
trailing end of the rock bolt incorporates a collar that, when
installed in the chuck makes a fluid tight connection to an upper
part of an injector within the drill.
11. A self drilling rock bolt according to claim 7, wherein the
channel within the rock bolt opens in the cutting tip of the
bolt.
12. A self drilling rock bolt according to claim 7, wherein the
channel within the rock bolt incorporates a fluid mixer within
it.
13. A self drilling rock bolt according to claim 12, wherein the
fluid mixer comprises a flow restriction.
14. A rock bolting system comprising: a drilling apparatus for rock
bolting with a self-drilling rock bolt, comprising within it a
fluid injector having an upper part that mates with a self-drilling
rock bolt inserted into the drilling apparatus for boring a hole;
wherein the injector includes three fluid inlets, three fluid
outlets in the upper part, and three fluid conduits extending from
respective inlets to respective outlets. a combination of the
drilling apparatus and a rock bolt; and, a self drilling rock bolt,
comprising an elongate body having a leading end with a cutting
tip, and around the tip a thread with a coarse pitch; the bolt also
has a trailing end with an integral collar for fluid connection to
a channel that extends axially through the body of the rock bolt to
the leading end, and above the collar a thread with a fine
pitch.
15. A method of using the system for rock bolting according to
claim 14, comprising the steps of: attaching a rock bolt to the
drilling apparatus for drilling, such that the nut on the rock bolt
is secured in the drilling apparatus against rotation, and the
upper part of the injector mates with the fluid connection of the
rock bolt in a fluid tight manner; then operating the drilling
apparatus to bore a hole such that rotation of the rock bolt drives
the nut against the collar; and simultaneously pumping water
through a first fluid inlet of the injector, through the respective
conduit and out, and into the channel in the rock bolt to exit the
leading end of the bolt.
16. A method according to claim 15 wherein, when the hole has been
completely bored, operation of the drilling apparatus and pumping
of the water are ceased before pumping resin and catalyst through
respective second and third fluid inlets of the injector, through
the respective second and third conduits, out of respective second
and third fluid outlets and into the channel in the rock bolt,
where they are mixed before exiting the leading end of the
bolt.
17. A method according to claim 15, comprising a further step of
operating the drilling apparatus in the opposite direction to the
direction used to bore the hole, to push the nut into abutment with
the opening of the bore hole and to compressively load a local
region of strata.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to self drilling rock bolting.
In particular, the invention concerns both a drilling apparatus for
rock bolting, and a rock bolt for use with the drilling apparatus.
In other aspects the invention concerns a system comprising the
drilling apparatus in combination with a rock bolt and a method for
rock bolting using the system. The invention has application, but
not exclusively, to rock bolting to stabilise the roof and walls of
underground coal mines.
BACKGROUND OF THE INVENTION
[0002] Self drilling rock bolts are known for providing a single
drilling and securing function. This negates the need to drill a
hole, withdraw the drill bit and subsequently insert a bolt into
the hole.
[0003] An existing method of securing a rock bolt to a coal strata
is to drill a hole in the coal strata using a drill mast with a
drill bit attached thereto. After the hole has been bored and the
drill bit retracted, the drill bit is removed from the drill chuck.
A rock bolt is then inserted into a drive dolly which forms an
adapter between the bolt and a chuck. A resin capsule is then
inserted into the bored hole. The bolt is then loaded into the bore
hole, and the bolt causes the resin capsule to rupture. The bolt is
then rotated to promote mixing and dispersion of the resin. Once
the resin has set, a nut on the end of the bolt is rotated and the
nut comes into abutment with the collar of the hole. The
interaction between the collar of the borehole and the nut places a
tensile loading on the stem of the bolt. Accordingly, the strata
adjacent to the bolt is compressively loaded, thereby locally
stabilising the strata.
[0004] A disadvantage with the above described bolting method is
that it is a multi stage, and is thus time consuming operation. The
complicated nature of this bolting installation technique also
requires significant manual handling, which results in slow bolt
installation cycle times.
[0005] One known self drilling rock bolting system uses a hollow
bar. A passage through the centre of the bar serves as a flow path
for water to flush rock cuttings out of the bore hole. The passage
is also used for the ingression of a cementious grout for
subsequently securing the bolt to the adjacent wall of the
borehole. The cementious grout is generally supplied in a secondary
process. Accordingly, this system also suffers from being time
consuming.
[0006] A known single stage self drilling rock bolt system is
manufactured by Hilti Corporation. This system utilises a hollow
bar with a chemical resin capsule housed in the centre of the bar.
Water for flushing drill cuttings is also permitted to travel
through the inside of the bar in a separate annulus leading to the
drill tip. In this system, after the hole boring has been
completed, water is injected into the cavity containing the resin
capsule. The water ruptures the resin capsule, forcing resin
through a hole in the tip of the bar to the bore hole. The resin
then sets, bonding the bolt to the rock strata.
[0007] The equipment used in the Hilti system is based upon
conventional drilling equipment, with the addition of the water
injection function to disperse the resin. A disadvantage with this
system is that the resin capsule may prematurely rupture during
transportation, or during the boring process, prior to completion
of the boring process. A further disadvantage is that the bolts
have a limited shelf life on account of the expiration of the resin
capsule.
[0008] Other known self drilling rock bolt systems use a mechanical
expansion shell, similar to a Dynabolt.TM.. The expansion of the
shell is affected by the tightening of a nut, against the collar of
a hole. The bored hole is then filled with cementious grout to
prevent corrosion, and to assist in the load transfer of the
supported strata. A disadvantage this type of system is that the
bolt is grouted in a secondary process, requiring the use of
grouting equipment that is separate from the drilling equipment.
This increases the installation cycle times and the labour required
to install the bolts.
SUMMARY OF THE INVENTION
[0009] In a first aspect the invention is a drilling apparatus for
rock bolting with a self-drilling rock bolt, comprising within it a
fluid injector having an upper part that mates with a self-drilling
rock bolt inserted into the drilling apparatus for boring a hole.
The injector includes three fluid inlets, three fluid outlets in
the upper part, and three fluid conduits extending from respective
inlets to respective outlets.
[0010] In use water, resin and catalyst are pumped through
respective conduits at selected times, and enter a channel in the
rock bolt. Mixing of the catalyst and the resin only occurs after
they have entered the rock bolt, and as a result there is reduced
risk of the drilling apparatus becoming blocked with prematurely
hardened resin.
[0011] The system may further comprise a hydraulically driven pump
to pump water to a first fluid inlet. It may also comprise pumps to
pump resin and catalyst to second and third fluid inlets. The pumps
may operate to provide different resin and catalyst flow rates. In
addition they may provide precise differential control, to allow
different resin catalyst mix ratios for different bolting
conditions.
[0012] The upper part of the injector is insertable within a fixed
collar of the rock bolt to make a fluid tight mating between
them.
[0013] In a second aspect the invention is a self drilling rock
bolt, comprising an elongate body having a leading end with a
cutting tip, and around the tip a thread with a coarse pitch.
[0014] The bolt also has a trailing end with an integral collar to
form a fluid connection to a channel that extends axially through
the body of the rock bolt to the leading end, and above the collar
a thread with a fine pitch. In use a nut is threaded onto the fine
pitch and engaged with a drill which operates to drive the nut
along the fine pitch thread to abut against the collar during
boring. After boring, reversal of the drill drives the nut away
from the collar.
[0015] The channel within the rock bolt may open in the cutting tip
of the bolt.
[0016] The channel within the rock bolt may incorporate a fluid
mixer within it. The fluid mixer may comprise a flow
restriction.
[0017] In another aspect the invention is a rock bolting system
comprising a combination of the drilling apparatus and a rock
bolt.
[0018] In a further aspect the invention is a method of using the
system for rock bolting, comprising the steps of:
[0019] Attaching a rock bolt to the drilling apparatus for
drilling, such that the nut on the rock bolt is secured in the
drilling apparatus against rotation, and the upper part of the
injector mates with the fluid connection of the rock bolt in a
fluid tight manner.
[0020] Then operating the drilling apparatus to bore a hole such
that rotation of the rock bolt drives the nut against the
collar.
[0021] And simultaneously pumping water through a first fluid inlet
of the injector, through the respective conduit and out, and into
the channel in the rock bolt to exit the leading end of the
bolt.
[0022] When the hole has been completely bored, operation of the
drilling apparatus and pumping of the water are ceased before
pumping resin and catalyst through respective second and third
fluid inlets of the injector, through the respective second and
third conduits, out of respective second and third fluid outlets
and into the channel in the rock bolt, where they are mixed before
exiting the leading end of the bolt. The resin then hardens to bond
the rock bolt to the surrounding strata.
[0023] A further step in the process then involves operation of the
drilling apparatus, in the opposite direction to the direction used
to bore the hole, to push the nut into abutment with the opening of
the bore hole and to compressively load a local region of
strata.
[0024] The drilling apparatus is then separated from the rock bolt
and removed from the site of the boring and securing operation. The
drilling apparatus may then be reloaded with a further bolt and the
process is repeated as required.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] An example of the present invention will now be described
with respect to the accompanying drawings, in which:
[0026] FIG. 1 is a schematic diagram of a rock bolt installation
system in a detached configuration and showing some of the interior
detail.
[0027] FIG. 2 is a schematic diagram of a rock bolt installation
system in a use configuration and showing some of the interior
detail.
BEST MODE OF THE INVENTION
[0028] FIG. 1 depicts a rock bolt installation system 10 for
securing a rock bolt 20 to a strata, such as a coal strata. The
system 10 includes hydraulically operated drilling apparatus
30.
[0029] The drilling apparatus 30 is selectively operable in both
clockwise and anticlockwise rotational directions.
[0030] The rock bolt 20 has a leading end 21 with a cutting tip 22
and a trailing end 23. The leading end 21 is threaded and has a
coarse pitch. Part of the trailing end 23 is also threaded but has
a fine pitch 24. The trailing end 23 of the rock bolt 20 also
includes a fixed collar 27. A nut 25 is threadingly engageable with
the fine pitch 24 of the rock bolt above the collar 27. The nut 25
which has a polygonal profile that mates with the chuck 31 of drill
30.
[0031] When the nut 25 is rotated toward the trailing end 23, it
comes into abutment with the collar 27, as shown in FIG. 1. This
abutment prevents the nut 25 from moving further toward the
trailing end 23.
[0032] The rock bolt 20 has an internal central fluid flow channel
40 formed therein which extends between openings in the leading end
21 and within collar 27 at the trailing end 23. A static mixer is
located within the flow channel. The mixer is in the form of a flow
restriction 41.
[0033] The drilling apparatus 30 includes within it an injector 50.
The injector 50 has water inlet 51 to receive water from a water
pumping system 61 or water source. Injector 50 also has a resin
inlet 52 to receive resin from a resin pumping system 62. And, a
catalyst inlet 53 to receive catalyst from a catalyst pumping
system 63. The resin pumping system 62 and catalyst pumping system
63 use pumps which are resistant to the aggressive chemical nature
of the resin. These pumping systems 62 and 63 permit different
resin and catalyst flow rates to be provided, with precise
differential control, to allow different resin catalyst mixes for
different bolting conditions.
[0034] The upper end 57 of the injector 50 is insertable within the
fixed collar 27 of the rock bolt 20. The connection between the
projection 57 and the collar 27, when the projection is inserted
into the skirt, is fluid tight.
[0035] The operation of the system 10 will now be described with
reference to FIG. 2. Within drill 30 a water flow conduit 71
carries water between inlet 51 and the upper end 57 of injector 50.
Likewise flow conduits 72 and 73 extend from the resin 52 and
catalyst 53 inlets to carry resin and catalyst to the upper end of
injector 50. Since the resin is unable to harden until it comes
into contact with the catalyst, by providing separate fluid flow
conduits for the resin and the catalyst, the risk of the injector
head becoming blocked with hard resin is significantly reduced.
[0036] When a rock bolt 20 is to be installed into a strata, such
as a mine roof, the trailing end 23 of the rock bolt 20 is inserted
into the chuck 31 of the drill motor 30, such that the nut 25 is
seated within the chuck and secured thereto. In this position the
upper end 57 of the injector 50 is inserted within the collar 27 of
the rock bolt 20.
[0037] The cutting tip 22 of the rock bolt 20 is then placed
against the coal strata 80 and the drill motor 30 is rotated in an
anticlockwise direction. The nut 25 abuts against the collar 27
preventing the rock bolt 20 from longitudinal movement relative to
the chuck. By simultaneously applying anticlockwise rotation and
thrust against the coal strata, the cutting tip 22 of the rock bolt
20 starts to bore a hole within the strata.
[0038] During the boring operation, the water pumping system 61 or
source delivers water into the conduit 71 of the injector 50. The
water passes axially through the injector 50 and out of its upper
end 51 before entering into the trailing end 23 of the rock bolt
20. The water passes through channel 40 in the rock bolt 20 and
exits from the tip 22 where it assists in dispersing drill cuttings
away from the cutting tip 22 of the rock bolt 20, and out of the
bore hole. The coarse thread 21 adjacent to the tip 22 of the rock
bolt 20 assists with clearing of the rock cuttings, and this
improves load transfer between the bolt and the strata after
bonding.
[0039] When the hole has been completely bored rotation of chuck 31
is ceased. The resin and catalyst pumping systems 62 and 63 are
then used to deliver the resin through conduit 72 and a catalyst
through separate conduit 73. The resin and catalyst pass through
injector 50 and enter into the trailing end 23 of the rock bolt 20.
While passing through channel 40 the resin and catalyst are no
longer separated from each other, and the static mixer 41
interrupts the flow of the resin and the catalyst, thereby
promoting mixing of the catalyst and the resin into a single
homogeneous fluid .
[0040] The homogenous mixture of resin and catalyst then exits from
tip 22 and fills the space between the rock bolt 20 and the
adjacent strata 80. The resin quickly sets and hardens, bonding the
rock bolt 20 to the strata 80.
[0041] The nut 25 is then rotated clockwise so that it moves
axially along the fine thread 24 of the trailing end 23 of the rock
bolt 20. This movement separates the nut 25 from collar 27 and
pushes nut 25 firmly into abutment against the opening of the bore
hole.
[0042] By further rotating the nut 25 in a clockwise direction, the
nut 25 starts to place the rock bolt 20 into tension. Since the
rock bolt 20 is now bonded to the strata 80, a local region of the
strata is compressively loaded. This loading secures the roof of
the mine and reduces the risk of a roof collapse in that area.
[0043] The chuck 31 is then released from the rock bolt 20 and
drill 30 is removed from the site of the boring and securing
operation. The drill 30 and chuck 31 are then reloaded with a
further bolt 20 and the process is repeated as required.
[0044] Although the invention has been described with reference to
a specific example, it will be appreciated by those skilled in the
art that many variations and modifications are possible. For
instance, the rock bolt may be secured to the drill in many
different ways, such as by using a threaded connection, a
frictional interference such as an expanding collet chuck, or
another suitable engagement.
[0045] Also, instead of a static mixer, many other mechanisms could
be employed which promotes non-laminar flow of fluid s passing
therethrough, and hence mixing to create a homogeneous fluid .
* * * * *